Horrible tooling marks, need advice, long,...

[chiere]

Greetings All!

Our shop opperates a PRSalpha96 with the Porter Cable router. We've had it now for about 3 years, and it's used every day, all day. We have 2 routers, so when the brushes go in one, it can be in the repair shop and we can continue production. We get about 6 months out of a set of brushes, =-)

We cut 1 lb EPS foam and 15 lb Precision Board with it. (it's like cutting butter.) We mainly use a 1/8" ballnose bit or a 1/4" ballnose bit. A bit will last us a year. I design using ArtCam software, and 99% of the files I design are bas reliefs.

Here's the problem; pieces used to come off the table very smooth, with few tool marks. But reciently, when using the 1/4" ballnose bit, the tool marks are extreme, and encompass the entire piece.

At the same time, I replaced ArtCam Pro with ArtCam 2008. (I know I am behind everyone else; I work from home and only just got the software from my boss)

I like the new software, so I am hoping it's not that, but I get the distinct feeling my boss believes the extreme tool marks are because of how I am designing stuff now. (Even tho it's no different that how I did it before with ArtCam Pro)

When we cut with the 1/8" ballnose bit, I am told stuff comes out smoothe (I even had him find an old file that cut great before and run a test) But when we cut with the 1/4" ballnose bit, it comes out looking very groovy, and not the good groovy. I even went back and redid the files in Pro and it still looked like poop. Then I redid the file in Pro using a 1/8" ballnose, and so far, he says it is looking better.

Before the Christmas holidays, I went to the shop and went over the machine. The waster board has deep grooves even though the operator uses the proper thickness of material for the job, and properly sets the z-home, the tracks were a bit crusty from ground and melted foam, the wheels on the z-rails didn't all touch any more (about half did,) I could jiggle the router by holding the bit and applying force to the tune of about 1/16th of an inch, and I think the thing still had the original collet. Also, when running the router at a diagonal across the table, it made a loud chatter/grinding noise in places, and when running the router up and down the z rails, it also made a nasty grindy thunk sort of noise.

So, we cleaned it, oiled it, and scraped off the crusty bits. I ordered new bits, suggested the wasterboard be replaced, suggested a new collet (the 1/8th inch bits and the 1/4" bits all use the same 3 year old collet) and suggested tightening up the z carriage. I don't believe the last three things have been done.

Is it the software? (I am trying to keep a straight face here, work with me,...) My boss is sure I am doing something wrong. I don't think so, but I want to double check just in case I am. I keep suggesting a new collet, cuz I think the heavier 1/4" bit is slipping, and a tightening up of the z carriage (which I am afeared to do, what if I screw it up! Oh, wait, it can't get much WORSE,)

Also, it sorta broke my heart to see my baby all grody and neglected, =-(

Anyway, here's a picture of the current end results. On the left is the old file using a 1/8" ballnose bit. On the right is the new file, created in the old program, with a 1/4" bit. Advice would be much appreciated!


8131

[gabepari]

When was the last time the pinion gears were replaced??

Gabe

[chiere]

I believe that would be a big fat never,.... Where are they, and how do I do it? (Or walk someone through it,...)

[dray]

it may be the resolution you created the file in or simply the step over value.

[donclifton]

Change the step over in artcam. you can edit the tool and make it about half of what you have it set to
Thanks
Donald Clifton

[chiere]

I'm already stepping it over .03 of an inch for the 1/4" bit. (normally, I step it over .06") On the 1/8" bit, I'm stepping it over .015" I suspect the 1/8" bit is also making tool marks, but it's hard to tell cuz they are so close together. I'll bet if I could see it in person it would look like fine corduroy, LOL!

[chiere]

Also, if a .06" stepover for a 1/4" bit worked great for 2 3/4 years, why would it suddenly not work any more? (but I still tried it at .03,...)

