Engraving Frustrations

[Axeman]

So, I've been trying to get around these engraving issues I've been having but I cannot for the life of me figure out how to fix it. It's really limiting the work we can do (having a business related this equipment engraving gets to be pretty important).

All files are vector based, made in Adobe Illustrator and goes through Corel Draw to be converted to a clean and functional DXF before going into here.

Here's my settings along with the issue you can see. We eventually caved and went to unilateralism because the amount of errors (rather the odds of the errors showing up) increased with bi-laterailism. Yes it takes more time...but it gave more clean engraving results but not 100%.

Ignore the PWM and power thing...this laser has been weird from the beginning and that's basically where the settings ended up landing and working years ago and didn't want to bugger up all the saved templates with the power profiles to adjust it to be more accurate.

[Axeman]

If this is a DSP thing, I have a AWC 608. If it meant me getting a new DSP to solve this, I would...

Or maybe I need to add a gear reduction down to my belt drive? I can do that too. Just want some insight as to what might cause this...

Heck I'll even go find error reduction stepper motors with rotary encoders. Anyone have experience with those?

[Techgraphix]

I use closed-loop steppers and servo's quite a lot, but only from Leadshine.
Machines build with these will travel at least twice the speed. and no step-losses. They are worth using them.
But your problem puzzles me a bit.. The displacement is over more than one scan and not over the entire width, so i don't think it is a step you miss or a loose timingpulley, for instance..
That is, when you are lasering in both directions (Bidirectional)
What is the reason for this odd Um/pulse? Normaly there is a timingpulley of x teeth and a specified distance between them. for example: if you have a GT2 belt (Pitch=2mm) and your pulley has 50 teeth, every rotation of the stepper is 100mm travel. Your stepper needs the microstep times 200 (common for most normal steppers) to do one full rotation.. If the microstep is set to 1/16 it needs 16x200 = 3200 steps.
So every step wil move 100(pitch x teeth)/3200 = 31,25 um. This number more logical.
Some steppers do work better with an other edge (Falling/rising).. You might experiment with that.
Also something with timing is the PWM-frequency. Normaly 20000-25000 is fine.
Kees

[Tech_Marco]

It seems that some parts are getting loose. Check mirrors and lens make sure that those items are not vibrating. Since the speed you were using was pretty slow so I think you may have some parts got “really “ loosen. I don’t think it has anything to do with the DSP card

Marco

[Axeman]

Thanks for the insight guys...really appreciate the ideas.

I'll be replacing some of my parts in the my linear guide, that will tighten it up some. I'll verify that I don't have any loose bits moving around...

As for the steps, I think that was a product of the calibration sequence in the software rather than a formula driven attempt like how you laid it out. There might be a weird rounding error there that causes that? I dunno...I can have a look and try the more solid um step rather than the setup I have now.

I'll try the rising/falling edge portion as well.

Thanks again, hopefully I can kick this.

[Tech_Marco]

If you're using one of our DSP controller, regardless X7, 608, or T9, there is 'um' calculator built-in
To see 'How to', check out my 'FAQ' from the main page of this forum

-M

[Tech_Marco]

By the way, it sounds odd but the motor gear, the Y coupling, or the Y axis gear could be escaping (lost traction)
If the focus lens loose, it shake while the X swinging and problems like yours could happen . Just a quick thought coming from my brain while I was reading your post.

-M

[Axeman]

I have a suspcion is will be my Y-Axis guide rails. They are heavily worn out and need replacements...I wonder if they don't occasionally just 'catch' or 'hang' for just a moment to cause this jarring.

I really need to upgrade this old machine Anyway, I'll try it out and see if that solves my problems. Thanks for the troubleshooting, you guys are the best!

[Techgraphix]

They are heavily worn out and need replacements

That makes sense... Never thought prehistoric or worn out equipment was used...
Kees

[Axeman]

They are heavily worn out and need replacements

That makes sense... Never thought prehistoric or worn out equipment was used...
Kees

Well, not that worn out but I'm not going to dump a pile of money into this thing. I'm saving up for that new hybrid machine Marco got. Want to cut me some metal!

This machine is going on....6 years old now. Hand built, outside of this mechanical issue, it's worked exceptionally well considering what we put it through on a daily basis. I have all the parts for the axis replacements sitting in the shop but my wife made me promise to wait until she finished up a particular project before I started tearing bits out for maintenance

[Tech_Marco]

I'm testing the Hybrid system. So far so good on stainless steel at 1mm, 1.5mm. Although there was some slag, it did cut through and can be cleaned pretty easy. I was able to cut through up to 2mm mild steel with a 130W tube. There was more slag than stainless steel. Plus, it is harder to cut sharp angle like a 'star' without burned angle. I'm still working on it with different lens and focus point. Hopefully I should be able to finish test in this week. I'll post video and images for sure! Stay tuned.


Marco

[SWMS]

I use closed-loop steppers and servo's quite a lot, but only from Leadshine.
Machines build with these will travel at least twice the speed. and no step-losses. They are worth using them.
But your problem puzzles me a bit.. The displacement is over more than one scan and not over the entire width, so i don't think it is a step you miss or a loose timingpulley, for instance..
That is, when you are lasering in both directions (Bidirectional)
What is the reason for this odd Um/pulse? Normaly there is a timingpulley of x teeth and a specified distance between them. for example: if you have a GT2 belt (Pitch=2mm) and your pulley has 50 teeth, every rotation of the stepper is 100mm travel. Your stepper needs the microstep times 200 (common for most normal steppers) to do one full rotation.. If the microstep is set to 1/16 it needs 16x200 = 3200 steps.
So every step wil move 100(pitch x teeth)/3200 = 31,25 um. This number more logical.
Some steppers do work better with an other edge (Falling/rising).. You might experiment with that.
Also something with timing is the PWM-frequency. Normaly 20000-25000 is fine.
Kees

Kees. I’ve just set up my machine with two closed loop leadshines.

Got any tips for the software and tuning etc? It’s working fine but you can usually make it work better.

Thanks.

[Techgraphix]

Not much.. The only things i change in this drivers (with the Pro-tuner app) is the level for alarm, as i set them in series with the emergency-stop.
I did experiment with some values (like Ki etc) but did not notice any significant improvements.. the Default is just fine.
Kees

[SWMS]

Not much.. The only things i change in this drivers (with the Pro-tuner app) is the level for alarm, as i set them in series with the emergency-stop.
I did experiment with some values (like Ki etc) but did not notice any significant improvements.. the Default is just fine.
Kees

Cool. Thanks for that.

So I have one more question.

A bit of background first. My laser had a fire so whilst I had to rebuild it I upgraded to the leadshines. Money wasn’t exactly abundant so I stuck with a similar design to the original design. One NEMA 23 running the y axis connected by a belt and an axle.

I think I have a little friction problem in the y axis because I have a little wiggle on on the top right and bottom left when cutting a circle. It’s only minor but I can see it and it bugs me. With so many joined parts it’s all only as good as the weakest link and the axle seems a bit bent anyway. It’s ok but I think the guy that built it skimped on the parts. A lot of the original laser was made from Derlin and that stuff doesn’t like flames.

I would change the axle but that means spending £75 for a precision bar with bearings and new pulleys. If I spend another £75 I can have a new motor!

So I am considering in the future upgrading to two NEMAS on the y axis and ditching the axle.

Do you think this would be overkill? I am thinking I would see a much smoother machine. The two leadshines have already made a huge difference.

See the attached pic.

Thanks for any advice!