Project: Laser Cutter

[macona]

Ever since TechShop went under one of the things that you found was really useful was a laser cutter. We had two different ones. An Epilog Helix 45W machine and a Chinese built Rabbit with a 80 watt laser. The chinese made machine was actually pretty good. Not as polished as the Epilog but in some ways was actually superior.

So I decided to build one. Not going to start from scratch though. At my friends surplus store two Hamilton Starlet Microlab fluid handling robots showed up. Its kind of a light duty gantry robot that can do repetitive tasks. A company that builds electron microscopes and FIB machines had bought these to try and automate loading wafers into a SEM. Didnt work out. So they are basically brand new. Here is a video of one:



He had it for a couple months and there was zero interest in it. The software is proprietary and you have to go to them to take a class before they will even sell you the software. Even the company that made it would only offer a pittance for it. The other day it hit me that it would be perfect for a laser cutter. Its completely servo driven. Maxon motors throughout. Rexroth slides on the Y and Z axis and THK on the X. Travel in X and Y is a little more than 36" x24"



Pic of the main board. Uses dual Infineon processors. Nice 41v, 15A Astec power supply.


The encoder for the X axis, magnetic, .01mm resolution.

[macona]

The Y and Z axis. The Y uses a little pancake style brushless motor from Maxon. 30W, 40v or so. It is coupled to a spinning nut that drives it along the leadscrew. The lead screw looks to be 7 starts, 1/2" per turn, 1/4" teflon coated.


I got a couple servo drives off ebay. They are made by Elmo. Pretty neat little drive, they will run either brushed or brushless motors and you can control them with step and direction pulse inputs in positioning mode. They also have dual loop support so you can have a encoder on the motor and a linear encoder on the axis.

[Evan]

For a proper gloat you are required to tell us how much you paid.

Looks like they were intended for automated medical testing chores. Specifically, one particular type of test judging from the name. ELISA stands for Enzyme-Linked ImmunoSorbent Assay which is used to detect food intolerances and similar related disorders.

I'm not surprised that there was no interest if the machine is that specialized. ELISA testing is controversial and is only offered by a few labs nationwide.

[macona]

OOPs, screwed up here.

[macona]

Really didnt pay anything for it. I trade back and forth for shiny things. Fix something, get shiny... And this was definitely shiny! He did sell the other one to a friend of mine who is doing the same thing with it for $750.

The one I got is not the ELISA variant. The ELISA one has the barcode scanner, incubator and a few other feature. The machine itself can connect to a lot of other lab equipment through a bunch of accessory connections or through Canbus. The unit itself talks to the channels (What they call the pipette station) through Can. Each channel gets a 8 pin FPC ribbon cable that supplies 40v and canbus.

Got wheels mounted on the base this afternoon and gutted the old electronics that I cant use.

Mach3 can handle cutting but it does not do well with raster engraving. G-Code is just not capable doing it efficiently since it needs to vary the beam power (PWM or analog signal to the laser power supply). There are ways to do it but you get huge code that runs slow. There are a couple options. There is the controller used in the majority of the Chinese machines, the Leetro MPC6515. Its what was on the Rabbit we had at techshop. Worked OK, software was kind of klunky but did a good job. It outputs step and direction signals to the stepper drivers and controls the laser. Has a whole lot more I/O that isnt used.

There are two new controllers out there now, another Chinese one, looks similar to the old one, this is supposed to be a new replacement for the MPC6515:

http://www.lightobject.com/4-Axis-DS...oCad-P321.aspx

There is another one made here in the US. They did the hardware and software. Looks promising (about 2/3rds down the page):

http://www.fullspectrumengineering.c...serv2-40w.html

There is one more, and open source controller that used an XMOS uC. But I have not seen any activity since March on the project.

http://www.buildlog.net/cnc_laser/xmos_controller.php

[Evan]

There are ways to do it but you get huge code that runs slow.

Set the look ahead to 500 lines instead of the default which is only 20. That makes a big difference. Then set the Z to maximum acceleration and very high IPM and use an up/down counter on the Z step and dir output to create a digital power value. For direct analog control use a simple R2R ladder with 1% resistors and you can have N bits worth of power resolution with very few parts. When programming the Z set the steps per unit so that it equals a single bit change in value per unit and program accordingly.

I have a servo controller new in the box that I haven't even opened yet that I will be putting on my mill as soon as I have time. It should make a big difference to the Z axis. Eventually the X and Y will also be converted. I have also converted my little laser to direct electronic power control via Z axis output. Presently it is only on/off but that will change when I get a more powerful laser.


BTW, nice price. me am green.

[macona]

The servo drives showed up last week and I am now trying to figure out just how I want to do this. I had though of making a lifting table for the Z axis but now I am thinking of just putting the optics on the existing Z axis on the gantry. My only worry is the little Y axis motor will not have enough oomph, its only 30W. Ill just keep things light and see what happens. I can always throw in a small DC PM motor if I am not happy.

Also trying to figure out what I want for a controller. The Rabbit we had used the MPC6515. It was not that bad but the software sucked eggs. There were always little issues in importing files. Once you got it in it was pretty decent and had a few advantages over the epilog software. But I am mostly looking at the controller from Full Spectrum. That looks right now to have the most promise. Though I have been around the block with new hardware that never lived up to expectations (Gecko G100, SmoothStepper).

I am probably going to install a 40W tube in the top of the machine and wrap the beam along the outside to the gantry. Since I believe the length of the tube is longer than the longest dimension of the enclosure I will probably have to install it diagonally. I have a bunch of kinematic mirror mounts lying around waiting for something like this and some real light ones that will be perfect for the flying head.

I think the next thing I really need to do is sit down and lay out boards that breakout the 30 pin flat cables that it uses to get power to the X axis encoder and up to the gantry. Also need to find a source of the FFC cables, 1mm pitch, 8 conductor, 40" Long.

Heres a pic of some of the controls. The two servo drives, Fuse holders, SSR and timer for the exhaust fan and some auxiliary relays.



Here are some of the mirror mounts I have:

[boslab]

We have a similar beasty connected to an ICP spectrometer in the lab, takes a pile of racks and can be left alone for hours, anyway besides that its a neat well built peice of kit, the price was definately right! [the one over here was originally a little shy of £30,000, different make same idea]
That will make a fantastic laser cutter!
Definately a megagloat as opposed to a killogloat, [1 x starret=1 gloat] Evan as usual supplies us with some wisdom [correct as usual, that boy is impressive, his brain/brains must be backed up with data!]
good luck with the build and a nice photo by the way.
regards
mark

[macona]

I heard these were obscenely expensive. As much as $100k with the options. This one was built in Switzerland. Everything is laser cut, welded, and machined.

All of the pics here were taken with my iPhone 4. Pretty darn decent camera!

[dp]

I'm amazed you found an affordable 80W laser. I priced a 30W unit a couple years ago and nearly died from sticker shock. Looking forward reading more to do with this project.