All posts by Kenney Skonieczny

Proud to say I am a 3rd generation Class A machinist ... who took his years of metalworking, cnc and machine shop experiences and followed my entrepreneurial drive to start my own business ... Kentech Inc. ... in 1986. For over 25+ years Kentech Inc. has been a pioneer and a leader in the realm of machine shop software. Please visit my website www.KentechInc.com for more. Thank You !!

The HOW’s and WHY’s of CNC Sub Programming

If you have done any manual G code program creation, you know you are always looking for some shortcuts  that can not only help cut down the data input … but would also help eliminate errors. Whether they be typing errors or movement errors … the less chance to create one the better.

One of the more powerful tools available to a programmer is the use of SUB PROGRAMMING. In this Making Chips post … we would like to touch on some of the basic ideas, concepts and uses for sub programming. This post will illustrate the Fanuc / Haas coding format … but check out the end of the post for Okuma explanations as well.

What is a Sub Program?

Basically, a sub program is a G code program that is called from another G code program. The contents of the sub program is not limited and can contain tool calls, spindle calls … just about anything any other G code program can contain. The sub program itself resides in memory under it’s own program number … and is separate from the “main program”.

Conversational

Why Would I Use a Sub Program?

As mentioned above … the less data entry means less chance for a mistake. let’s take this example scenario where we have to let’s say spot drilling then drill then chamfer then tap a series of holes. The less times we have to re-type those hole locations, the less chance we will have a typo and / or put a hole in the wrong place. If we can store the X / Y coordinates of the hole locations in one location and call them out as needed … that saves data input and reduces our chances for errors. This is a good example of how a sub program ( in this case it would be the program that stores the hole locations ) can be a big help.

How Do I Program and Call a Sub Program?

A sub program scenario consists of a main program and the sub program. The main program consists of all the code that doesn’t repeat itself … the sub program consists of all the data that will be repeated. In our above example … the tool calls, spindle calls, drilling cycles will all be different for each hole … so we will store that in the main program … but the hole locations will be the same so we will store them in the sub program.

When you create a sub program … it is done just like you would create any other program. On Fanuc / Hass controls you start out with an O number … and type the program as normal. Let’s take our above example of hole locations … the sub program might look like this :

O1234
X1.1 Y1.1
X2.2 Y2.2
X3.3 Y3.3
X4.4 Y5.5
M99
%

Notice that we have an M99 at the end … not an M30 or M02 like a normal program. This indicates that this is a sub program … we’ll explain the M99 command a little later.

This program is entered in the control as any other program … and resides in it’s own memory space.

When a Fanuc / Haas control wants to call a sub program to run … the programmer issues an M98 command in the Main Program. The M98 command is also followed by a P address … which is the “O” number of the external program to run. Our above sample sub program would be called with the command :

M98 P1234

When the main program reads the M98 command … it jumps out of the main program and starts to execute the sub program … in this case program O1234. When it reads the M99 command at the end of the sub program … it jumps back to the main program to the line after the one through which it left. In other words, it jumps back to the line after the M98 command.

The Complete Story

Let’s take a look at the full program and the sub program calls … see if you can follow the path.

Main Program

O0001
G00G91G28Z0
G28X0Y0
M01
N0001
(SPOT DRILL)
G00G91G28Z0
T01M06
G90S3500M03
G00X1.100Y1.100
G43Z.500H01M08
G99G81Z-.130R.050F20.0L0
M98P1234
G80
G00G91G28Z0
M01
N0002
(DRILL)
G00G91G28Z0
T02M06
G90S3000M03
G00X1.100Y1.100
G43Z.500H02M08
G99G73Z-875R.050Q.125F20.0L0
M98P1234
G80
G00G91G28Z0
M01
ETC.    ETC.    ETC.
M30
%

Sub Program

O1234
X1.1 Y1.1
X2.2 Y2.2
X3.3 Y3.3
X4.4 Y5.5
M99
%

Can you follow the path as the program jumps to the sub program?
Here is an in-depth explanation.

