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.

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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.</p>
<p>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.</p>

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 !

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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 :

1. Toolchanger dropping tools during the tool change process.
2. Loud noises and "bangs" when the tool holder is un-clamping or clamping during the tool change process.
3. 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.

1. The axis rapids until it hits the limit switch.
2. At which point the axis movement speed is reduced ... and the axis continues to feed until the axis feeds off the limit switch.
3. 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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CNC Lathe Headstock - Alignment Check and Adjustments

We've all been there ... Crashville. It's not a place you want to visit frequently ... but inevitably, we all make a visit. When I first started in CNC, one of my mentors told me "If you don't bump it once in a while ... you're not experimenting ... not trying new approaches ... and not using it to it's full potential." Well ... I'm not sure about that but there is a little truth in the concept.

Once you visit Crashville, you may notice some cutting errors and quirks developing in your workpieces. We are about to embark on a new series here in our Making Chips blog ... dealing with some of those unintended consequences of your visit to Crashville.

The first ... tapers developing on your CNC lathe when turning or boring ... the result of your headstock being bumped and not being square to the X axis ways. The result is that as the turret rides on the machine axis ways ... and the headstock and ways are not "square" ... you will be machining a taper. The amount of taper is the result of the amount of the mis-match between the headstock and the ways. It's important to remember that the ways ( base ) of the machine and the headstock are not one-piece ( normally ) ... the headstock is bolted onto the base. The illustrations below will give you a better idea.

So in our first post in our series ... we would like to point you in the right direction and give some tips on re-aligning your headstock.

As the above pic and notes convey, the headstock is normally bolted onto the machine base ... making the X / Z ways and the headstock independent of each other. Normally ... there are alignment screws on the headstock assembly that allow you to move the headstock and thus align it "square" to the machine ways. When you visit Crashville ... oftentimes one of those un-intended consequences is that that alignment is off because the headstock may have moved. So how do you get the correct alignment back?

There are a couple of methods ... let's start with my favorite ... the one I consider the simplest and the one I used most in the field.

First ... you'll need a piece of stock. Qualifications? You need a good material, easy to machine yet with the ability to produce a good finish. I didn't like using aluminum ... I preferred some grade of steel like cold rolled or similar. We want to insure that everything we do is reflected in the material ... not the workholding. So it's best to use hard jaws on the chuck ... and you want to make certain that the chucked material is not flexing ... so the material diameter to overhang factor should be appropriate to insure that the material isn't flexing when you're cutting. You also want to have a good length sticking out of the chuck ... after all the longer the area to measure the better your readings and the better your adjustments. Yes ... there are a lot of factors to consider here ... but you're a machinist !!! You know what to do and what is appropriate.

It's important to note here also what may be obvious ... don't use the tailstock. We don't want any mis-alignment in the tailstock to reflect in our measurements.

Next ... chuck up the material and clean up the stock by cutting the material the entire length. Take whatever cuts you need to clean up the stock ... just make sure the last cut is a nice finish cut and leaves a nice finish. Usually using MDI or the job / feed manual options are the best method. Creating a program is a little overkill and using the handwheel may result in an uneven cut and finish.

Now measure the diameter at the furthest and closest points to the chuck along the turned diameter. Not the same? That's the reflection of your headstock mis-alignment.

To adjust ... you'll need to find those adjusting screws on the headstock ... the above illustration might shed some light on where they might be and how they work. You will need to slightly crack the bolts holding down the headstock body to it's base ... then use the adjusting screws to move it in the direction you feel you need to move it to re-align it. Tighten everything back up ... and take another skim cut on the material. Repeat and re-adjust as necessary until the results are to your satisfaction. What should that be? As close as you can get it. If the material length in the chuck is short ... it really needs to be spot on because obviously the error will get magnified on a longer piece of material. As with everything you do as a professional machinist ... do it to the best of your ability.

One valuable hint : Place an indicator somewhere on the headstock to measure the amount you move the headstock with the adjusting screws. This will help you understand the relationship between the amount of movement with the amount of taper correction.

