Cut Direction Question

[Capstone]

Someone commented on my video herewith this:

Your machine appears to be running backwards. The cut wouldn't be noticeably different on thin gauge material but as you get to thicker material you will notice a beveled edge of the cut. This is normal with a plasma process. the way to compensate for it is to cut inside profiles in a counter clockwise direction and outside profiles in a clockwise direction. Basically the right side of whatever your motion is would be the straight cut and the left would show a bevel.

Is this actually true?! This seems like complete hogwash, but just in case there's something to this maybe Jim Colt or another expert would do a short "mythbuster" episode on this subject just for the benefit of the community as a whole?

Thanks

[pertneer]

Yes you are on the wrong side of the cut. It has to do with the direction the plasma rotates when it comes out of the nozzle. Jim colt explains it in this post

[Capstone]

Okay... thanks very much for the link. Please tell me that this is a super simple software fix like in Sheetcam?

[acourtjester]

see attached image of Sheetcam when you are setting up you cut you can select the direction of the cut operation.
Also in Sheetcam you view the direction of the cut by clicking on one of the icons at the top which up in the screen display with arrows.

I'm not sure but if but if you click on the cut path under the jet cutting operations and select "All inside first" under cutting rules that Sheetcam may do it automatically for you

dir cut.jpg (50.41 KiB) Viewed 1160 times

dir cut.jpg (50.41 KiB) Viewed 1160 times

[SeanP]

You're inside cuts are the right direction it's the outside cut that is wrong somehow, I have fallen foul of that tick box a few times!

Also I have the Velox z axis same as your's, I changed the spring positioning inside the unit fairly quick, to my mind they have them the wrong way around, it puts to much pressure on the torch leading to the sheet pushing down.

I took out the 2 springs and just used one as in the photo to get a better touch off, sometimes on thicker stuff I don't use any springs.

Not sure there thinking on fitting them that way around

That's how I have the spring now.
I also added another bearing on the lower part, mine seemed to get a little play in there.

[Capstone]

Thanks Sean. I found the SheetCAM check-box this AM as soon as I confirmed the direction issue. I hadn't thought about the VeloxCNC "Z" touch pressure as an issue, but now that you mention it, it does seem to require/put a lot of pressure on the material (and thus the machine torch) before the switch trips.

I keep trying to improve my gantry by making it beefier, while at the same time I keep reading about how so many people like me are having troubles with "shudder" wiggle in our cuts at anything above 225ipm which is a direct correlation to a heavier gantry trying to go too fast.

I just have to find the sweet spot for both thin and thicker (up to half inch) materials.

I have a PM45 so my cutting sweet spot is currently 10ga for both speed and minimal dross with no wiggle at the current weight, but that's practically no-mans-land in the world of real products between the Art and Fabrication disciplines, not thin enough for Art and not thick enough for Fab. I still have one troublesome issue to fix and that's the movement of the table itself. I don't have a permanent spot for the table as far as bolting it to the slab in my garage. I am using a pair of sunken 1/2" eye-bolts to literally strap the table down and it's failing to hold fast at the higher speeds. Once I re-org my garage and get rid of stuff, which is my task this weekend, I might manage to squeeze more space for a permanent spot.

I'm really vexed by this challenge of Gantry weight/speed.