N0001
(SPOT DRILL)
G00G91G28Z0
T01M06
G90S3500M03
G00X1.100Y1.100 ——————— Position to our first hole.
G43Z.500H01M08 ——————— Bring the Z axis to the clearance plane.
G99G81Z-.130R.050F20.0L0 ———- Call our canned cycle … but use L0 which means the control will hold the data … but will not execute the cycle.
M98P1234 —————————– Jump to our sub program O1234 which will cause a hole to be spotted at each X / Y location in the sub.
G80 ————————————- When the M99 is read … the program will jump back to here.
G00G91G28Z0
M01
N0002 ———————————- This sequence basically does the same thing …except we are establishing a different canned cycle before we jump to the sub program.
(DRILL)
G00G91G28Z0
T02M06
G90S3000M03
G00X.100Y.100
G43Z.500H02M08
G99G73Z-875R.050Q.125F20.0L0
M98P1234
G80
G00G91G28Z0
M01

Another Example …

Once you are able to follow the above … here is another scenario.

You can also call a sub program and have it executed a set number of times. Let’s take the example where we want to execute a program on our lathe to make a washer (3) times. We will enter the main program and sub program as below.

Main Program :
O0001
M98 P1234 L3
M30
%

Sub Program :
O1234
*********
between here is the complete machining program that includes
tool calls … spindle calls
the feeding of the stock
the machining of the part
the cut-off of the part
*********
M99
%

The cycle start is executed with program O0001 … which calls the sub program O1234 and executes that program (3) times … the L in the M98 line. This feature is different for the various Fanuc controls but is usually commanded either :

M98 P —- L
or
M98 P****$$$$ where **** is the program number and $$$$ is the number of times to repeat.

Differences Between Fanuc / Haas and Okuma OSP

The basic ideas of calling and executing a sub program is the same between these controls … the G code commands are a bit different. Those differences are outlined below.

Sub Program Call
Fanuc / Haas : M98
Okuma : CALL
Example : CALL O1234 will call sub program O1234

 Sub Program End

Fanuc / Haas : M99
Okuma : RTS

Sub Program Call with Repeat
Fanuc / Haas : M98 P1234 L5 or M98 P12345
Okuma : CALL O1234 Q5 with the Q value being the number of repeats.

That’s basically it … just some G code differences but the basic idea and execution is the same.

**************************************

Sub programming is a powerful tool … even if you are not trying to avoid re-typing and repeated data entry. Hopefully this Making Chips post will get you thinking and exploring all the ways sub programs can make you a better programmer.

Happy Chip Making !!

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

Conversational CAD/CAM

Quoting & Estimating

G Code Conversion

CNC Training

…. 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

At Kentech Inc. … We’re MAKERS and DIY’ers Too

There is no doubt that a lot of folks are letting their creative juices flow today and becoming members of what is touted as the “maker community”. It is so great to see … and to see that great American ingenuity in play in so many ways.

Being a machinist for almost 30 years now … I like to think I have a little of the MAKER in me as well … and not only in metalworking. Here at Kentech Inc. … our various Kipware® machine shop software software titles are used by thousands of professional machinists and machine shops around the world … and also by thousands of MAKERS as well. People doing everything from woodworking to metalworking in garage shops and professional machine shops around the world. We like to think that if a product is good … it finds it’s way into many places. And we are proud of the fact that our Kipware® conversational CNC programming software has made parts for SpaceX as well as that coat rack for Average Joe or Jane.

Kipware® software is also running our sister woodworking company — KÄRV. From quoting and estimating to CNC programming … Kipware® software gives us THE EDGE. Check it out at www.KarvWoodworking.com.

With that MAKER and DIY spirit bubbling inside ( watching Yard Crashers on the DIY network with some java certainly HELPS ) me and my wife decided that this summer would be the summer of our personal YARD CRASH. And so it began.