Another method which some people prefer ... instead of using a piece of stock and turning the diameter ... they will use a test bar. A test bar is a piece of stock that has already been machined and usually ground ... it's perfectly straight and true. They mount it in the chuck ... indicate it in ... and then use an indicator mounted to the turret which they then run back and forth along the test bar in Z as they adjust the screws on the headstock. This method works fine also ... but you need a qualified test bar to start ... and there are more variables that come into play. Is the bar indicated in and running true? Is your indicator on the turret reflecting the actual center of the test bar ... etc.. For my liking ... too many other variables ... and a piece of stock is simpler, more readily available and cheaper.

So as you can see ... this repair is not that hard ... a little time consuming ... but the result will leave you with a more accurate machine tool and a lot more money in your pocket ... the amount you'll save in a repair bill.

Hope this helps you recover from your inevitable visit to Crashville ... and insures you are MAKING CHIPS ... good chips ... for years to come !!

Happy Chip Making !!

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Machine Warm-up Routine - Why? When? How?

As former field service engineers ... one of the items we always stressed to our CNC customers was the importance of performing a machine warm-up routine. Below are answers to some of their most frequently asked questions ... which pretty much tell the whole tale about this activity.

WHY?
A machine warm-up routine benefits both the machine and the machining in a number of areas :

• Running the spindle and moving the axis give the oils in the machine ... spindle oil and way lube ... an opportunity to distribute and do their jobs. Especially in a colder environment ... start of the day when perhaps the heat in the shop was reduced for the night ... running the spindle and moving the axis gives the oils a chance to warm up to their appropriate temperature and "work" the way they were intended. The end result is improved machine life, operation and reduced down time due to break downs.
• It stands to reason also that when the oils are working as they were intended ... the accuracy of the machine can more easily be maintained. It is an unreal expectation to assume that you can walk in in the morning and start the machining and hold a tolerance of .0005" ... perhaps when the machine is brand new ... but not in the "real world". Starting your day like this will most likely result in offset adjustments being made due to the machine's "cold" condition ... and will begin the process of "chasing" size for quite a while. I heard countless times from customers how they spend 1-2 hours in the morning "chasing" size. Hello? Did you warm up the machine?

WHEN?
A lot of people assume that performing a machine warm-up routine is only appropriate after an extended "vacation" period ... either by the personnel or by lack of work flowing to the machine. While a longer warm-up period is recommended after an extended break ... an everyday warm-up routine is still recommended for the reasons listed above. Here are a couple of options for when to perform a machine warm-up routine :

• Start of the Day ... whether that's at the shop opening or the start of the 1st shift.
• After the machine has been idle for a time period of over 4 hours.
• After an extended vacation period.
• If the shop temperature is cold during the winter months ... a short warm-up should be performed even after lunch  / dinner breaks.
• If the machining requires holding a tight tolerance ... a warm-up routine should be left executing during ANY breaks in the machining ... inspection time, bathroom break, at machine deburring process, etc..

HOW?
Matching the situations above requires an assortment of warm-up routines. No matter what the length of time ... the warm-up routine should always include the following :

• Spindle running
• Axis moving along the full stroke of each axis.

The beauty part is that the various warm-up programs can be left in the CNC control and called up anytime as needed. Or in the case of just keeping the spindle warm ... it may be a case of just manually starting the spindle and leaving it running while you walk away and attend to something else.

Spindle Warm-Up
After an extended break the spindle should be run through all the speed ranges with substantial dwell times in between speed changes. Start slow and work your way up with at least 15-30 minutes between increases. An example of a Fanuc style program might be :

• G97 S100 M03
• G04 X1200.0 ( dwell for 1200 seconds or 20 minutes )
• S300 
• G04 X1200.0 ( dwell for 1200 seconds or 20 minutes )
• S500
• G04 X1200.0 ( dwell for 1200 seconds or 20 minutes )
• etc. etc. etc. until a speed of at least 3500 RPM is obtained.

You can create a program like the above to be run after extended breaks ... and a program with less dwell time to be run after shorter breaks.

