Recently I designed and built the LittleBox, a DIY Laser Cut Raspberry Pi Powered PC. One major factor in its cost was having the parts laser-cut by a third party, so I began the hunt for a laser cutter of my own....
Step 1: Research!
Before I jumped in and bought a machine I spent some time looking at the options.
The LittleBox frame is ~35cm x ~26cm in size. Any laser cutter I buy must be able to manage those dimensions, plus some working space.
There are quite a few laser cutters available, from several different manufacturers.
And I contacted just about every single one of them, but unfortunately they were, are, outside of my budget. So I had to look elsewhere.
eBay is a great source for things, and I'm sure most of you will have used it in one way or another. It is often my first port of call when I'm looking for something and it is where I found myself looking at a laser cutter.
Type 'laser cutter' into eBay and there is one machine which fitted right in what my modest budget. Titled NEW CO2 LASER ENGRAVING MACHINE ENGRAVER CUTTER AUXILIARY ROTARY DEVICE 50W its a bit of a mouthful but the machine seemed perfect for what I wanted.
I did some digging and found a video on YouTube demonstrating a similar machine.
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Step 2: Uncrating.
The Laser Cutter arrives in a crate. The net weight is a little over 116kg, it's heavy.
Step 1 | Unpack it. There are several large bolts holding the wooden crate together, they need to come out.
Step 2 | With the panels off one can now get at the insides. Stashed within the cutter are all the attachments; air pump, water pump, pipes, cables, manual, and sealant. To help reduce the weight they have been removed.
At the time I didn't have anyone to help with the lift and being impatient I set about moving the Laser Cutter. I had a heavy duty trolly reclaimed from a Tape Library so I used that to wheel the cutter around.
I highly recommend you have someone help you. I ultimately had to get another pair of hands because the cutter had to go up a flight of stairs.
Step 3 | Move it to it's final resting place within your workspace.
Step 3: Installing the Cutter
For the Laser Cutter to run safely the cutter needs pressurised air, circulated coolant, and sufficient ventilation.
Luckily the Laser Cutter comes with all three, but they need to be installed before the cutter can be used.
Cooling& Pressurised Air
The laser is cooled by circulating water through the glass laser tube. The Laser Cutter has a flow detector whereby if there is no water flow the laser will not operate. The supplied water pump is designed for immersion in a water reservoir. In this case I have picked a 25 litre bin as my reservoir.
I will be using the heavy duty trolley that I used to move the Laser Cutter as a sub-assembly for the cooling system and air supply.
Step 1 | The bin needs to be well supported on the trolly. To help reduce vibrations, and noise, I will be resting the bin on a section of foam sheet. The foam sheet was used to pack the Laser Cutter for transport. I used some scrap wood as bracing for the foam padding.
Step 2 | The Air pump is mounted on two rubber brackets. Taking measurements from the brackets, and the pump, I have built up supports to mount the pump. The pump is bolted on using some of the bolts used to hold the crate together.
Step 3 | A feed pipe for the Laser cutter connects to the water pump. There is an adapter to do this but it needs sealing to make sure there is no complications with the water flow. They supply a tube of rubber sealant with the Laser Cutter. You'll have to supply your own tie-wraps though.
Step 4 | The return feed from the Laser Cutter will need a support. The last thing you'll want is for the pipe to fall free and then have water pumped all over the floor. I have modified an old wire coat-hanger. Luckily I had a metal bar with a similar diameter to the pipe. Wrapping the wire around the bar a few times make the perfect grip for the tube. I have angled the coil grip downwards slightly so the water is safely piped into the bin, and not on the floor.
Step 5 | Before connecting the air and water lines to the Laser Cutter it is always a good idea to make sure things work. I have filled the water reservoir about 3/4 of the way up.
Connecting the Laser Cutter to an outside vent is essential. There is a huge amount of smoke produced when cutting and making sure it is extracted correctly is a must.
