Shop Efficiency Part 7 - CNC Programming

Our Shop Efficiency series has really taken off ... and we would like to take a few lines to say Thank You to all our readers for your email comments and support. We are very pleased that we have been able to take some of our real world machining and machine shop experiences and turn them into valuable tips and pointers and pass them on to so many of you. Thanks so much for your support.

First - A little background on this Post
At first glance ... since Kentech Inc. develops and sells CNC programming software ... this post might look like straight marketing and a sales pitch for our Kipware® conversational CNC programming software. Actually ... it's a story of just the opposite. Most of our software titles have been designed and developed based on what we saw was lacking in our many years on the shop floor. Our Kipware® conversational CNC programming software is a product of that experience.

One of my most telling personal experiences was working in a shop here in Masachusetts as a CNC machinist. The shop was your typical job shop with all kinds of work coming through the door. Most of it was fairly simple ... with a few plastic injection mold type jobs every once in a while. The CNC programming was supposed to be done by the shop floor machinists ... using a CAM plug-in for Solidworks ... which was a bit complex. No CAD/CAM training more than a simple tutorial was offered or provided. As a result ... since most shop floor machinists were great at cutting chips but lacked intense CAD/CAM experience ... and the jobs were fairly simple ... they often resorted to manual programming. The result was programs loaded with mistakes ... from typo-errors to incorrect toolpaths ... and the result from that was scrap, broken tools and sometimes worse ... but the overall effect was complete shop floor inefficiency.

The frustration level on the floor ... needless to say ... was very high. The machinists were basically unable to do their job ... because no one trained them on the complex CAD/CAM system ... and there were no other tools to help them ... other than an editor.

In this environment ... our conversational CNC programming concept and design was born. It was plain to see that the CAD/CAM and a CAD/CAM programmer was required for the mold work ... but clearly for the 95% of programming we did on the shop floor it was NOT required. In fact ... having the CAD/CAM option as the only option ... actually made things worse.

CNC Programming and the LINK to Shop Efficiency
Which brings us to this post and the subject of CNC programming as it pertains to shop efficiency. Obviously ... if the program isn't created in an efficient and correct manner ... the parts don't get made and the money doesn't flow. But just as important as tooling and fixturing ... the program creation process must have options also. You wouldn't think of placing a simple rectangular piece of stock in a custom made fixture ... you would use a vise. In the same way ... you shouldn't think of programming a simple part with a round pocket and bolt circle through a complex CAD/CAM system. The real key to efficient shop floor programming is having an ARSENAL of tools at your disposal. Thinking about your CNC programming as more of a tool ... with multiple choices for various situations ... will help your shop floor reach a higher level of efficiency.

CNC Programming Tools Available
We've listed what we consider to be the realistic options for CNC programming available to anyone creating CNC programs in a "job shop" environment ... the environment where our readers predominately are working ... and the options up for discussion in this post.

1. CAD/CAM
2. Off-Line Conversational CNC Programming Software
3. Conversational CNC Controls
4. G Code "wizards"
5. Manual Programming through an Editor

"Wizards" and Manual Programming
To narrow the discussion a bit ... let's remove the two options that are really not realistic in a professional machine shop environment. So called G code wizards are way too simplistic and act

more as hindrance and weight than any kind of efficient tool. Full conversational programming software makes much more sense both from a financial and capabilities perspective. Full, quality conversational software is a programming system ... not a simplistic crutch.

Manual G code programming should only be considered for the simplest of parts. Human error plays too great of a role in any other scenario and really renders this option a last resort choice for a professional programming environment.

That's not to minimize manual CNC programming knowledge and experience. Any CNC programming option used is made VASTLY more efficient and productive when operated through the hands of an experienced manual CNC programmer. A good Editor should always be available to allow that experienced CNC programmer the tool to alter or edit auto-created G code. The point here is that creating programs from scratch manually is not a good choice. Even for simpler programming ... a tool that will auto-generate the code provides stability ... and the manual tweaking of the code can enhance that output greatly.