As mentioned above ... to maintain the spindle temperature during the course of the workday ... manually starting the spindle at say 2500 RPM and leaving it running while you leave the machine can also be quite beneficial in maintaining machining accuracy.

Axis Warm-Up
After an extended break  ALL the machine axis should be made traverse the complete length of each axis ... or if fixturing / workpieces are in the way the maximum length of the stroke that is possible ... using various speeds. You don't want to start the movement under full rapid traverse speeds ... but rather work your way up during the warm-up cycle. The easiest way to accomplish this is to utilize the RAPID OVERRIDE feature on the machine. The G code warm-up program will call for G00 / rapid ... but start the program with the RAPID OVERRIDE switch at it's lowest percentage .... then work it up manually as the routine runs. A sample Fanuc style axis warm-up program might look like this :

• G00G91G28Z0
• G00G91G28X0Y0
• G00G91Z- ***** .... incrementally move the Z axis as close to the table as possible.
• G00G91G28Z0
• G00G91X ***** .... incrementally move the X axis to the opposite end of it's stroke
• G00G91Y ***** .... incrementally move the Y axis to the opposite end of it's stroke
• G00G91G28X0 ...... move the X axis back to the zero return / home position
• G00G91G28Y0 ...... move the Y axis back to the zero return / home position
• G00G91X ***** Y ***** .... incrementally move both axis at the same time to their stroke end
• G00G91G28X0Y0 .... move X and Y back to their zero return / home position.

The above routine gives you an idea ... and feel free to make additions as you see fit. The main idea is to move ALL the axis along as much of their stroke as possible. Not just a "square" pattern ... try to make "fancy" moves that can move all the axis through as much of the strokes as possible.

If you don't like or don't have a RAPID OVERRIDE option ... you can simple make a longer program using FAST feedrates ... such as :

• G00G91X ***** F100.00
• etc.
• etc.
• G00G91 X**** F200.00

You can get the idea ... repeat the program and alter the feedrates as the program progresses. Again ... the good part is that once it is written, you can maintain the program in the machines memory and recall it as needed. No need to re-create it each time.

Spending some time creating these warm-up routine programs ... and instituting a policy of when and how they are to be run ... can go a long way to improving your machine's life ... as well as your machining efficiency and accuracy.

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Happy Chip Making ... and may you Make Chips and Prosper !!

Don't Just Fill Your Oils ...

... Track Them ?

Why? I'm glad you asked !!

Did you know that filling your way lube tank can tell you a story about your machine's performance. It can, if you use the information to your advantage. How?

The best way is to make an oil fill reminder form and post it on the machine. Each time oil, any type of oil, is added to the machine, have the operator jot down the following:

• Type of oil added
• Date and Time the oil was added
• Amount of oil added
• On a turning center, when the chuck was greased

This data can be used for the following :

Type Of Oil : this tells you which oil tank might be giving you trouble. If you're filling the hydraulic tank (a closed system) - WHY and WHERE is the oil leaking from. Low hydraulic oil could result in a loss of pressure and perhaps an un-chucking of a part being machined with catastrophic results. If you're replacing way-lube (which you should), what kind of schedule are you on. This list should show a difference in the frequency of the filling which will easily and early show a way-lube system problem and head-off major repairs.

Date and Time the oil was added : this info gives you a clear view of the filling schedule. Again, not filling the way-lube tank, for example, will be easily seen and catastrophe can be averted.

Amount of oil added : as above, this info gives you a clear schedule of the filling schedule. Filling the way lube tank once every two days instead of once every three days will show up and might signal a line break or other problem that can easily be spotted and repaired in time.

As with everything in life, the info gathered is only as good as the person viewing it. Teach you operators to be hands-on people and to pay attention to this list, perhaps every morning with the machine start-up. Simple ideas like this TIP can help extend your machine's life and cut down dramatically on your machine's down time and repair bills.

Live Long ... and Make Chips !!

Spindle Load vs. Spindle RPM

Which is the true test of how hard your machine is working ?

