Ben's 2.x Laser Build

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Re: Ben's 2.x Laser Build

Postby BenJackson » Sat Sep 10, 2011 11:53 pm

My laser finally cut its own electronics tray:

P1000099.JPG


I should have put a bigger space behind the DIN rail. I forgot about how big the relay module Bart suggested for the blower was. I actually had to move the 24V PSU to be able to snap it onto the rail. I also pre-wired that side since it's not really accessible anymore.

I'm sure the neat freaks among you will also note I didn't re-cut the wire to fit the new layout yet. I figure when you do something like that you guarantee something will come up to make you need to move stuff around.

Out of sight behind the huge relay is a small terminal block that provides a hookup for the extended laser ground lead with a 1R sense resistor inline and two terminals to hook up a meter if I ever get a permanent one.
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Re: Ben's 2.x Laser Build

Postby BenJackson » Mon Sep 12, 2011 12:21 am

I had an "aha" moment about where my positioning error was coming from in my EMC2 rastering setup. I fixed it and my 500mm/s test patterns finally look great. I redid the Timbers logo on different plywood (much thicker top ply). The other stuff was very thin veneer on a balsa (?) core scrap from my Makerbot.

So this version is 600 DPI in X and 0.1mm or 254 DPI in Y at 470mm/s (vs 80mm/s before) and closer to 30W.

Image31.jpg
Image32.jpg
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Re: Ben's 2.x Laser Build

Postby dwessels » Mon Sep 12, 2011 6:20 am

BenJackson wrote:I forgot about how big the relay module Bart suggested for the blower was. I actually had to move the 24V PSU to be able to snap it onto the rail.

Hi Ben,

What DIN rail relay did you get? Where did you get it from.

Thanks
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Re: Ben's 2.x Laser Build

Postby BenJackson » Mon Sep 12, 2011 6:37 am

dwessels wrote:What DIN rail relay did you get? Where did you get it from.


I asked Bart for something that could switch a blower. He sent me that 3-phase monstronsity. It makes a hell of a clack when it turns on! If you want the model number you can probably read it off the enlarged image.

My vague plan is to split the rear outlet, switch one side with the smaller relay (for cooling and air assist) and the other side for the exhaust blower.

At the moment I have everything plugged into a power strip and no power switch on the laser at all. I have a front panel rocker for it that I need to cut a new panel for.
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Implementing Frequency ala Epilog

Postby BenJackson » Mon Sep 12, 2011 6:44 am

In the interest of less charring on wood and clean edges on paper I am trying to replicate the Epilog-style "frequency" in EMC2. I wasted some time trying to figure out how to piece it together with existing realtime modules and then I discovered how simple it is to write new ones. EMC2 even comes with a tool to build them an install them. My implementation of pulse-per-mm controlled by "M3 Sxxx" is a ~40 line realtime component plus 1 stanza in the HAL to hook it up.

Right now I'm using 1/5000th second laser pulses (though that's really a random selection based on "5000" being Epilog's max, but that's 5000/inch, not 5000/sec). I did a few test cuts and it does seem to reduce charring on paper, but of course it requires higher power to make the same cut. I would really love to see a scope trace on an Epilog at various settings, but really all I care to recreate are "500" and "5000" and "5000" is just "always on", so if I can nail a setting for paper/wood I'll be happy.
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Blown capacitor on Pololu driver

Postby BenJackson » Tue Sep 13, 2011 5:02 am

I was lasing just fine last night before I shut down, but when I fired up today I had zero stepper activity. I further noted that not even the 5V fan was turning. Measuring across the 24V at the board I only saw about 2.5V. Luckily the PSU must have gone into current limiting because it seems to be fine.

I removed the PSU connector and ohmed out +24V to GND and got about 1R which means there's probably a dead short somewhere on the board.

Since I could do it without removing the whole interface board I started by pulling the Pololu drivers and sure enough the short went away. I ohmed out the VMOT to GND on each of those and found my Y axis was a dead short. I looked at it under magnification and noticed some solder balls (usually a sign of too much solder paste applied during manufacture). I ended up removing the primary capacitor because it looked iffy and sure enough it was a dead short. I replaced it with a handy junkbox .22u I had (later I measured the others at probably 4.7u -- probably doesn't matter much because Bart's mainboard cap is so close) and swapped that to the Z axis. Motion restored!
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Pulsed edge on wood vs continuous

Postby BenJackson » Tue Sep 13, 2011 8:14 am

Using 20 pulses/mm (about 500 PPI) vs continuous wave on 5mm plywood: Both pictures have the pulsed cut on top and the continuous cut on the bottom. One picture is with the grain and the other across it (for the surface plies). The color is more noticeable in person, with the pulsed cut being a more golden color where the continuous cut is blackened. The pulsed cut also has a much lighter smell (almost none).

Currently my pulses are 1/200th mm (5um) so that "200 ppmm" (about 5000 PPI) is continuous. This is just based on the Epilog setting. I haven't really tuned the setup. Both cuts were at full power and the pulsed cut was about 1/4th the speed of the CW cut to do single pass.

I also did some 20ppmm cuts on paper and the edge is barely browned and the kerf is noticeably smaller than the CW cuts.

Image35.jpg
Image36.jpg
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Re: Ben's 2.x Laser Build

Postby bdring » Tue Sep 13, 2011 2:46 pm

zero stepper activity


I had a Pololu driver fail in dead short recently. I did not do an autopsy, but I still have it. Fortunately the 24VDC P/S handled it well.
Bart
"If you didn't build it, you will never own it."
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Re: Ben's 2.x Laser Build

Postby BenJackson » Tue Sep 13, 2011 4:05 pm

bdring wrote:I had a Pololu driver fail in dead short recently. I did not do an autopsy, but I still have it. Fortunately the 24VDC P/S handled it well.


If you have soldering tweezers or a couple of irons I'd like to know if removing the main cap makes the short go away.

If so the ESR on your mainboard cap may be too high, leading to too much ripple in the small ceramic causing it to overheat.
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Re: Ben's 2.x Laser Build

Postby bdring » Tue Sep 13, 2011 9:07 pm

The main board cap is on the 5VDC line. The 5VDC power supply has short circuit protection, so it is not supposed to take down the 24VDC power supply.

The 5VDC current is quite low in the drivers and the cap is so close to the driver that I don't see it inducing ripple in caps on the driver. I think the cap that failed on your board was on the VMM (motor) line.


On my first use of Pololus, I was having issues where the laser could trigger a step, or some kind of jump in the motors. I tried to address everything that could cause that. The big caps were added as local storage in case something was causing the 5VDC supply to droop and cause a reset on the Pololus. That probably was not the cause, but it seemed like a good idea.
Bart
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