bodger: (Kim Possible)
A worry with the laser cutter is fumes from the cutting condensing on the focussing lense, leading to all sorts of badness. Additionally, cutting materials like acrylic is improved by having an air stream to blow the melted plastic away. Accordingly, I decided to add air assist to the laser cutter. In short, this consists of adding a nozzle to the cutting head, and running an air line to it. Lindsay Wilson did a similar modification.

First, I had some shopping to do )

Since the new head will require a new mirror bracket, and another method to hold objects to be cut at the correct height, I haven't yet given the new air assist system a tryout. I'll need to realign the optics once the new mirror mount is fabricated and installed, then I can give the new air assist system a test drive.

bodger: girls in photo booth (photobooth girls)
Now that I have the EiBot board running the steppers, I'd like to have it turn the laser on and off too. Normally, the Egg-Bot this board was designed for has a servo to raise and lower the pen. This is controlled with a pulse width modulation (PWM) output. But I needed an on/off signal to feed to the laser. Looking at the documentation, I noticed references to a solenoid output, which sounded like just what I needed. Looking at the earlier versions, I could see the circuitry to drive the solenoid, but that circuitry isn't present on the board I have. Looking at the schematics, the I/O pin that drives it is now used for another purpose. I downloaded the firmware source code and tried to dope out what the current code did, but I wasn't able to figure it out. So I sent a note to the designer and asked him about it. He sent back a prompt and helpful reply, stating that the RB4 output should have the solenoid signal. I soldered a header on the appropriate pins and hooked up an LED (and current limiting resistor). At first, I had the LED hooked from +5V to RB4, but that voltage isn't supplied by the board when it's running from just USB, so no joy. So I hooked the LED between RB4 and ground, and sure enough, it followed the pen up/pen down state.

Sweet! )

bodger: xkcd android girlfriend arc weld cherry stem (arc weld)
The controller board that the laser cutter came with is designed to connect to a PC with a parallel port. I planned from the outset to replace this. The board I chose to use instead is the EiBot Board, a derivative of the UBW (USB Bit Whacker) board. This board was designed by Brian Schmalz for the Egg-Bot, a little robot for plotting on eggs, lightbulbs, and other small round objects. It's available from Evil Mad Science and SparkFun.

My interest in it was as a stepper motor driver I could control via USB from any modern computer (it appears as a serial device, and it is controlled by sending it simple ASCII commands).

The trick is to connect the EiBot board to the laser cutter )

bodger: (What terrible problems you have)
I didn't get a reply to my email for a couple of days, I assume because they were celebrating the New Year. Then I got a note reading:

1. NOw we comfirm your machine is 110V

2. Please check the laser tube has the broken or not inside.  and then tell us, because we think it is mostly the laser tube broken

Much apprecaite

I explained that the laser tube was intact, and I was convinced that the laser power supply was broken. They replied:

Can you please return the problem laser power supply and we will send you a new one

OK?

So I removed laser power supply from the unit, and figured it was worth a look before sending it halfway around the world for replacement. Since the supply appeared totally dead, not even the fan running, I suspected the problem was something pretty basic, and perhaps something I could fix.

So I took the cover off the power supply, and found this:

It's unplugged!

The power supply had an internal connector that was unplugged! It is a locking connector too, so it had never been fully engaged at the factory. I plugged it in firmly, buttoned up the supply, re-installed it in the cutter, powered it on, and the fan spun! Thus encouraged, I fired up the cooling pump and hit the test button. Nothing. Maybe the tube doesn't strike at minimum power. I turned up the power a little and tried again.

It worked! )

I did a few other tests, and determined that the laser was emitting plenty of power (even unfocussed, the beam burns through a sheet of paper immediately).

I wrote the manufacturer and explained that I had repaired the power supply and wouldn't need a replacement.

Next step is to replace the control electronics with something more useful. The existing controller only works with nasty ancient software on an MS-DOS PC with a parallel port.

bodger: http://hyperboleandahalf.blogspot.com/ (Bap)
I decided to buy a cheap Chinese laser cutter, with the intention of replacing its electronics so I could use it with a Macintosh. It is intended for use with a DOS PC with a parallel port, and comes with DOS-only software. I asked the vendor if it was available without the software, and found it would be only $40 cheaper. The vendor also stated the unit would not operate without the software. Yeah, right.

I elected to buy it from the eBay listing, even though it cost me $40 more, so I'd have the eBay feedback process to use as leverage if the unit was DOA. I told them I preferred the engraving software, as that seemed like something I would be able to resell. I also told them I wanted a 110V unit.

When the unit arrived, it showed up in two boxes completely covered in yellow tape, pretty banged up by EMS/DHL. The small box contained the smoke fan, which was a 220V, 50Hz unit (oops). Its motor was also loose on its mounting. It also contained the software and some clear plastic tubing.

The large box contined the laser cutter itself, double boxed with styrofoam spacers. It also contained the (crushed) smoke vent pipe, an aquarium pump (for cooling the laser), a UK style power cord, two UK-US adapters, and a combination "surge suppressor"/ adapter with no ground prong.

The laser cutter was in fairly good shape after its journey halfway around the world. The orange plastic viewing window was cracked (no big deal, I planned to replace it with a clear one, the orange plastic is of no benefit for a 10.6µm laser, it just looks cool or something). There was a loose screw rattling around, and the fuse had fallen out.

The laser tube was intact, but the water cooling channels had some cruft in them (so much for "use purified water"). The water tubing also had random cruft in it.

I hauled it down to my lab, rounded up a bucket and US power cord, hooked everything up, and turned it on. The fan spun up, and the steppers zipped to their home positions. So far, so good. Then I pressed the "laser enable" button, and the "laser test" button. No result. No glow in the tube, no current on the current meter, nothing.

So I had a good look at the innards. The unit has two power supplies, one for the logic (and fan), and one for the laser. The logic supply had a sticker warning "make sure switch is set for the right voltage", and pointing to one end, where there was no switch.

I tried powering it up with the electronics access door open, and could see that the laser power supply fan wasn't turning. I got a voltmeter and determined that the laser power supply was indeed getting power. I also measured its 5V control output, but that only yielded 0.69V. Looks like either the laser power supply is a dud, or perhaps it's a 220V one.

The unit was packed with a polite note requesting that I contact them if there's anything wrong, not to leave negative feedback. I'd do this anyway, naturally. So I sent them email detailing what I'd found. We shall see.

I got back a response:

Dear friend

1. YOu machine is 110V verison and also all the accessary is 110V. please do not plug to 220V or it will damage

2. can you please check the back of the machine and see it is mark as 110V or the 220V

I replied that the machine is marked 110V, the laser power supply still doesn't work, and asking what to do next. No reply yet. I have found the power supply manufacturer's website.

April 2016

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