If you had to watch the spindle speed meter or the spindle load meter on your CNC machine ... lathe or mill ... to determine if your machine was working too hard, which one would you choose?

The truth of the matter is that although the spindle load meter does tell you the power draw on the spindle motor, the RPM gage is a more accurate representation of how hard the spindle is working. Most machines come with a specific rating for load % per a specific time such as (in laymans terms) : "You can run this machine at 100% for 30 minutes."

That is of course a true statement and you can watch the load meter while cutting and reach that spec. However, if you watch the RPM gage while cutting and see it fluctuate wildly - basically because the motor is trying to keep the spindle at the specified (programmed) RPM - you'll never reach that 30 minute time frame. Because the cutting is so heavy in this type of case, the motor must keep "powering up" to keep the programmed RPM specified. This takes much more power draw on the motor than simply running constant at 100% load for the 30 minutes.

The Solution : When your machine is cutting, watch the RPM gage first to insure that the cutting conditions are resulting in a smooth RPM for the spindle and not wild fluctations as the motor fights to keep the speed constant. Secondly, adjust the cutting conditions so that the load meter is as high as you think you want (there is nothing wrong with 70-75%) and then recheck the RPM gauge to make sure that the RPM's are smooth at those settings. Smooth RPM cutting will result in better life for the spindle motor and smoother surface finish on the workpiece as well.

Happy Chip Making !!

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Your Way Lube System - Friend or Foe ?

Your CNC machine is equipped with an automatic oiler system. Great ! You won't have to think about oiling the machine and an alarm will tell you when the tank is dry. What a great device ? Right ?

Well, that is the design. Unfortunately, along with the "automatic" description of the system comes the "out of sight, out of mind" aspect of the system. Because many people know it is an automatic system, many people put it out of their minds and simply wait for the alarm to come up showing that the tank is empty and needs to be filled. But what if that alarm never comes on because the tank isn't empty ? Why wouldn't the tank be empty ?

As your machine gets older, the way lube system will require service just like any other mechanism. The main problem, which often gets overlooked, is that the "tank empty" alarm never comes on because the tank never drains and nobody ever notices it. Now your machine runs for months on end with no lubrication on the ways and when you finally notice a problem, it's too late. Here is the "Rest of the Story ..."

PROBLEM :  The machine's ways are not receiving any way lube oil.

SYMPTOMS - IN ORDER OF SEVERITY :

• Positioning / Repeatability Problems
• Axis makes noise when moving
• Axis Drive motor overload alarm coming when the axis is moving

POSSIBLE CAUSES :

• Way Lube Pump burned out.
• Way Lube Pump distribution flow set too low.
• Way Lube Pump filter CLOGGED
• Way Lube line BROKEN
• Metering Units are CLOGGED

POSSIBLE CAUSES EXPLAINED :

(1) Way Lube Pump Burned Out : If the way lube pump is burned out, obviously there will not be any lube getting into the system. These pumps are usually set using a timer system. There is basically two types of timer systems used :

• The pump is on a cam and the way it works is that the pump is always running. One gear turns another which acts like a step-down system and the second gear raises a "primer" lever. When the lever reaches the top of the stroke, the "primer" lever is released and the oil is pushed into the lines. This whole cycle can take 5-20 minutes meaning that even though the pump is always running, the lines get lube only every 5-20 minutes.
• How to Check It : Take a flashlight and look in the tank or remove the oil tank. Once looking inside, you can see the main gear that should be constantly moving. It may be at a very slow pace, but you will see it moving.

• The pump is set to an electrical timer set in the controls PC (programmable controller) or an actual physical electrical timer in the cabinet. This type of timer only supplies power to start the pump for every cycle.
• How to Check It : On some pumps there is no primer lever but a light comes on on the tank when the pump is activated. Make sure this light comes on every 5-20 minutes or some other sign comes on to show the pump is activated every 5-20 minutes.

