Repair a Universal Laser Cutter Lens Holder With Sugru!

Over at ATX Hackerspace we have a Universal PLS 6.60 laser cutter, circa 2008. It's a great laser cutter, but with the use and abuse we give it day in and out ... the lenses break and wear out.

A replacement lens from Universal Lasers can cost upwards of $300. That's a lot of money for a hackerspace like ours, so we've learned how to rebuild and replace the lenses using imported lenses we buy from a supplier in China.

The lenses are made of the same stuff ( Zinc Selenide ) and are of the same focal length, size, and quality of the originals provided by Universal, but they only cost about $40-60 with shipping. For the PLS 6.60, that means 19.05mm ( 0.75" ) in diameter, no more than 2.3mm thick, and a 50.8mm focal length ( 2" ).

In order to proceed with this repair, we assume that you have already removed the original broken lens from the holder, and cleaned it up with an appropriate solvent ( we like to use Goo Gone for 24 hours. )

You will need:

• One mini packet of Sugru
• One new laser lens, purchased from China ( eBay is good )
• Cleaned lens holder
• Pair of clean, new non-latex gloves, that have no powder or oil residue.
• Clean lens tissue, and a clean lens clot
• A very very soft toothbrush.

Open the pack of Sugru. You will need only a tiny amount, about the size of a lentil. You may want to only open up one end of the pack, so you can reseal it immediately and save your Sugru for later, since it's kind of precious stuff.

PUT ON YOUR GLOVES

Never, ever get body oils onto the lens or lens assembly, and never pick up the lens with your bare finger. It also will prevent the Sugru from sticking to the lens and performing it's job. As the lens heats and contracts, the Sugru has to be able to keep up or the lens could fall out.

With the gloves on, roll the Sugru into a very thin line, like making a snake. Take your time, make it even, and make sure it can go the full circumference of the holder.

Using your gloved finger, spread the Sugru evenly along the edge of the lens holder. Take your time, and make sure it's a thin, consistent layer. You don't want to overfill this area. The goal is to create a very, very thin "windowsill" to seat the lens edge into.

NOTE: Laser lenses are made of Zinc Selenide, a polished piece of crystal salt. It is a very, very soft material that is extremely easy to chip, crack, scratch and break. For this next step you will need to be very careful, and apply even, gentle pressure.

Take careful note of the correct orientation of the lens in the holder. If you get this wrong and install the lens upside-down, there is almost no chance of salvaging the lens from the holder to try again.

Install the lens, pushing gently down and seating it completely. Press down, and make sure the lens is installed FLAT, ALIGNED, and completely seated into the holder. Some Sugru will "squish" out the bottom side. Use the super-soft toothbrush to brush away this extra material.

Finally, polish away any leftover material with the soft lens tissue with great care.

Leave the assembly exposed to air for 24 hours. The Sugru will cure, and mount the lens into place safely and securely.

If you have a vacuum sealer, you can now reseal your Sugru packet to keep it for future use. It will stay good for about 6 months.