Ben's 2.x Laser Build

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Re: Ben's 2.x Laser Build

Postby BenJackson » Wed Jun 22, 2011 5:23 am

I wired up another pin on the AVR to TH so I could have gcode control of the laser. I cut myself a vanity tag:
IMG_0610.JPG
About 110mm wide, cut from the other side


Took several trials to learn what power to use to cut through. One early version turned to char.

I'm not sure how high you can actually set the knob for continuous cutting (i.e. how close to 5V) or whether the peak voltages are meant for pulsed operation, but there was certainly power to spare at about 1/4 turn at 500mm/min (about 20 IPM)

The other good news is that the glue in this 5mm plywood I got at home depot does not stink to high heaven like that scrap I tried before. Also, despite the fact that the random stencil font I downloaded is not really meant for true stencil work (the bridges are tiny, about 0.5mm) it came out just fine.
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Don't push the Y all the way back and close the door...

Postby BenJackson » Sat Jun 25, 2011 2:41 am

I was attaching the air assist nozzle after finally getting around to cutting deeper threads and removing all but one barb from the brass fitting. I wanted to be sure I wasn't blocking the beam so I started making test spots in all 4 corners. I was able to push the Y too far back because I did it where the laser carriage didn't hit the Z plate. When I started to close the door the door stop hit the right gantry plate and torqued my Y way out of alignment (like nearly an inch). It popped at least a few of the V wheels loose of the bearings in the process. I assume it spun the pulley on the threaded rod. I had to get out the Del Monte Gantry Alignment tool again.

So mind where the gantry is when you close the door! I might look at shaving down that door stop a bit just in case.
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Re: Ben's 2.x Laser Build

Postby bdring » Sat Jun 25, 2011 3:51 am

Seems like a bit of a design flaw. We have to look for a way to prevent that.
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Re: Don't push the Y all the way back and close the door...

Postby dirktheeng » Sat Jun 25, 2011 2:37 pm

BenJackson wrote:I was attaching the air assist nozzle after finally getting around to cutting deeper threads and removing all but one barb from the brass fitting. I wanted to be sure I wasn't blocking the beam so I started making test spots in all 4 corners. I was able to push the Y too far back because I did it where the laser carriage didn't hit the Z plate. When I started to close the door the door stop hit the right gantry plate and torqued my Y way out of alignment (like nearly an inch). It popped at least a few of the V wheels loose of the bearings in the process. I assume it spun the pulley on the threaded rod. I had to get out the Del Monte Gantry Alignment tool again.

So mind where the gantry is when you close the door! I might look at shaving down that door stop a bit just in case.



I took that door stop off... we don't need one on both sides fo the door. On my mods to maximize the y azis travel, the right side door stop hit the right side gantry plate, so I took it off. The door holds up just fine with only the left side door stop. Now if the gantry hits anything it is the z axis bearing holder and I set those so that they hit at the same time and dont' rack the axis.
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Re: Ben's 2.x Laser Build

Postby dirktheeng » Sat Jun 25, 2011 3:00 pm

Ben,

Hey, check out the code I am developing on github. I could really use a partner to make this work well and speed up the development. GRBL works, but it has holes that need to be fixed and is missing several options that would be very useful for operating a CNC and specifically a laser CNC. I've made several upgrades already and tested them on the laser. I have a development plan put together in the readme file.

https://github.com/dirktheeng/grbl

Do you think we can work together? What code are you using?
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Re: Ben's 2.x Laser Build

Postby BenJackson » Sat Jun 25, 2011 7:01 pm

Drik,

I have looked at your GRBL branch but not extensively. I am impressed by the GRBL code, having looked at several similarn gcode interperter firmwares targeted at 3D printers.

Right now I'm using a board I put together with an L297 + L298 stepper controller and an Atmel AVRUSBKEY development board. I happened to have the stepper parts from a long ago PCB I intended to make but never did:
IMG_0555.JPG
Prototyped stepper controllers with AVRUSBKEY


The firmware I'm using is Teacup which is a 3D printer firmware written in C (rather than built with Arduino and compiled as C++). Having examined most of the 3D printer firmware out there, Teacup shows the most engineering rigor and best software practices by far. However, it is not widely popular as a 3D printer firmware. I think this is mainly due to the fact that the principal developer does not actually have a working 3D printer, much to my surprise.

The structure of Teacup (and lack of reliance on Arduino) made it possible to port it to the at90usb1287 on the AVRUSBKEY. Using the LUFA library the board now connects directly to a PC via USB and shows up as a serial port. In order to jump on GRBL development I would have to do a similar port or buy another AVR dev board.

Bart has just shipped my new interface board so next week sometime I should be able to hook up to that and try PC control. Ultimately I'd like to reach "laser as windows printer" levels of convenience and I don't think an AVR + GRBL can fully satisfy that, but it may be part of the solution. I expect I'll try all the options just to learn about the pros and cons. I've got an old PC and an EMC2 live CD ready to go.
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Re: Ben's 2.x Laser Build

Postby tylerv » Sat Jun 25, 2011 11:32 pm

I'm using GRBL in the early stages of getting motion working on my laser, but I like the idea of the "laser as a printer" and will probably try to get there eventually.

