Cuts are not perfect!

pencrafter
Posts: 7
Joined: Wed Mar 13, 2013 6:00 am
Model of CNC Machine: Legacy Mini Arty

Cuts are not perfect!

Post by pencrafter »

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.
Attachments
Test Cut.jpg

User avatar
Adrian
Vectric Archimage
Posts: 10563
Joined: Thu Nov 23, 2006 2:19 pm
Model of CNC Machine: ShopBot PRS Alpha 96x48
Location: Surrey, UK

Re: Cuts are not perfect!

Post by Adrian »

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.

User avatar
TReischl
Vectric Wizard
Posts: 3626
Joined: Thu Jan 18, 2007 6:04 pm
Model of CNC Machine: 8020 Build 48X36X10 RP 2010 Screenset
Location: Leland NC

Re: Cuts are not perfect!

Post by TReischl »

If'n I were a betting man, I would put my money on the machine losing steps.

User avatar
zeeway
Vectric Wizard
Posts: 3157
Joined: Thu Feb 11, 2010 9:24 pm
Model of CNC Machine: Self-built
Location: SC, USA

Re: Cuts are not perfect!

Post by zeeway »

My bet is for machine looseness somewhere.

Angie

User avatar
martin54
Vectric Wizard
Posts: 4945
Joined: Fri Nov 09, 2012 2:12 pm
Model of CNC Machine: Gerber System 48,Denford Triac Modified
Location: Crossgates, Scotland

Re: Cuts are not perfect!

Post by martin54 »

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.

garylmast
Vectric Wizard
Posts: 1081
Joined: Fri Oct 23, 2009 4:03 pm
Location: Sandy, Utah

Re: Cuts are not perfect!

Post by garylmast »

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.

User avatar
dealguy11
Vectric Wizard
Posts: 1559
Joined: Tue Sep 22, 2009 9:52 pm
Model of CNC Machine: Anderson Selexx 510
Location: Henryville, PA
Contact:

Re: Cuts are not perfect!

Post by dealguy11 »

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?
Steve Godding
D&S Artistic Woodworking http://www.dsartisticwood.com

Strat
Vectric Apprentice
Posts: 68
Joined: Wed Nov 06, 2013 7:44 pm
Model of CNC Machine: Laguna IQ CNC / HHC
Location: Gurnee, IL USA

Re: Cuts are not perfect!

Post by Strat »

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.

User avatar
rscrawford
Vectric Wizard
Posts: 982
Joined: Mon Jan 17, 2011 6:49 pm
Model of CNC Machine: CAMaster Cobra 408 ATC, ShopSabre IS408
Location: Wetaskiwin, Alberta
Contact:

Re: Cuts are not perfect!

Post by rscrawford »

Might also be hold down. If the part isn't held down tightly, the lateral force of the cut could be moving the workpiece.
Russell Crawford
http://www.cherryleaf-rustle.com

pencrafter
Posts: 7
Joined: Wed Mar 13, 2013 6:00 am
Model of CNC Machine: Legacy Mini Arty

Re: Cuts are not perfect!

Post by pencrafter »

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.

PaulRowntree
Vectric Wizard
Posts: 1687
Joined: Sun Oct 24, 2010 7:28 pm
Model of CNC Machine: homebuilt 4'x2' (Mach3+G540)
Location: Guelph, Ontario
Contact:

Re: Cuts are not perfect!

Post by PaulRowntree »

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)
Paul Rowntree
WarpDriver, StandingWave, Topo and gadgets available at PaulRowntree.weebly.com

pencrafter
Posts: 7
Joined: Wed Mar 13, 2013 6:00 am
Model of CNC Machine: Legacy Mini Arty

Re: Cuts are not perfect!

Post by pencrafter »

There is a backlash in Y axis about 1/4". Can Mach3 calibration fix this or there is something wrong with the motor?

PaulRowntree
Vectric Wizard
Posts: 1687
Joined: Sun Oct 24, 2010 7:28 pm
Model of CNC Machine: homebuilt 4'x2' (Mach3+G540)
Location: Guelph, Ontario
Contact:

Re: Cuts are not perfect!

Post by PaulRowntree »

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.
Paul Rowntree
WarpDriver, StandingWave, Topo and gadgets available at PaulRowntree.weebly.com

pencrafter
Posts: 7
Joined: Wed Mar 13, 2013 6:00 am
Model of CNC Machine: Legacy Mini Arty

Re: Cuts are not perfect!

Post by pencrafter »

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.
Attachments
20140321_204624.jpg

Greolt
Vectric Wizard
Posts: 916
Joined: Fri Sep 21, 2007 1:44 pm
Model of CNC Machine: 900 x 750 2hp UCCNC Router & others
Location: Australia

Re: Cuts are not perfect!

Post by Greolt »

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.

Greolt

Post Reply