Cuts are not perfect!

Cuts are not perfect!

Postby pencrafter » Sun Mar 16, 2014 6:31 am

Hi, I'm new to the world of CNC. Attached is a picture of my test cut attempt. I have a Legacy CNC and used Aspire 4 & mach3 to do the test cut. Cuts are not uniform and are wavy. Need Help Please.
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Test Cut.jpg
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Re: Cuts are not perfect!

Postby Adrian » Sun Mar 16, 2014 9:28 am

That's almost certainly going to be movement somewhere in your machine. Check nothing is slipping or binding on the axes and make sure the router/spindle can't move in it's mountings.
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Re: Cuts are not perfect!

Postby TReischl » Sun Mar 16, 2014 9:43 pm

If'n I were a betting man, I would put my money on the machine losing steps.
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Re: Cuts are not perfect!

Postby zeeway » Mon Mar 17, 2014 10:40 am

My bet is for machine looseness somewhere.

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Re: Cuts are not perfect!

Postby martin54 » Mon Mar 17, 2014 1:27 pm

It's an issue with the machine rather than the software as has been said already but could be caused by a few different things, apart from the obvious errors were there any other problems like the shapes being the wrong size?
Did the machine come set up or did you set it up in mach3 yourself?
what speed & feed rates did you use because you may be trying to cut faster than your machine can handle.
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Re: Cuts are not perfect!

Postby garylmast » Mon Mar 17, 2014 2:17 pm

I was having similar problems, except mine was in the 'Z' axis. After greasing the rails and bearings, replacing a bearing, it turned out to be a bad stepper motor.
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Re: Cuts are not perfect!

Postby dealguy11 » Mon Mar 17, 2014 6:10 pm

Time for you to call Tracy or Andy at Legacy. Things to check in the meantime:

- Do you have a loose pinion gear on the x or y axis?
- Are your racks tightened down securely?
- Have you been lubricating the bearings? Is anything sticking?
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Re: Cuts are not perfect!

Postby Strat » Mon Mar 17, 2014 6:23 pm

Cut the same program again, if it looks different its the machine, if it looks the same, it might be the node points on the objects.
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Re: Cuts are not perfect!

Postby rscrawford » Mon Mar 17, 2014 9:15 pm

Might also be hold down. If the part isn't held down tightly, the lateral force of the cut could be moving the workpiece.
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Re: Cuts are not perfect!

Postby pencrafter » Tue Mar 18, 2014 3:14 am

I have checked and re-checked all the nut & bolts, clean and lubricate the machine, but still the same issue. I'm cutting @ 8000RPM, feed rate 20. The machine was set up and calibrated before it was shipped to me. It cuts clean on straight line (X&Y). Well, I think I need to contact Legacy. Thank you all for your help.
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Re: Cuts are not perfect!

Postby PaulRowntree » Tue Mar 18, 2014 5:58 am

pencrafter wrote:It cuts clean on straight line (X&Y).


One more check would be to get it to do a straight line where X and Y are both moving, say from (0,0) to (+10, +10)
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Re: Cuts are not perfect!

Postby pencrafter » Sat Mar 22, 2014 3:59 am

There is a backlash in Y axis about 1/4". Can Mach3 calibration fix this or there is something wrong with the motor?
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Re: Cuts are not perfect!

Postby PaulRowntree » Sat Mar 22, 2014 4:32 am

A mechanical problem on this scale has to be fixed. I have never heard of a motor having an error like this ... are you sure that there isn't a loose or bad coupler? 1/4" should be traceable just by shaking the machine with your hands, and looking for the play.
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Re: Cuts are not perfect!

Postby pencrafter » Sat Mar 22, 2014 5:05 am

When the machine is on, the X axis is solid and if I try to move it by hand there is no play, but if I do the same on Y, it moves about 1/4". I have checked the gear on the motor it is solid ad tight. Attached is a picture of Y axis drive gear.
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20140321_204624.jpg
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Re: Cuts are not perfect!

Postby Greolt » Sat Mar 22, 2014 7:30 am

By CNC router standards 1/4" play is enormous.

You should be able to see where it is occurring.

By the way that pinion looks to be a long way out of alignment with the rack. Might be a clue.

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