Checking and securing a chinese CO2 laser

[Downunder35m]

The price difference between a "proper" CO2 laser and one of the many chinese knock-off's is big enough so that many people jump on the wagon.
But having a cheap laser cutter can bring expensive problems....
For starters there is the total lack of any safety features on the budget models.
Not just simple things like a control switch for the lid and a flow switch for the water pump.
If you know what you are doing and how to check for water flow you can do fine without, not legal in safety terms of most countries but it works.
But what about all the other shortcuts taken to make this low price possible?
After all you get a complete machine for the price of a budget laser tube from your local dealer - or for even less....

The case and mounts...
One of the first things I noticed was that it seems china never heard about washers, lock nuts or spring washers at all.
I was unable to find a single one in my machine, just plain nuts and bolts for everything.
Most is in the 4-6mm region so just grab a big pack of washers and spring washers...
In the perfect world you would want to fix all nuts and bolts on the machine, in the real world you might do it bit by bit during service and repairs.
But after some time of use you will notice things do come loose and the last thing you want is a metal nut or bolt causing a shortcut somewhere....

Wiring...
To be honest the wiring in machine is shocking to say it nice.
Wires are fed through metal holes that have sharp edges with no protection at all.
The HV wire just dangles around in the case over the electronics and the earth wire is connected outside leading to a dead end inside LOL
You want to make sure that all holes where cables or wires go through are protected, even if you just cut some rubber hose to glue it onto the corners of the metal.
One big problem are soldering connections and plugs.
I made it compulsory for me to take electronics coming from china apart before first use to check for bad soldering and solder rubbish left on the circuit board.
In the case of the laser the entire machine was littered with metal shavings from drilling holes and filing to make it all fit.
Even on the laser tube they landed so it was obvious that I had to clean out the power supply as well.
Speaking of: The fan on the power supply, in my case, is blowing out but not onto the electronics inside - you might want to check and rectify that.
The soldering on the limit switches is often bad too, mine were only held in place by the heatshrink around them - so wigle and pull a bit to check!

Alignment...
When I got my machine the x-axis was at an angle of about 15°.
Tried the connecting rod on the motor but turned out the problem was the rail itself.
Where you would expect a machined 90° cut the rail was just cut with a saw and ended up crook - on both ends in the same way.
It seems to be impossible to buy these rail anywhere so I "fixed" it by gluing a washer in one corner to get the axis straight on the mount.
Similar story for the bed.
You would expect that knowing the focal length of the lens and all mechanical parts should make it possible to mount the bed in the right spot.
Wrong. It seems in china they ship these lasers with two different focal lenghts and to compensate 8mm nuts are added between mounts and cutting surface - a pain to adjust as they love to fall down all the time.
Once the plate is out you can see the mounts have been forced into "alignment", all is bend more or less to give impression of a levelled cutting area.
There are lots of option on how to mount the bed properly if you use your phantasy but IMHO the best is to build a height adjustable platform.
When the machine is shipped a basic alignment of the optics is performed to test all funtions of the laser, that's why you sometimes find water drops in your new tube.
But it also means noone paid real attion to do it properly, which means you have to do it.
Please don't expect your chinese laser to be aligned properly when you unpack it!

Lifetime...
When it comes to laser tubes with labes noone can read you left to assume the actual laser power is far below what was stated in the listing.
So most 40W systems will be more in the 30-35W region but certainly never able to produce 40W without burining out fast.
Newer models now comes with digital power control, it is the same PWM signal generation as before, just with a nice display and buttons instead of a potentiometer and ampere gauge.
Problem is that you never really know what power is really going into the laser tube.
If you have a analog meter on your machine make sure to keep it if you updgrade the controller!
If you are already without it then it really pays of to buy one and to add it so you have a real sense of what power is going into the tube.
The one thing that officially causes a short lifetime of the tube is high power levels.
A good recommendation is to never use more than 50% of power and best to stick to values below 40%.
That is why in the industry most systems are totally overpowered - it is cheaper to get one 200W tube that lasts a few years than several 100W tubes that need replacing twice a year.
The mechanics are not fool proof either.
These plastic rollers on the x-axis wear out over time without you noticing much - get replacements before you notice otherwise you might have a hard time getting them fast engough when needed!
Adding a cover, even just a slip of paper on the underside of the x-axis will protect the belt system from getting soaked in sticky fumes and ensure a much longer lifetime of your belt.
Again buy a 5m lenght of belt (should be 2.3mm pitch) so you have a replacement ready when you need it!
The latest during your first replacement you should add the cover.
Laser power supplies are usually a thing you just use and forget about, not so much if they are cheap and from china.
Shortcuts are taken to keep the price low, this includes but is not limited to:
Missing opto couplers to seperated mains, low and HV voltage areas.
Isolation paths too narrow.
Cheap parts with little to no reserves - all is designed to the limit.
Bad wiring - especially for those big current limiting resistors mounted somewhere on the frame.
Bad insulation for the HV cables - double check the connections on the tube!
All this means that not only the operator might be risk if something fails but also that these power supplies love to have a premature death for no good reason.
By the way: the laser tubes are often of low quality too as in a lot of cheap models you can find refurbished tubes.
Usually 50W tubes are re-gasses and labeled as 40W units.
The procedure is highly dependent on the gas mix used and good it was evacuated and filled again but the optics are usually not replaced.
So you might have a laser tube that looks new but when you check the internal optics you sometimes see the signs of long use already.
Not much you can do here except hope your tube still lasts long enough.

[Jamsal]

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