k40 laser shattered new mirrors.

[Mike Grudowski]

Hello all,

I am new to the forum and to laser cutting. I have a cheap k40 laser and I am wanting to replace the mirrors. I purchased these mirrors off of amazon. https://www.amazon.com/gp/product/B01DP2FNQ0/ref=oh_aui_detailpage_o01_s01?ie=UTF8&psc=1 They worked for a few seconds and then they shattered. I had the laser at about half power. Where these they wrong type of mirrors or where they just cheap. Can anyone direct me to some cost effective mirrors that should work with the k40. Thank you so much in advance for any help that you may be able to provide.

[Mark Canada]

They should have been fine - did you clean them before installation? Maybe they had some residue on them when shipped or from handling as you installed them?

[Mike Grudowski]

I cleaned them with rubbing alcohol and a cloth like what you use on your glasses. I did this on the old mirrors with no issues.

[Gary Hair]

Either the rubbing alcohol or the cloth could have left a film. It's best to use lens cleaning tissues and acetone. I have 10+ year old lenses that I have cleaned this way on a regular basis and they look as good as new.

[Bill George]

You might try the K40 group on FaceBook I think your the only one using that machine here. This is really not a hobby / build Forum.

[Mike Grudowski]

Thanks will do

[Gary Hair]

You might try the K40 group on FaceBook I think your the only one using that machine here. This is really not a hobby / build Forum.

If you chased away all of the hobbyists this place would be a veritable ghost town. I don't think that's the intent of this forum and it's certainly not your call. Not that I want to read about a bunch of K40 problems, but no matter what brand/model machine it goes on, if it's a low powered CO2, the lenses all need the same maintenance.

[Mark Canada]

Even if there was a film left by a low purity IPA or dirty lens cloth, it shouldnt be bad enough to pop the mirror THAT fast. Considering how smokey i've seen lenses on 100W lasers without popping them.

Might be worth spending a little more on the next set of lenses.. maybe the substrate the gold was deposited on was inferior, or the plating was...

[Dave Sheldrake]

K9 mirrors are the worst it's possible to buy, they are usually poor quality glass that is PVD'd with gold, Next up is Si mirrors, then Mo if you really want tough one's

Copper and exotics Like Ge are a waste of money on normal home user machines

[Kev Williams]

I'm curious about: "they" shattered-- it would be a trick to have all 3 mirrors break at or near the same time. Rapid heating and cooling I guess would do it...

[John Lifer]

Kev, kind of curious also. I mean, shattered? Granted they were only $8 each...... In too tight? Backwards? or did he clean the gold plating off of them

[Mike Grudowski]

I'm curious about: "they" shattered-- it would be a trick to have all 3 mirrors break at or near the same time. Rapid heating and cooling I guess would do it...

Here is a picture of one.

mirror.jpg

[Mark Canada]

Wow, it looks like the gold was blown right off the centre and then the glass was heated rapidly by the whole beam. It looks like there is a very clear centre with no gold?

I wonder if the gold deposition was too thin, allowing the beam to directly heat the glass, but enough beam still reflected to do the same to the other mirrors. Crazy.

[Dave Sheldrake]

badly adhered PVD plating, not uncommon with K9's

[Matt McCoy]

If they all shattered, did the mirrors break in reverse order (e.g., mirror 3, mirror 2, then mirror 1)?