The Vision

Looking aerially at the yard … I laid out my vision to see if the wife approved. First … a curved walkway leading from the house to a brand new firepit. Not one of those metal, cheap firepits … I mean a new brick firepit with a metal inner ring and nice stone cap. Halfway down the walkway … a detour to our own designed and constructed water feature … waterfall or fountain.  And here’s where the wife chimed in. “How about this” she says later in the evening. She shows me a pic on Pinterest of a bamboo themed waterfall. “I like it” I reply … we’ll think about the design in more detail as we get closer. But there it is … our vision.

The START of Construction

The DEMOLITION and DESIGNER MAKER

The next day we begin the layout in the space where we decided to work … marking the area with string … and removing all the sod. Big job … but we get it done in a couple of days … and start the remodel.

construction2
Aerial view #1 of the “construction site”
construction1
Aerial view #2 of the “construction site”

PHASE 1 – Privacy Panels

The CARPENTER MAKER

The first item in the rebuild was to install some privacy panels to insure our nights spent by the firepit were nice and cozy and private. My wife had a “bamboo theme” in mind … which carried over from the waterfall idea … so we got to designing. We came up with a wooden frame clad on both sides with bamboo fencing. Came out and looked great … just the right amount of light coming through and bamboo effect was very elegant.

PHASE 2 – The Fire Pit 

The MASON MAKER

We purchased a stone firepit kit from a local stoneware vendor and during the week I got the area prepped and the firepit installed. Leveling and preparing for the first layer was quite a job … but it came out great and the feeling of accomplishment was fantastic. If you’re a MAKER … you know what I’m talking about. Friends always say “We just have someone build it” … but there is nothing like that feeling of accomplishment that lasts for years as every time you look at it .. you can proudly say “I built that !!”.

With the fire pit installed … I lay out the artistic walkway … line the outer edge with cobblestones … and fill the inside with stone dust. I was a little apprehensive about using the stone dust as a bottom … it was quite dusty to start with … but it turned out fabulous. Once a good rain shower did it’s thing … it hardened up nicely and makes for a great walkway.

The completed fire pit.
The completed fire pit and walkway area around the pit. The right hand side leads to our nature trail through the woods behind the property.

PHASE 3 – The Water Feature

The ENGINEER and PLUMBER MAKER

The more I viewed my wife’s idea for the water feature … and the more we discussed the details … the more confidence I gained that I could do it. I don’t think my wife was quite as confident though … a lot of probing questions like “How you gonna do this?”

First … we needed to bring electricity from the house to the waterfall area. Following the local code … we dug our trench ( what a b*&%$ ) … layed our cable inside our PVC piping … and presto. 4 new plugs … an outdoor switch … and plenty of juice for our pump. Tough job but very professionally done … and all to code. The wife was the hardest worker through it all. Chipping in with the ditch digging … and keeping me straight and focused through all the aggravation and  at times frustration and hard work.

Next … I bought some reclaimed wooden beams … 6x6x10 … that were once used in the old railroad yard in our city. They became the perfect uprights to support our bamboo “waterfall”.

construction_start
Reclaimed railroad ties in cement and in position.

After the ties had set in their concrete moorings for a week … and another trip to Home Depot ( it became our Saturday morning breakfast trip ) … I began the plumbing work. Again … with the constant nudging from the wife to keep me on the straight and narrow … we got it all in and we’re ready for the big reveal. Remember this was only a vision and a theory … we had never really tried the design. Judge for yourself with the video below :

You can see it all in the video … the bamboo privacy panels and the working waterfall feature. Below is a closer look at the design “behind the scenes”.

Behind the scenes of the waterfall.
Behind the scenes of the waterfall.

The BIG REVEAL …

And that was that. After the wife lent her gardening touches … the big reveal :

The big reveal
The big reveal

… and CONFIRMATION !!

As I mentioned above … I’m a big fan of YARD CRASHERS on the DIY network. A lot of great memories of sitting and binge watching the show on rainy days … getting stoked to start projects of my own around the house … fueling the MAKER spirit if you will.

So when the project was completed … I couldn’t resist tweeting a pic to the host of the show, Matt Blashaw. And low and behold … it got his attention and he replied … AND APPROVED !! WoooHooo !!

