Need Help!- Trouble cutting UHMW, need help programming

[bman356]

Hello,

I am pretty new to the mazatrol world. I have done plenty of fanuc g-code programming but i have changed jobs and i am on a Mazak Quick turn lathe. I don't know much about it,

I am making some parts out of UHMW. I am having a hard time with the chips. I Have to do a lot of turning and just about after every cut i have to stop the chuck to remove the chips by hand.They wrap around the piece. It is not very effective. I am using kennametal inserts that are made for plastic. The finish i get is great. I have tried taking cuts from .03 to .3 and using feeds up to .02"/rev i am using a cutting speed of 950 for roughing. I really need to figure out a better way. i have a lot of these to make and this is taking too long.

I know that on fanuc you can use a peck drilling cycle to do turning. This would work because the chips would be short. Unfortunately i have no idea how to go about that on mazak.

If anybody has any advice on UHMW in general or the mazatrol programming tips i would be happy to hear from you. Thanks in advance.

Brad

[Philabuster]

Do you have live tooling on your machine? If so, you can cut a slot with an endmill a few thou above finish dia to act as a chipbreaker for the turning operation. Works great.

[bman356]

Unfortunately i don't have live tooling. If i did that sounds like the way to go. Thanks anyways.

Brad

[jimiscnc]

instead of a mill tool, you can program a finish turn tool with a ludicrously high feed rate at finish depth. this will scribe a helix into the part and when finish turned properly, the scribe will make the finish turn an interrupted cut.

Using this method on shoulders would have some problems, as you are no longer using just the "point" of the TNR.

You will scrap a few practice parts until it works to your satisfaction. Or not. No guarantees here.

Plan B is to use the chipbreaker roughing cycle if you have a Matrix control. This is for the roughing tool only and you program a feed length that, when reached, dwells by a rev count set by parameter. (There may be a related parameter also needed to get the function to work at all.) Then you have to copy the unit and tweak the rough tool so you don't cut air and have the right FR. This cycle does not work with the finish tool.

-jim

[HuFlungDung]

You could experiment with an Iscar cutgrip style tool. You could probably use a fairly wide insert, maybe 5mm or more. There are two ways to use these, the first being in longitudinal turning, but I think it will still likely result in chip wrapping, however you can use some ultraheavy feeds to get through the cut in fewer revolutions, which might permit the chip to fall away before it wraps.

The other method is plunge roughing with the tool. Chances are good that with a heavy feed, you will get clean clockspring chips that will fall away.

You can always write your own interrupted cut routine, no need to throw up your hands in despair if you cannot use a peck drill cycle. If you have lots to do, that just makes it more worthwhile to hand code the program.

[CNCRim]

Originally Posted by bman356 Hello, I am pretty new to the mazatrol world. I have done plenty of fanuc g-code programming but i have changed jobs and i am on a Mazak Quick turn lathe. I don't know much about it, I am making some parts out of UHMW. I am having a hard time with the chips. I Have to do a lot of turning and just about after every cut i have to stop the chuck to remove the chips by hand.They wrap around the piece. It is not very effective. I am using kennametal inserts that are made for plastic. The finish i get is great. I have tried taking cuts from .03 to .3 and using feeds up to .02"/rev i am using a cutting speed of 950 for roughing. I really need to figure out a better way. i have a lot of these to make and this is taking too long. I know that on fanuc you can use a peck drilling cycle to do turning. This would work because the chips would be short. Unfortunately i have no idea how to go about that on mazak. If anybody has any advice on UHMW in general or the mazatrol programming tips i would be happy to hear from you. Thanks in advance. Brad

For being platics, there are alot rule you can ignore. Ok, some tips hopefully it help.

Insert: for roughing get noncoating positive insert.
RPM: keep it running high like 1500 or more.
Rough: .2-.3 deep per cut, feed rate try to keep it between .007-.010, you can go crazy with the feed like .02-.03 to cut down cycle time but there is a problem for being platics is it heat up quick and it will change dimension. whatever you measure at the time take off the machine, it will change 10 mins later up .005.
Fin: HSS work great, if the company don't mind spend money ask for noncoat positive ceramic or diamond(work out the best but $500-600/tip) insert.

Get a vaccum hit the light out of you? work nice on long elastic chip.

[CMSGlassGuy]

Other down and dirty solutions are an air jet.. could be marginal or spectacular depending on how tough the chips and strands are..
.. or a mounting a stationary scraper/chip breaker.. which may not be either safe or practical depending on the application.
.. or either in combination with a vacuum nozzle

[bman356]

First off, thanks for all of your responses. jimiscnc your idea was pretty cool but i did not get a chance to try it. I will keep it in mind for next time. I dont have a Matrix control so the chip breaker cycle is out of the question.

What i did try was a bunch of turning cycles that were .2 long so the chips were shorter. This worked better but still gave me some problems. In the end i ended up roughing the od with a 1/8 wide grooving tool and taking .03 deep pecks with a .05 retract to break the chip. Sounds a bit wierd but did a nice job.

Thanks again,

Brad C

[MadMax]

Did you try using the grooving tool and starting the cut close to the chuck? I'm not sure if you can sacrifice part stiffness with a roughing cut starting closest to the chuck, but sometimes that helps to push the chips away from the chuck instead of tending them towards the chuck.

Philabusters live tool slot would result in shorter chips than a OD turn/peck cycle as each chip would be one circumfrence long while a peck cycle would result in chips that were many multiples longer.

I've always wanted to try putting a shopvac somewhere where it could inhale the chips. You'd have to empty the vacuum quite frequently though. It might be more effective to direct the chip with an air blast so they'd go up the conveyor, but the likelihood that a chip could drift up and wrap the chuck is kind of high with UHMW as it's quite light. It's too bad you can't just set the stuff on fire...

While I'm throwing around the stupid ideas, can you do an OD turning cycle on your headstock with a boring bar to automatically strip off the chips? Maybe a light finishing pass.

[bildoo]

A coworker of mine started some plastic (Nylon) chips on fire while milling without coolant. Lucky he was only a few steps away I guess it really flares up fast. Good thing the machine has a built in fire extinguisher by turning the coolant back on.

[MadMax]

Sorry bman, I didn't initially notice that you didn't have live tooling. Can you mount a razor blade and push a slit though the stock? UHMW is pretty soft stuff I think you could do a static sweep through the bar.