The Laser Cutter comes with a length of 150mm (4") pipe. In my case this wasn't long enough so I had to pop down to the local hardware store and purchase a 1 metre extension. This then left me with the problem of extending the supplied pipe.
The solution was to modify a tin and use it as two connecting pipes.
Step 6 | I spend a few minutes hunting around the house looking for a tin of the correct diameter. I found a Tetley's Tea container of the right size. Firstly I cut the bottom off with a tin-opener. Then, using a sharp Stanley Knife, I cut it in half. Be warned, the edges will be sharp. To help protect myself, and the ventilation tube, I covered the edges with thick masking tape.
Step 7 | I chose to cut the supplied tube in half, and fit the extension in the middle. Using a sharp knife the tube was sliced in half. Into the first tube section is inserted one of the two tube connectors, it should go about half way into the tube.. I have wrapped some PVC Tape around the tube to help form a seal and hold the pipe in place. Repeat this with the other section of pipe.
Step 8 | The extension comes with two Tie-Wraps. Slip one end of the extension over the tube connector. Hold the extension in place with one of the tie-wraps. Repeat with the other tube section. The ventilation tube is now ready for use.
The ventilation pipe needs connecting to an external vent. In the room where I have the cutter there is no vent, only a window.
Step 9 | With the window open, and using some of the packing foam from the Laser Cutter I have filled in the space in the window frame.
Step 10 | Take a flower pot. Cut the top off. Make sure the ventilation pipe just fits over the pot.
Step 11 | Mark a hole in the foam using the flower pot top and cut out the hole.
Step 12 | Feed the ventilation pipe through the hole.
Step 13 | Place the flower pot top inside the ventilation pipe and secure it in place using a stapler.
Step 14 | Press the flower pot top, with attached tube, into the foam.
Step 15 | Re-fit the foam in the window frame.
Step 16 | Attach the other end of the ventilation tube to the Laser Cutter using the supplied jubilee clip. I used another wire coat-hanger to help support the tube.
Step 17 | Check all connections, cables, pipes and settings. Thoroughly check the entire Laser Cutter for obstructions, packing materials, and general detritus.
Step 18 | Power On!
The first time I power up the Laser Cutter there was some rattling from the access panels. To cure this I stuck some foam strip along the edge of the access panel hatches on the opposite side to the hinges. There's no need to put the strip all the way around the hatch, you might find the hatches won't close if you do.
Step 4: Optical Path Alignment
Naturally the first thing I did after turning it all on was try and cut something. Unsurprisingly this didn't work.
Step 1 | RTFM.
Step 2 | Cut something.
The problem was a simple one. The cutting head needs to be about 10mm from the cutting surface, and not 10cm like I was trying. The Laser Cutter comes with a strip of acrylic cut to the right height to help adjust the cutting table to the right position. I of course totally missed it the first time around.
But that isn't the full story.
There is something called Optical Path Alignment and it makes a huge difference to the cut.
The Laser Cutter uses a series of three mirrors and a lens. The laser beam needs to be aligned in the centre of each mirror and in the middle of the lens. If the alignment is out it can lead to some weird effects, like two laser beams for instance. This effect is demonstrated in one of the photos.
To fix this problem the laser tube must be aligned correctly. The starting point for the alignment is with the laser tube itself.
The laser tube produces the laser beam, the beam then goes to the first mirror. To have the beam dead-centre of the first mirror the laser tube needs moving. According to the instruction manual to find the position of the laser beam in relation to the mirror we must place some masking tape over the mirror aperture.
The Laser Cutter control panel has a button called Pulse. Pressing this button will fire the laser. If the button is pressed while a strip of masking tape is over a mirror aperture we can see the position of the laser beam burnt into the tape. Using this process we can adjust the beam to sit centre to all the mirrors.
Step 1 | Open the inspection hatch covering the laser tube at the rear of the Laser Cutter. Place a strip of masking tape over the mirror aperture, close the hatch. Pulse the laser.
