Serrations and Poor Definition - Another cut quality issue.

[spacenerd23]

Evening all,

Tried my best to troubleshoot alone and avoid posting but could really do some with additional input and thoughts now as I'm stumped.

I'm experiencing some poor cut quality, typically appearing as serrations/wavy edges/general poorly definitioned cuts. Photo examples attached. The serrations are intermittent and typically appear at the same time as a 'sputtering' sound from the plasma. In the first picture, you can see how part of the external perimeter is serrated, but other parts are not. There is no consistency to where this is on the cut, it will change each time I run the job. The sections of the perimeter where there are no serrations are perfect, no dross, good lag lines.

Example of current cut

Example of current cut serrations - 1

Example of current cut serrations - 2

I have had reasonable cuts previously, but i've never been 100% satisfied with the quality.

Example of previous cuts - better but not perfect? 1

Example of previous cuts - better but not perfect? 2

Example of previous cuts - better but not perfect? 3

I'm running a DIY table, RTECH Plasma50CNC, MyPlasm software. Air supply is clean and dry ('Drop-Out' filtered).

List of the things I've tried so far:

- Triple checked air supply, definitely clean and dry.
- Everything is tight. All the bearings are snug, the drive gears are double grub screws, and there is no backlash.
- The carriages travel freely in all directions when powered down. No tight spots.
- Slats are bent in a c-shape, and 'secured' in three spots and i've had additional weights on the work piece just to be sure. No slat wobble.
- I've made a spring loaded pen holder and tested on the machine - results look good (to me - thoughts please?) so i'm reasonably sure it's not a mechanical issue.
- The speeds that i did the pen test at, and have been trying to cut at are from the Hypertherm 45 manual (rough starting point, appreciate it's not a hypertherm) - 6600mm/min, 60% speed for anything less than 25mm, 1.5mm cut height, 3.8mm pierce height, 300ms delay.

Pen test results - 1

Pen test results - 2

Pen test results - 3

- I've lowered the water level in the table so it was approx 2" below the work piece. No improvement.
- I've replaced the work clamp and cable. It's clamped in one corner, directly to the work piece. No improvement.
- Throughout the troubles, I've changed from a used PTM-100 torch, to a brand new UPM-105 torch in an effort to improve cut quality. In both torches i've tried a full suit of new consumables. I've also switched back to the PTM-100 torch, neither are producing good cuts.
- I do have a THC module, i've operated with this off and on. No improvement. I've also disconnected the Z-Axis motor after setting the cut height to be double sure, still no improvement.
- I've re-designed the Z-Axis assembly to massively improve stiffness and prevent torch 'wobble' at the tip. Still no improvement

My next thought is the plasma cutter itself - do i push the button on a new plasma? This one was second hand to me when i bought it.

Another thought, when on the UPM-105 torch, i get bubbles blowing from the tip in-between/after cuts. Thoughts on water getting into the tip flashing off? Worth trying with the table completely dry? Do others see this?

Apologies for war and peace, but hopefully it helps covey where i'm at.

Some videos of the machine cutting:

UPM-105 torch -
PTM-100 torch -

Any and all ideas are welcome and appreciated.
Many Thanks,
Con,

[adbuch]

"Another thought, when on the UPM-105 torch, i get bubbles blowing from the tip in-between/after cuts. Thoughts on water getting into the tip flashing off? Worth trying with the table completely dry? Do others see this"

Bubbles blowing from the tip most definitely does not sound right. I would dry out your consumables, drain the water tray, and try some dry cuts.
David

[spacenerd23]

Morning David, I thought as much.

This morning i've drained the table entirely and performed a set of dry cuts using both the 'Old' and 'New' torches.

No improvement, actually appears to have made the cuts marginally worse with the washboarding effect almost all the way around the perimeter. The low pitch buzzing/humming/sputtering was present everywhere I see the washboarding.

[adbuch]

Perhaps the problem is with your actual plasma cutter machine. How does it do when you do some straight cuts by hand using a hand torch with a straight edge guide? I assume you are UK based judging from your plasma cutter brand.

David

[acourtjester]

First off I am not an expert, just another DIY builder, my comments are from theories I have and used on the tables I have built.
Here are 3 screen shots from your posts/videos that I have concerns about that may effect your problem.
Image 1 shows areas about your table construction I disagree with, I prefer a completely welded table base, yours is bolted together.

angled cuts 2.JPG (36.83 KiB) Viewed 489 times

Image 2 is the amount of stick out of the torch from its holder and the holder itself with a tall torch. Any movement of the torch cable will have an effect on the torch tip position.

anbled cuts 3.JPG (53.19 KiB) Viewed 489 times

Image 3 shows a taper in the cut top to bottom and since it appears in both directions your cutting height may be off. The Plasma stream is in a candle shape which does effect the taper by its height.

anbled cut.JPG (110.38 KiB) Viewed 489 times

You are doing exactly what is need to address your problem, looking at all areas and asking questions. I may not be correct but just things that can effect the types of problems you are having.

[weldguy]

Can you post images of a used up nozzle and electrode from your torch? If it is intermittent it could be moisture and/or oil in your air supply. What size compressor are you using? Do you drain the tank everyday? What are you using for air filtration?

[spacenerd23]

Thanks all for the comments and suggestions.

