Tag Archives: cnc

X-Carve Programming … Shop Floor Programming … with KipwareM®

As we continue to ramp up our sister woodworking company … KÄRV … we continue to demonstrate  and prove our mantras for our Kipware® machine shop software. Metalworking operations … woodworking operations … both have a lot of similarities and requirements and we continue to prove our Kipware® real world machine shop design and features in our now real world woodworking environment.

We recently blogged regarding how we utilize our KipwareCYC® and KipwareQTE® machine shop cycletime and cost estimating software to estimate retail costs for some of our wood products. If you missed it … see the full article HERE.

We are also proving our “not every job requires a CAD/CAM system” programming mantra at KÄRV as well. We recently put our KipwareM® – conversational CNC programming software for milling … to work on a shop floor programming project we were working on in the KÄRV workshop. If you haven’t read our article on shop floor programming vs. CAD/CAM programming … it’s quite the eye-opener … you can read the full article HERE.

The Rest of the Story …

We came up with an idea for a unique clock design that featured a quartz clock movement inside a slice of an oak log. To house the clock body … we needed to mill a 3″ diameter hole in the slice … and we wanted to use our X-Carve CNC router to mill the hole. Simple enough … and it really illustrates how a simple programming project could turn into an overblown programming project if we were to use a CAD/CAM program to create that G code program.

Here’s the finished product

In a CAD/CAM system we would have had to first create a drawing … why? … and then use that drawing to create the toolpath. Some extra steps that would not only cost us time but that time expense has to go somewhere and that would mean additional labor costs associated with the cost of the clock … which would eventually be for sale on our website. Want one … get it HERE !!

So we started KipwareM® … no drawing required … and with a couple of fill-in-the-blank forms completed … we had our G code program to rough pocket and finish mill … using a helical milling routine … the 3″ hole needed to mount the clock movement. Here are some screenshots of the forms … simple, plain english, fill-in-the-blank forms with tons of machining options that created a quick and efficient toolpath … no drawing nor drawing time required Bang bang done !!

As I mentioned we roughed the pocket using a pocketing routine … but we finished the side walls using a helical type cutting routine. Very easy to create in KipwareM® and posted out using KipwareXC® with our X-Carve Profile. We sent the G code and drove the X-Carve using the Universal G Code Sender application. The results were outstanding and the fit for the clock movement was perfect … first shot.

Needless to say we saved ourselves a ton of time by not having to create a drawing and by using our shop floor programming ( not CAD/CAM programming ) model and KipwareM®. We did the programming right at the machine … no expensive CAD/CAM system required and no drawing or CAD/CAM experience required.

AND … we like the results !!

Another unique wood design produced in the KÄRV workshop !!

If you would like to learn more about KÄRV woodworking and see our other products and designs … please visit our website … www.KarvWoodworking.com

If you would like to explore our conversational, shop floor programming applications or any of our other REAL WORLD machine shop software … please visit our website … www.KentechInc.com

Kenney Skonieczny
President – Kentech Inc.
Woodworker – KÄRV Woodworking

Shop Floor Programming … Why It’s Different and Why It Matters

If you have ever worked and lived on the shop floor … as we did for over 30+ years … you know there is a difference between programming in a job shop type environment  … what we call every day programming / shop floor programming … and complex “die and mold” programming which is the true essence of CAD/CAM and CAD/CAM programming.

It’s a fact … it’s real … and it can DEFINITELY mean the difference between profit and loss. 

This post is dedicated to exploring exactly what we mean …. because there is a HUGE difference in employing a SHOP FLOOR PROGRAMMING model vs. a CAD/CAM PROGRAMMING model. 

SHOP FLOOR PROGRAMMING

Our definition of shop floor programming is the programming of the simpler, everyday type workpieces on the shop floor … perhaps directly at the machine … by the shop floor personnel using simpler G code creation tools like Kipware® conversational. It is in contrast to the CAD/CAM programming model where CAD/CAM software … with the start of everything dependent on a CAD drawing … is used by dedicated “CAD/CAM” guy(s) to create G code programs. Our 30+ years of shop floor experience have proven to us that everyday operations like simple milling … drilling … tapping … turning … grooving … boring … for the everyday type parts machined in 95% of job shops around the world every day … can be created more efficiently using the  shop floor programming model.

In a job shop and / or production environment … shop floor programming can especially pay big dividends when the statement “the more the merrier” is employed. The more personnel that are involved in the creation of G code programs … the better the efficiency and the better the output. And of course, allowing shop floor personnel to create the simpler, everyday CNC programs using tools like our Kipware® conversational means increased profits along with that increased efficiency and output.

