Buying a Laser Cutter from China (Part Two)…

by Stephen Hobley on April 12, 2011

2012 UPDATE: Check out the new laser cutter I built from scratch here -> New 24×18″ CO2 Laser

Yesterday I wrote about the Laser Cutter / Engraver I received (40W Craftworks CO2 Laser Engraver&Cutter by strong_signstech). In this post I’m going to hook up the laser and do some initial system tests.

Laser Cutter

Having read the posts on Andy Slater’s blog it seemed a good idea to remove the lens and mirrors and give them a good cleaning. For this I used Isopropyl Alcohol and some lens-cleaning swabs. The instructional video supplied with the laser indicated I should use cotton buds – but these are far from “lint-free” so I thought that lens cleaning tools were probably better. The lens goes convex side down* – just in case you were wondering…

Stand offs

Quite a few screws and bolts had come loose during shipping, these were intended to attach the laser power supply board to the case – unfortunately one of the stand-offs was completely missing, so I had to run to the store to find a replacement. I installed these and checked the rest of the boards to make sure they were secure. One cable was unplugged, but it was obvious where this went, so I hooked it back up.

The laser tube requires cooling – using distilled water circulated by an aquarium pump. After another trip to Wal-Mart and I found a $3 plastic bucket (with lid), along with about 5 gallons of distilled water.

Water Pump

One important tip here – clip off the ends of the rubber hoses. These are bent over and tied back during shipping and the kink left in them will restrict the water flow.

Since cooling is essential I will be installing a flow sensor in this line, but for now I twisted a simple support from wire. The return flow is suspended above the water level and makes lots of noise while running.

It’s also very important to get all the air bubbles out of the laser tube as these can result in “hot-spots” and damage the laser while running.

Next was the X/Y gantry. It was pretty obvious that this was not perpendicular, and removing the screws that held the left hand side proved this. The horizontal gantry was about 1/4″ off. To fix this I needed to remove the entire X/Y assembly, loosen the sleeve holding the motor spindle and slide the two halves of the gantry back together. Once everything was tightened up things looked, and ran, a lot better.

Misalignment

As delivered, the two mirror mounts are impossible to adjust – they need to have longer bolts and return springs added. The only small bolts I had were made of nylon – and are prone to flexing. But they were all I could find, so they’ll have to do. At some point I’ll either replace the bolts, or replace the mounts completely. Now at least the mirrors move when the screws are turned.

Springs

The control panel is pretty simple, but it does contain a mystery button – the bright green one below the text 40A. It turns out this is part of the circuit to test fire the laser, you have to press both the test and the green button for it to engage. It might be in the manual somewhere, but I couldn’t find it.

Laser Cutter control boards

Alignment takes quite a time, especially when you cannot have the laser running while making adjustments. The video suggests using some chipboard discs, but I didn’t have any of the those, so a nickel will have to do. I taped the nickel to each mirror and test fired the laser. I am aiming to get the laser to strike the mirror in the center over the complete range of motion and then hit the condenser.

Tricky.

Finally you need to adjust the table so that the material is approx 2″ below the lens.

Here’s a video showing the laser in action, this is just the unfocused beam, at about 1/3 power:

If there’s enough demand :) I’ll crank it up to full power and run some focussed beam tests – however I’m scratching my head to think what would make a good target – most card I try gets cut through on a fraction of full power – I’m sure metals won’t react, maybe I should try some plywood – although it’ll probably just catch fire.

In part three – control software…

* There’s been some debate about this, but the manual states that it goes convex side down, even though, intuitively you would think it would be the other way round…

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{ 3 comments… read them below or add one }

Stewart Butler April 12, 2011 at 12:22 pm

We use our laser cutter (35 watt Epilog) to cut Acrylic and other plastics pretty often. With the right settings (100 percent power, 5000hz) you can cut 1/4 inch acrylic fairly well. Will also etch glass.

With the right software you can also do some neat things with rubber blocks — you can cut 3D stamps and such.

Wood will work if you set the pulse rate correctly. Make sure you traverse quickly — you can make mulitple passes at mid- to low-power, and the wood surrounding your cut won’t heat up enough to combust. Will take a while, though — stick to soft woods at 1/4 inch max for best results doing vector cuts. Better just etching at thicker material than that.

Caution: if you cut plastics, check the MSDS to be sure that it won’t produce any toxins when burnt. PVC, for example, will produce chlorine gas. Other materials will also leave nasty films on your optics, resulting in loss of focus and diffusion of the laser, reducing efficiency.

Big_Al April 12, 2011 at 2:54 pm

Screw Walmart. Also, crank it up!

Steve Jebbitt April 13, 2011 at 3:22 am

Hi Steve, as Stewart was saying probably best to use acrylic for testing. Good luck!

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