I don't have a hand torch for this machine unfortunately and yes, UK based. I've ordered a new plasma to be delivered tomorrow to determine if it is the plasma, I can always return it should results be no different. Gut feel is it's not plasma, and it's something i've done or am doing, but why not rule it out ay.

I am getting better results if i slow it down significantly, but this obviously comes with increased dross. The washboarding is still there. The below photos is the best effort from today. 2mm mild steel, cut at 45A, 3850mm/min, 60% speed for anything less than 25mm. The sample test came out acceptable, went for a more detailed cut and just gets ruined with dross/overheating. Is this a case of error-in-chair and not in machine?

Test sample:

Todays best cut

Todays best cut

Todays best cut

Detailed cut:

Dross

Dross

Am I just expecting too much from an R-Tech machine? Does anyone have any experience with 'book' speeds for the R-Tech plasmas? The OEM (from what I can find) doesn't provide any detailed cut charts as you see with other brands.

Acourtjester, completely agree with your observations. I would still rather stay bolted together for ease of assembly/portability, but if I was to build another one I’d make sure it was constructed a little more like the crossfire machines with a 3-point pocket type bolted arrangement.

What you can’t see from that picture is the water table has tabs welded to it front and back and they’re also bolted to the uprights - adding additional stiffness.

I had toyed with the idea of lowering the entire moving assembly as I’d considered the same regarding the height/extension of the torch. I think this is worth while effort so I’ll add it to the list to work tonight/tomorrow.

However for both of these points - the pen tests look okay? No?

Weldguy - photos below of the consumables I’ve been using today. Probably had approx 1hr cutting use?

Using a Clarke Boxer II, 14cfm 150Litre 3HP Belt Driven Air Compressor, yes it gets drained daily, using a 'Drop-Out' filter (https://drop-out.co.uk/product/do00300pab/) directly before the plasma table.

Used tips

Used tips

Used tips

[weldguy]

From looking at your consumable pics I would say that your problem could very likely be dirty air. The black stains are carbon deposits from the contamination in your air supply burning up. This will disrupt the arc and overheat your consumables and def cause the problems you are seeing. Better filtration will be required, the filter you linked to is fine for air tools to keep raw water out but will do little to nothing for oil and humidity.

[acourtjester]

I agree with weldguy on the electrode, it looks bad, I would use a white rag and blow your air supply through it for about 2 minutes. There should be no change of color in the rag from the air passing through it. Understand the Pen test is mainly to test for drive issues and or calibrations of each axis.
The cutting action of Plasma introduce other types of issues. There are many post here about air flow problems from bad "O" rings or nozzle deformations, THC causing torch bouncing, bad air are just a few. Keep going the "Aha moment" is close.

[spacenerd23]

Thank you both. Sometimes you end up in your own echo chamber without external input.

I've picked up a coalescing filter tonight and will get that routed inline with the compressor and will report back on the white rag test.

[SegoMan DeSigns]

I recommend the use of an automatic tank drain along with the new filter:

https://www.ebay.com/sch/i.html?_from=R ... n&_sacat=0

[Deezl Smoke]

From looking at your consumable pics I would say that your problem could very likely be dirty air. The black stains are carbon deposits from the contamination in your air supply burning up. This will disrupt the arc and overheat your consumables and def cause the problems you are seeing. Better filtration will be required, the filter you linked to is fine for air tools to keep raw water out but will do little to nothing for oil and humidity.

I have also found that electrode condition to be poor fit to the nozzle base, and/or poorly made hafnium.

[spacenerd23]

That automatic tank drain tickles the right part of my brain, i've put one on order. Thanks!

Wife has asked me to paint the fence today so no plasma progress unfortunately, maybe some looking at it tonight.

Does anyone have any reference pictures of 'good' consumables after a period of cutting? I got these with the torch when it bought it from Xtreme, so i'd have hoped they'd be good fit. Is there a good way to check?

[weldguy]

Don't have any pics but ideally what you want to see is a clean nozzle and electrode with nothing more than discoloration from heat, no carbon deposits or staining.

[spacenerd23]

Had some progress over the weekend. I believe the issue has been resolved *touch wood*.

I tried the new plasma machine - no joy. Issue was still there, will be returning.
I installed the new coalescing filter and performed the white rag test - all good, no dirty air.
I lowered the gantry by approx 4" to get the length torch protrusion down, and in the progress of doing so re-built each individual axis carriage too.

Thanks to all that have contributed. Time to get everything else dialled in!
Con,

[acourtjester]

Sometimes the finer details do take time but you will be happy when they are done. I have built 10 tables and some when smooth and others had small hick ups along the way. I am fighting a noise problem on the last one now but soon it will get my boot out the door. You will learn from problems and your posts here will help others down the road. Sometimes finding what is not wrong is a help too.

[weldguy]

Good to hear. A lower, lighter gantry, with a solid drive system is always a winner when cutting thinner materials. Curious to see how your latest cuts are turning out.

[SegoMan DeSigns]

That automatic tank drain tickles the right part of my brain, i've put one on order. Thanks!

I rigged mine to a separate switch (Light Style) so it can be turned off at night. When turned on it will start with a preset dump, this allows you to cycle it several time to take care of the condensate build up, then allow it to run it's program.. I recommend you run the dump line outside to cut down on the noise and the "Startled Jump Factor" associated with it

Glad your getting things resolved..