In most cases … being a good chipmaker is the key experience requirement. Someone who can cut chips … knows material removal and all that that encompasses … and knows fixturing and workholding. While the knowledge of G code in any CNC environment is always essential … tools like Kipware® conversational can assist those chipmakers with limited G code knowledge create fast and efficient  G code programs from scratch. Many chipmakers have a handle on G code but creating a G code program from scratch can be a daunting, cumbersome and sometimes slow task. The reverse is also true … CAD/CAM / computer operators often lack the chipmaking and fixturing expertise of the shop floor personnel resulting in non-efficient CAD/CAM programs or constant re-programming because of real world consequences.

CAD/CAM PROGRAMMING

Is contrast to the points outlined above … the programming of complex … what we’ll call “die and mold programming” … should be the main prerequisite  behind a CAD/CAM programming model. CAD is an essential tool for design and engineering … and while the the CAM portion of the CAD/CAM model can be disputed … for complex, 3D programming die and mold programming … it to is essential.

However, using a complex CAD/CAM system and requiring CAD/CAM trained personnel to create G code programs for the simpler, everyday type workpieces can mean the exclusion of valuable chipmakers from the programming process. It can oftentimes lead to slow program creation and thus decreased efficiency, productivity and output. The fact is … CAD/CAM was never designed for EVERYDAY programming. It was created to handle complex design and the programming of complex aircraft and die / mold components. It was always an afterthought to adept it to production programming. The mere fact that everything starts with a drawing inherently makes it more complex and cumbersome for this task.

 Debating the CAM in CAD/CAM

Even when utilizing a CAD application for design … still not every workpiece should be or needs to be programmed through the CAM module nor by the “CAD/CAM programmer”. The point we want to make here is that CAD can be different than CAD/CAM. While having a drawing and design application … a CAD program … can be and oftentimes is essential … the CAM part is up for discussion. Handing off a drawing and having the simpler workpieces … the everyday type workpieces … programmed on the shop floor can free up additional programming resources to concentrate on the more complex programming required for the more complex components. Shop floor programming can be the key that unlocks increased efficiency and productivity … even when using a CAD ( and / or CAD/CAM ) programming model.

And home and hobby shops?

One man, small shops and hobby makers can also reap the rewards of NOT programming every workpiece through a CAD/CAM system and using a shop floor programming application. The quick and efficient programming made possible through tools like Kipware® conversational can assist in realizing the quick and accurate production of workpieces … whether a single component, multiple components or in production. Spending time creating drawings … because every CAD/CAM program starts with a CAD model … for even the simplest of operations … can slow down, bog down, and waste time that home and hobby shops can’t afford to waste.

Although usually a CAD system is required in these environments … mainly because small shops and one man shops also do their own design … shop floor programming and tools like Kipware® conversational can also be an essential part of their efficiency.


Bottom line …

CAD/CAM is a great tool. But it can be overkill … can often bog down a programming environment … and can remove good chipmakers from the programming process. These chipmakers are more often than not the keys to unlocking a good SHOP FLOOR PROGRAMMING SYSTEM and the benefits that can come from that.

Don’t be fooled by the CAD/CAM marketing.
Don’t get caught in CAD/CAM overkill.

We invite you to explore Kipware conversational and see how shop floor programming can set you and your shop floor free !!

Kenney Skonieczny – President
Kentech Inc.

When is a CNC Program More Than JUST G Code?

… 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 :

  1. ( THIS IS A FANUC AND OKUMA COMMENT ) … any text inside (  ) is considered a comment.
  2. ! THIS IS AN ACRAMATIC COMMENT … any text following the ! is considered a comment.
  3. ; THIS IS A FAGOR COMMENT … any text following the ; is considered a comment.
  4. 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?

  1. 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.
  2. Complete info is there for all to see at any time … no rummaging for loose paperwork or docs.
  3. 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 !!
Kenney Skonieczny – President
Kentech Inc.

Deciphering M CODES 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. 

  1. 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.
  2. 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.

electrical_circuit_pic

electrical_circuit_zoom_pic

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?

Like what you see?
Please visit us at www.KentechInc.com

Kenney Skonieczny – President
Kentech Inc.

Product Spotlight : ID Clamps from Carr Lane Manufacturing

Every once in a while we like to bring attention for our readers to new and innovative machining and workholding products and process that we feel are beneficial to our readers. Such is the case in the Making Chips post as we focus and bring attention to a new workholding clamp from Carr Lane Manufacturing – a leading supplier of workholding and fixture components.

