Making Chips: 2014

Friday, December 12, 2014

Shop Efficiency Part 2 : Face Drivers for CNC Turning

In our second installment in our series on Shop Efficiency we are about to take an in-depth look at a workholding option for CNC turning that very often goes unconsidered. "In the old days", turning between centers was the method of choice for any type of shaft or similar type workpieces. The process began with manually drilling center holes in each end of the material ... then attaching a drive dog on one end that was used to drive the parts rotation ... using the tailstock at the other end for support ... and the cutting began. With the advent of CNC ... turning between centers has for the most part become a lost and forgotten art. The use of soft jaws and the process of turning the part around has become the method of choice. Most machine tailstocks are pushed to the end limit and left there to collect chips or worse ... are not even considered or purchased when the machine is bought.

But with shops looking to increase production ... decrease set-up and set-up times ... and at the same time increase quality ... face drivers are getting a face-lift and are becoming more and more popular for many types of machining. The ability to machine the entire workpiece in one set-up gives shops the ability to maximize their production capabilities with only a minimal expense. So let's take a deeper look at face drivers ... the concept and the design.

Introduction to Face Drivers

As the above illustration shows ... the use of face drivers in conjunction with your CNC machine's tailstock ... allow complete access to the entire workpiece. This not only reduces the number of operations and set-up ... it greatly increases the accuracy of the workpiece machined. With everything machined in the same set-up ... tolerances and concentricity are greatly increased. Although most used for shaft work ... a quick look around the shop would probably reveal a lot of "shaft type" work where face drivers could be considered for the workholding option. Right and left hand turning can be employed as necessary without any restrictions.

How Does a Face Driver Work

The above illustration shows that the face driver consists of (2) main features ... the center and the drivers. The center fits into the spot drill or center drill hole that is pre-machined into the stock. The driver pins are what drives the workpiece in rotation and can either be hydraulic or mechanical ( such as spring loaded ). So as the workpiece is located between centers ... it is also pushed up against the drive pins which dig into the end of the workpiece and cause it to rotate as the spindle rotates.

Attaching the face driver to the spindle can be done with a variety of methods ... the easiest and most common is probably holding it in the chuck jaws. Depending on your spindle face and configuration ... other methods might be Morse Taper or a flange mounted directly to the spindle face.

The "clamping" of the workpiece is two fold ... centering followed by clamping. As the workpiece locates on the center points ... the action of the tailstock forces the workpiece onto the spindle side center and up against the drive pins. As the workpiece is forced deeper onto the center ... the drive pins dig into the face of the workpiece. The drive pins adjust individually to accommodate any irregularities in the face. Under the continued load of the tailstock, the drive pins penetrate and "clamp" the workpiece ... while the centers maintain the axis of rotation.

Points to Consider When Selecting A Face Driver

Here a couple of major points to consider when selecting a face driver ... these may also effect your decision to consider a face driver for your situation :

The diameter of the face driver ... as measured across the driver pins ... should be smaller that the diameter where it will be locating to allow for complete access to the workpiece material.
The diameter of the raw stock should not more than 3 times the diameter as measured across the driver pins.
Drive pins are different for CW and CCW rotation ... consider how you will be machining the workpiece and what direction the spindle will be rotating when selecting a face drive.

One of the top manufacturers of face drivers is Riten Industries Inc ... they can be found on the web along with additional information on face drivers and other CNC turning workholding options by clicking the image below.

Please come back for our next installment in our series on Shop Efficiency.

Until next time ... Happy Chip Making !!

At Kentech Inc. we are MACHINISTS who create Real World Machine Shop Software.

Who creates the machine shop software guiding your shop's future ??
Check out all our REAL WORLD CNC & MACHINE SHOP titles at

www.KentechInc.com

Tuesday, December 2, 2014

Shop Efficiency Part 1 : Cutting Time VS. Workholding and Fixturing

It's the age old manufacturing quest ... how to reduce the cycletime and machine parts faster. And although cycletime is a major factor in the making profits equation ... concentrating too much on cycletime can sometimes make you miss the bigger problems ... the bigger deficiencies in the shop ... the bigger money wasting issues. While you are trying to shave seconds off the machining ... the time your machine spends not running is hands down a much bigger problem. Any machine not cutting is burning money and profits. It's easy to focus attention on cutting speeds and feeds ... it's a fairly obvious item especially for non-professional metalworkers. The fact is, however, every second or even minute you shave off the cycletime is probably no match for the large quantity of time you're machine spends not machining.

What is the BIGGEST cause of your machine not cutting chips ??
The biggest contributing factor for shop machines not cutting chips and therefore making money ( other than not having work for the machines ) are primarily load / unload operations and changeover of the machine from one job to another.

We are starting a new series here in our Making Chips blog to deal with these biggest money wasting areas in almost every shop ... fixturing and workholding. Whether it's the time needed to changeover the machine from one job to another ... or the time required to load and unload the part ... non-machining time is the biggest profit killer in any shop.

To start things out ... I would invite you to take a walk out to your shop floor ... and count the number of machines that are running? ... how many IN-CYCLE lights are lit? I am betting you will be amazed at what you find. And if you look deeper into why the machine is not running ... the reasons can usually be classified into two categories. The machine is being set-up to run production ... or the workpiece is being loaded for machining.

Everywhere people are jumping on the "lean" manufacturing bandwagon ... as they should ... and striving to achieve the 80%-85% percent "in the cut" time target. The fact of the matter is that lean manufacturing goes well beyond just direct chip making. The time spent ... or lost ... in changeover or part loading / unloading ... is probably a bigger profit losing factor than the time the tool spends in the cut.

This series will pull from our shop floor experiences to talk about the various areas of workholding for both milling and turning and machine / fixture changeover ... two topics that are certainly inter-connected. We will publish new articles interspersed with our other topics of interest ... so we invite you to check back frequently and keep up with the discussion.

