Ben's 2.x Laser Build

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Re: Ben's 2.x Laser Build

Postby BenJackson » Tue Dec 25, 2012 6:20 pm

jv4779 wrote:I have been very happy with my kluge analog out method of getting the raster data into a HAL component. It has proved to be very reliable and easy work flow. How will you get the bitmap data into the FPGA ?

It will get into the FPGA via the HAL, so it's independent of what method is used to get the data into the HAL in the first place (where I used the streamer module and you used sneaky analog data).

Given that I'll have to modify LinuxCNC to make it work at all (there's no way to extend hostmot2 with pluggable modules) I could just add some way (similar to yours, perhaps) to get bitmap data in via gcode.
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Finally a red spot for aiming!

Postby BenJackson » Tue Dec 25, 2012 10:09 pm

I have long admired http://danielbauen.com/make/index.php/l ... n-extra-m/ but it's got some annoying features for printing on a home printer (mainly a shoulder on the hinge point, but also some unnecessary bridging).

I finally re-created the upper corner of the frame in CAD well enough to produce: http://www.thingiverse.com/thing:39188

The thing has all the files and a description of how to assemble, so I'll just leave these pictures:
P1000319.JPG
P1000321.JPG
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Re: Ben's 2.x Laser Build

Postby kbob » Wed Dec 26, 2012 12:08 am

Wow, Ben! I can't decide whether to be grateful or annoyed. You're doing exactly what I wanted to do, _again_, but you have a year's head start. (-:

This is awesome. I will steal your design post haste, since I just got the top door installed. Thank you!

Two questions. What laser module did you use, and how well does the laser return to position each time you open the door?
Bob
"If you didn't code it, it will never own you." (-:
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Re: Ben's 2.x Laser Build

Postby BenJackson » Wed Dec 26, 2012 12:41 am

kbob wrote:Wow, Ben! I can't decide whether to be grateful or annoyed. You're doing exactly what I wanted to do, _again_, but you have a year's head start. (-:

I'm dragging my feet as much as I can! ;-) I wanted to print one of these as soon as I saw it, but my attempts to edit the STL to make the original (Daniel Bauen's) version printable all failed in various ways.

kbob wrote:This is awesome. I will steal your design post haste, since I just got the top door installed. Thank you!

Two questions. What laser module did you use, and how well does the laser return to position each time you open the door?

I'm pretty sure my module is one of these: http://dx.com/p/red-laser-module-focusa ... m-5mw-5914

They also make other (non-focusable) modules which are sometimes superior (in line, cross, dot) but they are smaller so you'd have to tweak the design.

If the hinge is in the right place the arm registers against the beam it's attached to (on the front face). I've flipped it up and down with my finger to see if I can get it to mis-register but it seems to return fine. The motion is very smooth so there's no real chance of it getting hung up. The aiming isn't even super-critical.

My red dot is about 1mm from the actual laser hit at this point but that's close enough for me.
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Increasing Y travel by moving the Z drive

Postby BenJackson » Thu Dec 27, 2012 12:08 am

I'm thinking about ways to refit the Z drive so that the drive pulley is not in the way of the X carriage wheel at the rearmost Y travel.

Dirk moved his to the bottom: viewtopic.php?f=16&t=514#p3442

I'm thinking about an alternative which doesn't waste any useful Z travel. If I move the large Z pulley below the 2020 rail I lose about 30mm of Z travel (thickness of 2020 plus thickness of the fat part of the pulley). At that point I can still focus on paper-thin material on the surface of the bed (or even run the bed into the air nozzle). Now the Z motor can't just move 30mm straight down because it would hit the Y drive shaft. However, there should be room for it between the drive shaft and the back rail. So here's my proposal:

Take the existing Z drive plate (mounts a bearing to hold the Z shaft and the stepper motor) and cut it basically in half. This yields one bearing holder (basically like all the others) and one stepper mount plate. Move the big pulley from above the plate to below (trimming off excess 1/4" rod). Remount the Z stepper plate (pulley facing upwards) to the bottom of the back rail. The back rail is 2040 so the net motor pulley movement will be 40mm. The centerline of the large pulley on the Z rod also moved 40mm. Voila! Just need a slightly longer MXL loop belt (and any odd length can be compensated by offsetting the stepper plate).
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Increasing Y travel by moving the Z drive, continued

Postby BenJackson » Fri Jan 11, 2013 6:28 am

My Stock Drive order with new Z belts arrived so I went ahead and rebuilt the Z axis drive. I went from 285mm of Y travel to 310mm. The next obstacle is the bolts on the laser tube brackets. I actually just barely clear those (or just barely rub) but I've exceeded 12" which was my main goal. With low-profile bolts on the laser tube I could probably get another 1/2" at least.