Additional information and specs on the Carr Lane ID Clamps are available on their website through this link : CARR LANE MANUFACTURING

Carr Lane ID Clamps – A Brief Outline

id_clamps

Many of you will undoubtedly be familiar with expanding mandrels … most commonly used to grip on the ID when turning on the OD. The new Carr Lane ID CLAMPS bring that concept to locating and workholding for milling fixtures. As the image illustrates … the ID CLAMP is similar to the expanding mandrel technique where the id CLAMP expands and clamps on the ID of a workpiece, leaving the outside free for machining.  Tightening the tapered center screw with a hex wrench pushes the clamping segments outward, and slightly downward, to exert force on the workpiece’s internal bore. These clamps are designed to have their outside diameter finish machined by the customer to suit the bore size, because maximum diameter expansion is limited.

The flange diameter on the ID CLAMP is a machined to a close tolerance … which allows for maximum locational accuracy. A recess can be machined in the fixture base to fit exactly with the clamp’s close-tolerance flange diameter and the ID CLAMP can be mounted using flat-head mounting screws.
id_clamps2

In the image above … you can see how the larger ID is used for locating as well as clamping … and a smaller ID CLAMP is used in the slot to provide additional locating and holding force. With this type of set-up, the entire outside contour is available for machining.

This set-up also illustrates the fact that these ID clamps need not be confined to round holes … they can be utilized in almost an unlimited number of ID clamping roles … use that machinist mind and explore !!

Estimating

We are always on the look-out for new and innovative machining processes … techniques …. and workholding tips. If you see one which you think would be of interest to our followers of professional machinists and engineers … please drop us a line at Sales at KentechInc.com.

Until next time … Happy Chip Making !!

www.KentechInc.com

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

Who creates the machine shop software guiding your shop’s future ??

Cutter Compensation – A Programmers Best Friend

In this post … we would like to touch on some of the points regarding cutter compensation … when turning angles and radii … on Fanuc based CNC controls.

Many programmers shy away from cutter compensation … primarily because they have never taken the time to fully understand both it’s power nor how to use it properly. But the reality is that cutter comp is one of a programmers best friends. The most common reason goes something like this “It’s just as easy to have the CAD/CAM system compensate for the TNR ( tool nose radius ) and out put the hard numbers.” That is true … but life on the shop floor makes this a bad practice. A couple of reasons why :

  1. The “numbers” in the G code don’t match the “numbers” on the part … because they are taking into account the TNR. If manual edits need to be made … even simple edits … this makes it much harder because the part dimensions don’t match the G code numbers.
  2. Say after cutting … the conditions warrant either a bigger or smaller TNR for better cutting conditions. If cutter comp is used … it’s a simple offset change. If not … it’s a trudge back to the CAD/CAM guy or system to re-post and make a new G code program for the revised tool and it’s TNR.
  3. In milling … let’s say I broke my last perfect .250R end mill … but I have a re-ground one that is .245R.. Again, if cutter comp is used … it’s a simple offset change. If not … it’s another trudge back to the CAD/CAM guy or system to re-post and make a new G code program for the revised tool radius.

Conversational

But here we are going to stick with turning here … and here are a couple of simple rules for when to use and when not to use cutter compensation.

  • Whenever angles or radii are involved … you must use TNR compensation or the angles and radii will be off. Because the programmed point of the cutting tool, an imaginary sharp point, does not coincide with the actual point of the cutting tool which always has some corner radius. For this reason, when machining close tolerance angle or radius cuts, inaccurate workpieces will be produced. The amount of error is proportional to the amount of the tool nose radius.
  • Only worry about using it for finishing … It’s really not worth the effort to use it roughing … the amount you leave for finish allowance will probably “hide” the mismatch due to the TNR.
  • You must start cutter comp with a “start up block”. This block is usually the move as you approach the part … the move distance must be greater than the radius in the TNR offset. So if your tool has a radius of .032 … make a move at least .035 … preferably more.
  • Make sure that your TNR is less than any radius on the part … don’t try to jam an .032 tool into a .020 radius … alarms will greet you somewhere along the way.
  • We’ll cover some additional thoughts at the end of the post.