(2) Way Lube Pump distribution flow set too low : As stated above, the way lube pump usually is set using a timer system. The flow amount that gets distributed into the lines during every cycle is usually set and adjusted at the pump with a manual setting mechanism. This type of adjusting mechanism is usually a knob that can be turned higher or lower to set more or less flow. Also, just look at the primer lever. During the mentioned 5-20 minute cycle, you should see the primer lever raise slowly and then start to drop after reaching the top of the cycle. Check the stroke of the lever - short stroke, less flow.

• How to Check It : The normal pump usage is in an 8 hour shift, you should fill the tank every 2-3 days. Also, you should see way lube flowing onto the ways. Always remember, the more flow the better. Yes, it may contaminate the coolant but that is better than ruining the ways and thus the machine just to save a couple of bucks.

The photo above shows a way lube pump unit which includes a manual flow control device. Adjusting the white knob adjusts the amount of lube being distributed per one cycle of the lube pump. When this type of pump is working correctly, you can see the white knob rising slowly then retracting, pushing the lube into the lines. The amount of rise and fall, and therefore the amount of lube distributed, is determined by the flow adjustment.

(3) Way Lube Pump filter CLOGGED : The way lube tank usually has a filter between the tank itself and the oil line that starts the distribution. This filter is usually in the tank itself at the bottom of the primer lever or in-line right after the main distribution line leaves the tank. It will get clogged over time, especially if there is no filter at the oil fill hole or if someone takes off the filter when filling the tank.

• How to Check It : Disconnect the main lube line where it exits the tank to feed the system or after the in-line filter if so equipped. When the cycle reaches the pump stage as outlined above, oil should flow through this connection. The flow should be strong at this point. If not, remove the oil tank and search out the filter or remove the in-line filter. They can often be cleaned with a cleaner but the best remedy is to replace it.

(4) Way Lube line BROKEN : Oftentimes a lube line in the system gets crimped or broken during machining or during service. These way lube systems are usually "pressurized" so to speak and if the pressure is released at one point, say at the broken line, the oil will flow all to that point, depriving all the other lines of fluid.

• How to Check It : When the pump is in the pumping stage, the primer lever should fall slowly. This is due to the fact that it is pushing the oil into the system. If a line is broken, the primer lever will fall quickly as all oil is funneled to the broken line area only. On systems without a primer lever, the pump may have a pressure gauge on the pump. During the pumping cycle, the pressure should register for a couple of seconds as the oil is pumped into the lines. If the pressure is low or does not come up at all during the pumping cycle, a line in the system may be broken.

(5) Metering Units are CLOGGED : In order to create the "pressure" of the system needed for even distribution, each oil line leads to a "metering unit" where the flow is lowered and the oil is discharged. When the pump forces oil into the lines, they all fill and flow to the metering units where the flow is stopped. Each metering unit is set to discharge the desired amount or "drops" of oil and perform their individual duties. Since some areas require more lube, the metering units can be different for each line or area. Since these metering units have actual valve type components in their very small bodies, over time these units can be become clogged or the inner workings can become stuck.

• How to Check It : This is a much harder area to check. The best remedy and prevention is to change these units every year as part of a yearly maintenance program. Because these units allow only drops to flow through, they are harder to see when troubleshooting. These metering units are usually located in "clumps" around the machine. Several lines lead to these central areas and lube lines are branched out from here to the various areas of the machine. Replacement metering valves should be obtained from the machine tool builder or dealer to insure that you are getting the correct replacement part. When changing these units, pay close attention to the flow arrow that is commonly marked on the units themselves. This arrow shows the direction of installation and flow. Check the original unit before removal and replace accordingly.

The photo above shows an example of some metering units. These individual fittings are usually located in one or two main terminal blocks that feed certain areas of the machine such as the axis and ball screws. As the system fills with pressure and lube, these fittings discharge the lube at their pre-set flow rate into their lube lines. Over time, like cholesterol in the arteries, these units become clogged and no longer allow lube to exit and thus deny vital areas of the machine the way lube they require. As part of a yearly maintenance program, metering units in the machine should be replaced as a precautionary measure.

Due diligence and a little tracking will 

insure your Happy ( and ACCURATE ) Chip Making

 for years to come !!

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