A plain, well-proven air-assist head for the K40, sold alone or as a full optics refresh with a CVD focus lens and a set of three 20mm silicon mirrors.
Most K40 heads solve one problem: no air assist. The MCWlaser bundle solves the one that usually sits behind it, which is tired optics. It pairs the air-assist head with a D12 FL50.8 CVD ZnSe focus lens and three 20mm gold-plated silicon mirrors, one for every position in the K40's beam path.
Stock K40 optics are the cheapest parts in the machine, and they show it. Mirrors dull, lenses pick up baked-on smoke, and every surface in the path throws away a little power. Replacing the whole set together gives you a clean baseline: if the machine still cuts weakly afterwards, you know to look at the tube, the supply or the alignment instead.
The mirrors are 3mm-thick silicon with a five-layer gold film. Silicon mirrors reflect well at the CO2 wavelength and handle heat better than the coated glass mirrors many stock K40s ship with. The lens is CVD zinc selenide, the grade most lens makers treat as their better option over PVD.
| Spec | Value |
|---|---|
| Brand | MCWlaser |
| Manufacturer | Shanghai Top Nine Industrial Co., Ltd |
| Model number | K40-I |
| Part number | LH-K40-I |
| Designed for | K40 engraving and cutting machines |
| Carriage bracket fit | M22 or M23 fixed bracket |
| Focus lens fit | D12mm or D18mm, FL50.8mm |
| Air assist | Built-in air-assist connector |
| Air connector outer diameter | 5.3mm |
| Hose | 5 x 8mm silicone (5mm ID, 8mm OD) |
| Material | Alloy steel, metal |
| Head-only box | 1 x K40 laser head |
| Bundle focus lens | D12mm FL50.8mm CVD ZnSe (USA material) |
| Bundle mirrors | 3 x 20mm gold-plated Si, 5-layer gold film |
| Mirror thickness | 3mm |
MCWlaser is specific about fit. The head works on a K40 when the fixed bracket that joins it to the moving axis is an M22 or M23 type. K40s are not all built the same, and the maker says so plainly: not every K40 has the same mount and setup.
Unplug the machine, open the lid and look at how your stock head meets the carriage. You are checking three things:
The air connector is 5.3mm across, so standard 5 x 8mm silicone hose pushes straight on. Route it along the gantry and tie it down every few inches so it cannot snag on the belt.
| What you see | What it means |
|---|---|
| Stock head with an M22/M23 bracket | Direct swap, align and go |
| Different bracket or plate | Adapter plate or drilling needed |
| Rebuilt gantry or custom head | Look at a full carriage set instead |
If the carriage itself is bent or cracked, a head swap will not save it; see the CNCOLETECH carriage set for a full rebuild.
Keep the stock screws. Metric threads on K40 carriages are usually small, and the originals are often the right length when the new head's hardware is not.
Changing all three mirrors and the head in one session is where many owners lose an evening. The trick is to work in beam order and align after each change, not all at the end. Unplug the machine and leave the cover off only while it is unplugged.
Use short, low-power test pulses. You only need a mark on the tape, not a hole through it. The full method, with corner checks and shim tricks, is in the K40 alignment guide.
When the spot sits centred at all four corners, run a ramp test on scrap to find focus height. A fresh lens and mirrors often let you drop the tube current for the same cut, which is kinder to the tube.
Keep the old mirrors, cleaned and bagged, as emergency spares. They are not as good as the new silicon set, but a dull mirror in a drawer beats a machine that sits idle while a replacement ships.
Several K40 air-assist heads look nearly identical, so let the lens range and the bundled optics settle it. The MCWlaser head covers D12 and D18 FL50.8 lenses; it does not list a 20mm lens. Of the three, its bundle alone packs three mirrors rather than one.
A 12mm CVD lens in the bundle keeps you on the stock lens size, which is simple but narrow. If you expect to cut 5mm plywood or acrylic often, plan an 18mm FL50.8 lens as your next spare; the head already takes it.
Run through this before you pay:
For the order in which K40 upgrades pay back, see the upgrade list. Optics and air assist sit near the top for good reason.
One more reason to take the bundle on a second-hand machine: you rarely know what the last owner did to the optics. Some clean mirrors with the wrong solvent, some never clean them at all. Fitting a known set on day one removes that guesswork from every cut test that follows.
It fits K40s whose carriage uses an M22 or M23 fixed bracket. Other mounts may need an adapter plate or drilling.
The air-assist head, one D12 FL50.8 CVD ZnSe focus lens and three 20mm gold-plated silicon mirrors, 3mm thick.
Yes. The head takes D12 and D18 lenses with a 50.8mm focal length.
The connector is 5.3mm across; MCWlaser suggests 5 x 8mm silicone hose, 5mm inside and 8mm outside.