The Details :

The CNC control has the capability to automatically compensate for the tool nose radius thru the CUTTER COMPENSATION codes of G41 and G42. G41 is called cutter compensation left. The left side is explained as the side of the workpiece the cutting tool is on when viewed in the direction of cutter movement or the cutter is moving on the left side of the programmed path. Once commanded, G41 or G42 are modal commands and remain active until the G40 or cancel condition is obtained.

In Fanuc controls, in addition to commanding G41 or G42 direction, the programmer must also tell the control two other aspects of the cutting tool which are : (a) the amount of the tool nose radius and (b) the imaginary tool tip location. Both these values are entered in the tools geometry or wear offset table. In the offset table, the R value is the amount of the tools nose radius. If the program called T0101 in the tool command, in offset table #1, under the R column, the nose radius of the tool would be entered. The T column in the offset tables holds the imaginary tool tip location.

Cutter compensation must be programmed using what is commonly referred to as a start up block. This block, which must be a G01 type block, is used to activate the cutter compensation before the cutting tool actual contacts the workpiece. The movement amount in the start up block must always be greater than the nose radius of the tool stored in the R column of the offset table. Circular commands using G02 or G03 are not allowed on start up blocks.

G40 is used to cancel the automatic compensation of the tool nose radius. G40 should always be commanded on a G00 block as the tool moves away from the workpiece with the tool in a clearance position.

More Rules and Thoughts :

Many rules apply in the use of cutter compensation as the control is always checking the tool position so it can calculate for the tool nose radius. Three rules of thumb apply and should keep you free of the controls cutter compensation alarms :

(1) Always command a start up block before contacting the workpiece and move in the G01 mode with a move greater than the nose radius of the tool.

(2) Use cutter compensation primarily in the finishing cut and try to eliminate it in the roughing passes. The more moves made with G41 or G42 modal, the more likely for a problem. To finish the part, use the start up block, finish cut the part and command G40 when done. Ifadditional cuts are required, use another start up block and cancel the cutter comp each time as soon as the profile cut is finished.

(3) Always cancel G41 or G42 using the G40 command. The best place to command G40 is on a G00 block, at a clearance point or moving to a clearance point. Because cutter compensation causes the control to perform some powerful calculations and is a complex command, you should also consult your controls instruction manual for further info on G41 or G42.

Happy Chip Making !!
Check out our Real World World machine shop software at www.KentechInc.com
Conversational CAD/CAM
Quoting & Estimating
G Code Conversion
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…. and MORE !!!

Move That Vise !!

MOVE THAT VISE !!! … It could mean more years for your machine tool.

It seems the simpler, often overlooked things can be the downfall of most shop equipment. Focusing on a few simple ideas can avoid those big repair bills and keep machine tools running like new much longer.

When most setups are done on a VMC, the workholding fixture is neatly mounted right in the middle of the table. Although it looks good, this is actually one of the worst “habits” for the machine. Locating the vise or fixture in the same place has the following harmful effects on the life of the machine:

  • Table wear, resulting in dip or sag in one spot.
  • Boxway or guideway wear on or around the spot, causing loose surface and gib contact, and shuck in the ways.
  • Ball screw wear, resulting in excessive backlash in that one area of the screw, which cannot be repaired through CNC compensation.

Of course you’re going to clean the table completely before installing the vise.

Then are you going to place the vise so it looks nice and neat in the center of the table?

NO !!!

Placing the vise or fixture in or around the same area of the machine table will cause all of the above, with the most common symptom over time being backlash of the screw. When trying to compensate and set the backlash, the person making the repair will often find different backlash values when checking along the length of the axis stroke. This most often results in the need to replace the whole ball screw. Because most CNC machine controls only permit one backlash compensation value to be set in the parameters, compensating for the backlash cannot be effectively performed through the control.

Conversational

You also may find that the gibs need to be adjusted in that area of the boxway, because the axis has some side-toside movement to it when moving. Squareness in that area will disintegrate; and, in the worst case, this shucking can be heard when the axis changes direction. The most common remedy of adjusting the gib in that area causes the axis to bind when it reveals to the other areas, because the boxway wear is different along the stroke. In this repair, the machine’s boxways may need to be reground, rescraped or both. In either of these cases, the repair bill will be huge.

The remedy is to make sure to move the vise or fixture location around on the tabletop whenever possible. You will see a more consistent wear pattern for the machine, and any backlash that occurs can be taken up correctly through the control. You will not be able to stop machine wear, but you can distribute it more evenly along the machine, which provides a longer life for all the components involved.

 Happy Chip Making !!

Check out our Real World World machine shop software at www.KentechInc.com

Backlash in Your CNC – What 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.

Conversational

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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