Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: mike2700 on June 06, 2018, 01:09:17 PM
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HELP, I have a wood CNC 48X48 from CNC routerparts, had it for about 5 years. All of a sudden I am getting errors of 1/16" too large on inside of a 2" pocket cut and minus 1/8" on outside diameter of 12 1/2" cut.
went through the whole machine and am very certain its not mechanical. Is it in Mach3? or could it be Vcarve pro?
Thanks for any help you can offer
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Did you measure your tooling? I had this once, was using sharpened 1/4" two flute bits. So the bit was no longer 1/4" wide. However I think your problems are opposite that.
Does this machine have timing belts? I know I get stretchy ones before they break and that messes things up. Slop in the rack and pinion?
Could be VCarve pro if you picked the wrong tool in the program.
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Hi; Thanks for the reply, double checked the machine, and everything is tight. Just tried axis calibration and its spot on. Has to be either Vcarve Pro or Mach3
my tool is exactly 1/4 end mill, tool offset is set to 0
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Well I am about ready to commit harry carry, there is nothing more frustrating than having aCNC machine and not being able to use it.
I am 99.9% sure the problem is Mach3 but dont know how to fix it, I am still getting 2 1/16" ID on a pocket cut when I clearly asked for 2"
my out side dia. is supposed to be 12 1/2" well in Y axis its 12 1/2 but in X its 12 3/8" I know its not my machine I spent close to three
days going over the whole thing, I damn near tore the whole thing apart and put it back together again, its as tight as a frogs ass.
I have my steps per in. set right, what else could it be?? HELP please!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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Hi Mike,
If you post (or send me) a copy of your problem Gcode I will run it here and see if I can find the problem.
Tweakie.
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I am 99.9% sure the problem is Mach3
I'm 99.9% sure the problem is NOT Mach3.
These questions come up all the time. The issue is almost always deflection, most often in the machine. Tool size can also be an issue, but would be much more minor.
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Hi Tweakie, Here is the xml file
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to ger21, if my machine was deflecting 1/8 " would it not show up in this test?(http://)
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neednto explain the pictures , the 1/4 steel pin fits perfectly into the kerf, the roundness of the cutouts is within .0025. the hole on the left is supposed to be 3" the plug on the right is supposed to be 3"
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Can you post the g-code?
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ger21 I did in post #7
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Hi Mike,
The attachment in post #7 is not good. You need to attach your actual Gcode file (it has the file extension .tap, .nc, .txt, etc.).
Tweakie.
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Sorry about that Tweakie: I will work on it right away
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Try this one, ( Ihope I got it right)
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Mike,
This is a backplot of the gcode you posted. Don't think it's the correct one for the pictures you attached ........
RICH
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Hi Rich: That is the file I am having trouble with, the outside DIA. is supposed to be 12.5, the ID of the pockets is supposed to be 2"
the pockets keep coming out 2 1/16" and the OD is 12.375"
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Hi Mike,
You mentioned in post #5 that your outside diameter was not completely round (my out side dia. is supposed to be 12 1/2" well in Y axis its 12 1/2 but in X its 12 3/8"). Checking your Gcode indicates that Mach3 will be following a toolpath which will produce equal dimension in both the X and Y planes and this is confirmed by the Program Limits of +/- 6.3438 (shown in the toolpath screen).
It would appear that you have a mechanical issue with your machine (backlash or flex, etc) which is causing the inaccuracy in the machined dimensions.
Perhaps ensure that the cutter you are using is truly 'sharp' and possibly reduce the feed-rate or depth of cut to reduce the loading on your machine components.
Hope this helps,
Tweakie.
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The toolpath for the large circle is for a 12-11/16" diameter circle. Subtract 1/4" for the bit, and you get 12-7/16".
So either your drawing is incorrect, or the toolpath parameters are incorrect.
I don't have time to look at the pockets right now, but I'm guessing it's a similar issue.
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The outside diameter is also made up of a combination of arcs and straight segments, which would point to an incorrect drawing.
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Thanks guys for all your help, I will go back and re-do my drawing and recut
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To tell you the truth, I'd be much happier programming a simple part like that by hand. I bet you could do it in under 30 lines including the comments and you'd have a much nicer time de-bugging it.