Engraving on large machine

(george) #21

I do have some play. Enough to account for the resolution. But the offset is very consistent, so I get stuck thinking it can be addressed in software.

I did buy a new head, but I need hardware to mount in on the gantry. I’ll take a look at that.

Also, how tight should the belt be? Maybe I could lessen the slop tightening the belt a bit. Just don’t want to go too far.


(Nigel Conroy) #22

this might shed some light on that.

(Nigel Conroy) #23

This one may also be of interest

(Nigel Conroy) #24

I’m going to stop linked videos in case I shouldn’t be! but he also speaks about some interesting points in Learning Lab 117 (you can skip to approx min 35)

(george) #25

Fantastic videos, thank you! I’ll watch in full tonight when I can focus and digest.


(george) #26

I want to spend some time on the mechanical. Maybe fabricate the bracket to mount the new head. I see a lot of slap in the belt driving the Y axis also. Surely enough to affect cutting and engraving. I may look into mounting a constant tension pulley, like you find on motorcycle drive chains and belts. Slapping robs power and speeds wear.


(Bo) #27

I can’t say anything about your machines, but I have a 6090 and 1390 in 100W and 130W and they cut and engrave flawlessly.

There’s no issue with the mass of the gantry or head - the motors and drive are sized correctly.

Fine detail is no problem.

No issues with differing focus across the working area - I guess a lot of the 380kg is in steel framing.

Have you considered that there are aspects to your machine’s design that are sub-par?

Things to look at: how many power supplies have you got? Do you have a seperate 36v or 48v psu just for your steppers? What steppers and drivers are you using? Are the drivers set correctly? Are the steppers adequate for the task?

Shimming or otherwise adjusting your bed is the very last step I would take and only if you can prove parallelism of the beam path is out, rather than there being warpage due to the machine not being square and flat to the floor. On a heavy machine that doesn’t have as good a frame as it could, being one or two mm out can be enough to induce enough twist to make your beam-to-bed look like it’s wrong, when it’s really torsional forces from being out of whack.

(Bo) #28

Just finger-tight. You need to be tight enough so the tooth can’t ride up the shoulder of the cog on the pinion. I only ever adjust by pulling with a couple of fingers - any more and you risk introducing unwanted tension.

(george) #29

Thanks! It’s very encouraging to know your large machines are engraving fine detail.

I mentioned that I have very little point of reference, so I’m attacking this somewhat blind and evaluating what I can see and measure. I can see that the laser head has too much play and that there is a lot of slap in the Y axis belt when alternating motion. Whether addressing those things will cure the engraving shortcomings remains to be seen.

I had read that large machines are not as well suited for fine engraving and deduced that was part of my issue. Perhaps wrongly. More accurate to state might be: poorly designed and/or under-spec’ed large machines will have issues with fine engraving. To answer your question, I have considered aspects of my machine are not up to par. In fact, it was apparent from the first power on. And, I’ve been upgrading parts from day 1. I suspect that will continue. LOL

My steppers operate on a 24V power supply. But it also supplies the controller.

I’m not sure what the steppers and drivers are, I’ll note this tomorrow.

I am certain the bed is not level, focus varies a lot over the span of 1.26 Million sq mm (did I do that math right? 1400 x 900mm). But the front half and left-most 2/3 is fairly level and consistent.

I am systematically troubleshooting this machine as time allows. Today I had zero time to dedicate. So, I’ll continue to research and reach as much as I can. Always more productive when I go back at it with a plan and checklist.

Going back to my lack of reference: it would be very helpful to know what parameters I should be able to operate at. I am going strictly from trial and error.

For example, I found the X and Y axis acceleration settings set at 3,000mm/S for engraving. The simple rectangle test revealed wavy horizontal lines. I lowered by a factor of 10 (300mm/S for each) and instantly had straight lines. Noted, but is this an indication of a problem and the machine should engrave fine at 3,000?

With zero support on this Chinese machine I feel I’m left to my own devices. But, maybe not! Would you kindly share parameters (speed, power, acceleration, offset etc) that work on your large machines for fine engraving? Give me a target to shoot for. Just a reference will help me identify bottlenecks and shortcomings. Then I can spend more money upgrading this behemoth!

Oh well, I’m all in and I’m learning hard lessons. So long as at the end of this journey I can design and fab the parts I need it will all be worthwhile.


(Anthony Bolgar) #30

You should be able to engrave with a 100W+ tube, however, you will never get the fine detail a 50 or 60W tube can produce as the dot size is larger on the higher powered tubes. This can be mitigated somewhat with the use of a compound lens setup to reduce the dot size.

(george) #31

Very good to know!

I installed the 38.1mm lens and the dot size is much smaller. In the ramp test I measured a cut that was .2mm wide.

The ultimate goal here is to engrave control panels with text as small as 3-4mm tall.


(Bo) #33

Sounds like a very budget machine.

You could put in an additional 350W 36V psu and significantly improve stepper performance. Leave your 24v unit powering the rest of the electronics.

I can’t give you any settings - machines are crated and in a container awaiting shipping - we’re moving. But, 3,000mm/s is 3M/sec and probably way outside the envelope of what your machine can achieve.

My big one uses closed-loop steppers at 48v and I doubt I’ve ever gone over 500mm/sec

Could it be that you’re just wildly outside your performance envelope?

(Bo) #34

.2mm is wide for such a small lens. I would expect to see another decimal.

(Bo) #35

This may offer a starting point for feeds and speeds: https://nova-labs.org/wiki/_media/equipment/hurricane-charley-material-settings.pdf

(george) #36

Ok, noted. I should specify, I measured a .2mm cut in 3mm Birch ply. Not the actual diameter of the beam.


(george) #37

Sadly, it is very budget. Just over $4,000. on Ebay. Lesson learned, over and over.

I’m definitely limited by the performance now. If I can improve it, great. If not… it will be relegated to cutting my girl’s craft stuff.

In the rectangle test: 300 accel. in Y axis yielded straight lines. 500 yielded wavy lines. So that’s the current threshold. This is acceleration parameter in vendor settings, not the transit speed.


(Bo) #38

Wood’s a bugger for measuring. I cut notches in acrylic and subtract the kerf/2

(Bo) #39

I don’t think I’ve ever touched acceleration, etc. why? Is it too slow?

FWIW, my 1390 with Reci W4, Ruida, closed-loop, etc. was US$3800 to my door, plus 5% tax.

Nothing I’ve seen on eBay has impressed me and all of it was more expensive than buying the equivalent direct.

(Bo) #40

Value for money, adding a stepper PSU would probably give a great return.

Assuming you’re in the USA, a MeanWell NES-350-36 or NES-500-36 is a cheap upgrade and will make it all run a lot better from a motion-control perspective: https://www.amazon.com/Enclosed-NES-350-36-MEAN-WELL-Switching/dp/B06WVT5ZY7/ref=sr_1_3?keywords=NES-350-36&qid=1557884217&s=gateway&sr=8-3

(george) #41

Great, thanks. I’ll look at my motors tomorrow and see how much current they require. Surely this machine would benefit from the upgrade. Seems like a no-brainer.