[donclifton]

Gabe might be right and you have foam in the rack and gears. I cut a foam madalion that was 6'x6' and 4" deep, I had foam in everything. I also had a problem with my gantry flexing and had marks in the work. I could hold the work up to the rack and the marks matched the teeth.
Thanks
Don

[dubliner]

"My boss is sure I am doing something wrong" - You are doing something wrong... youre working for a mental patient if he thinks a neglected machine will actually perform the same as when it was new. Software usually gets better with age, machinery gets worse. OK except when Windows is involved. Refit the machine, its' time.

[randydimmette]

Cheri, I had the same problem with my prt and it was the control board. Make sure all you drive motors are working. Mine was one of the motors on the x rail.I thought it was the motor but after talking to shop bot i figured out is was the control board.I checked mine by unplugging one motor and telling the bot to move by using the arrow keys.

[gabepari]

Neville, you said what I was thinking


Cheri, if the machine was in such a sad state of disrepair, I wouldn't change anything on your end until the bot was brought back to life mechanically. No point in trying to put a band-aid on a severed artery.

Gabe

[dana_swift]

There are a lot of things it could be..

Do you have a jewelers loop with a reticle? Does the spacing between "furrows" correspond to the stepover value, or some other distance? That will be a big clue.

Also is the bit new, or been around since the Mississippi river was just a creek?

Since the machine has been in use for years, did it start doing this suddenly, or just gradually get worse?

If you can jiggle the router bit in the bearings as you describe.. that is VERY wrong, get those bearings replaced, that isn't helping anything.

The culprit will reveal itself in due time- then the correct solution becomes obvious.

D

[chiere]

Thanks everyone for the suggestions. I passed them on, and also e-mailed the shopbot wiki link to the current operator.

I would be happy with a new collet to start,....

Dana, I suspect the culprit will indeed reveal itsself, but pro'lly after the situation deteriorates more,... Right now, I can only repath everything for a work around. But eventually, the situation will just get to the point where it won't work at all,.... =-(

[cnc_works]

The grooves look too uniform to be from mechanical issues, especially since they did not appear until a change in software. I would continue to inspect software problems connected to the tool pathing, especially stepover. If possible, both increase and decrease the stepover on a test cut and see what happens. For 3D finish work, I am still at about 10% of diameter, with rough cut being maybe 50%.

Certainly the mechanical issues you describe will affect the quality of the cut and should absolutely be addressed. Sounds like the CNC needs a complete tuning at the very least. But I would expect much more irregularity in the cuts with the machine problems you describe.

Donn

[bcondon]

Cheri

Can you cut this using a 1/8th ball like you did before?

You have two variables here...
the cutter (1/8->1/4) and
new software.

===
Take the new software and produce the file with 1/8" and have them cut it... If it comes out the same as the left (both nice and smooth), then the issue is moving to the new cutter size and focus on THAT problem...

If the new cut is similar to the results above where the new cut has extensive tool marks, then the software is impacting the operation.
(then blame your boss for that damn software)

8-)

We all know that in the end, it is the boss's fault

[gpari]

I still vote for pinion gears...

Gabe

[erik_f]

I'm with Gabe. Also if on my old PRT I had the v-bearings loosen up on my Z so there was play in the actual Z. If you haven't done anything to keep the machine up in 3 years the thing needs a tune up. Ask your boss the last time he changed the oil in his car or took his dog to the vet. My guess is that he hasn't. I know you said it's a PRS but double check and make sure its not a PRT. Either way these machines need service just like any thing else you want to work well long term.

[zeykr]

How about sending the file to one of us and let us cut on our machine. Should tell us whether it's machine or program.

[khalid]

Hello... I bit you are getting waviness in your toolpath..am i right..????

I am confident that you are having play in the Y and Z axis rack-pinions... Justdo a simple test, put a little force on the z-axis or spindle router from side way and check the movement..also stand infront of the spindle , grip the spindle router and move it from bottom to top check the movement... If the movement persist then you have some play in the pinion or rack..

Second i am thinking of u have some dust particles accumulated in the rack and pinions..just clean all of them and run the file again..

May be you have runout in the spindle collet or the bearings are not correctly installed in the last maintenance..