Step 2 | Note the beams position in relation to the mirror. In my case it was some 5mm too high, and slightly off to the right.
To adjust the laser tube on the horizontal (left & right) is pretty straight forwards, loosen off the bolts and side the laser tube until it is centre, but to move the tube in the vertical plane (up & down) it is far more complicated.
The laser tube rests on several 8mm plates. To lower the tube by the required 5mm I'll need to replace one of the places with a 3mm alternative. Luckily I have some 3mm plywood sheets.
Step 3 | Take measurements of the plates as best as you can, transfer those measurements to a digital medium.
To save you some effort and time I have attached a copy of the file I made for the plates.
Step 4 | Cut out two plates, one for each mount point. I had to do some minor adjustments so the plates would fit. The file has been adjusted for you.
POWER OFF THE LASER CUTTER!
Step 5 | VERY CAREFULLY disassemble the laser tube mountings.
Step 6 | Remove a plate from each stack and replace it with one of the 3mm plates.
Step 7 | Reassemble the laser tube mount.
Power on the Laser Cutter.
Step 8 | Check the beam position on the first mirror with a new strip of masking tape and make any adjustments to the laser tube before finally securing the tube.
The mirrors have three adjustment screws. Each screw has a locking nut which needs to be released before you can make any adjustments and re-locked once you have finished.
Step 9 | Place a strip of masking tape over the second mirror and pulse the laser.
Step 10 | Adjust the first mirror so the beam is centred on the second mirror. Make sure to replace the masking tape after each pulse.
Step 11 | Repeat the process for the third mirror.
Step 12 | The third mirror adjusted the beam as it enters into the lens. Make sure there is no masking tape covering any mirrors. Position the cutting head at the correct height above the cutting surface and pulse the laser. If the mirror is aligned correctly there should be a tiny black dot. If it is not positioned right you might see a broader dot with what looks like an arc. The arc is the result of lens flare. Adjusting the mirror will fix the problem.
Particles from the burnt masking tape with inevitably find their way onto the mirrors. Any dirt on the mirrors can greatly reduce the lasers power. You will need to clean the mirrors before putting the Laser Cutter to work.
When everything is setup correctly the Laser Cutter performs very well. The cuts are consistent and the accuracy is good too. It has taken the best part of a day to align the laser beam but it has been worth every minute.
Step 5: 28 Days Later
I've been using the Laser Cutter for a few weeks now and there's a few things I have learnt.
Tip 1 | Raise the cutting surface off the cutting table. If the material you are cutting, in my case it's mostly plywood, rests on the cutting table the beam will bounce off the table and mark the plywood. There is also a lot of smoke and residue and leaving a gap underneath leaves room for air to ventilate clearing out the smoke and residue. There will be a build-up of residue on the table top over time but if you are raised off the table it shouldn't be a problem.
Tip 2 | The cutting surface must be as flat & level as is possible. Any deviation in height across the work surface can lead to inconstant cuts. Weigh down the cutting surface with weights.
Tip 3 | Before committing to a cut, run a simulation on the software to make sure it cuts in the right order. I use colours to help with the cut order.
Tip 4 | Experiment with power settings and cutting speeds to find the best configuration for the material you are working with.
Tip 5 | Monitor the water coolants temperature. I have attached two temperature strips to the water reservoir to check the temperature.
Tip 6 | Keep the rails lubricated. Use a cotton bud to spread some grease onto the rails.
Tip 7 | Vacuum out the bottom often. There will be lots of little bits which can gather underneath and sometimes they get sucked into the ventilation fan.
I have found that prolonged use can raise the coolant temperature close to unsafe levels. In the manual it suggests adding ice to lower the temperature. This does work, but only for a short time. I will be fitting a radiator design for cooling a CPU and I'll be matching it to a 120mm fan. I'll update the 'ible when the fan arrives!