Matt Blashaw approves !!
Matt Blashaw approves !!

As the summer nights and weekends go by … we are enjoying the fruits of our work with fabulous fires in the pit with friends and family … accompanied by the zen like sounds of the waterfall. In fact … we have christened the garden with the name the KenZenSue Garden.

Being a machinist I always took a ton of pride in my work … but a lot of it was “business”. It was great to unleash my MAKER side and work on a “for fun” project … and to enjoy the results. To all the fellow MAKERS out there … be proud and go get’em.

Kenney Skonieczny – President

Kentech Inc.

Accurate Machining Cycletime Estimating – THE KEY

No matter what system you utilize to create your cost estimates and quotes … everything starts with an accurate machining cycletime estimate. The phrase … “Oh, that should take about two and a half minutes to machine.” … is doing more harm to your bottom line than you are probably even aware. This type of guesstimating … especially when it comes to machining cycletime … is throwing the whole cost estimating process that comes down the line into question.

If the machining cycletime estimate is not correct … you could be winning work … but unprofitable work. And that’s just what your shop doesn’t need … wasting time manufacturing parts that are losing you money. Taking machine time and employee energy away profitable work.

So what is the KEY to accurate cycletime estimating?

Having lived and “grown up” on the shop floor … we realize that the MAIN KEY to accurate cycletime estimating is to utilize the cutting conditions and parameters that can actually be reproduced on your shop floor … with your equipment.

It doesn’t do any good to estimate using an RPM or SFM and feedrate that your shop floor can never duplicate … or utilize a method of machining that your shop floor would never follow or duplicate.

Sure cycletime estimating software that has feature recognition and auto-determines the method of machining will get you a time quickly and get that estimate done quickly … but what good is it if your shop floor would never machine the part using the method the software determined?

Cycletime estimating software that boasts thousands of materials and speeds and feeds is expensive and seems powerful and complete … but if your shop floor can’t duplicate that “book knowledge” speeds and feeds … what good is it?

Estimating

So Kentech’s KipwareCYC® software is different? How?

It certainly is … and I’m glad you asked.

First : 

KipwareCYC® is a database driven application … utilizing a user-defined database for machine specifications ( max RPM, rapid rates, tool change time, etc. ) and user-defined cutting parameters ( speeds, feeds for various materials and machining operations ). This insures that the calculated times accurately reflect what happens on your shop floor … the key to accurate cycleltime estimating. You create the database and input YOUR specifications and cutting parameters.

Second : 

Using the various outputs and travelers available from KipwareCYC® … the more you use the software, the more accurate it becomes. For example : the Routing Sheet that is automatically created from KipwareCYC® provides the operator / set-up personnel with a complete list of cutting parameters and times for each operation as the part moves through the shop. This means he has a targeted RPM, feedrate and time for each operation. If any of those factors cannot be achieved … a report back to the estimate creator will result in an adjustment to the database information … perhaps a revision to the SFM or feedrate or chip load used for a specific machining operation. Next time … the RPM and feedrate will be more accurate. So the more you use the software … the more accurate it becomes.

Ugh … Entering ALL that database information !!!

Actually … a couple of points that may have crossed your mind. First … we do ship KipwareCYC® with installed database information for common machines, materials and cutting parameters. But again … this is just to get you started … you really need to make the database information your own. Here is what we recommend.

Let’s say today you receive an RFQ for a 316 stainless part that requires some turning. You gather the machine specs for the lathe you’re going to use and grab the normal cutting parameters the shop uses for 316 stainless. One additional point here … most shops use a common insert that works well for them for specific machining operations … there really isn’t a need for a dramatic, all encompassing speeds and feeds database with info you’ll probably never use … let’s keep it simple and keep it real. So you enter that data and now … 316 stainless is done !! Next time you get an RFQ the info is all there and ready to go. With this system … you are building the database as you are preparing quotes and winning work !!! It’s a win -win … with long term benefits.

So … the moral of the story is?

No matter how you are arriving at your machining cycletime estimate … the one certainty is to insure that it is utilizing the cutting conditions and parameters that can actually be reproduced on your shop floor … with your equipment.