Bart pointed me to LAOS Laser as another open source project to have a laser cutter act like a printer. It's worth at least a quick look, though I don't remember if they have any production code available yet. Just FYI.
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Re: Ben's 2.x Laser Build

Postby dirktheeng » Sun Jun 26, 2011 1:47 am

BenJackson wrote:Drik,

I have looked at your GRBL branch but not extensively. I am impressed by the GRBL code, having looked at several similarn gcode interperter firmwares targeted at 3D printers.

Right now I'm using a board I put together with an L297 + L298 stepper controller and an Atmel AVRUSBKEY development board. I happened to have the stepper parts from a long ago PCB I intended to make but never did:
IMG_0555.JPG


The firmware I'm using is Teacup which is a 3D printer firmware written in C (rather than built with Arduino and compiled as C++). Having examined most of the 3D printer firmware out there, Teacup shows the most engineering rigor and best software practices by far. However, it is not widely popular as a 3D printer firmware. I think this is mainly due to the fact that the principal developer does not actually have a working 3D printer, much to my surprise.

The structure of Teacup (and lack of reliance on Arduino) made it possible to port it to the at90usb1287 on the AVRUSBKEY. Using the LUFA library the board now connects directly to a PC via USB and shows up as a serial port. In order to jump on GRBL development I would have to do a similar port or buy another AVR dev board.

Bart has just shipped my new interface board so next week sometime I should be able to hook up to that and try PC control. Ultimately I'd like to reach "laser as windows printer" levels of convenience and I don't think an AVR + GRBL can fully satisfy that, but it may be part of the solution. I expect I'll try all the options just to learn about the pros and cons. I've got an old PC and an EMC2 live CD ready to go.


GRBL is a decent code... it isn't really awesome, but it's ok. It's a messy code and has some hangups, but I'm working through all of them and fixing a lot of poor programming. My goal is to have a solid all purpose g-code controller that I can run with my computer, but doesnt' have to. It will also run off of USB so I can use my laptop. It's going to take a while, but I hope to write a PC based program to communicate and display information and have a user interface much like MACH 3.
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Expanded aluminum table

Postby BenJackson » Sun Jun 26, 2011 11:11 pm

As mentioned above I got my aluminum honeycomb material from Morgan Haynes at HoneyCommCore. It''s 1/2 cell and .787" (20mm) thick. Here you can see me fanning it a bit with my fingertips: It's quite "soft":
IMG_0612.JPG
1/2 ACG NP UNXP .787 X 48 X 96


This arrives as a stick just over 5' long (since it gets narrower as you expand it). Reasoning that I need under 16" for the table (in the narrow direction) I sliced off 1/3rd of it (21") with my horizontal bandsaw. I supported the cut with some wood blocks and C-clamps. The cut came out very clean. The factory ends are actually ragged (looks like every aluminum strip was cut individually).

In a further effort to expand as little as possible I then took my 21" stick and split it down the middle, trying to make one 16x96 sheet into two 16x48 sheets. This is much trickier than simply sawing off part of the stick. You've got to find the middle, open it up, hold it in place with wedges and then try to snip the right hex segments. It's tricky to follow a hex in a straight line and easy to head off on a crazy diagonal. This came out fine, though. Given that I could get 2 tables out of the 1/6th of the stick I expanded I think you could get a full 12 tables out of one $80 stick if you were so inclined. Mainly I didn't want to have to store expanded material.

Expanding is harder than I expected because I hadn't thought about how it would want to get narrower. I placed the 1/6th stick so it straddled two 2x4's and used roofing nails to tack end loops to the boards on both sides. With the back board clamped to the bench I just pulled the front 2x4 until I couldn't really expand the sheet any more without the edge and end cells popping open. THe secured ends were not usable because they didn't expand evenly, but a large central area (enough for 2 tables) was fine.

Cutting it to shape was very tedious. I used ordinary scissors which were a pain because they had to be carefully opened just enough to go into each cell for every cut. Some spring-loaded aviation snips would make it much easier. I did two straight sides and then eyeballed where to cut the other sides but it didn't work out that well because the honeycomb itself isn't even enough to use as a guide. If I were doing it again I'd just use a sharpie to mark every single cell exactly where I wanted to cut.

To support it I used some 1/2" (1/16" thick) angle aluminum from Ace Hardware. I attached it across the longer table dimension so that the table can still slide in and out of the Z lift. To secure it I used M5x12 into holes drilled diagonally into the corners of the supports. With the supports cut I just stacked them up and held them in a drill press vise. It was actually very easy and works quite well:
IMG_0613.JPG
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Finding focal distance

Postby BenJackson » Tue Jun 28, 2011 4:36 am

I had been waiting for my interface board so I could do some "3D" gcode to work out the best focal distance. Then I realized I could just prop a bit of cardboard on a block and make a ramp to cut a pattern of lines on. Picking the finest line gave me 73.5mm from the top of the laser carriage, or about 70.5mm from the bottom of the carriage.

I imagine this is already posted here somewhere (perhaps in re the lightobject optics kit) but this forum is difficult to search.
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