Series Topic #1 :
Bringing The VMC Machine Table
Into the 21st Century

If you take a look at the table on your new VMC ... and compare it to the table on a 1940's milling machine ... you'll quickly notice that not much has changed.

T-SLOTS, T-SLOTS and more T-SLOTS. Not much has changed in the design of the milling machine table since around 1940 ... and that's our first issue to tackle.

While no one will deny that the T-SLOT is an essential element in the table design ... in today's day and age we really need to think outside the box ... or in this case outside the T-SLOT. A couple flaws enhanced by relying on the T-SLOT design include not utilizing all of the space available in the Y axis ... and not having the flexibility of positioning fixturing anywhere on the table to maximize the whole table surface. The first step in accomplishing this is to change the table surface.

One way of altering the surface of the machine table is to use a sub-table ... made from aluminum tooling plate or other suitable material. The main criteria is that the material is durable ... while being fairly easy to machine because we will want to machine a variety of locating options into the sub-

table. The two biggest advantages with a sub-table as mentioned above is that we now have the freedom to machine locating components to accommodate a wide variety of fixturing ... we can more easily utilize all the area of the table surface ... and we can always remove the sub-table and go back to the original table configuration if required. Some of the major points for consideration when considering a sub-table and it's design :

Material : durable yet fairly easy to machine ... aluminum tooling plate is one recommendation.
Size : it should cover the majority of the table ... thickness should be kept to a minimum as to not reduce the Z axis travels by an unreasonable amount ... but thick enough to accommodate our locating components and maintain rigidity.
Weight : aluminum will keep the weight down ... but lifting components should be included in the event the sub-table needs to be removed or re-installed.

Locating pins can be used for
T-SLOT alignment
Locating the sub-table can either be done with keys machined into the bottom surface or with the use of locating pins and dowels that can be used in conjunction with the original table T-SLOTS.
Once the table is installed ... it may be necessary to skim the top surface to insure it's parallelism with the machine axis. Keep this in mind when determining the size of the plate and the travels of the machine to allow for this type of machining. Periodically ... this may have to be repeated if excessive wear of the table surface occurs. Also make sure to account for this when selecting and installing your locating components ... which will most likely be hardened materials and not easily machined ... and will need to be installed below the top surface of the sub-table.

Best Ways to Utilize Your New Table Surface

Now that you have transformed your table surface into a 21st century table ... how can you get the most out of it? That really is only limited now by your imagination and design capabilities ... but here we will tackle what we would consider the top option.

Our recommendation ... we have used this system extensively ... is to utilize fixture plates located and clamped by a "ball lock" system. Fixture plates should be used for everything mounted to the sub-table ... from a simple vise to multiple vises to dedicated fixturing. This allows for greater flexibility

for positioning of workholding components and allows for quick changeover to other workholding components.

The ball-lock system allows for quick and accurate positioning of the fixture plates to the sub-table. When designing the sub-table surface ... create as many ball-lock receiver positions as possible to allow for multiple positioning options for your various fixture plate assemblies. You can machine and install these receivers prior to mounting the sub-table ... but they can also be machined in place as their need arises.

Fixture plates can also be made from the same aluminum tooling plate material used for the sub-table. They should, of course, be quite thinner for weight considerations and should always include some kind of lifting component. Handles, as the ones included in the illustration, may need to be removable with a quick attachment mechanisms to reduce their interference in the machining motions.

If you have an HMC ... you can take the same lessons learnt here and apply them to your tombstone or angle plate. Rather than using the standard "vise tombstone" ... a tombstone which utilizes fixture plates can open up new possibilities for your HMC as well.

Changeover Advantages

As mentioned above, the cycle start light goes out and the profit stops flowing when the machine is being changed over from one job to the next. The system described above can have a massive impact in reducing that downtime. Take for example the simplest task of working with a vise. To remove the the vise ... just un-clamp the plate with the vise and remove it. When re-installing it ... just lock the plate with the ball-lock system ... no tramming ... no indicating ... no center locating. The ball lock system locates the vise in a known position in seconds every time.

The same applies for all your fixtures ... they mount in seconds in known positions. Fixture design will also be improved because the know facets of the fixture plate location and much of the needed configuration is pre-determined. With pre-set variables in place ... your engineering mind will run rampant and you'll be exploring many more time and money saving options as you go down the road.

Seems Like a Lot of Work and Expense

The above statement is true ... but it's not easy to get from 1940 to the 21st century. The fact is that once you have completed the transformation ... the possibilities for added efficiency are endless and the reduction of lost machining time will be fantastic ... the payback and ROI will be fast. You will have new flexibility to :

Utilize more of the machine table and Y axis available stroke ... more chip making means more profit.
Quickly and easily mount your fixture plates making for faster changeovers ... which means more time cutting chips ... and making money.
Have new capabilities to mount multiple jobs with multiple fixture types ... easily run more than one job at a time.
If utilizing a 4th axis ... the new table design will give you more positioning options and result in faster mounting and removal of the 4th axis table.

Final Thoughts and What's Next
As you can see from some of the ideas outlined here, changing the surface design of your machining center's table can have quite an impact. While everyone is concerned with shaving seconds of the chip making ... shaving hours off your set-up's and changeovers will have an even greater impact on your bottom line. We hope that some of the ideas outlined here spur on your engineering juices allowing you to realize even more efficient fixture designs and ideas.

Make sure to return and check out other articles in this Series that will deal with fixturing and workholding ... for both turning and milling. We'll touch on things like vises ... face drivers for turning ... chucks and chuck workholding ... and much more.

After all ... we're MACHINISTS ... WE BUILD THINGS !!

Until Next Time ... Happy Chip Making !!

At Kentech Inc. we are MACHINISTS who create Real World Machine Shop Software.

