Sad laser

Pro tip: Never accidentally run your laser without first turning on the water pump.

There was a loud crackling noise and now nothing.

Stay tuned for our next exciting installment where I attempt to source, fit and align a new laser tube.

It's only a 40W invisible laser beam triggered by 20kV and surrounded by water, WCPGW?

Slicing

There are several 3D printers built from mainly lasercut parts. I've looked at the printrbot-LC and the Prusa-i3/Graber-i3.

Unfortunately, they all have parts too large for my small laser cutter. Without modifying the mechanism, I can only reliably cut about 30x20cm. All of the designs also need 6mm thickness material, which I haven't tried cutting.

So, I'm experimenting with building the large parts in two 3mm layers with each layer sliced at different points.

So far, so good...

Storage

I have a lot of junk.
Having more storage for all my bits and pieces is useful, so I cut out and assembled some of these open top boxes. Originally, they were meant for 5mm MDF, so I scaled the design for the 3mm plywood I have.

Very useful.

Accuracy test

The DC-K40III is mechanically sound. But, the controller board and software aren't. Once I had Moshidraw working, one of the first tests I did was to cut out the spirograph business card to check whether the scaling was right.

Not bad at all.

Nexus 4 Charging Dock mk.1

To charge my Nexus 4 mobile phone while sitting on my desk, I designed a simple dock.
The USB cable is embedded inside it and held in place with a little glue.

http://www.thingiverse.com/thing:126459

It works, but the design isn't quite right. The notification LED on the phone is obscured by the base and it could do with being a bit bigger for stability. Next time, I may try to angle the phone a bit as well.

But, this is the magic of rapid prototyping!

Ratchet rattle/gragger

Here's my design for a spinning rattle, a bit like a traditional football rattle or a gragger.

http://www.thingiverse.com/thing:33910

To assemble it, you'll need some glue and a rod, I used a small section from a bamboo cane.

Warning - this thing is noisy and really irritating - it was banned from the house within minutes.

Othello (aka Reversi) mk. 1

Othello is a game I've liked for a long time. In the game, there's an 8x8 board and 64 pieces. Each piece is white on one side and black on the other.

Here's a design I made for a simple board and some pieces, etched on one side, plain on the other.

http://www.thingiverse.com/thing:124002

My first attempt at cutting a set of pieces worked, but I'm not satisfied.
I'm seeing two problems:

• The laser is firing slightly late when starting an arc path (hence the unetched gaps)
• The (old) air compressor wasn't working well and allowed some pieces to get scorched (this should now be fixed)

A toy cart

I was curious to see if I could build a working laser cut toy cart without needing any glue, screws or other materials.

The square axle works surprisingly well and pushes to fit with the wheel.

http://www.thingiverse.com/thing:124712

Better air assist

My lashed up air assist stopped fires, but wasn't very good.
I still got bad scorch marks on cut edges and the tyre inflator air compressor was very noisy.

What I needed was a better way to direct air at the cut. I found another user of the DC-K40III, who gave me a design for a 3D printable nozzle. The STL file is here.

Using Shapeways, I ordered a 3D print (cost ~20UKP, took under a week to deliver) and got back this:

It's now fitted to the laser head along with a small visible laser showing a crosshair.

I replaced the noisy tyre compressor with a cheap airbrushing compressor (AS18-2 from eBay).

Now, I get very little soot left on cuts and I can hear myself think.

Air assist

The DC-K40III is sold as a "laser engraver".

But, I want to use the machine as a laser cutter. It's more than capable of this.

Out of the box, I tried to cut paper and wood. Unless I was very lucky, the edges would begin smouldering or even catch fire.

To stop materials from burning, laser cutters need "air assist", a stream of air directed at the cut to blow out any flames and cool the material.

I rigged up a simple system using an electric car tyre pump from Halfords, some PVC tubing and cable ties.

Using this system, I get fairly good cuts without smouldering or flames. This is a small box cut from 3mm plywood.

MicroLoom

MicroLoom is a tiny loom I designed for weaving a patch of fabric.It would make a nice gift for a crafter. My kids enjoyed playing with it. There's the frame, a needle and a comb to help compact the threads after each line of weaving.

The design files are on Thingiverse http://www.thingiverse.com/thing:123412

MicroLoom can be cut from wood or acrylic (I used 3mm). I found that acrylic is much stronger, letting me put the frame under more tension.

More pictures on flickr.

Unboxing

For anyone considering buying a DC-K40III laser cutter, this is what you get in the box.

When the cutter arrived, it was well packed.

The laser tube had some padding inside the case. After removing, it was all in good condition.

 

The laser head was tied securely in place.

 

Supplied with the machine was an extractor fan and tube, US to UK mains adapters, water pump, software and dongle.

The front panel has a potentiometer to set the laser power. When it fires, the meter reflects the pot.

The controller board is for Moshidraw.

The laser power supply (the laser is enabled through an optocoupler at the bottom right of the picture)

The motors and controller board are powered from a 24V PSU.

A fool and his money

My laser cutter is a DC-K40III. It's a budget Chinese machine available on eBay.

I chose the machine for its low cost, it's half the price of any other new laser in the UK of similar spec.

Owning one of these is not for everyone:

• It is missing important safety features
• No lock on the lid to prevent opening the lid while running
• No lid switch to cutoff the laser when the protective lid is lifted
• The front panel is likely not earthed properly
• No temperature sensor/cutoff for water coolant reservoir
• Poor/non-existent seals in the casing (fire risk, smell of burning materials)
• The control hardware and PC software are locked to a USB dongle
• Both of the limit switches misfire causing the machine to grind
• X is a microswitch with a loose arm
• Y is an IR beam sensor which is poorly aligned
• The PC software is Windows XP only
• The PC software (and/or control hardware) cannot cope with complex designs and will randomly skip entire paths

However:

• It is mechanically good
• It is optically good
• It's hackable - it's just a CNC bed with a PWMable death-ray! What Could Possibly Go Wrong?
• I'm not dead/blind yet

I've owned the machine for about 9 months. Today, it works well enough for everyday use.

I have spent less money than buying a better laser cutter. But, it's still not as good and it's taken a lot time to get to this point. If you want a general purpose laser cutter for hobby or home use and have no interest in fiddling with it - do not buy a DC-K40III.

That said, I can't resist a bargain and I like a challenge.

I've run with the original control hardware, attempted (and ultimately failed) to replace it with an OSHW board. Currently, I'm using it with a "drop-in" semi-open control board - giving me a limited feature set, but good reliability.

I've added air assist (compressed air at the cutting point), joystick control and a laser crosshair for calibration.

This blog will record some my my experiences and projects with the laser.