 If you are looking for a software application what will insure that key … we invite you to check out our KipwareCYC – Machining CycleTime Estimating software HERE.

Kenney Skonieczny – President

Kentech Inc.

3 Ways To STOP Your Machine Shop From Losing Money

In today’s age … every machine shop is looking for an ADVANTAGE. Most, however, are looking for the “home run” … and overlook the advantages / solutions they trip over every day. It’s not always that big hitter but a lot of little things that can contribute to your shop losing money and profits.

We know that the task of turning around a non-profitable shop is daunting … so we decided to help by focusing on some of the small fixes … that can mean big profit reversals. Hope they help and get you thinking … and turning your shop around.

#1 – Break the “CYCLE”

cycle

The Problem :

For many shops, every day is business as usual. The same cycle … day after day. Doing the same things … producing parts the same ways … working with the same clients. Unfortunately, it’s the cycle of losing money .. and most don’t know how to get out of it … or are scared to make a change.

Also unfortunately … doing things this same old way won’t turn things around.  Most shop owners simply think that by just getting more business … they can turn profits around and solve any and all financial problems. The truth is … the more business you bring in … the more the existing problems will be exacerbated.  Probably … the more money and profits will be lost … the hole will just get deeper.

The Solution :

The first step is to step back … take a breath … and realize “Houston, we have a problem.” The first act of fixing a problem is realizing that there IS a problem … and being 100% committed to working to fix the problem. But how do you identify the problem?

You need to look deeply at every aspect of your business. All the things as a business owner you do every day need to be assessed completely. Most times … you already know the things that frustrate you and that you know “aren’t right”. Each week … take one … focus on it … and it alone. Try to come up with some ideas either yourself or in group discussions to move it along … and implement at least two.

Will they work? Will they be the right solutions? Maybe YES … maybe NO. But as I mentioned above … you need to break the CYCLE. Sometimes just changing things up highlights another road or opens another door.

Realizing that there is a problem … and being 100% committed to trying to resolve it … is an monumental first step.

Estimating

#2 – Chasing Your Tail

tail_chasing

The Problem :

RFQ’s are coming in the door left and right … and your sending out bids and quotes to match. At this clip business must be good. Right?

There is a huge difference between winning WORK … and winning PROFITABLE WORK. If your shop is losing money … the first place to start looking is in your bidding process. OBVIOUSLY ( doesn’t really need to be stated does it? ) … quote to high you won’t win the job … quote to low you won’t make any profit.

The Solution :

WARNING … SALES PITCH AHEAD. You knew it was coming … but it’s true. Spreadsheets and an outdated quoting and estimating process is almost all the time a big culprit. NUF SAID about this. OBVIOUSLY … we recommend a trip over to HERE and explore some options we have to offer. Created from our almost 30 years in a variety of manufacturing environments … including running shops from small to high volume manufacturers.

TURN LEADS AWAY. That’s right. One effective way to “fix” your quoting and estimating process is to turn leads away. Not every job or RFQ you receive is the right job for your shop. As mentioned above … sometimes getting more work will simply lead to losing more money.

PRE-QUALIFY. Invest some time upfront in qualifying those RFQ’s. Ask about their budget … ask when they plan on making a decision … find out who the decision maker is and make sure you’re in contact with the right person. A little bit of pre-qualification will save you a lot of time and frustration with leads who will never result in business.

TRUST YOUR PROCESS. You need to have a cycletime and cost estimating process in place that you can trust. Take some time to compare jobs you won … against the costs of actually manufacturing and delivering the job. Time consuming I know … but definitely time well spent. Once you know that your bids are turning a profit … that’s a process you can trust.  When you work up the numbers … that’s it. That’s the cost … period. No undercuts. No additional discounts. If you lose the job … good .. you wouldn’t have made any money anyway.  Don’t spend valuable time running after profit-losing business … invest your time in winning profitable work. It makes no sense in bringing in work just to bring in work. The mantra needs to be ONLY PROFITABLE WORK. Maybe … just maybe … this will open other doors and shed light on other problems … some you want to see and some you don’t. But reality is what it is.