Who creates the machine shop software guiding your shop's future ??
Check out all our REAL WORLD CNC & MACHINE SHOP titles at

www.KentechInc.com

Tuesday, November 18, 2014

Tuesday, November 4, 2014

Chip Removal at Your CNC Machine - AIR vs. WATER

A standard component of almost every CNC machine in almost every shop is the AIR GUN. They exist in a variety of forms and power ranges ... but are the tool of choice for cleaning chips off workpieces and areas of the machine itself. Fast and easy to access ... easy to configure and expand.

But are there any serious drawbacks to the use of the air gun at the machine?

As a former CNC field service technician ... I can emphatically state YES !! I would say that the air hose and air gun are one of the leading causes of major CNC component failures such as backlash and ball screw replacement as well as other axis positioning inaccuracies caused by machine way failures due to scoring. The innocent act of blowing off those chips can actually be one of the more destructive acts a machine operator can do to the machine. Why?? Here's a brief run down of some of the more common problems ... as experienced first hand from my experiences "in the trenches".

Backlash and Ball Screw Replacement
Of all the damage I have witnessed due directly to air gun use ... the need for the replacement of the axis ball screw assembly is by far the most common. Now for the most part I'm not talking about

simply blowing off the chips at the end of the machining operation ... I am primarily talking deep-cleaning the machine. Cleaning the machine and machine table table during a change over ... cleaning the chuck getting ready to install the collet assembly ... the "before the weekend" type cleaning of the machine where the operator may be charged with cleaning the machine from the weeks activities and is using the air gun extensively to gather the chips and "deep-clean" the machine. This type of extensive chip blowing will inevitably lead to the chips being blown into areas not designed to handle them. Perhaps the chips build up in a corner ... out of sight ... or under a way cover or find their way into a telescoping way cover. Looks clean ... but these chips are hiding and waiting. As new machining starts ... the motion of the machine forces the chips deeper and deeper into those areas until eventually they find their way onto the ballscrew where they "work their black magic". The wiper systems for both the machine ways and the ballscrew assemblies are not designed to stop chips being forced in under pressure from the force of an air gun ... but rather are designed to be effective in conjunction with the water flow of the coolant. What starts out as some axis backlash will some worsen and eventually will require the replacement of the ballscrew assembly.

Axis Way Scoring
In conjunction with the destruction mentioned above ... a different scenario occurs when the chips get lodged between the way covers and the machine ways. As the axis moves ... the chips dig and score the ways of the machine. What starts out as some simple score marks are soon magnified as more chips and more metal shavings lodge in those scores and they deepen and worsen and so on and so on and so on ... until the damage is extensive. This type of damage is a much harder to remedy ... the ways of the machine cannot simply be replaced. Now the repair consists of re-scraping or re-grinding the ways ... a major machine rebuild ... or replace the machine tool completely.

Other Common Component Failures

Over the years I have witnessed many other component failures that I would attribute directly to the use ... or over use ... of the air gun by the machine operator. These range from electrical components where chips were blown into cabinets or through seams of cabinets ... CNC lathe turret issues because chips had found their way into the indexing mechanism ... and ATC issues where chips were interfering with the tool change mechanisms. In short ... excessive use of the air gun and blowing of the chips inside the machine enclosure is very destructive ... and expensive !!

The Better Solution - COOLANT
The fact that blowing chips is a destructive act ... doesn't help with the everyday need in the machine shop and at the machine to clear away and deal with the metal chip issue. But I can definitively state that COOLANT and WATER FLOW is a much better alternative. One easy way to eliminate the overuse of air pressure is to provide an alternative like the following.

Create a coolant hose line by installing a T-joint right after the coolant pump. Attach a standard garden hose to the T and run the hose to the front of the machine. Install a standard garden spray nozzle at the end. Now when the coolant pump is on ... the operator will have pressure and in essence a garden hose with coolant flowing at his station. Instead of using the air gun in all instances ... he now has the option of using the coolant as a cleaning medium. The water flow is a much better and safer alternative to the high pressure air gun. BUT NOW IT'S UP TO ALL TO INSURE THE COOLANT MIXTURE IS MAINTAINED. With a healthy coolant mixture ... another benefit is the application of oil to the areas where the coolant is sprayed. Instead of leaving behind metals chips and shavings ... the spray will leave behind a coating of beneficial lubricating oil.
The flow and lesser pressure of the coolant hose provide a much safer and still as efficient chip removal alternative.

Blowing chips seems like such a simple act ... and one that is so common at the machine. But given a more in-depth look ... one can certainly see the possible destructive side effects this simple act can have on the machine tool. If you are in a production environment ... no doubt you have even experienced these destructive end results first hand.

I hope this glimpse into the "real world" can start you and your shop thinking in the direction of utilizing coolant and coolant spray as a chip cleaning alternative. Your machine tool will thank you !!

Until next time ... Happy Chip Making !!

Kenney Skonieczny
Kentech Inc.

At Kentech Inc. we are MACHINISTS who create Real World Machine Shop Software.

Who creates the machine shop software guiding your shop's future ??
Check out all our REAL WORLD CNC & MACHINE SHOP titles at

www.KentechInc.com

Wednesday, October 15, 2014

Brief Overview - Automatic Corner Override (G62)

When milling, have you ever experienced chatter and poor surface finish when you are attempting to machine an inside corner radius using the same feedrate as the rest of the workpiece?

Oftentimes, this results in the programmer having to decrease the cutting feedrate in the blocks where the tool cuts in the corner areas. Is there another way to have this done automatically ?

The most common situation above occurs when cutter compensation (G41 or G42) is active and you are attempting to cut in a corner where the toolpath inside radius and the TNR offset value are of similar size. You can use the machine to calculate an automatic decrease in feedrate using the G62 - Automatic Corner Override command ( This is a Fanuc G code ... check your programming manual if you are programming a non-fanuc compatible machine ... there is probably a similar command.) When G62 is commanded, the machine adjusts the feedrate automatically to maintain the cutting quantity per unit time in the corner. This often results in improved surface finish without the intervention or alteration of the programmed feedrate.

