Monday, 3 November 2014

Cheap Chinese laser cutter

Grumpy Paul was in the market for a laser cutter.
We've been reading mixed reviews about the cheap chinese laser cutters coming out of China; most say they're rubbish and should be avoided. But every now and again, someone will strip one down, reassemble it and conclude that, with a bit of care and effort, they can be made into half-decent machines.

We've been watching them on eBay for a few months now.
A while back there were a few available for about £350. That seemed a pretty good price, compared to the £1200+VAT we paid HPC for our laser a few years ago (HPC customers in recent years have complained about their lack of support, and their latest machines just look more and more like cheap chinese machines re-sprayed red and cream).

Then they'd all disappear off eBay and nothing would be available for under about £550 plus delivery. For the last few weeks, cheap laser cutters have been few and far between on both eBay and Amazon.

Recently (as in, a few days ago recently) quite a few appeared on eBay for the princely sum of £280. This seemed too good to pass up on - even if they're a bit of a gamble, so collectively a few of us clubbed together to try one out.

Bang! The trigger was pulled on Thursday.
On Saturday, a massive box turned up at Nerd Towers. A few hours later, and it was setup in Grumpy Paul's flat. They certainly didn't mess about with the amount of bubble wrap!


The machine is definitely not a high-end cutter. But the quality of the assembly was surprisingly not-too-bad-for-a-cheap-chinese-machine.


Unlike many people who've had these machines, there were no loose wires or badly crimped connectors


The MoshiDraw software and hardware dongle looked decidedly "eBay"


There's no air assist, or red dot on the cutting head. These can be retro-fitted, once the machine is up and running, but it also means that there's no cable-chain running on the x-axis (luckily, Martin Raynsford posted some plans for one he built a little while back)


The MoshiDraw software installed easily enough onto a Windows XP machine, so it was soon time to fire up the laser and try it out. First things first, connect up the water pump and give it a whirl.


After about twenty minutes, there were still massive air bubbles in the water jacket. On our HPC machine, any (small) bubbles usually clear after just a few minutes of running, or by tipping the machine and pinching the inlet water pipe quickly.

Trying the same techniques on this machine made no difference. There was a large, continuous air bubble in the top third of the entire length of the glass tube.

Robot-Laser-Steve (who has experience of dismantling and re-building at least three laser cutters) suggested that maybe the pump wasn't powerful enough to clear what had effectively become an airlock in the top of the tube.

We tried tipping the laser cutter up onto one end, to get all the air into one end of the tube. At this point, the problem became apparent:


The neck of the laser part of the tube (inside the outer glass tube) had cracked. Even after forcing the tube to fill a bit more (by pinching the outlet pipe closed for a few seconds at a time, to force some of the air bubbles out) the problem looked irreparable.


 The photo above shows the inner tube leaking, as the outer jacket fills with water.
No lasering would be going on this weekend!

To be fair to the sellers, the problem was pointed out and they immediately sent out a replacement tube. Although this isn't something we were planning on fitting ourselves, if it means that Mr Grumpfire can get lasering for under £300, it'd still be great purchase.

If the replacement tube doesn't work, however (or arrives damaged as well) the whole lot can go back and we'll ask Mr eBay for a full refund. It'll probably be a few days yet before anything actually gets done - one of us is at the other end of the country, one of us is waiting for a baby to pop out any day now, and one of us has no idea what they're doing. We'll leave it to the reader to decide which is which!