Three flat silicon mirrors with a five-layer gold film, each vacuum sealed in its own pack. The lead set is 25mm; CNCOLETECH also makes the same silicon mirror in the K40's usual 20mm, and a cheaper 20mm set in gold-coated K9 glass.
CNCOLETECH builds its lead mirror on a 25mm silicon disc, 3mm thick, with a gold film laid down in five layers. It quotes reflectivity up to 99.8% at the CO2 wavelength and a 40W to 400W power range. Each of the three mirrors arrives vacuum sealed on its own.
The individual sealing is a practical touch. Gold-coated mirrors do not like humidity or fingerprints, and a mirror that sits unsealed in a drawer picks up both. With three separate packs, you can fit one and keep two sealed as spares, or change all three and still have clean packaging to store the old ones in for reference.
CNCOLETECH pitches these as the replacement for the K9 glass mirrors many K40s ship with. That is the upgrade most owners make first in the optics, because glass holds heat and its coating wears through sooner.
Three bounces sit between the tube and the lens, and losses multiply along the way. A burnt glass mirror early in the path robs power from every cut, and no amount of extra current fixes it without costing tube life.
The size you order still decides whether any of this helps, and that comes next.
| Spec | Value |
|---|---|
| Pieces | 3 mirrors |
| Diameter | 25mm (0.98 in) |
| Thickness | 3mm (0.12 in) |
| Shape | Plane (flat) |
| Substrate | Silicon (Si) |
| Coating | Gold, 5-layer film |
| Reflectivity | Up to 99.8% at 10600nm |
| Wavelength | 10.6 µm CO2 laser |
| Power range | 40W to 400W |
| Packaging | Each mirror vacuum sealed against oxidation and corrosion |
| Item weight | 0.845 oz |
| Package size | 3.82 x 3.27 x 1.02 in |
| Other versions | 20mm gold-plated Si x3; 20mm gold-coated K9 x3 |
| Replaces | Stock K9 glass mirrors in K40 and other 40W machines |
The lead set is 25mm, and most K40s use 20mm mirrors in 20mm mounts. A 25mm mirror will not seat in a 20mm holder. CNCOLETECH makes the same gold-plated silicon mirror in 20mm, three to a pack, and that is the version a stock K40 wants.
Measure before you choose. Unplug the machine, remove the retaining ring on the first mirror with a nut tool or careful fingers, and put calipers across the disc.
| Your mount | CNCOLETECH version |
|---|---|
| 20mm, stock K40 | 20mm gold-plated Si, 3 pcs |
| 20mm, budget refresh | 20mm gold-coated K9 glass, 3 pcs |
| 25mm, upgraded mounts | 25mm gold-plated Si, 3 pcs (lead set) |
A 25mm set makes sense only if you have already changed your mounts or plan to. Larger mirrors give a wider target, which helps on long beam paths. The K40's path is short, so that margin is small, and mounts are the harder part to change.
Order by what the calipers say, not by a machine name in a product title. K40 is a family of look-alike machines from many factories, and a few left the line with 25mm mounts or mixed parts.
If your mounts are loose or at the end of their adjustment, a head and mount kit may be a better buy than mirrors alone. The upgrade order guide helps decide. For the 25mm route, Cloudray's 25mm set is the closest rival.
CNCOLETECH's third version is a 20mm set in gold-coated K9 glass, sold for the K40. It is the same kind of mirror many K40s ship with. It works, but it gives up some qualities that make silicon the usual upgrade.
The difference is in the disc under the gold. Glass conducts heat poorly, so the beam spot warms the coating more, and once the coating wears or burns through, the mirror is finished. Silicon draws heat away from the spot and holds its flatness as it warms.
| Quality | Gold-coated K9 glass | Gold-plated silicon |
|---|---|---|
| Heat handling | Poor; heat stays at the beam spot | Good; spreads heat away |
| Durability of coating | Wears or burns sooner under dirt | Lasts longer when kept clean |
| Weight | Heavier | Lighter |
| Cost | Lowest | Moderate |
Choose K9 if you want a cheap set of spares or your machine sees light, occasional use. Choose silicon if you cut regularly, or if your current glass mirrors have burned. Neither material turns a 40W tube into a stronger one; what they do is lose less of what the tube makes.
Replace glass mirrors that show any burn mark in the centre. Glass cannot shed the extra heat a burnt spot absorbs, and a mirror running hot can crack under the beam, sending the path out of alignment mid-job.
Molybdenum is the third route. OMTech and TEN-HIGH make uncoated Mo mirrors that tolerate firm cleaning, at the cost of a little reflectivity.
Gold films scratch and hold fingerprints, and skin oil baked under a CO2 beam leaves a permanent mark. Handle the mirrors only with powder-free nitrile gloves or finger cots, and only by the rim. Everything else follows from that.
Swapping even one mirror shifts the beam slightly, so plan a full alignment session afterwards. The K40 alignment walkthrough uses tape targets and short, low-power pulses. Wear 10600nm safety glasses for every test fire.
To clean later, blow loose dust off first, then wipe once, lightly, with a lens tissue wet with isopropyl alcohol. Never rub in circles and never press on the gold. A mirror with a burnt or bare spot in the beam's path should be replaced; it will only get worse.
Air assist and a working exhaust cut cleaning frequency sharply, which protects the coating as much as anything else you can do.
Keep the old mirrors in the empty vacuum packs, labelled by position. If a new mirror ever fails early, you have a known reference to test against while you wait for a replacement.
The 20mm versions. Most K40s use 20mm mirrors, so choose the 20mm gold-plated silicon set, or the 20mm K9 set for a cheaper refresh. The lead 25mm set needs 25mm mounts.
K9 glass holds heat at the beam spot, so its coating wears sooner. It suits light use; silicon is the better choice for regular cutting.
Vacuum sealing protects the gold film from oxidation and corrosion, so you can keep spares sealed until you need them.
Three: at the tube, on the gantry and above the lens. Each CNCOLETECH pack holds three.