CONVERSATIONAL and CAD/CAM
Efficient CNC Programming Requires an ARSENAL of Tools
It's more about OPTIONS than OPTION
In a professional environment ... really the two main options are CAD and / or CAM and full, quality conversational programming software. The CAD/CAM option can really be broken down into two options. First the CAD option is a must for any design environment ... even when that is just supporting the shop floor with fixture design. Professional CAD can range from the simple to the complex ... and from the FREE to megabucks. Each shops design and CAD needs would drive that discussion. However ... going from the CAD drawing to a G code program does not necessarily have to through the expensive and complete CAD/CAM system.

Using conversational software ... that CAD drawing can also be turned into a G code program. DXF import can be used in quality conversational software and a variety of other applications to go from a CAD drawing to a G code program.  And of course ... the integrated CAM option can be used to go from that CAD drawing to a G code program.

The main point is that no two workpieces are exactly alike ... and the right programming option for one will most likely not be the right programming option for another. From our experiences ... the best programming method for any job involves (2) main factors :

• Who is the best choice to create that program? Shop floor? Dedicated programmer?
• What is the best tool for that individual to use to create that program quickly and accurately?

Letting the correct answers to these questions guide the process ... rather than forcing the path because of limited options ... will increase your shop efficiency when it comes to programming your CNC's. Some thoughts :

• Maybe the best person to create the program is not full CAD/CAM proficient but would be the best chip-maker for the job ... a shop floor conversational programming option might be the best solution. 
• Perhaps the job is very complex ... and the only solution for an accurate and efficient toolpath is the CAD/CAM alternative. 

The point to make is that with an arsenal of tools available ... the experience of your personnel and the complexity of the workpiece / programming can dictate the most efficient path to take for the program creation. This allows for the free flow of efficiency ... rather than ramming the square process through a round hole.

Machine Tools with conversational CNC controls
Conversational CNC controls mounted directly to a CNC machine appear to be the perfect solution ... but actually have some important points to consider. The alternative of purchasing a laptop or Windows based tablet ... loading it with conversational software ... is more often than not the better alternative. Here are our major reasons to support this claim :

1. CHEAPER ... conversational CNC controls can be quite expensive. A tablet with conversational software will cost less than $1200.
2. PORTABILITY ... having the ability to do the programming on the shop floor, in the office, at home ... makes a portable alternative very attractive.
3. PROGRAM MULTIPLE MACHINES ... the ability to simply move the laptop around or pass it off to someone else gives you the ability to use the "conversational control" on multiple machines. Other machines can also be purchased without the conversational option ... you already have a "conversational control".
4. PROGRAMMING AT THE MACHINE ... even though most modern conversational controls have basically (2) modes ... the conversational programming mode and the machine operation mode ... they can often result in headaches and frustration. Either the machine is not runnning waiting for a program to be created ... or the machinist is programming the next job while trying to run production. Not the best environment to say the least.
5. CNC CONTROLS ARE NOT COMPUTERS ... most industrial grade CNC controls do not have the power or capability of a desktop or laptop PC ... they are simply not constructed from the same components. And if they are a PC ... they are most likely NOT an industrial grade PC and not fit for the harsh machine shop environment.
6. CONVERSATIONAL SOFTWARE IS MORE POWERFUL ... backed by the power and capabilities of a PC ... conversational SOFTWARE is more powerful and has more options than conversational software operating on a CNC control.

Some Closing Thoughts ... 
The main reason for combining this post into our Shop Efficiency series is to get shops thinking about all the potential programming tools available. Our experience shows that the most efficient CNC programming is accomplished when an ARSENAL of good tools are made available. Inevitably users might find and use their favorite tools ... but the key is that they have the ability to choose from an assortment. Also ... that the other tools remain available when the need arises ... providing choices. Also ... when an assortment of tools is available ... shops can increase the number of people who can create those programs ... and that is a huge jump in shop efficiency. Creating CNC programs faster ... using more people ... means more spindles turning and that means more profits being generated. And isn't that the true test of Shop Efficiency?

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

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 :

1. Material : durable yet fairly easy to machine ... aluminum tooling plate is one recommendation.
2. 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.
3. 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

4. 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.
5. 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 :

1.  Utilize more of the machine table and Y axis available stroke ... more chip making means more profit.
2. Quickly and easily mount your fixture plates making for faster changeovers ... which means more time cutting chips ... and making money.
3. Have new capabilities to mount multiple jobs with multiple fixture types ... easily run more than one job at a time.
4. 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

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

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