A couple of notes for G62 use :

Once commanded, G62 becomes MODAL and must be cancelled by commanding G64 (normal cutting mode) or by Power Off as G64 is usually the normal power on mode.
G62 can only be used effectively in conjunction with Cutter Compensation - G41 / G42.

Until Next Time ... Happy (and accurate) Chip Making !

Please visit our website for the best in Real World Machine Shop Software ...

just CLICK the pic below !!

Wednesday, September 24, 2014

Backlash and Your CNC - Things You Need to Know

( NOTE : This article references FANUC controls but is basically applicable to all CNC controls. )

A machine is a machine is a machine. Just because the words CNC are attached to your machine tool doesn't mean it doesn't get old or lose it's accuracy. And one of the main reasons your CNC machine losses it's accuracy is due to the ever infamous backlash.

What is backlash ?
The axis motion that makes up your machine tool is done through the use of ballscrews attached to your machining center's table and spindle housing or your lathes tool turret. The nut for the screw is usually attached to the table or turret and is connected to the ballscrew which is connected to your drive motor. As the motor turns the ballscrew, the nut moves the table or turret and your machine has motion. All ballscrew assemblies have some "slop" or backlash at assembly - the match between the screw and the nut. Basically backlash is the amount of motion the screw has to make when reversing direction before the nut and therefore the table or turret start to move.

How is backlash compensated?
Using the machine tools CNC controller, the builder can tell the controller how much motion is lost when the axis reverses direction due to the backlash. This value is stored in the machines parameters and when the particular axis goes to change direction, it looks in this parameter to know how much motion it needs to have (how many revolutions of the screw it needs to make) before the axis will physically start to move. The value of the parameter is usually in MM, although they may be in INCH settings in some instances

Why should I care ?
As the machine tool wears or as contaminants get onto the ballscrew and therefore in the nut, the original backlash settings lose their accuracy and therefore effect the accuracy of the machine tool. Positioning problems arise, straightness problems arise, as do a host of other related problems. Basically, the machine does not meet the specs like it did when it was new.

As mentioned above, sometimes contaminants can get onto the screw and then get carried into the nut. Although most nuts are protected against chips and debris, poor conditions can sometimes force the debris into the nut causing premature wearing of the screw and a pronounced backlash problem. Those contaminants can range from coolant to cutting chips. That is why it is essential to keep the machine areas clean and free from an excessive amount of chips. If chips are allowed to accumulate, they can become packed and when the machine tool moves, it forces the chips under guards and into areas where they shouldn't be. Eventually they get forced into the screws and nut areas causing un-repairable problems. Ballscrew replacement is not a cheap repair. Keep the expression: "An ounce of prevention is worth a pound or cure" in mind when planning your maintenance efforts.

What can I do about backlash ?
The normal method for adjusting the machine's backlash involves adjusting the backlash parameter values. This can be done by a qualified technician or you can give it a try. Outlined below is a brief but complete explanation of how to check for backlash and how to adjust it in FANUC controlled machine tools.

How often should you check it ? Recommended time frame would be about every 3-6 months. If you create the following sample programs in your memory and leave them there or upload and download them from a shop floor PC, you shouldn't spend much more than one hour or so keeping your machine accurate and at the same time you'll be checking for any other damaging problems. For example, if you see the backlash changing drastically, you might find a way lube problems or chip build up problem before they cause bigger problems.

How much backlash compensation is acceptable ? As mentioned above, all machines have some backlash adjustment, even when brand new and at ship time. As the machine wears, that value needs to be increased. Normal wear might have .005" - .010" adjustment in a ballscrew. If the value needs to be more than .010", it might be time to take a deeper look. Also, you need to check the backlash at various areas of the screw as it might be wearing more in one area than another. One example might be on a machining center where the set-up people always mount the vise or fixture in the middle of the table. Looks good but also causes a massive amount of wear in one confined area. the best scenario is to mount the vise or fixture all over the table, changing the location for every job - spreading the wear around evenly.

The best way to check the backlash is to first clear out the current parameter value in the control. The various parameter numbers for the variety of FANUC controls are listed further down in this page. First, write down the current values, then clear them by setting them to zero. Then make the machine move through the memory mode. We have found discrepancies in the past between the machine's handle or MPG mode and the memory mode, so we recommend you run the machine through MDI or through the machines memory mode. Below are a couple of sample programs for FANUC controls that you can use to gather your backlash data. Remember, the backlash is the amount of wasted motion when the particular axis changes direction.
If possible, check the backlash at different areas of the screw. On a machining center, mount the block in different areas of the table and check. On a lathe, check the backlash as various distances away from the chuck. If the values are different in the different areas, this could mean that the screw is worn in one place different than others. On a lathe, this tends to happen close to the chuck where the majority of the cutting is performed. You can's do much about to prevent it on a lathe but on a machining center, you can help yourself by mounting the chuck or fixture in various places on the table to allow for even wear. If you find big differences in the backlash in different areas, it may be too late and you may have to replace the screw.

Machining Center Backlash Adjusting Program.
If you have a Vertical or Horizontal machining center, the following program will give you an idea of how to create a program to test the backlash for each axis.

The following is a sample program for the X axis. Start the program with an indicator mounted to the spindle, touching a block mounted on the table, touching the right side of the block.

You can let the program run a couple of times to make certain that you get the same readings at the M00's in the program. The difference between Reading #1 and Reading #2 is the amount of backlash in your X axis.

You can use the same style program making changes as required to perform the same function for the other axis as well. Basically, you just want the machine to move one way then back, stop so you can and collect the indicator reading, then move the other way and back and collect that reading.

CNC Lathe Backlash Adjusting Program.
If you have a CNC lathe, the following program will give you an idea of how to create a program to test the backlash for each axis.

