Thoughts on material properties for fiber laser machines?

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09 Apr 2024 01:41 #297839 by shasse
I've been working on using QtPlasmaC to control a fiber laser machine, and we've had a few threads going on over in the "Hardware & Machines  Plasma & Laser" forum. I'm sure many of you are in both places. We had a discussion over there that raised the idea of materials properties for fiber laser cutting, and I wanted to start a thread here as that discussion seems to make more sense here.

If it would make sense to add fiber laser-specific materials properties it appears to me it is not as simple as just adding the materials to github.com/LinuxCNC/linuxcnc/blob/master...qtplasmac_handler.py. There are other things like the qtplasmac-materials converter and magic comments that depend on the current specific schema for materials. So it definitely should not be done lightly as it could quickly become a maintenance burden for marginal benefits.

I believe the current plasma material properties are:
  • PIERCE_HEIGHT
  • PIERCE_DELAY
  • CUT_HEIGHT
  • CUT_SPEED
  • NAME
  • KERF_WIDTH
  • THC
  • PUDDLE_JUMP_HEIGHT
  • PUDDLE_JUMP_DELAY
  • CUT_AMPS
  • CUT_VOLTS
  • PAUSE_AT_END
  • GAS_PRESSURE
  • CUT_MODE
I am currently repurposing CUT_AMPS as laser power 0-100% and that seems to work fine. I also actively use PIERCE_HEIGHT, PIERCE_DELAY, CUT_HEIGHT, CUT_SPEED, NAME, and KERF_WIDTH for their intended uses. I can see a potential to use GAS_PRESSURE for an actual gas pressure. Beyond that, I could see the utility of:

GAS_TYPE to choose e.g. O2, Air, or N2
FOCUS_HEIGHT if there are machines that have a motor-driven manual focus
and some sort of NOTES might be helpful to store the nozzle type, but since that might be useful for Plasma as well and does not exist maybe people keep track of that separately?

So for my current purposes I don't need any different material properties. But even in the long run, ignoring something like NOTES, fiber lasers could use CUT_VOLTS for FOCUS_HEIGHT. This leaves just a GAS_TYPE which is probably an edge case to automate within a machine.

I'm no fiber laser cutting expert, but I am wondering if there are people on here that understand the universe of potential materials properties better that could confirm that is all would be needed to effectively support operationalized fiber laser cutting.

If that is the case from my perspective I don't know if it would be worth the effort to add laser-specific properties. The juice might not be worth the squeeze. But I am interested in the diverse perspectives of the wise folks on this list.

I do think it might be worth considering adding a handful of generic custom properties to materials that would allow free-form handling of whatever custom material properties might be needed in the future. This could allow storing things like nozzle notes, gas type, etc. with the machine integrator making use of the custom properties in whatever way made sense, potentially even customizing the QtPlasmaC GUI with custom property names. That could get confusing as well though. I'm also interested in perspectives on that idea.

Thanks much!

Scott
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09 Apr 2024 11:48 #297860 by tommylight
Thank you for all the info you share here and on other topics, and for persisting on things working the way you need/like them, utmost respect.
-
Question:
Does the kerf width change so much as to be relevant when laser cutting up to, say 5, 10, 20mm ?
Gas types seem the same as for plasma cutting used on industrial machines, using those does change other cut parameters, like more speed or thicker material, although way out of hobby reach, i have a Hypertherm 3070 with O2/N2 capabilities collecting dust. :(
Focus height is a must for manual focus laser heads, probably cut_height works for that, it should.
As for material properties, adding steel, alu, stainles would be nice to have, although thin plates work with same settings, thicker stuff will probably need changes, especially alu.
I resorted to naming materials
03 for 3mm mild steel
13 for 3mm alu
And so on, makes it also easier to find quickly, rarely cut alu so those remain down on the drop down menu.
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10 Apr 2024 03:07 #297890 by shasse
Thanks for the kind words but my part of it is pretty easy. I stand in awe of the people that have given their time to make LinuxCNC and QtPlasmaC what it is today, and the people that given their time freely to provide support on these forums. I hope someday to be able to contribute in a more meaningful way.

We're doing the same like you do for naming materials.

I don't know the answer about kerf width changing, but my guess would be yes. I expect someone on here knows much better.

Focus height and cut_height are two different things from my perspective. Our laser head has a mechanical setting to change the focal length. Changing that does change what would work for cut_height, but the material thickness also matters. I've attached a pdf that a user taloot shared here a while back that shows some example parameters for different materials including independent cut heights and focus. Maybe focus height is not what it should be called.

Thanks!

Scott
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10 Apr 2024 14:26 #297930 by RDA
The kerf does not change that much. Your typical kerf is around 0.2mm and even in lets say 20kW and 40mm thickness is might be 0.4mm.
Maybe you want to add the nozzle type as a different nozzle would require different parameters.
And you are correct about the focus and cut height, these are 2 separate things. One is the focal point of the laser ”dot” and the other is a physical height of the cutting head.

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13 Apr 2024 14:59 #298171 by Uthayne
This video goes over all of the cut settings for Cypcut, which seems to be the main control software for fiber lasers.



One that stood out to me that would be beneficial to add in addition to the ones you've already mentioned is "Delay time" which allows gas pre-flow before the laser turns on. A lot of the other ones are already in Plasmac, which is nice.

Dynamic power adjustment based on speed would be nice, there's some good info already here: www.forum.linuxcnc.org/10-advanced-confi...-velocity-controlled

I have been thinking about trying to implement a capacitance calibration component. I switched from a 1.5D nozzle with O2 to a 1.2S nozzle for compressed air and my capacitance (voltage setting) was not working well. The numbers need to be tweaked and it would be helpful to have a somewhat automated tool to aid. I haven't tested how repeatable the sensor is, but it is possible that taking the nozzle on and off again could adjust the target capacitance tracking value. I haven't drained the water yet from my plasma table, and that is definitely affecting the readings.

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