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Cut definition help please, images included!

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Sharp
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Cut definition help please, images included!

Postby Sharp » Wed Oct 18, 2017 11:20 am

Hi guys, I'm looking for some advise, I have drawn up a job for a customer but the final cut is not nearly as crisp as he would like. I have attached a shot of the turbo cad drawing and the cut end result, You will notice that the squares and rectangles look more like circles and ovals.... He wants crisp sharp corners, Is there a way I can get that result? I am cutting out of 18g and have tried both 45 amps and tried slowing it down with 30 amps and the end result is the same. I have a powermax 45.I am using turbocad, Sheetcam and Mach3, where would I be able to turn off the radius that the software seems to be adding ? Also I have .200 Arc lead in and lead outs, would i be better off with Perpendicular lead in and no lead out?
The piece is only 7" wide so I understand that this is a lot of detail to be asking from plasma, but I want to try to improve on it as I have put many hours into the drawing and would rather not have to redesign or loose him to a waterjet/lazer place...
TIA for any help!

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BTA Plasma
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Re: Cut definition help please, images included!

Postby BTA Plasma » Wed Oct 18, 2017 12:08 pm

If the drawing showed up in sheetcam correctly then you have a target velocity issue. Most likely caused by a low acceleration. You can start to play with numbers in config/general config and use the options in the lower right for stopping at angles...ect.

Sharp
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Re: Cut definition help please, images included!

Postby Sharp » Wed Oct 18, 2017 1:14 pm

I just slowed it down to 150ipm and its looking good! The top cut is at 150imp vs 250 on the bottom and I got rid of looping of sharp corners in sheetcam

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acourtjester
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Re: Cut definition help please, images included!

Postby acourtjester » Wed Oct 18, 2017 2:47 pm

Have you checked the motor tuning working with the acceleration and velocity setting. You want to have it going as fast as it can without the motors stalling. Here is a video that talks about the motor tuning that may help. I run mine with the velocity numbers about 4 times the acceleration (example 100 velocity 25 acceleration)
https://www.youtube.com/watch?v=JzHdGG90TCw
Something the will help is to attach an ink pen to the torch mount and mark on paper until you find the cause. when using the pen you should see exactly the same as you CAD image
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srp
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Re: Cut definition help please, images included!

Postby srp » Wed Oct 18, 2017 6:02 pm

I believe the looping of sharp corners in Sheetcam refers to outside corners. It still might have been messing you up in the inside corners. The second cut series looks much better. This is a good opportunity to learn about how to tune your machine to the best it can do and the limitations of your machine. I believe you will be able to use fine cut parts in the near future with the PM45 which at 30a will bring your cut speed down in the 150 ipm range with a narrower kerf. Man vs machine - It is a interesting trip. Good Luck

marcnaz
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Re: Cut definition help please, images included!

Postby marcnaz » Thu Oct 19, 2017 11:17 am

Looks like slowing it down definitely fixed the majority of the cut issues. I'd also increase the lead in length (and/or angle) and check the pierce delay to clean the cut up even a little more. It looks like a bump where you start the cut to close to the final cut line.

srp
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Re: Cut definition help please, images included!

Postby srp » Thu Oct 19, 2017 4:42 pm

If you rotate the piece 45 degrees when you cut there will only be one axis working at one time on many of the smaller cuts. Might try that. I don't use a lead out. I overburn .03. 18 ga shouldn't need a pierce delay. Don't ignore tuning your motors. I think you have issues there.

tcaudle
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Re: Cut definition help please, images included!

Postby tcaudle » Thu Oct 19, 2017 6:42 pm

Mach3 rounds corners and sharp turns based on the performance of yoor table mechanics. It gives preference of speed over accuracy with CV on. Problem is if you turn CV off and there a bunch of nodes it will start and stop on each one. You need speed to cut the thinner material . The move speed you need the higher the acceleration . Its in IPS/sec where as velocity is in IPM. The more acceleration it can muster the sharper turn it can make. You can setup rules in SHeetCAM to slowdown on a corner but if you have THC it needs to turn it off of it will dive like crazy.

If you don't mind lots of slag cut even slower so it can make the sharp turns . . Use the smallest tip size , the lowest Amps, and go as slow as you can to get more detail.

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Re: Cut definition help please, images included!

Postby motoguy » Thu Oct 19, 2017 6:44 pm

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