Square corners come out round

General discussion of laser machines

Square corners come out round

Postby edmond22 » Sat Mar 17, 2012 8:40 pm

My machine is finally alive but I have a problem, if I cut a square two corners diagonally opposite come out round and the other two come out nice and square, see attached pic
17032012296.jpg
square corners come out round


I assume this is a mechanical problem somewhere or what.
Any pointers would be appreciated.
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Re: Square corners come out round

Postby bdring » Sat Mar 17, 2012 8:54 pm

Is it Mach3?

If so, it looks like constant velocity gone wild. Try turning it off.
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Re: Square corners come out round

Postby edmond22 » Sat Mar 17, 2012 9:11 pm

Yes Bart I am running Mach 3.

Thanks I will do a test with the CV off tomorrow.
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Re: Square corners come out round

Postby edmond22 » Sun Mar 18, 2012 6:55 pm

I turned the CV mode off and that worked on the straight pieces but on arcs the exact stop cuts horrible and very rough.
I found a Mach 3 CV mode article on the net so will just read through that and see what I can do.
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Re: Square corners come out round

Postby MBF » Sun Mar 18, 2012 8:11 pm

Hi

does your config. look like this, if not try the settings in the red circles

/Mike
Attachments
Mach3.PNG
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Re: Square corners come out round

Postby BenJackson » Sun Mar 18, 2012 8:33 pm

The other obvious thing to check is acceleration. The lower your acceleration the more CV mode has to anticipate a turn.
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Re: Square corners come out round

Postby edmond22 » Mon Mar 19, 2012 5:45 am

Thanks Mike im gonna use the settings you suggest.

Ben I need to check the accel values, what accel values are you using?
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Re: Square corners come out round

Postby BenJackson » Mon Mar 19, 2012 5:44 pm

edmond22 wrote:Ben I need to check the accel values, what accel values are you using?


I'm using 7500mm/s/s on X and 5000 mm/s/s on Y. I was afraid to go higher on Y because at that point it was threatening to slam the lid from shaking the whole table (my table is on carpet).

In this thread: viewtopic.php?f=28&t=971 I show the math for distance to accelerate given velocity and acceleration. You should be able to work out how much rounding you will get at a given cut speed for any given acceleration.
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Re: Square corners come out round

Postby edmond22 » Mon Mar 19, 2012 6:39 pm

My accel values are way too low, I think they are in the hundreds somewhere.

I need to up them to your values Ben and see what happens. hopefully tomorrow I can have a look at them.
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Re: Square corners come out round

Postby edmond22 » Tue Mar 20, 2012 9:29 pm

I upped the rapid speeds to F15000 and the accell to 2500mm/s/s, and changed the settings in Mach 3 like Mike suggested.
The problem is sorted but the letters come out slightly distorted see the photo.
Attachments
20032012298.jpg
distorted letters and shapes
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