Wavy cuts on small letters, Now Tons of Dross

[jjstrat]

[img][img][img]Hello,
Here is the issue that we were having. Cutting 14g cold rolled steel. With a Hypertherm 45 set at 45 amps.
we just switched from the 4x4 Plasma Cam... to the 510 PlasmaCam. While we were using the 4x4, our cut qualify was very good, minimal dross requiring very little clean up. Hardly had any issues with cutting.

Now that we have switched to 510, we first started having significantly wavy and junky cuts on small lettering (you can see this in the attached picture ). the large lettering cut good, minimal dross as before, but we could not cut any letters that were small or thin. We attempted cutting straight lines, and spiral lines, and those all cut well and minimal dross.

After working days on making sure that the table is level, multiple new consumables, draining the air compressor, we have the table grounded on each end, we found that if we changed the "corner acceleration" (under the Machine Control tab, in the Cutting Motion Section) to 0.05 - 0.08, the letters cut out very clearly, but now it is cutting the metal too hot and we are getting blueish coloring around the letters and a ton of dross on the back. We have never had an issue with this much dross on the back, it is almost fusing back to the piece of metal.

We attempt to increase the Cut Speed above 255 (because we know it is cutting too slow to have these blue coloring and increased dross) it does not change the speed of which it actually cuts. We attempted to do a drastic cut speed increase to 400 and it still cut out the lettering, but the amount of dross did not change, without changing the actual cutting speed at all.

So increasing Cut Speed in the system doesn't change with the "corner acceleration" set to anything at all. we attempted to use many different settings in the "corner acceleration" tab. and when we went about 0.1 the lines became more wavy again, but the dross cut back drastically.

The torch ht is set a the following for Pierce Ht - 0.15, and cut ht - 0.047. We adjusted all the way up to cut ht of 0.07 with no change at all. cut ht of 0.047 is our normal cut ht.

Any help would be appreciated!
Thanks, Jimmy

[Capstone]

My 2minute diagnosis... you've got mechanical slop where the sharp turns are causing shudder in your cuts as the torch comes out of sharp turns.

That said, the first thing you need to do is use book settings for cut height all the time. .15 pierce .06 cut. Those are the correct heights. Hypertherm has spent thousands of more hours than all of the other mfr's put together to prove that their cuts heights are accurate and there's no other "normal cut height" that's correct. The only reason those heights would change is if your automatic Torch Height Control adjusts your DRO height based on matching the voltage to keep the absolute .06 torch height constant once you've established the voltage at that cut .06 height to account for metal warping.

If you're already making speed adjustments to the cornering then I'd refer again to my first point. Your gantry must have some kind of sloppiness.

[jimcolt]

The 510 should have the same cut characteristics as the 4 x 4 PlasmaCam, assuming all of the motion related settings are the same. I suspect incorrect height as well.

1. Are you using the ohmic sensing function? If so, are you checking the box on "auto zero z axis" and "auto zero arc voltage" after every change in settings? This calibrates the z axis. If you do not do this...when you set the height to the book spec of .06"....the machine will set it to something else.
2. Shut the height control off, program a 4" rectangle, set the height at .06" with a feeler gage...then cut at the optimal book speed (or whatever speed you had good results with on the 4 x 4 ). Does the part look better?

Jim Colt Hypertherm

[tm america]

Well the samson and plasmacam are both designed the same so this means they are using the gear track as part of the linear rail I.E. only one wheel on one side of the gantry and two on the other plus it is riding on a powder coated surface.. so you are using a non smooth surface as your rail .Which means any bumps in the powder coat or play in the gear track-gear mesh are gonna show in the cut..Not gonna get super smooth cuts with it no matter what you do but making sure the gear track and pinion gear are clean will help also make sure your powder coated surfaces that the guide wheels ride on are not chipped or flaking?..The extra dross in corners is usually caused by the machine not being able to maintain speed-slowing down and then re-accellerating in corners....Not much you can do with this..

[jimcolt]

Plasmacam does not use the gear track as part of the linear rail, rather, it uses cam follower bearings to ride on the gantry and frame surfaces. I agree that over time the surface gets a bit rough....which shows as a bit of roughening effect on the cut edge. Simply clean the edge, sand out the imperfections and back in business. Plasmacam has very high acceleration / deacceleration capability (servos, lightweight design)....it is adjustable in the software. If you have excess corner dross simply increase acceleration. If too high you will see some waviness on small features and holes, too low and you will see corner dross. My current Plasmacam DHC2 has been in moderate use for 10 years.....about as maintenance free as you could have! Contrary to those that are not familiar with the Plasmacam cut quality....here are edges on 1/2" steel, as cut! Jim Colt

IMG_2948.jpg (51.09 KiB) Viewed 1538 times

[Bobcat320]

Jim,
You just answered the question I had on my machine as well. Couldn't figure out why I was getting the wavy cuts even though I had the cam followers clean, tracks and gears clean, etc until I went back and looked at the edges after your post. Sure enough, cleaned them up and now it is back to perfect!