The following is a sample program for the Z axis. Start the program with an indicator mounted to the spindle or chuck, touching a block mounted on the turret or the tool turret itself, touching the spindle side of the block or turret.

Once you collect the value and know the backlash for your machine, you'll need to adjust the parameter values. Parameter values for FANUC controls are usually given in MM values, without the use of decimal point. So, for example, a parameter value of 30, actually means .030 mm - the decimal point is imaginary and placed three places from the right. You can use the following conversion formula to change your backlash data to mm, then enter that value into appropriate parameter - don't forget to drop the decimal point and add any zeros as required.

MM = inch x 25.4

For reference, 1mm = .0394 in.

On a CNC lathe, the value can either be a radius or diameter value. Since there is no easy way to tell, input a radius value then re-run the test program. Adjust as necessary and make a note so next time you will know.

When you're done, you should re-run the particular axis program again to double check that you did the backlash adjustment correctly. When you re-run the program, you should see less than .0001" backlash.

FANUC Backlash Parameter Numbers.

Listed below are the parameter numbers for the various FANUC control models. One note, lathe controls are T models whereas machining centers are M models.

FANUC Version 6T :

X Axis = Par # 115

Z Axis = Par # 116

FANUC Version 6M :

X Axis = Par # 115

Y Axis = Par # 116

Z Axis = Par # 117

4th Axis = Par # 118

FANUC Version 10/11/12T :

Par # 1851

Seperate line for each axis.

FANUC Version 10/11/12M :

Par # 1851

Seperate line for each axis.

FANUC Version 0T :

X Axis = Par # 535

Z Axis = Par # 536

FANUC Version 0M :

X Axis = Par # 535

Y Axis = Par # 536

Z Axis = Par # 537

4th Axis = Par # 538

FANUC Version 16/18/20T :

Par # 1851

Seperate line for each axis.

FANUC Version 16/18/20M :

Par # 1851

Seperate line for each axis.

NOTE : This 16/18/20 series of control can have a seperate backlash amount when moving at a feedrate and for moving at the rapid rate. This is an option - check with your machine tool builder. If this is the case, Parameter number 1851 is for feedrate and # 1852 is for rapid. You can use the programs above, just change from G00 to G01 and add a feedrate to test for the feedrate backlash amount.

Until Next Time ... Happy (and accurate) Chip Making !

Please visit our website for the best in Real World Machine Shop Software ...

just CLICK the pic below !!

Monday, August 25, 2014

Guidelines for Calculating Machining Hourly Rate

We tout this fact all the time in our marketing ... at Kentech Inc. we are MACHINISTS ... we cut chips, we programmed, we ran shop floors for years ... then we became software engineers and designers and built software products we saw were lacking during those years. What we refer to as Real World Machine Shop Software.

As a result, many of our clients come to us to take advantage of that experience ... especially those just starting out. Since quoting and estimating is one of the first tasks a new shop needs to get right ... we get asked quite a lot of questions about these areas. Our KipwareCYC® ( machining cycletime estimating software ) and KipwareQTE® ( cost estimating / quoting software ) titles are two of our most popular titles. One of the "hot" topics we encounter during online presentations of these titles is often concerning the cost to charge for a machining or a shop rate. So we thought it was a good time to add a blog post with some guidelines we feel are simple enough ... but important enough ... that can get you to an accurate figure.

Since many shops will utilize an hourly rate as a basis for charging for machining time, this post is dedicated to some helpful guidelines on how to calculate that machining hourly rate. Below are some points we consider important when calculating the hourly rate for a particular machine. The areas requiring calculations include :

Equipment – Cost Per Hour of Operation ... a common formula :
(machine purchase cost + expected lifetime maintenance cost) / expected hours of operating life.

Direct Labor Cost per Hour ... a common formula :
(total annual labor costs + taxes + benefits + paid time off) / (total annual hours worked – breaks and training time)

Overhead Cost Per Hour :
Any costs not directly involved in machining a part is overhead. These include costs for administrative staff salary, equipment, furniture, building lease, maintenance and office supplies. Calculate the annual costs of these, then divide by total labor or machine hours for the year. This will be your overhead cost per hour

Once the above costs are calculated … you can use the formulas and guidelines below to arrive at either a
“general” shop hourly rate or an hourly rate based on a specific piece of equipment.

General Machine Shop Hourly Rate ... a common formula :
Average overall shop rate = (average machine cost per hour + labor and overhead cost per hour) x markup

Machine Specific Hourly Rate ... a common formula :
(specific machine(s) cost per hour + labor + overhead cost per hour) x markup

Somewhat simplified ... and usually a work in progress as factors may change. It is important to gather all the figures in the formulas above as best you can ... as accurate as you can ... and to keep tabs on any factors that may change along the way.

Kenney Skonieczny - President
Kentech Inc.

You can check our all our Real World Machine Shop Software at our website :

www.KentechInc.com

Tuesday, August 12, 2014

Why Use Cutter Compensation - Follow the Crowd ??

The story has been circulating here about a support issue that was raised recently where a Kipware® conversational customer inquired about how to have KipwareT® output program coordinates using the tool center vs. using G41/G42 cutter compensation and the imaginary tool tip on the control. The conversation went something like this :

Support Staff : "Why would you want to do that? That's really not a good programming practice."

Client : "Well all our programs are written like that."

Support Staff : "OK ... but that's not a good programming practice. When we created Kipware® conversational we wanted to include best programming practice so KipwareT® outputs G41 / G42 and does all the calculations and automatically includes all start-up and cancel blocks and code ... so it creates a better program. No worries ... even if you don't know how to program it KipwareT® does it all for you."

Client : "Yes but nobody programs like that."

Really? Nobody out there programs like that? We find that hard to believe.

