The head most owners bolt on before any other upgrade: it adds a proper air nozzle and opens the door to a 20mm focus lens, which the stock K40 head cannot hold.
The stock K40 head holds a 12mm focus lens and nothing else, and it has no air nozzle. That one design shortcut is why so many machines scorch plywood, fog their lens and start small fires on the honeycomb. The Lightobject head fixes both problems in one part: it has an air-assist connector, takes 15, 18 or 20mm focus lenses, and holds the same 20mm mirror your K40 already uses.
Do not skip past the 20mm option. Most replacement lenses made for CO2 machines are 20mm, so a head that accepts them gives you the widest choice of focal lengths and lens grades. You stop hunting for the small 12mm size every time a lens cracks or gets pitted.
Here is what changes when this head replaces the stock one:
One detail needs settling first. The product name mentions a 12mm lens, but Lightobject's own spec sheet lists 15, 18 and 20mm. If you plan to keep your stock 12mm lens, confirm it seats securely, or budget for a larger lens now.
Keep the old stock head in a drawer. It costs nothing to store, and it gets the machine running again if a new lens cracks mid-job and the replacement is still in the post. Label its screws in a bag with it.
| Spec | Value |
|---|---|
| Model number | LSR-LH1820B |
| Maker | Lightobject |
| Designed for | K40 series desktop CO2 lasers |
| Focus lens diameter | 15mm / 18mm / 20mm |
| 12mm lens | Named in the product title; confirm fit |
| Mirror diameter | 20mm |
| Body material | Aluminium |
| Finish | Metallic blue |
| Air assist | Built-in air-assist connector |
| Air plug outer diameter | 5.5mm |
| Hose | 5 x 8mm silicone (5mm ID, 8mm OD) |
| Replaces | Stock K40 head without air assist |
| Package size | 6 x 3 x 3 inches |
| Air Enhancer version | Brass tubing, manual air valve |
| Air Enhancer packed weight | 1.2 pounds |
Fitting this head is a bolt-off, bolt-on job on most K40s, but stock machines vary. Different factories use slightly different carriage plates, and a head designed for the K40 series still has to meet your particular plate. Measure your existing head's mounting before you order, and expect to re-align afterwards.
Now re-align. The third mirror sits in a new position, so the beam will not land where it used to. Work through the mirrors in order with the method in the K40 alignment guide, then set your focus distance again.
A different head height changes the distance from lens to bed. Check that your material still reaches the focal point; you may need to raise the work, which is one reason owners pair this head with an adjustable bed later.
An air nozzle with no air behind it does nothing. The head is only half of the upgrade; the other half is a pump that delivers a steady stream through the hose without pulsing. A small aquarium pump works for engraving, but cutting benefits from more flow.
| Air source | What it suits | Watch for |
|---|---|---|
| Aquarium pump | Engraving, thin card and veneer | Low flow; smoke still lingers in deep cuts |
| Piston air pump | Cutting plywood and acrylic | Noise and heat; keep it outside the enclosure |
| Shop compressor | Heavy cutting with a regulator | Moisture and oil in the line; fit a filter |
Turn the air down for engraving. Strong air on a fine raster can blow smoke residue across the work and spread light scorch marks. Turn it up for cutting, where you want the kerf cleared.
After the swap, run a ramp test to find focus. Tilt a scrap of plywood under the nozzle, fire a line across it, and look for the thinnest part of the mark. Measure from the nozzle tip to that point and cut a small spacer block to that height.
Lightobject makes a second K40 head built around its Air Enhancer. It uses a different airflow method from a plain nozzle tip, with brass tubing and a manual air valve, and it targets engraving rather than cutting. Lightobject pitches it at three jobs: keeping pixels crisp in wood photo engraving, cutting down the white powder on engraved acrylic, and clearing coating residue from tumblers.
No head adds power. These parts put more of the tube's existing output onto the work by keeping the lens clean and the cut clear. If your cuts got weaker over time, check the mirrors, lens and tube current before blaming the head; the upgrade order sets out what to fix first.
Walk through this list with the lid up:
It is designed for K40 series machines, but factories use different carriage plates. Measure your stock head's mounting first and expect minor fitting on some machines.
No. It is the head with its air connector; reuse your 20mm mirror and fit a 15, 18 or 20mm focus lens.
The plug is 5.5mm across, and Lightobject specifies 5 x 8mm silicone hose: 5mm inside, 8mm outside.
Yes. The third mirror moves with the new head, so walk the beam through all three mirrors again and redo your focus test.
