My Newb Plasma Table Attempted Build

rodw wrote:

Its taken me a good while to get my head around Sheetcam. Thre are lots of hidden gems. One thing that annoyed me that it seemed to have a mind of its own about cut order. So last full nest on 2mm I overrode it and it took for ages for me to set the order of each piece. So when I cut it I had a lot of warpage so I got to learn what the Sheetcam setting "Minimise for thermal distortion" really meant. Anyway, Les from sheetcam is a good guy and has contributed a bit of code to Linuxcnc and has always provided me with awesome support.

I tried out Sheetcam yesterday on a simple part, same one I referenced with Phil that I tried to run a post on in fusion 360. Sheetcam did the post and I attempted to cut it, but my torch was diving after some long lines into the float switch and shutting off. I disabled THC and it took care of it, so there's something to work out on the table itself. The holes came out really strange. I used the pp for Sheetcam that Phil posted, although until I redraw the dxf in fusion I'm not going to say it was 'this' or 'that' that caused the cut issues (aside from the torch diving, which isn't a Sheetcam issue at all).

Pat

I've been messing around with Fusion 360 and Sheetcam. Working through some issues with the pp and whatnot with Fusion 360. The files I get using Sheetcam are cuttable. I'm having an issue with the Sheetcam-generated files causing one side to dimension slightly different from the other. I've attached pictures of a test piece I've cut. I started fresh in 360 and made the part from scratch, then loaded the dxf file into Sheetcam. If you look closely at the actual part the upper reversed 'F' letters have different widths. Also on the sides where the fins transition into the main body of the bomb shape they are a bit different in dimension from each other, and at the bottom as well. Very strange as the file in the preview tab of plasmac looks symmetrical, and when I open the dxf in both 360 and Solidworks the dimensions are symmetrical as well. Has anyone ran across this before? It has me really dropping F bombs!

My guess would be losing steps/or something loose in the Y direction
(look at the height of notches where the fins join the body of the bomb)

I think you can see where it slipped: right top V cut of right hand fin

I'll check it out with a marker. Funny thing is that on 2 parts it's doing it in the same spot.

Pat

I got after it this morning. Discovered the pulley on Y2 set screws both had backed out. I went back and put locktite on all of them and retightened all of the belts. Problem solved, cuts really nice now.

I only have 60A consumables, so the charts call for 211ipm on the 10ga. Trouble is my compressor is way too small to keep up with that lol. So...gonna get a bigger one and probably some 40A consumables, as I won't be cutting very frequently any material over 7ga thickness.

The bracket was cut at 150ipm, but 195ipm was leaving nearly undetectable amounts of dross on the back. I guess it's time to get the water pan finished up...thing is leaving tons of the typical fine plasma cutting residue in my shop.

Thanks for the help.

Pat

I have the water pan finished and I'm doing some test cuts. Couple of issues I can't seem to get hammered out, and I'm sure they're somehow tied to each other.

Whenever I attempt to use Auto or Enabled THC, i get two errors within maybe 12 or so inches of cutting...valid arc lost, and float switch, which pauses and stops the cut. Also, holes aren't slowing down per the cut rules I've set in Sheetcam...presumably due to the same underlying cause. Whenever I disabled THC, it cuts fine but still does not slow for corners and holes...however with the THC disabled there is never any valid arc lost or float switch tripped errors either. Any insight is appreciated, as always.

I think I do have the cut settings dialed in pretty well. This is 1/4" thick HR steel with zero cleanup, front and back. Just the corners and holes aren't slowing speed.

Pat

phillc54 wrote:

Does the torch actually hit the matarial and cuase this?

Yes, It starts going - (down) very slowly and then valid arc is lost and it triggers the float switch. Attached the gcode file.

Pat