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post #1 of (permalink) Old 10-16-2003, 08:37 PM
jeepfiend
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OT: Bridgeport 308 Discovery

At work I recently became burdened wtih a 308 Discovery. The machine is a 91 model with the Boss 10 controller. I am having a problem with cutting arcs at the correct radius. I have an arc programmed to be cut clockwise, and the radius ends up wrong, every time, sometimes by a factor of 10 or more. If I edit the G-code and cut CCW, the arc will cut correctly. I have a bit of CNC experience, but this has me flummoxed. If anyone has any experience with this machine or the controller, I would appreciate any help. I can't really get help from Bridgeport, they went out of business in the US. Now there are private companies supporting the Bridgeport CNC machines, but they charge a lot of money. I am using the BobCad/cam software (a choice made purely by economics, the software is counter-intuitive and pretty crappy all in all). I don't think the arc problem is software related since all I have to do is change the cut direction to remedy the problem.
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post #2 of (permalink) Old 10-16-2003, 08:57 PM
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Re: OT: Bridgeport 308 Discovery

My experience with CNC is very minimal and was a few years ago in high school. We used Mastercam and I loved that program. Anywho, it sounds like it might be a software issue. For some reason its writing the G-codes wrong when its cutting clockwise. At least thats what it sounds like to me. I don't know the software you are working with, but is there a way to change its default cutting direction? I'm wondering if that is possible.

Now again....my time with CNC machines is very limited and was a few years back. I'm really shooting in the dark here so if everything I said makes no sense ignore it. But if it helps then ok. If anything I'm keeping this up top for you.
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post #3 of (permalink) Old 10-16-2003, 09:47 PM
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Re: OT: Bridgeport 308 Discovery

We use Mastercam at our shop also. It is a really impressive CAM package. However, sometimes when programming some of our older machines, the post processing will fail to add the cutter comp to a tool path. Are all of your other cuts with this particular tool on location?
Also, does it cut the same bad path each time, or just randomly do whatever it wants to?
Like Nick, my experiance is pretty limited, but I thought I'd mention the cutter comp problem that we've experienced when older equipment meets new software.
Let me know if you don't figure out your problem and I can get with one of the old guru's at the shop for some help. I think a couple of them programmed pieces for the Pyramids.
Good Luck,
Jim
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post #4 of (permalink) Old 10-16-2003, 09:56 PM
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Re: OT: Bridgeport 308 Discovery

MasterCam is definitely better, way better. But, at ten times the cost, for the prototype work I do, I could not justify the expense of the mastercam. The bad cuts are repeatable, the odd thing is that when I change the cut directoin, that is all I change, not the start stop point, the radius or anything, only the CW or CCW command. The Boss 10 is a pretty old controller, I am almost wondering if it is a sequence problem. Tomorrow I am going to try some different start points on the same arcs and see what happens. I would really like to get it working, not only to get the heat of the bosses off of me, but I could be able to make some Jeep parts when the bosses are not looking.
post #5 of (permalink) Old 10-17-2003, 07:53 AM
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Re: OT: Bridgeport 308 Discovery

Just a guess, but maybe it's not the software or controller.... Since you describe it as "only happening while the arc is moving in one direction", it could be a mechanical or component issue. Once upon a time I worked for a small repair & job shop and saw similar weirdness. On one CNC mill, the acme threads(?) that moved the table were heavily worn on one side...only effected it while moving to the left of the head/cutter. We guessed it was from repeated movements in the same direction, rather than altering the path between jobs. Found out the guy programming did'nt think about starting from the right....ever!
On another, a stepper was shot(still moving, but not incrementing correctly) and wanted to take too big of bite. A lathe would randomly start fritzing until we found the dropcord plugged into the same curcuit. It was snaked thru the shop & connected to a dang spotwelder with a bad ground... I thought the operator was going to kill the guy in the welding shop!

Keep looking, it'll jump out at you. Probably about 0300 when your trying to sleep [img]images/graemlins/crazy.gif[/img]
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