So ... we decided to post some of our main reasoning for considering the use of cutter compensation on the control as "Best Programming Practice". If you agree with our points ... we hope that you will consider making the change ... getting educated ... and to start creating your G code programs using G41 / G42 cutter compensation.

Program Coordinates ... programming to the tool tip center means that coordinates in the program do not reflect actual part print coordinates. Coordinates are based on the tool tip center rather than on the part dimensions. You can imagine the trouble and confusion that happens when edits need to be made.
Tool Interchange - Turning ... since the G code was written for a specific tool radius ... the program will only function correctly for that tool radius. Decide to use a 1/64 radius for finish when the program was written for a 1/32 radius ... re-program or re-generate the toolpath.
Tool Interchange - Milling ... I think this point probably comes into play more for milling G code than turning G code. Does your shop always have perfect .500 end mills? If so ... WHY ???? Re-grinding end mills is quite a cost saver ... but it means your end mills might be .485 or something odd. If you use G41 / G42 ... who cares? Just enter the correct offset value.
Dimensional Adjustments ... Come on, this is the real world. There is no reason to keep running back and forth to the CAD/CAM guy or programming office when dimensional adjustments need to be made during production ... and they will be because cutting conditions are not theoretical, they're real !!. Cutter compensation and part / tool offsets can handle probably 99.99% of all dimensional adjustments. Use the power of the control !!

Some of the main reasons we hear for why clients don't use cutter compensation ( and none of them are valid by the way ) ...

Nobody taught me. Come on ... grab a hold of your future and do some "playing" at the machine ... or read for yourself. This is a truly important programming tool ... you need to know hoe to use it if you want to go anywhere.
Nobody uses it. Like our scenario above ... just keeping following the crowd ... over the cliff. If I ran that shop ... the guy that comes to me and says "I think we need to change the way we think about cutter compensation" would have more of my respect than the guy who gives me the excuse "That's the way we always did it."

"I'm not stubborn ...

it's just that doing things your way is stupid."

After having spent more than 30+ years creating ... editing ... teaching ... G code and running shops on a day-to-day basis ... cutter compensation is one of the most mis-understood and mis-used programming feature. And also the most important tool a programmer and operator and shop foreman has at his/her disposal.

If you agree ... want to learn more ... or just want some additional reading ... below is a link to one of our previous posts that dealt with this issue also :
http://kipware.blogspot.com/2013/03/cutter-compensation-programmers-best.html

Unfortunately CAD/CAM systems have made it o easy to program with tool tip radius ... but in the real world, on the shop floor, it can be a real detriment to productivity and efficiency. We urge any CNC programmer out there who is not using cutter compensation on the control to step up and take control of your future ... get educated on cutter compensation ... and use cutter compensation in your G code. Your future will be a lot brighter ... and profitable.

Until Next Time ... Happy Chip Making ... with G41 / G42 !!

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Wednesday, July 30, 2014

Homemade Bar Puller for Your CNC Lathe - Resurrected

We first published this tip a few years ago ... and it has become so popular and copied on many other sites and in many trade journals ... and is asked about by so many of our clients ... that we had to bring it back for a repeat post ... once again !!

Enjoy ... and profit from this simple yet super efficient plan.

----------------------------------

One of the best ways to add efficiency to your CNC lathe is to make it run unattended. Using a bar feeder or a simple bar-puller, you can make your lathe run in a more complete AUTO cycle, stopping only for the refilling of the stock and minor offset adjustments. In this article, we'll share a simple but efficient design for a bar-puller and show you a programming example of how to put it to use.

Granted, a little work is required but when put to the right use, unattended operation can really help your bottom line. For example, how about being able to leave the shop at 5:00 and still have your lathe running producing another 50-60 parts while you're home eating dinner. Or for the one man shop, how about having production being run while your on the phone getting that next deal. With the right combination of cutting conditions and unattended operation, there's no telling where you can go.

The CONCEPT
The idea behind this bar-puller is to fill the spindle with a bar length of material, then using an auto cycle perform the following sequence :

Grab the stock with the puller
Open the chuck
Pull the stock to the desired length
Close the chuck
Retract the puller
Machine the part
Cut-Off the part

Then simply repeat the cycle again, the number of times for repeat depends on the number of parts that can be made using the length of bar stock in the spindle.

The SET-UP
To create your bar-puller feature, you'll need a couple of other items other than the bar puller to be outlined here.

First, you'll need to cut the bar stock the length of your spindle so the stock can be slid inside your spindle and pulled by the bar puller through the chuck or collett nose in the front. NEVER, NEVER, NEVER hang any size stock outside the end of the spindle - all stock must fit inside the spindle housing and be supported with spindle liners or a support ring as outlined below.

Since the difference between the stock OD and the spindle ID is usually pretty big, you can't just put the stock in the spindle. It must be supported in the spindle to prevent the stock from rattling around. This can be done with commercially purchased spindle liners or you can make a simple spindle liner ring using the design and concept outlined here. Please note that these liners take up the "slop" between the stock size and the ID of the spindle and must be used to prevent possible whip or damage to the spindle bearings or other possible injury.

One method is to make a ring out of plastic or similar material that attaches to the end of the stock with a set screw. The OD of the ring fits snuggly into the spindle ID and the ID of the ring attaches to the OD of the stock. This ring will move along the inside of the spindle along with the stock as it gets pulled toward the chuck. Calculate the number of cycles so this ring will reach the end of it's possible stroke as the max count is reached.

The BAR PULLER
Now the homemade bar puller needs to be made. The concept behind this puller is that you can make the size required as needed for the size material you are currently working with. You can make a few at a time, leaving some finishing operations until the ID size is determined. This way you'll have maybe 70% of the puller made then you can simply finish the rest when the time approaches and the final sizes are determined.

