Many parts of your new K40 may break or wear out, and it probably didn’t come with a catalog of replacement parts. Here’s where to start.
The laser tube in the K40 is what industry calls a “wear item”, and it will wear out in the normal and proper use of the machine. Glass CO2 lasers are often rated for a life of ~5000 power-on hours. When they are misused by running them with too much current (power) they wear out faster. When they are poorly cooled, they wear out faster. When they are just abused by letting their cooling water freeze inside, or get full of thick algae, or miss-wired, they can fail completely. General wear-out causes a long, slow loss of cutting power. Premature failure due to low quality, improper cooling, or excessive current often initially manifests by shifting Transverse electromagnetic (TEM) mode to TEM₀₁* (donut), TEM₀₁, TEM₁₁, TEM₀₂, or higher modes, which manifest as multiple dots on witness paper or tape at every mirror, rather than the optimal TEM₀₀ mode, which will burn a plain circle on witness paper or tape in front of the first mirror.
The tubes in K40s are not first-quality tubes in general, because of the intense pressure on the sellers to offer the lowest price. You can get replacements from some online vendors. I have seen reports of good results, including “Wow! This is great! It never cut/engraved like this with the original tube!” Some vendors that come to mind from forum posts include Ten High, Cloudray, and Lightobject.
You’re looking for a 700mm to 720mm max length and 50mm diameter. That’s the biggest that will all fit inside the enclosure. This limits you to 35-40W rated tubes. Your original tube was probably only producing 25-30W max, and possibly much less, as the OEM tubes were generally not the first, best quality tubes. Here are some links I found on a quick search. They are in no particular order.
If you have the “Mini” version, you’re going to have to find a vendor for the 600mm long shorter laser tube. Start with the vendors above and see if they carry it.
If you replace the tube, you may also need to replace or connect the high voltage wire. This is not normal wire. It has special insulation that can withstand 20,000V or more. You cannot connect it using normal connectors, and you cannot insulate it with electrical tape or normal insulated connectors. This can kill you.
If you need high voltage cable, a good choice is:
If you just want a connector, try:
For more information, including how to splice two high voltage wires together without a connector, read:
Here is Lightobject’s training video on the subject:
There are many replacement Laser Power Supplies (LPSs). Some do not include an integrated 24V supply like the typical K40 stock LPS, and thus require that you add a separate 24V power supply. Here are a few options that are intended to be able to fit inside the K40 case:
- Cloudray MYJG-40 MYJG-40 OW and MYJG-40 NG include built-in 24V power supply. Cloudray also sell on Amazon
- Lightobject LSR-JN40W-N20 does not supply 24V; you will need to add your own.
The stock lenses are 12mm diameter zinc selenide (ZnSe) material and have a yellow-orange cast to my eye. Zinc selenide is toxic and fairly fragile, so always handle your lens with care when cleaning it.
CO2 laser lenses can also be made from GaAs (gallium arsenide) and Ge (germanium). These more esoteric lenses may appeal to you. Read up on them before spending a lot of money on therm.
Common mirror materials are Si (silicon) with gold plating, polished copper, molybdenum, and perhaps others. If I understand what I read, the gold plated silicon has the possibility of being the absolute best reflectance, but may also degrade quickly, and may also be poorly made. Copper is not often seen in K40s. Molybdenum (MO) mirrors are solid polished metal, and probably the toughest and most reliable, even though they are slightly less reflective. MO seems to be the most resistant to damage and/or poor cleaning technique.
One reference I read said that the coating or reflective surface of the mirrors may degrade over a fairly short time, leading to a 25-50% power loss through the mirrors absorbing the heat.
The belts are NOT the common 2mm GT2 toothed belts so common on 3D printers and in hobby CNC. They are instead standard imperial MXL 0.08 inch belts (in metric, 2.032mm) in order to support motion in exactly 1/1000 inch increments.