Need help with rough cut

[duramaxer]

Does anyone know what can be causing cuts like this it's a home build table nema 23 hypertherm45 mach3 and sheet cam .cv is enabled . Torch height is set at .06. I checked the gantry and it seems to be solid no looser parts or play ...any input will help

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[plasmamatt]

Can you feel any vibration in your gantry? Also check to see if your torch is moving or vibrating too.

[flyinwilly]

try reversing your cut direction. Looks like swirl marks.
If you are using Sheetcam, check the reverse cutting box when you set up the operation.

Willy

[duramaxer]

I tried reversing the cut and I get same results it seems to be worse on arc or round cuts more than straight cuts

[Beefy]

Looks like the typical Z axis overshoot oscillation to me, I'll never forget when I first encountered it years ago.

Your first test is to switch off THC and see if the problem disappears. If it does I'd say that's a good confirmation that's where the problem lies. When using THC you have 2 settings - "THC Correction Speed" in Mach3 and a dead band setting in your THC.

Correction Speed is the speed at which your Z axis moves when under THC control.

Dead Band, hysteresis, or whatever your particular THC calls it, is a small voltage above and below the Set Volts where your THC "doesn't care".

What happens with this "jackhammering" is the THC corrects an either too high or too low voltage, and the Z axis is going too fast and shoots through the dead band zone. Thus the actual volts is now on the other side of the fence and the THC tells the Z to correct in the opposite direction, and the cycle repeats causing a jackhammering Z axis.

The first and easiest fix is to try lowering your Mach3 THC Correction Speed. This gives the Z the ability to stop within the dead band. Of course if your dead band (if you have that adjustment on your THC) is too small you may also want to increase that a little.

Good luck.

[duramaxer]

Looks like the typical Z axis overshoot oscillation to me, I'll never forget when I first encountered it years ago.

Your first test is to switch off THC and see if the problem disappears. If it does I'd say that's a good confirmation that's where the problem lies. When using THC you have 2 settings - "THC Correction Speed" in Mach3 and a dead band setting in your THC.

Correction Speed is the speed at which your Z axis moves when under THC control.

Dead Band, hysteresis, or whatever your particular THC calls it, is a small voltage above and below the Set Volts where your THC "doesn't care".

What happens with this "jackhammering" is the THC corrects an either too high or too low voltage, and the Z axis is going too fast and shoots through the dead band zone. Thus the actual volts is now on the other side of the fence and the THC tells the Z to correct in the opposite direction, and the cycle repeats causing a jackhammering Z axis.

The first and easiest fix is to try lowering your Mach3 THC Correction Speed. This gives the Z the ability to stop within the dead band. Of course if your dead band (if you have that adjustment on your THC) is too small you may also want to increase that a little.

Good luck.

I actually don't have thc it's a floating head . I don't remember it being this bad I use to get clean cuts not sure if it's a bad. Arch of consumables

[Steelman327]

Hard to tell from the pictures, but looks worse on arcs than straights. I would guess backlash compensation. I had a similar issue at one point.

[warrenb]

Change out your consumables and see what happens.

[tommylight]

That is due to one of your a is vibrating while moving so check for play on both axis, if using rack and pinion check the tooth aligment and proper seating, if you hav motors directly driving pinions you will have to put in reduction or use quality microsteping drives. If you have to much distance betven the x axis rails and the torch head try puting something under the sheet and do a cut as high (near the rails) as posible.

[duramaxer]

how did you fix it

- - - Updated - - -

Change out your consumables and see what happens.

that was with a new consumable haha

[BTA PLASMA]

If you are direct driving with no reduction it might be your not microstepping or your running too course of a step. You can also get that very edge from cutting too fast.

[duramaxer]

i think i found the problem after taking apart the motor i noticed the pinion gear had some weird ware marks so i compared it to a spare i had and after rolling it on the rack by hand i can feel the binding with the old pinion gear and the new one was smooth im gonna replace both the pinion gears tomorrow and see if that fixes the rough cutting edges im getting i will attach a picture so you can see the difference the right one is the new one .

[Alan Bradford]

Hi,
It looks like you hit on the problem. Any vibration of the machine will show up in the cut edge.
A good 'Vibration Sensor' is to attach a long (12 inch or longer) ty-wrap to the top of the torch lead, and do not cut off the end.
Any vibration the torch sees will be easily seen on the end of the ty-wrap. I attach one to each machine I rebuild to help align everything.
It works real good.
Another trick to see if your pinions are aligned properly (Perfectly parallel to the rack). is to put a piece of white paper into the pinion while it is running slowly.
When it comes out of the back side you can see the contact points of the teeth and rack.
If it is a uniform pattern, everything is good.
If the angle of the pinion is off, you will see dark spots where the teeth contact and light where the teeth are not touching.
Also make sure the pinion is at the right tension. too much and it will cause wear like you are seeing, and it will wear out the thrust bearings on the motor/gear reducer.
Not enough and it can skip, or change the part size from partially pulling out from the rack. (It changes the pitch diameter of the gear).
Hope this helps.