Rippled cut edge???

nsmart

I have finally finished my 4x4 table and have it cutting corectly!! My issue now is there is a ripple effect on the edges of my cuts. Does anyone have any idea what causes this?? My air is the cleanest possible air that you can get from a air compressor so I know it cannot be that. I am using a fresh air breathing system and it rocks!!

ironman_gq

might be traveling too fast or have some chatter in your drive. I'm just speculating I dont have a CNC system but I have some experience with CNC equipment and if they are run too fast you can get a chatter and with a plasma that will definately translate to the part being cut.

nsmart

I am using the hypertherm suggested speeds and I even slowed it down by 10 ipm and I get the same ripples. What do you mean by chatter?

jeepsr4ever

Your Z axis is overshooting in Mach 3 for DTHC. Change your DTHC rate to 20% in the settings tab in Mach 3.

nsmart

I tried that and it helped some but I still get a small ripple. Can I lower that setting more to make it better?

jeepsr4ever

If you have a cut profile button in mach 3 open it and change the span gap to 8/4

jimcolt

Sure looks like a drive vibration.....if you put your hand on the torch body while cutting a part....you should be able to feel the roughness. As a test try the same part in trial mode without the plasma running....if it feels smooth then....then it may be some sort of a noise issue caused by the plasma power supply....though that is unlikely. While I am not familiar with your cnc, this can usually be tuned out with drive parameter settings such as gains, acceleration rates, etc. Another common cause of ripples like the ones pictured is with loose cutting beds slats that can get into an oscilation, however that usually only shows on one axis. Another cause of ripples can be THC (torch height control) related....if you are observing the z axis oscilating up and down rapidly...the the THC needs to be tuned. Jim Colt Hypertherm

Creepy

I'm guessing something is loose on your table. check your pinion setscrews, then check the Z head is tight on the vertical rail.

My build thread shows where to tighten. I'm gonna go with 100% fixed if you tighten the head. After running my table for months now, I had to dis-assemble the Z-head, clean the rail, and re-set the clearance to chase out that exact ripple.

easiest way to check - lower the Z to the work. Wiggle the head. If it wiggles, fix it. the bearings are on cams, you just move 'em over till there is no play on the rail.

Here is my documentation on the same looking ripples you have -

something is moving/not rigid. looking at the toolholder.

hhmm, floating head on Z is shakey, needed to preload these two bottom bearings on the rail. the one on the left is adjustable on a cam to preload.

frigged with that a bit.

I'm after doing this twice in 6 months, once right at start-up, like you are seeign now, and once a few weeks ago after a bunch of use.

Hope this helps.

wingnut165

When i ferst ran my table i was haven some what the same issue but i noted the z head hit some spots that would chater i fixed it with some water prof greas on the gear rack on the gantry seem to smothe it right out

Creepy

yeah, i've greased all the racks on mine as well. we need an update!

nsmart

Sorry I forgot to update the thread!! The settings solved the issue for the most part but I did tighten the ecentrics on the head as well and everything is good now. I am still getting a cut edge angularity on 1/4 inch plate but I will get it fine tuned. I have read numerous amounts of information from Jim Colt on getting the best possible cut edge. The Hypertherm 45 is kicking some butt!! I burned through a entire 4x4 sheet of 1/4 plate yesterday and am loving this setup! I am looking for a program that I can scan in a template and cut from that. I am not sure that is possible but it would help me alot since I have a friend that owns a 4wd shop and has tons of templates that he has made to cut with atorch and now he wants me to cut stuff for him. Also how do you save the material in sheetcam so that you can open it back up later and know where everything was already cut out of that sheet. Thanks guys for the help getting this thing up and running. Nick