lense holder

[Jim Reinhard]

I would like to try a 4" lense for my laser pro mercury 3 .But dont want to spend $500.does anyone have one they could post the lens holder dimentions and hole sizes for one.I could cut one out of aluminum and drill the holes with a drill press if I had the dimentions and then order a lense off ebay or somewhere.

[Rodne Gold]

I have a 4" lens for my GCC lasers..almost NEVER use it , its kinda useless for any fine detail engraving , the cut width is not so good and the 30 watts I got isn't enough to maintain a decent energy density for cutting thick stuff due to the 4" lenses much bigger spot. It is useful for not so detailed work on items that need clearance from the engraving head.
Make the holder out of acrylic or mdf on your laser to begin with, the hole will be dependant on the diameter of the lens you buy off the internet. You need a lip to retain the lens.

[Richard Rumancik]

As there are only a few measurements, you should be able to put a calipers on your existing lens holder and make a sketch in a couple minutes. I have made acrylic lens holders for a Mercury as Rodne suggests with the idea of making aluminum ones when I proved out the design but guess what - I have never been motivated enough to make the aluminum ones. Find some acrylic sheet that is just a bit thicker than the lens holder; you will need to grind or sand it down. I vector cut the outline and lens hole and rastered in a lip for the lens to sit on. I secured the lens with three #2 screws with nylon washers just catching the edge of the lens.

[Richard Rumancik]

Jim, what did you want to cut with the 4" lens? I only use my 4" lens for cutting 1" grey foam for making instrument case inserts. I don't think I would be able to go thicker than 1" due to depth of field. I have not used it for cutting acrylic or wood as the spot size is too large and beam intensity too low.

[Jim Reinhard]

I want to cut 1" foam to make cutouts for some of my glassware for shipping.Also to see if It would cut thicker acrylic with a better cut .I cut 3/4 with my 2.5 lense in one pass but its slow..
The 4" lense sits in a different place in my holder and is a differnt shape than the 2.5 lense .Thats why I was looking for dimentions.I didnt think acrylic would work for a holder didnt know if they got hot during cutting but will give it a try.Does the lense diameter make a difference like 18mm or 20mm ?

[Richard Rumancik]

Jim, as long as the plate that will hold the lens is wide enough, you can use a 20mm lens instead of an 18 mm diameter lens. On the older Mercury I measured the lens plate to be 1.096" x 1.256" x .150" thick with the lens hole centered on the plate. This is about 27.8 mm wide so a 20mm lens works. You need to measure the width of the guide slot in the aluminum carriage to make sure it will clear the lens diameter you want to use when the plate is slid in. I was able to fit a 22mm dia lens into mine but that is pretty much the maximum.

I suppose there is some heating of the lens but I don't know whether the aluminum plate was intended to dissipate the heat. If you are worried you may need to watch for overheating (check lens temperature with an IR thermometer after cutting?) (The mirrors can get warm with high wattage lasers and some mirrors are mounted to metal plates which will sink some heat.)

Aluminum is better if you have the tools to make it.

In the Mercury, the 2", 2.5, and 4" lens holder have a chamfer and the 1.5" lens has a step on the edge. I don't know how yours is set up. But I think you should be able to use whichever slot works best for you. The standard Mercury 2" lens sits up close to the mirror. I made a new 2" mount that sits in the bottom slot so I can keep the nozzle farther away from the work. It seems to work fine in that position.

I doubt that you will have good success with acrylic using a 4" lens. The spot size will reduce the energy density such that it won't vaporize well. I expect it will take multiple passes and the edge will not look good at all.