Raytools Protective Lens D27.9 x 4.1mm - for 4KW Fiber Laser Cutting Heads
The Raytools Protective Lens D27.9 x 4.1mm is a genuine fused-silica focus protection window built for 4KW-class Raytools fiber laser cutting heads. Fitted just above the nozzle, it takes the direct hit from spatter, smoke and metal fume so the far more expensive focusing lens sitting behind it stays clean and undamaged. As a low-cost, frequently-replaced consumable, it's one of the simplest ways to protect cut quality and avoid unplanned downtime on the shop floor.
This protective window is precision-cut from high-purity fused silica (quartz) and carries an anti-reflective (AR) coating on both faces, tuned for the 1064-1080 nm wavelength band used by fiber laser sources, so more than 99% of the beam passes through with minimal loss. At 27.9x4.1mm (diameter x thickness), it is the standard focus-side protective window used on Raytools' 4KW-class heads, including the BM109, BM111, BM114S, BT210S and BT240S, and it drops straight into the drawer-type lens holder for a quick, tool-free swap - no realignment needed. Every piece we sell is a genuine Raytools optic, not a mixed-quality local copy, dispatched with a proper GST invoice from our Ahmedabad, Gujarat warehouse to sheet metal fabricators, automotive component manufacturers and laser job-work shops across India.
Key Features of the Raytools D27.9 x 4.1mm Protective Lens
Genuine Raytools fused-silica (quartz) protective window, sized 27.9 x 4.1mm
Dual-side AR coating for 1064-1080 nm fiber laser wavelength - over 99% transmittance
Purpose-built for 4KW-class Raytools heads: BM109, BM111, BM114S, BT210S, BT240S
Drops into the standard drawer-type lens holder for a fast, tool-free swap
High laser-damage threshold for stable, continuous-duty cutting
Precise diameter and thickness tolerance for a snug, light-tight fit
Genuine part with GST invoice, ready stock and fast pan-India dispatch
Applications & Industries
Fiber Laser Sheet Metal Cutting Machines (4KW Class)
Benefits of the Raytools D27.9 x 4.1mm Protective Lens
Features
A precision fused-silica window, dual-side AR coated and sized to drop straight into the focus-lens holder of a 4KW-class Raytools head - no modification or realignment needed.
Benefits
Keeps spatter, smoke and fume away from the actual focusing lens, so cut edges stay clean and you're not paying to replace an expensive optic every time the head gets dirty. Because it's inexpensive and quick to swap, a job that could mean half a day of downtime becomes a two-minute changeover.
Technical Specifications
Parameter
Specification
Brand
Raytools (Genuine)
Product Type
Focus-side Protective Lens (Protective Window)
Diameter
27.9 mm
Thickness
4.1 mm
Material
Fused Silica (Quartz)
Coating
Dual-side Anti-Reflective (AR)
Wavelength Range
1064-1080 nm
Transmittance
Over 99%
Power Class
4KW
Compatible Heads
BM109, BM111, BM114S, BT210S, BT240S
Holder Type
Drawer-type lens holder
Consumable Type
Sacrificial, routine-replacement part
Which Raytools Cutting Heads Use the D27.9 x 4.1mm Lens?
This is the focus-side protective window fitted on Raytools' 4KW-class cutting heads, including the BM109, BM111, BM114S, BT210S and BT240S. If your machine runs a different Raytools head, or you're simply not sure which lens sits where inside yours, the fastest way to confirm is to measure the damaged one you're replacing - a genuine lens in this size measures 27.9mm across and 4.1mm thick - or message us your head model on WhatsApp and our team will confirm the right part before you order.
When Should You Replace This Protective Lens?
Because the focus-side window sits closest to the cutting zone, it's normally the fastest-wearing consumable inside a Raytools head - in busy production, some shops swap it every few days. Replace it as soon as you notice:
Visible pitting or small burn spots on the glass
A hazy or cloudy patch that wasn't there before
A fine crack or chip near the edge
A drop in cut quality - more dross, rougher edges, or slower piercing than usual
Running the machine on a damaged protective window doesn't just affect the cut - the heat and spatter it would normally stop start reaching the actual focusing lens behind it, and that's a far more expensive part to replace.
How to Replace the D27.9 x 4.1mm Protective Lens
Swapping this lens on a Raytools drawer-style holder takes a couple of minutes. Power down the machine, slide the drawer out, and lift the old lens out by its edge - avoid touching the coated faces with bare fingers, since skin oils leave marks that show up as burn spots later. Wipe the holder clean, drop the new lens in with the same orientation as the old one, and check both faces are free of dust or fingerprints before closing the drawer. If you're unsure which face should point towards the beam, check your cutting head's manual first - getting the orientation wrong is the most common reason a freshly-fitted lens looks damaged within a day.
Genuine Raytools D27.9 x 4.1mm Lens vs Generic Lens
Parameter
Genuine Raytools Lens
Generic / Local Lens
Substrate
High-purity fused silica
Mixed / unspecified glass
AR Coating
Tuned for 1064-1080 nm, both faces
Inconsistent, sometimes single-side
Transmittance
Over 99%
Lower and variable
Damage Threshold
High - built for continuous production
Burns and pits faster
Fitment
Exact 27.9x4.1mm, drops in with no play
Slight size mismatch, risk of light leakage
Why Choose Us
Genuine Raytools optics in the exact 27.9x4.1mm size - not a "close enough" local substitute
Ready stock for same or next-day dispatch, so your machine isn't down for long
GST-registered supplier (GSTIN 24AFSFS3212F1Z2) with a proper tax invoice on every order
WhatsApp support to confirm size and head compatibility before you buy
Bulk pricing for fabrication units and pan-India delivery from our Ahmedabad, Gujarat warehouse
Frequently Asked Questions
It's a sacrificial fused-silica window fitted in front of the focusing lens inside a Raytools cutting head. It absorbs spatter, smoke and fume from the cutting process, keeping the focusing lens clean and your cut quality consistent.
It's the standard focus-side protective window for Raytools' 4KW-class heads, including the BM109, BM111, BM114S, BT210S and BT240S. Share your exact head model with us on WhatsApp if you'd like it confirmed before you order.
Yes - we supply genuine Raytools optics, not unbranded or mixed-quality local glass, and every order is dispatched with a proper GST invoice from our Ahmedabad warehouse.
High-purity fused silica (quartz) with a dual-side anti-reflective coating tuned for the 1064-1080 nm fiber laser wavelength, giving over 99% transmittance.
It depends on the material and thickness you're cutting, but since it's the first line of defence against spatter, it's normally the most frequently changed optic in the head - some production shops replace it every few days. Pitting, haze or a drop in cut quality are your signal to swap it.
Current price and stock availability are shown above on this page. For bulk or wholesale quantities, contact us on WhatsApp or through the quote form for a per-unit rate.
Yes - every order ships with a valid GST invoice, and we deliver pan-India from our warehouse in Ahmedabad, Gujarat.
Yes. Measure your existing (damaged) lens - a genuine D27.9 x 4.1mm window is 27.9mm across and 4.1mm thick - or send us your Raytools head model on WhatsApp, and our team will confirm the correct part before you buy.
Get the Best Price on the Genuine Raytools D27.9 x 4.1mm Protective Lens
Need this lens for a 4KW Raytools cutting head? Add it to your cart above, or contact us for bulk pricing, a GST invoice and pan-India delivery from our Ahmedabad, Gujarat warehouse.