#3 – Manage Your Cash Flow

cash_flow

The Problem :

Bad cash flow will sink any size business. The work might be flying out … but if the money isn’t coming as fast or faster, you can’t fund the process. It’s that simple … and it’s that important. It’s a job nobody likes … but has to be done. PERIOD.

The Solution :

Think of innovative ways to get paid faster. Discounts for early / quick payment … but build these into your quotes and estimates … we don’t want to effect the bottom line.

CREDIT CARD PAYMENTS. This is the first and best alternative. Be proactive on this … and clients who choose this method are your #1 clients. Let the bank or CC company worry about dept collection … not your cash flow. Sure the “big companies” will have an issue … but there are plenty of smaller players that can fill the gap.

ONLINE STORE. OK I shouldn’t even have to mention this … but I will. Your shop MUST HAVE a web presence. NUF SAID. If you don’t … get one … period. And if you manufacture any kind of product that can be sold online … a web presence with an online store that accepts credit cards is ESSENTIAL !! I can’t emphasize this enough. IT’S HUGE. No cash flow issues here … no collection issues here … no chasing orders here … the web site does all the work … 24/7. Even getting real innovative … accept RFQ’s through the site and have clients accept and pay through the site. There are really too many points and roads to point down here … but your business mind should be scrambled by now with all the innovative and new ways to grow your business and better manage at least a portion of your cash flow.

———————————————————-

OK … it’s a start. Just some initial ideas we have experience with … and some solutions we found effective over the years. But hey … you’re a business owner. You’re an entrepreneur. You just need a shot in the arm. Hopefully … we have provided some food for thought … some stimulation … some energy. NOW GO GET ‘EM !!

Kenney Skonieczny – President

Kentech Inc.

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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Chip Removal at Your CNC Machine – AIR vs. WATER

air gun for blowing chips at a cnc machineA 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 !!

Estimating

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 ??

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Machine Shop Efficiency Series

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In addition to this Blog we also host our Making Chips blog over on Google Blogger .. which has a lot of great articles and content. As we ramp up this blog … we thought a good way to get information flowing was to gather some of the most popular Making Chips posts here … to bring that content to our readers here as well.

We would like to start with one of all time most popular series … our Shop Efficiency series. Below are list of the (8) posts in the series and a brief description. Please feel free to browse the list and click the links to jump over the Making Chips and read the articles of interest.

Shop Efficiency Part One – Cutting Time VS Workholding and Fixturing … CLICK HERE

Shop Efficiency Part Two – Face Drivers for CNC Turning … CLICK HERE

Shop Efficiency Part Three – The Infamous Milling Vise … CLICK HERE

Shop Efficiency Part Four – Re-Thinking Your Lathe Tooling … CLICK HERE

Shop Efficiency Part Five – Re-Thinking Your Height Offset Strategy … CLICK HERE

Shop Efficiency Part Six – Multi-Function Tools … CLICK HERE

Shop Efficiency Part Seven – CNC Programming … CLICK HERE

Shop Efficiency Part Eight – Gauging Your Shop Efficiency With The Magnificent Seven … CLICK HERE

Well there you have it. Tons of great ideas and information … all related to shop efficiency. Hope you enjoy … and get a leg up on the competition.

Kenney Skonieczny – President

Kentech Inc.

Welcome to The CNC Machinist Blog !!

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Thanks so much for your visit and welcome to the NEW KentechInc.biz … now to be known as The CNC Machinists Blog.

As time goes on we’ll be digging into our 25+ years of machinist … metalworking … shop management … chipmaking … engineering … and various CNC related experiences to post what we feel is worthwhile commentary and information on all things CNC … machine shop … and metalworking.

Please check back often …  we will try not to disappoint.

BTW … for all things CNC and Machine Shop Software … please check out our complete line of business software … conversational CAM software … G code conversion software and more at our website … www.KentechInc.com

Thanks,

Kenney Skonieczny

President — Kentech Inc.