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sizes aren't correct anymore please help !
« on: December 16, 2014, 05:39:48 PM »
I'm scratching my head here with a situation I'm currently having. Ill start from the top. I have a benchtop grizzly mill which is converted to a cnc with double nut ball screws, nema 34 stepper motors, microstep driver (ebay). This machine ran great for the past year but recently I've been having problems with motors stalling. I quickly jumped to the conclusion thinking it was just my motors were out of wack and stupid me started changing everything around with the motor tuning and mach 3 setting to get it up and running again. Needless to say it was my ways that needed the adjustment not the electronics. I believe I changed all electronic settings back to the way I had it and continued on making parts.

Heres my issue. I make and sell small aluminum covers to a local company. The covers are made from aluminum and measure .250 thick x 2.43 x 1.73 . I drill all the blanks first then they got bolted to a jig so I can do the outer profile to that size.  My sizes are coming out around 2.46x 1.75. I though maybe its just the motor tuning but using a dial indicator I'm within .001 with no backlash, I then changed my steps per on the microdriver from 1600 to 800. Same exact results. It can't be the program since I've used it hundreds of times. I use the exact same cutter every time. Would the Kernel speed affect this in any way? I'm currently at 45000hz and I believe previously I was at 25000hz

 

Offline Hood

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Re: sizes aren't correct anymore please help !
« Reply #1 on: December 17, 2014, 03:46:03 AM »
If you do not require the kernel to be 45KHz then set it lower. Some computers have problems with even 45KHz.
Hood
Re: sizes aren't correct anymore please help !
« Reply #2 on: December 17, 2014, 03:38:19 PM »
Unless you are running the steppers at high speeds you shouldn't need over 25khz in most cases. Sounds like your xml file is corrupt probably from making numerous Mach program changes trying to solve a mech problem. Rewriting over any existing profile can sometimes cause strange problems. I would suggest creating a new profile and start fresh and reset the stepper driver back to original settings. Once the problems are solved make a backup copy of the profile.  
Re: sizes aren't correct anymore please help !
« Reply #3 on: December 17, 2014, 06:13:19 PM »
Thank you both for the reply . Today I changed the kernel back to 25hz with no results. Heres where it gets really weird. I started to second guess my programming so I had a piece of aluminum that was held in the center by two screws, I milled the left side and set it as my x0. I figured ill manually mill it to a certain size just to be eliminate if its my programming or not. I then told it to move x2.375 and milled the right side. This part should be 2" exactly. Nope it was at 2.020. Ok must just be the motors off right? Put on the dial indicator yet again and moved the axis .100 and was right on. Went back the other way to check for backlash and was dead nuts. I then moved it .900 and it appeared to be off be .004 but returned back to .100 with no problems. ?I checked the cutter diameter thinking I accidentally put the wrong one in but its a 3/8" cutter.  Can a corrupt xml file be the problem in this case?
Re: sizes aren't correct anymore please help !
« Reply #4 on: December 17, 2014, 06:28:33 PM »
Tomorrow I will try and make a new profile and pray that it fixes the issue.
Re: sizes aren't correct anymore please help !
« Reply #5 on: December 17, 2014, 09:21:05 PM »
Are you using a sharpened bit that is no longer 3/8?
Re: sizes aren't correct anymore please help !
« Reply #6 on: December 18, 2014, 09:37:05 AM »
No. It's never been resharpened. It appears that all my measurements are off on these parts including the hole spacing .
Re: sizes aren't correct anymore please help !
« Reply #7 on: December 18, 2014, 09:49:51 AM »
Could it have anything to do with cutter compensation? is there like a G41 or G42 in your program?
Re: sizes aren't correct anymore please help !
« Reply #8 on: December 18, 2014, 11:23:44 AM »
I thought about that too but when I just manually cut the aluminum to a specific size using mdi it was still offor by about .020 . I guess I can try typing in g40 then try manually cutting it again
Re: sizes aren't correct anymore please help !
« Reply #9 on: December 18, 2014, 11:25:42 AM »
Actually now that I think about it I have a g40 in the beginning of the program