The bar puller uses a "split" piece of aluminum or other material softer than the material you will be machining. It uses simply a piece of bar or tube that is machined with the OD to fit into an ID tool holder station in the turret, and the ID slightly smaller than the OD of the stock. You may need to turn down the front end as per the sketch below to maintain a wall thickness that is thin enough to slide over the stock when split yet strong enough to pull the bar, depending on the weight of the bar stock determined by the diameter of the stock. The puller is then split in two or three or more places using a hack saw or slitting saw and an O-Ring placed on the OD of the puller to keep the tension. This allows for the puller to split and feed over the bar stock with the O-Ring providing tension to pull the stock and for the puller to return to it's original shape when done.

The PROGRAM
In the program, the puller is mounted in the turret, in our example Tool #3. Then in the CNC programs AUTO cycle, it is fed over the bar stock, the chuck opened, the turret moved to position taking the stock with it, the chuck closed, and the machining begun.In the example below, we are simulating a Fanuc series 10T or higher CNC control. Your M functions may be different, please consult your programming manual for your specific commands. Use this program as a guide, not a bible. The X0 is the center line and Z0 for this tool is set at the face of the stock as it sticks out of the chuck after cut off.

N0001 --------------- sequence number for this operation
M05 ----------------- make sure the spindle is stopped
G00 T0303 ---------- index to the bar puller station
G00 X0 Z.200 ------- rapid to a clearance point
G98 ----------------- change feed to IPM
G01 Z-.750 F20.0 --- feed onto the stock
M11 ----------------- open the chuck
G01 Z2.000 ----------feed to needed length plane
M10 ----------------- close the chuck
G01 Z3.500 ---------- feed off the stock
G00 X8.00 Z8.00 ---- rapid to index position
T0300 --------------- cancel the tool offset
G99 ------------------ return feed to IPR
M01 ----------------- optional stop

This sequence should be placed at either the top or bottom of the machining program. The best way to put the AUTO cycle into use is with the use of sub-programming. The MAIN program would be the call for the machining program including the number of times to call the program depending on the number of pieces you can make from the length of bar stock in the spindle. The SUB program would actually do the pulling and the machining. For example, in the example below, program O0001 is the MAIN program, calling the SUB program O1111 - 12 times, which actually does the pulling and the machining.

O0001 ------------ Main Program
M98 P1111 L12 -- sub program call
M30 --------------- program end
..
..
O1111 ------------- Sub Program
N0001 ------------- Bar pull sequence
--
--
--
M01
N0002 ------------- machine the part
--
--
--
M01
N0003 ------------- cut off
--
--
--
M01
M99 --------------- sub program end

In the above example, the operator only presses the Cycle Start on the MAIN program. This starts a 12 piece cycle that will include the pulling out of the stock, the machining of the part, and the cut off of the part. Recalling and executing the cycle 12 times.

Happy Chip Making !!

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Tuesday, July 15, 2014

Deciphering M Functions for Your CNC Machine

Recently we have been working with some Kipware® conversational clients assisting them in setting up their Kipware® post processor blocks for their G code output. With the addition of our EIA MENU option ... users now have greater flexibility in using machine functions ( M ) functions in their G code to accomplish specific tasks. One example might be ... parts catcher UP or DOWN to catch a part being parted-off ... or chuck OPEN and CLOSE during a bar feed operation ... or 4th axis CLAMP and UNCLAMP for CNC mill.

During these sessions we are coming across the situation where the end user doesn't know the specific M for their machine to accomplish some of these tasks. And for whatever reason ... manuals lost or misplaced ... machine was purchased used and no manuals were included ... or whatever ... the end user does not have any Operator or Programmer manuals for their machine which would normally outline the M codes and their function. Without the manuals ... they have no way of finding out what M functions control what. OR DO THEY ??

Let's start this journey with a brief explanation of the HOW's and WHY's of CNC M functions.

First ... there is no "industry" standard for M functions. Although you might find that M08 and M09 or M03 and M04 work for most CNC machines ... there is not an industry standard that says they must meet a certain criteria.
M functions are designed by the machine tool builder ... not the control manufacturer. So you may have (5) Fanuc controlled machines in your shop ... some Mori Seiki's some Hitachi some Leadwell ... all with different M functions. Because the M function circuits are designed by the machine tool builder and not Fanuc.

With those basic facts ... when you ask your buddy "What's the M function to open the chuck?" ... and he says "M11" ... and it doesn't work on your machine ... now you know why.

So how can you find out the M functions for your machine WITHOUT
an Operators or Programming manual?

One of the best ways is to use either the electrical or ladder diagram for the machine. Although most Operator or Programming manuals get lost along the way ... mostly because they are not kept with the machine but rather float around the office or shop ... electrical diagrams ( which outline the electrical circuitry of the machine ) and ladder diagrams ( which outline the logic of the machine ) are most often kept inside the machines electrical cabinet. Open up the doors and you will usually find one or the other or both.

Even if you're not electrical savvy ... the circuits are pretty clearly labelled and you can find say the CHUCK OPEN circuit and trace things back to find the appropriate M function. Again ... because they are built and designed by the machine tool builder and their electrical outline is outside the realm of the control ... these circuits are contained in the machines electrical documentation ... not the docs for the control.

Above is a pic of an electrical diagram for a Shizuoka CNC vertical mill ... with an exploded view on the bottom. You can see fairly easily even without any electrical savvy that the M10 command will control the 4th axis clamping function.

With today's more sophisticated controls ... oftentimes the ladder diagram is available directly on the machine controls CRT. You can pull up the ladder and even search for the appropriate function command ... but in other cases the "old fashioned" printed ladder can also usually be found in the machines electrical cabinet.

Taking a look at either the electrical diagram or ladder will usually result in some additional road or path to travel to find the appropriate M function on your machine. A simple execution of an MDI command is a good test to see what happens. The old Trial and Error method will open up additional doors or produce the desired results.

M functions are powerful options on your CNC machine that can help automate many tasks and make your manufacturing more efficient. Know that you know the trick to discovering the M functions on your CNC machine ... why not peruse your electrical or ladder diagram and see if there are any you might be missing in your programming?

