Leaving small pit/puncture on back side of the sheet

Having problems with or questions about SheetCam? Post them here.
Post Reply
Daka
Posts: 9
Joined: Sun Aug 11, 2019 1:25 am
Location: Nellore, India

Leaving small pit/puncture on back side of the sheet

Post by Daka »

Hi All,

I am cutting a design on 2 mm MS sheet and getting small pit/puncture on back side of the sheet. Please find attached the picture. This seems to be problem with lead out as I verified by pausing the cut after lean in and there was no puncture. Have tried different types of lead in/lead outs available but no luck.With arc type lead in and lead out, I can see problem is minimising but not able to avoid it completely. Have been googling the internet and on this forum as well. As I understand overburn/overshoot option seems to be a solution for this problem however I am not getting the steps to follow this feature. I am currently using sheetCam evaluation version 6.0.30.

Could some one please guide me on the steps to follow to use overburn/overshoot option or any other solution to overcome this problem?
Attachments
IMG-20190830-WA0003.jpg
IMG-20190830-WA0003.jpg (31.74 KiB) Viewed 822 times
robertspark
Posts: 257
Joined: Thu Feb 26, 2015 12:11 am

Re: Leaving small pit/puncture on back side of the sheet

Post by robertspark »

is that not where the kerf crosses?

what are you cutting with (laser, plasma?)

what machine is it (controller)
Daka
Posts: 9
Joined: Sun Aug 11, 2019 1:25 am
Location: Nellore, India

Re: Leaving small pit/puncture on back side of the sheet

Post by Daka »

Hi Rob,

Sorry forgot to mention, it is plasma cutting. I am not sure if it is kerf crossing however I am getting the same result when I tried with no lead out. I assume kerf crossing would happen when lead out is crossing lead in contour. Correct me if I am wrong.

and I am using Fangling controller.
Daka
Posts: 9
Joined: Sun Aug 11, 2019 1:25 am
Location: Nellore, India

Re: Leaving small pit/puncture on back side of the sheet

Post by Daka »

Hi Rob,

It may be worth to mention, when we look from top view of the contour it looks perfectly fine. Puncture mark is getting created only on bottom side of the sheet.
robertspark
Posts: 257
Joined: Thu Feb 26, 2015 12:11 am

Re: Leaving small pit/puncture on back side of the sheet

Post by robertspark »

some m codes are (or could be ) synchronous

most mcodes are not synchronous

the above will probably mean nothing to you (it took me a little while to understand when I first started out)

it means that most mcodes require the machine to slow down before the mcode is activated.... this means that you get low speed cross

low speed cross is dross that forms on the bottom of the plate because motion is slowing down and instead of the plasma cutting and blowing a clean kerf through the material extra material is heated at the edge of the kerf and because of the downward vortex formed by the plasma gas it is fixed downward but cools at the edge of the kerf.

there are a few guides which are useful to understand the kerf

https://www.hypertherm.com/en-US/learn/ ... t-quality/

https://www.google.com/url?sa=t&source= ... 7172752568
User avatar
djreiswig
Posts: 471
Joined: Sat Feb 20, 2016 4:47 am
Location: SE Nebraska

Re: Leaving small pit/puncture on back side of the sheet

Post by djreiswig »

It's from the delay from when the controller tells the plasma to shut off and when the arc actually dies. The metal melts away before the arc dies. It's pretty common. Really the only way to fix it is to make the plasma shut off slightly before the cut is finished. That was the arc dies as soon as it runs out of metal.
Accomplishing this is the challenging part. Mach 3 causes a delay if you add cut rules, which causes other problems.
A Linux system would probably be easy to fix, but I'm not really familiar with that system.
robertspark
Posts: 257
Joined: Thu Feb 26, 2015 12:11 am

Re: Leaving small pit/puncture on back side of the sheet

Post by robertspark »

with mach3 or uccnc you can use m10/M11

with mach4 or Linuxcnc you can use m62/m63

these are the mcodes that run in sync with motion.

these codes won't help you out with that controller
Post Reply