cutting circle

Kev20009
Posts: 14
Joined: Wed Jan 18, 2017 6:35 pm
Location: uk

cutting circle

Postby Kev20009 » Thu Feb 09, 2017 9:47 am

hi guys not sure if this as been brought up, but I cut square of 100mm x 100mm and done the um settings and its all good, but if I cut a circle I get a flat line on top and bottom about 13mm long before it gets round again, hopfully someone as seen this and can point it out,

looked in software but cant see anything that controls this so could be in the mechanics of the cutter, but where to start,

thanks guys for any help kev

Tech_Marco
Posts: 4302
Joined: Mon Jun 15, 2009 3:00 pm

Re: cutting circle

Postby Tech_Marco » Thu Feb 09, 2017 4:21 pm

Can you post the result here?
Also, please post parameters from the software


Marco

Kev20009
Posts: 14
Joined: Wed Jan 18, 2017 6:35 pm
Location: uk

Re: cutting circle

Postby Kev20009 » Fri Feb 10, 2017 2:43 am

hi marco thanks for help photos attached, not the best as I don't now how to get screen grabs,

as you will see the circle is flat top and bottom, any help you could give, kev
Attachments
marco 4.jpg
marco 3.jpg
marco 2.jpg
marco 1.jpg

fnaranjob
Posts: 63
Joined: Thu Aug 11, 2011 10:57 am

Re: cutting circle

Postby fnaranjob » Mon Feb 13, 2017 9:08 am

Looks like backlash to me

Kev20009
Posts: 14
Joined: Wed Jan 18, 2017 6:35 pm
Location: uk

Re: cutting circle

Postby Kev20009 » Tue Feb 28, 2017 7:39 pm

Thank you for replying, only now been able to log back in, still got problem tried backlash, but it would only let me enter 1 if I tried higher it went back, Marco did ask for photos but waiting for him to take a look, thanks kev

Tech_Marco
Posts: 4302
Joined: Mon Jun 15, 2009 3:00 pm

Re: cutting circle

Postby Tech_Marco » Tue Feb 28, 2017 8:30 pm

I will look at your case when I landed
I am heading to the East (Hong Kong/ China)

Marco

Kev20009
Posts: 14
Joined: Wed Jan 18, 2017 6:35 pm
Location: uk

Re: cutting circle

Postby Kev20009 » Wed Mar 01, 2017 12:17 am

Thank you marco, have a nice trip, kev

Kev20009
Posts: 14
Joined: Wed Jan 18, 2017 6:35 pm
Location: uk

Re: cutting circle

Postby Kev20009 » Thu Mar 02, 2017 2:33 pm

hi guys been trying to solve this, cut a square really good, engrave a circle don't get this, so looks like its in the y axis, as im new to laser not sure what numbers to put in backlash as if I do 1.00000 it wont let me put any other numbers as it always goes back to 1.00000 after save and reset,

thanks guys kev

fnaranjob
Posts: 63
Joined: Thu Aug 11, 2011 10:57 am

Re: cutting circle

Postby fnaranjob » Fri Mar 03, 2017 10:00 am

If it is backlash you can easily check by turning the machine on, and with the steppers locked in place try to push the X axis beam back and forth to see if it's loose, it should be super tight, if it does move, even a little, your problem is there and the best way to solve it is to fix the mechanics (it could be a loose setscrew on a pulley, loose belt, etc.), I've never tested the backlash compensation in lasercad so no advice on that.

If you're using servomotors it can be poor tuning too.

Cheers
Fernando

Kev20009
Posts: 14
Joined: Wed Jan 18, 2017 6:35 pm
Location: uk

Re: cutting circle

Postby Kev20009 » Fri Mar 03, 2017 10:59 am

thanks for the reply, done like you said x axis solid, y axis moves, think I can see the problem stepper couplers have them slits in them, when I push gantry can feel them move just the one side, so think I will order 2 solid couplers to see,

the other thing I have not asled is what is best pitch belt to use, mine is t5, 5mm pitch, 10mm wide, with 20thooth pulley, and 2 pulleys as guides, on the steppers I have to have 3200 steps to stop them stalling, using nema23,

attached is photo of pulley setup any advice you could give if this is ok or change to 2.5 pitch belt, thanks for your help kev
Attachments
lightobject.jpg

fnaranjob
Posts: 63
Joined: Thu Aug 11, 2011 10:57 am

Re: cutting circle

Postby fnaranjob » Fri Mar 03, 2017 3:54 pm

T profile belts are not really ideal for precision positioning, Try AT profile, the mesh between pulleys and the belt are better on them, AT5 should be fine for your machine, even AT2.5 maybe, look for the belts with steel cords, they don't stretch so no added compliance there.

Glad I helped,
Fernando

Kev20009
Posts: 14
Joined: Wed Jan 18, 2017 6:35 pm
Location: uk

Re: cutting circle

Postby Kev20009 » Fri Mar 03, 2017 10:15 pm

Fernando thanks for help, will see if marco takes a look to say if backlash compensation works, as everything else is perfect just circles not, but will change belts if I have to, Thanks kev

Kev20009
Posts: 14
Joined: Wed Jan 18, 2017 6:35 pm
Location: uk

Re: cutting circle

Postby Kev20009 » Sat Mar 04, 2017 1:08 am

Fernando just another one, my nema23 are 20tooth pulley 1to1 would is any better stepping down 2to1 20 tooth on motor 10 on belt, this is where I'm not sure what's the best way to run on lasers, if 1to1 is better than reduction for acuaracy and tuning,

Thanks again kev

fnaranjob
Posts: 63
Joined: Thu Aug 11, 2011 10:57 am

Re: cutting circle

Postby fnaranjob » Mon Mar 06, 2017 1:45 pm

Kev20009 wrote:Fernando just another one, my nema23 are 20tooth pulley 1to1 would is any better stepping down 2to1 20 tooth on motor 10 on belt, this is where I'm not sure what's the best way to run on lasers, if 1to1 is better than reduction for acuaracy and tuning,

Thanks again kev


If your motors are not complaining or losing steps and the cuts are looking smooth then I say leave it like that, reduction adds torque and resolution, which don't seem to be your problem here, just to be sure you're not losing steps send the machine to make a saw like pattern (constantly changing direction) as fast as your machine can do it, use low power to just mark the material, not cut it, and repeat it several times in the same place, if you're losing steps the marks will appear to shift position each time you repeat the cut, if that happens then yes, you can benefit from gearing, or you can just work slower.

Techgraphix
Posts: 450
Joined: Fri Jan 20, 2012 1:39 pm
Location: Appelscha, the Netherlands
Contact:

Re: cutting circle

Postby Techgraphix » Tue Mar 07, 2017 12:51 am

As fnaranjob said: T5 belts are not the best.. I only used them for the Z-bed-level, which will be stationairy during the job.
I replaced all T5/10mm wide belts for GT2-10mm wide white (steelwires enforced) belts and had the pulleys made in China.. (for a 20 tooth T5 i replaced it with a 50 tooth GT2)
I'm very happy with the results so far..

For the backlash: have you checked if the pulley is still tight to the motor? Sometimes they come loose.. When there are little screws in the pulley, see if the motorshaft has some flat sides.. Align thes with the screws prior to tighten them..

Kees


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