Laser Protective Lens
Fused-silica protective windows that take the spatter so your focusing lens does not. Stocked in the drawer sizes used by Raytools, Precitec, WSX, Bodor and HSG cutting heads, with 1064 nm AR coating.
What the protective lens actually protects
In a fiber cutting head the beam leaves the fiber, is shaped by the collimator, focused by the focus lens, and then passes through one last piece of glass before it reaches the workpiece. That last piece is the protective lens, sometimes called the protective window or the drawer window. Its only job is to intercept what the process throws upward: spatter, fume, fine dust, coolant mist and the occasional ricochet from a pierce.
It is deliberately the least expensive optic in the stack, and the only one designed to be thrown away. When a window is doing its job you never think about it. When it stops doing its job, the focus lens behind it starts absorbing energy, and a consumable that costs a few dollars takes a lens with it.
Why the material matters more than the price
We supply fused silica rather than ordinary glass, with a high-LIDT 1064 nm anti-reflective coating. LIDT is the damage threshold, and it is the number that decides whether a window survives a pierce at full power or hazes on the first shift. Fused silica carries the near-infrared beam with low absorption, tolerates the thermal cycling of a production shift without cracking, and holds a hard dielectric coating that survives cleaning. Soda-lime glass will pass the beam for a while; then it pits, hazes, and starts scattering light. The result is a slow loss of edge quality that almost nobody traces back to the window, because the cut still goes through.
The coating is the part that fails first in most workshops. A coated window that has been cleaned with the wrong cloth, or wiped while dry, loses its AR layer in the middle and turns into a hot spot. That is why the handling rules on this page matter as much as the specification.
Choosing the right variant
Protective windows are not interchangeable between head families. Diameter, thickness, coating and the way the window seats in the drawer are all family-specific. We stock the drawer sizes used by the head families below, and confirm the exact variant against your head model before anything ships.
| Head family | How the window is normally identified | What we need from you |
|---|---|---|
| Raytools | Drawer-style window in the head body, ordered by head series | Head model, or a photo of the old window with a rule in frame |
| Precitec | Window sits in the cartridge under the nozzle assembly | Head model and cartridge type |
| WSX | Window retained by the lower protective cover | Head model and the marking on the old window |
| Bodor | Window matched to the head series fitted to the machine | Machine model and head series |
| HSG | Window matched to the head series fitted to the machine | Machine model and head series |
| Other heads (BOCHU, HAN'S, Friendess, Mazak, NTC) | Varies; usually a standard drawer size | Photo, diameter, thickness and coating |
Reading a failing window
Most window failures present as a cut-quality complaint rather than as a broken part, so the diagnosis starts with the symptom and works backwards.
| What you see | What it usually means | First check |
|---|---|---|
| Brown or grey haze that will not wipe off | Coating burnt through; the silica underneath is absorbing | Replace the window, then check assist gas purity |
| Small pits clustered around the beam centre | Spatter reaching the window through a worn or oversized nozzle bore | Inspect the nozzle bore and the standoff distance |
| Milky marks near one edge | Condensation from chilled water or humid shop air | Check chiller set point and the condition of the desiccant |
| Crack running in from the rim | Mechanical stress from an over-tight retaining ring or a seating burr | Check the seating face and the retaining cap |
| Window looks clean but the cut is poor | The window is not the problem | Check the focus lens, the nozzle and the centring |
Handling rules that extend window life
- Never wipe a coated window dry. Loose dust becomes abrasive under a dry cloth.
- Hold the window by the rim only, with gloves or finger cots, and inspect under a lamp against a dark background.
- Fit with the coated face towards the beam, and never force a window into a dirty seat.
- Replace the window whenever the nozzle is replaced after a crash; the impact that killed the nozzle usually reached the window too.
Stocking and supply
These are consumables, so the useful question is not whether you can buy one, but whether the replacement is on the shelf when a shift stops. We supply the common drawer sizes for the head families above as regular stock lines, in wholesale quantities and under OEM packaging for distributors and machine builders. Tell us the head model, the quantity you go through in a quarter, and whether you want neutral or branded packaging, and we will confirm the variant and the lead time.
If you are not sure which window is fitted, send a photo of the old part next to a rule. That single photo resolves most of the cases where a customer has been shipped the wrong size before.