In my previous description I talked about re-using the existing stepper plate, but I just 3D printed a bracket to mount the stepper to the back rail. I remember the top Z plate being a pain in the ass to align to the bottom (being a different size/shape than all the others) so I worked really hard to avoid taking it off. I had to take the lid off its hinges so I could slide the threaded rod straight up out of the machine. The other tricky bit was unbolting the stepper which was hiding partly under the end of the laser tube. You can see the clearances issues in one of the above pictures.

I ordered two belts from Stock Drive (since the S&H dominated anyway). One was 117 teeth (which I had estimated to be just enough) which is what I ended up using. The other was 125 which I could have made work by offsetting the motor mount. The P/N are A 6Z16-117025 and A 6Z16-125025

I am now beyond out of post-install T-nuts. The relocated X endstop is only held on by one bolt. Too many accessories!

New setup from below and above:
P1000325.JPG
P1000328.JPG


Endstop relocated:
P1000326.JPG


Reminder to remove the right door stop or you're gonna have a bad day:
P1000327.JPG
Attachments
ZMotor.zip
STL of the mounting plate.
(38.13 KiB) Downloaded 1072 times
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Re: Ben's 2.x Laser Build

Postby kbob » Fri Jan 11, 2013 7:40 pm

I wish there were a way that didn't require a new belt. I can think of a couple, but they are complicated or flimsy. Oh, well. A belt isn't that expensive.
Bob
"If you didn't code it, it will never own you." (-:
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Re: Ben's 2.x Laser Build

Postby BenJackson » Fri Jan 11, 2013 9:39 pm

kbob wrote:I wish there were a way that didn't require a new belt. I can think of a couple, but they are complicated or flimsy. Oh, well. A belt isn't that expensive.

With a 3D printer you could probably print a series of gears (one on the stepper, an idler or two, one on the threaded rod). In the end it was about $20 with S&H to get two $4 belts from Stock Drive.

Maybe I can work a trade with someone for my spare (long) belt for some post-install t-nuts (I'm sure ordering them from Misumi will kill me on S&H too).

(BTW you can move the drive to the bottom (with the stepper inverted and held up with spacers) and use the same belt, you just give up some Z travel. Honestly I've never needed all the Z travel but I might engrave boxes or build a rotary attachment some day. The advantage of my mod is that the lost Z travel is where the table is out of focus anyway)
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Lost steps for the first time!

Postby BenJackson » Sun Jan 13, 2013 12:06 am

I just cut some big circles to make http://www.thingiverse.com/thing:41958 and the ends of the cuts don't match the beginning. All my settings are identical from parallel port to FPGA, except the FPGA is actually able to make the 1us pololu pulses. I assume I will need to stretch those a bit, which shouldn't have any effect on my max speeds. I could also put a scope on the pololu if I want to do some contortion to check the signal quality.

I will add that having a red dot to position the laser made it much easier to efficiently use my material than ever before. I should have done that a long time ago!
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Re: Lost steps for the first time!

Postby BenJackson » Sun Jan 13, 2013 7:47 am

BenJackson wrote: All my settings are identical from parallel port to FPGA, except the FPGA is actually able to make the 1us pololu pulses. I assume I will need to stretch those a bit, which shouldn't have any effect on my max speeds. I could also put a scope on the pololu if I want to do some contortion to check the signal quality.

I made another spool with the timings bumped from 1us/200ns to 2us/400ns and no lost steps. Makes sense that you'd have to consider the waveform at the pololu and be less aggressive. The min step time on the pololu is around 30us anyway so the signalling time hardly matters.
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