Laser Etching issues with Hurricane Agnes (Gweike)

[Jonathan Bowen]

So I've noticed something with my laser that is kinda getting annoying. When I etch it seems like it is digging deeper on the initial edge. So letters and stuff are deeper around the edges but only on the one axis. It's subtle but might be a symptom of my other problem. So I'm trying to etch a barcode onto an anodized aluminum dog tag. The edges are not crisp and I've even noticed some waviness to the line. I decreased the waviness by decreasing the speed a bit. I'm also seeing some ghosting on a few experimental cuts. I'm not sure whats going on but I;d like to get this project off the ground. I've tried increasing the DPI as well as slowing it down and increasing the power settings but it's still not giving me a clean cut. Any ideas?

Thanks!

[Matt McCoy]

Can you post a pic?

[Clark Pace]

YOu know what. I have a similar problem on my Gweike. It slows down when I am vector cutting when it's going to change direction. So as it slows down more power his my material. I have contacted Gweike and am waiting for a reply.

[Dave Sheldrake]

Clark,

It's a read ahead function at higher speeds to prevent wobble on corners (or a way to make up for less powerful step motors) Change "Corner Power" in the dialog box to reduce power when changing direction

cheers

Dave

[Jonathan Bowen]

Here is one of the barcodes. This is a dog tag in anodized alluminum. Everything is a bit fuzzy like I'm slipping or something on each pass. The motor doesn't seem to be slipping or catching at all but I'm not sure. I've tried slower speeds but it still does not improve the resolution. I was cutting at 0.001 spacing. So that should be fairly high resolution.

[Allen Rawley]

A few suggestions to try:

1. Perform single direction engraving. In other words, select the check box to engrave only in one direction, then examine the results

2. In the laser engraving parameters, in the setup parameters, reduce the acceleration/deceleration for your velocity setting. There is typically a pre-programmed table that contains acceleration for various speed settings. Even though you reduced velocity (speed), a high acceleration setting that requires more force than the motor/belt can maintain may be causing unwanted belt stretch.

3. The numbers look unusual. The number five has un-engraved sections. Create several vertical rectangles using the rectangle tool (sized the same as the bar code) and perform the same test to verify that it is not the bar-code design file itself.

[Jonathan Bowen]

I tried single direction. I also reduced the X-axis accelleration from 1000 to 500. It took forever to cut this and it looks the same. The vector file is fine. I stopped at 1.5 hours into the cut.



EDIT: Could it just be out of focus? I have been having alignment issues and I might have it out of focus slightly.

[Kev Williams]

I don't think it's backlash, if it was you'd have a zig-zag on each pass. Something is loose or there's some 'interference' in the form of grit or something, and it has to do with the Y axis. As it's scanning down the X position is drifting. You may have a loose Y axis drive rod. You may have some guck on one of the Y drive belts or toothed cogs, maybe a bad tooth on a belt... One of the Y belts may be looser than the other, or have some stretch. Any of these will issues can cause one side of the gantry to move slightly less or more than the other side at given points, and this will affect where the beam is hitting. Check the gantry itself to make sure it's tightened down securely, years ago I found the left Y rail on my ULS was loose, it happens! Also check the short belt from the Y stepper to the drive rods.

The missing spots in those 5's IS weird. Loose tube, mirror or lens could cause your problems...

If the wobble repeats nearly identically, even at different speeds and resolutions, I'd be looking at the belts and cogs for damage or crud...

[Jonathan Bowen]

It can't be loose mirrors and I just tested it in a different place on the y axis. Also shift over on the Z axis. Same result. The right 55 is 0.001 spacing with 300 mm/s and 60% power (60 watt tube). The left one is 0.03 spacing with the same power settings. I checked the file again and it doesn't seem to be the problem. I also adjusted the z down a lot. I got it pretty close to spot on. I had the table way too high when diagnosing some power issues. Now I have full power again and forgot to move the table down. I did notice my kerf was a bit larger on my MDF stuff so I roughed it in to close. It didn't seem to have an effect.


2014-05-09 15.12.30.jpg
I did just upgrade my tube to a 60 watt. However not sure that would affect it unless the tube is having power issues. I have not seen that when cutting anything else.