Until next time ... Happy M Code Hunting ... and Happy Chip Making !!

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Wednesday, July 2, 2014

When is a CNC Program more than a G code program ?

... when it's a set-up sheet as well.

Most people are familiar with the ability of most CNC controls to include COMMENTS in the CNC G code program itself. Comments are designated in a variety of ways from :

( THIS IS A FANUC AND OKUMA COMMENT ) ... any text inside ( ) is considered a comment.
! THIS IS AN ACRAMATIC COMMENT ... any text following the ! is considered a comment.
; THIS IS A FAGOR COMMENT ... any text following the ; is considered a comment.
and on and on we could go.

Comments can be a real help when they include operator messages ... such as :

M00 ( TURN PART AROUND )
or
M00 ! CHECK DIMENSION A

... but comments can go well beyond operator messages and can turn your G code program into a complete set-up doc as well that includes tool information, part zero locations and even stock descriptions.

Most people will create either a paper or digital tool sheet / list and / or set-up sheet / list that is stored and re-called when the corresponding G code program is going to be run again. The set-up personnel refer to these docs to set the machine up ... loading required tools and setting height offsets and work offsets. Works great ... no problems. But is there a better alternative? The answer is a "could be" yes. By storing this information directly in the G code program using the COMMENT capability of your CNC control. For example ... something like this :

O1234
( PART #1234 )
( PROVEN PROGRAM : 7/2/2014 )
( PROGRAMMER : JM )

( PART LOCATED IN VISE USING JAWS JW-1234 )
( STOP SET-UP IS RIGHT SIDE - WORKPIECE STOP AGAINST FLANGE )
( X/Y PART ZERO IS LOWER LEFT CORNER )
( Z0 = TOP FINISH SURFACE )

( T1 / H1 = #3 CENTER DRILL )
( T2 / H22 = 1/2 DRILL )
( T3 / H3 = .500 CARBIDE END MILL )

So what is the advantage of keeping this info directly in the G code program using the COMMENTS capability of the CNC control?

Harder to misplace ... if you're going to run the program, you need the program ... and all the set-up info is right there stored right inside the G code program.
Complete info is there for all to see at any time ... no rummaging for loose paperwork or docs.
Any edits or changes can be made directly in the program ... when the running program is saved after execution ... all the current set-up info is changed and saved as well including all updated data.

We often get asked ... "Won't this slow down my program execution speed?" The truth is that it will ... but it will also be so minimal that usually the cost savings of having comments and all the convenience that comes with it far outweigh any reduction in program execution time. Rummaging around for lost documentation or re-creating lost documentation would be the real money waster.

Just a little something to think about if you haven't considered COMMENTS already in your CNC programming. We touched on only a few points here ... but we're sure you can find many more benefits depending on the capabilities or lack thereof pertaining to your particular CNC programming operation. The fact is that expanding the use of COMMENTS in your CNC programming could be a real time and money saving alternative to digital or paper documentation.

Until next time ... Happy Chip Making !!

Please visit our website for the best in Real World Machine Shop Software ...

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Tuesday, June 17, 2014

ATC Alignment - A Quick and Easy Alignment Check

One of the most common types of ATC ( automatic tool change ) issues is mis-alignment between the ATC tool change arc or mechanism and the toolholder when it is in position, clamped in the spindle. Their are many symptoms and results from this mis-alignment ... some of the most common can be :

Toolchanger dropping tools during the tool change process.
Loud noises and "bangs" when the tool holder is un-clamping or clamping during the tool change process.
ATC arm or mechanism jamming in the tool holder under the spindle.

In this Making Chips post ... we wanted to share a quick, down-and-dirty method of checking the alignment of your tool change arm or mechanism with the tool holder when in position and clamped in the spindle. This check is pretty accurate and can be done using only a machinist 6" scale ... and will give you a good indication if the ATC problems you may be experiencing might be related to ATC mis-alignment.

Step #1 :
Place one of your tool holders in the spindle and clamp it as normal. Using your 6" scale ... measure from the face of the spindle to the center of the V in the toolholder. +/- 1/64 of an inch is usually a good tolerance to use when measuring.

Step #2 :
Next ... remove any tool holders from the spindle ... leaving the spindle with no tool mounted. Step through your ATC process until the ATC arm or carousel comes into position under the spindle. Here you are mimicking the ATC process ... step by step ... and are pausing the process as if the ATC mechanism is under the spindle as it would be to change the tool. Again using your 6" scale ... measure from the face of the spindle to the male part of the V that would fit into the tool holder. Again ... +/- 1/64 of an inch is a good tolerance.

If the dimensions from Step #1 and Step #2 are off by more than 1/64" ... ATC mis-alignment may be the cause of any problems you may be experiencing with your ATC mechanism.

The Fix :
In a Fanuc controlled machine ... the Z axis stops at the "tool change position" through the use of the Zero Return or Home position ... G28 command line. Although a hard limit switch is activated during the zero return process ... the real process works like this.

The axis rapids until it hits the limit switch.
At which point the axis movement speed is reduced ... and the axis continues to feed until the axis feeds off the limit switch.
After the limit switch is switched off ... a certain additional amount of movement is executed ... this additional movement amount is knows as the "grid shift".

This Grid Shift amount can be adjusted through a control PARAMETER setting to make the dimension obtained in Step #1 match the dimension required in Step #2. Fairly easy to do ... but depending on the machine tool and Fanuc control model with which it is equipped ... depends on which parameter # is involved. Probably better left to an experienced technician ... although a gander at your Fanuc parameter list or manual can yield the correct GRID SHIFT parameter that can be adjusted.

Performing this simple check can give you a better idea if ATC mis-alignment may be causing your ATC problems ... and which track to pursue to obtain the correct method of repair.

Until next time ... Happy Chip Making !!!

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