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maria galligan
12-31-2011, 4:31 PM
Hi can anyone give some advise on the best cheap lens to buy and from were for a cheapo chinese laser engraver. I need to replace the back lens the one at the the laser light. It is had it but am unsure as to what to buy. Have looked but am confused to know exactly what I need to order. We are only doing engraving no cutting and only on leather soft wood like mdf and plastic. any help will be appreciated.
Thanks Maria:confused::)

George M. Perzel
01-01-2012, 2:56 AM
Hi Maria;
Are you talking about the lens or the mirror? Output lens on glass chinese tubes are part of tube assembly-not sure how they can be replaced without damaging integrity of tube.
Best Regards,
George
Laserarts

maria galligan
01-01-2012, 3:06 PM
I spoke with Shenhui lasers yesterday and they told me it was a reflection lens. Maybe I used the wrong term as I'm new to this. And this k40 machine has been a complete pain in the you know what and the seller has been no help what so ever. We are having to search ourself's to find out what we need and how to fix this heap of nuts and bolts. All we want is to get it going because we have not had the machine running very much since we got it. Because of the non existent technical help given from the seller. Any help please?

George M. Perzel
01-01-2012, 6:29 PM
Maria;
Calm down and help us to help you.
1. Did you buy this machine from Shenhui?
2. If not, from who?
3. Shenhui has pretty good tech help once you understand how to ask questions and state what you are doing and what the problem is.
4. You have two posts here trying to get answers-close one.
5. Show pic where "lens/mirror" is when mounted in machine-is it directly in front of tube?
From what I can gather from the two posts, what you are dealing with is a mirror, not a lens.
Do you have a spare mirror? Did it come with your machine?
Best Regards,
George
Laserarts

Dan Hintz
01-01-2012, 6:34 PM
Maria, you have either lenses or mirrors... if the objects purpose is to change the direction of the beam, it's a mirror (and you can see your reflection in it). If you can see through it (and it has an orange tint to it), it's a lens.

maria galligan
01-01-2012, 6:50 PM
If you look on my other thread Changing laser lens there are photos on there. But O bought machine off Ebay and there was no spares. It is orange but I can see a reflection in it>It is mounted directly in front of the laser tube. So what was just said it is a mirror. I contacted Shenhui to get some help as I can't get any from Ebay seller. Have left us high and dry. Look at the pictures, they show the mark and the mount.
Thanks Maria

Dan Hintz
01-01-2012, 6:57 PM
IF you can see a clear reflection (and nothing behind it), it is a mirror. If you can se your hand waving behind it, it's a lens.

maria galligan
01-01-2012, 7:03 PM
I can see reflection in it, can't see through it so it's a mirror. Thank you for that. Now all I need to know is how to replace it? Get it out of the mount.

maria galligan
01-01-2012, 7:08 PM
here are photos

Rich Harman
01-01-2012, 8:47 PM
That looks like someone mounted a lens where a mirror is supposed to go.

Dan Hintz
01-01-2012, 9:25 PM
That looks like someone mounted a lens where a mirror is supposed to go.

I have to agree... that looks like a lens, but it's in a mirror mount. Is there a hole in the back of the mount? If not, it's supposed to be a mirror.

maria galligan
01-01-2012, 9:51 PM
Well I can now see how to get it out the round part screws off. Yes there is a hole in the back of the mount. This mount was right opposite the tube. So the beam comes out of the tube hits this and then goes inside the machine to another mirror then goes into the laser head. This is how we got the machine from new.

maria galligan
01-01-2012, 10:00 PM
The round front screws off. But there is a whole in the back of the mount. This mount is opposite the laser tube. So does this mean it is the wrong mount with the wrong lens in it. It should have a mirror in it?

Rich Harman
01-01-2012, 10:27 PM
It should have a mirror in it?

I think so.

It would be really helpful if you would take a series of pictures all around and inside your machine so that we all can see exactly what you are talking about.

Rich Harman
01-01-2012, 10:40 PM
Here is a picture of the first mirror assembly of a DC-K40 laser;

217966

Khalid Nazim
01-01-2012, 10:41 PM
Its possible that if a lens was mounted in this mirror holder and the mirror holder is the first one next to the laser, that the laser could have burnt a hole at the back of the mirror holder.

maria galligan
01-01-2012, 11:34 PM
Here are some photos of the machine ant the mounts. One showing the hole in the mount. The machine has no manufactuers name on it but the photo in the ebay add had shenhui on it so we think it is there machine.

maria galligan
01-02-2012, 12:00 AM
What would happen if the mirror was put in the wrong way? Would the laser burn a hole in the mirror?

Rich Harman
01-02-2012, 12:20 AM
Lasers use a first surface mirror - a CO2 laser beam will not pass through glass. A typical bathroom mirror has the reflective coating on the backside of the glass but a laser mirror has the reflective coating on the front side. The laser beam will bounce of the silvered surface without ever passing through any glass.

When you get your replacement mirrors they will will be shiny and reflective. My mirrors appear to be made of solid metal, one side dull and the other silvered. It's hard to imagine how one could be inserted backwards, or a lens mistaken for a mirror.

maria galligan
01-02-2012, 12:35 AM
So when I buy replacements I need to buy reflective mirrors is that right? I have been talking to Shenhui lasers to buy from them.

Rodne Gold
01-02-2012, 12:35 AM
Did you laser EVER work?
Unless the "mirror" was made of something unusual , its unlikely the beam can burn a hole, mine are made of steel . When I was in China in may last year , Shenui had one or 2 of those K40 type lasers in their showroom when i visited em , they declined to sell me one as they consider them substandard. I didnt see any being constructed on their factory floor and none were packed for shipping , not sure if they still supply em, they indicated that they were just more trouble than the sale was worth , I got the impression they bought em in. At least they giving you some help...

I know its frowned upon mentioning other boards here , but on cnczone there is a guy thats extensively modifying one of these lasers and he might be able to help you more and I think it might be ok to post this under these circumstances .. if any other mods think its not , feel free to edit

http://www.cnczone.com/forums/laser_engraving_cutting_machines/138554-cheap_laser_cutter_modifications.html

here's the thread

Rich Harman
01-02-2012, 12:42 AM
So when I buy replacements I need to buy reflective mirrors is that right? I have been talking to Shenhui lasers to buy from them.

Don't take this the wrong way but... is there any other kind? :)

Make sure to get the correct diameter of mirror.

What do the other two mirrors look like?

maria galligan
01-02-2012, 1:19 AM
It worked for about 1hr but the engraving was not good. I tried to align the beam as the engraving got lighter the more letters were engraved. But then it stopped engraving all together. The beam was not getting past the first mirror as the whole is right in the middle of the first mirror. I don'y know what the hell the seller did to it but they did a real good job. We got it off ebay,never again.

maria galligan
01-02-2012, 1:53 AM
Thank you very much for all your advice. I have a better understanding of the problem and how to fix it now thanks to all your advise

Dan Hintz
01-02-2012, 10:18 AM
Here is a picture of the first mirror assembly of a DC-K40 laser;

217966

Maria,

If this is where you pulled the mount from, this should be a mirror.

Khalid Nazim
01-06-2012, 11:00 AM
You should also be able to buy the mirror and mirror holder from Light Object (http://www.lightobject.com/CNC-CO2-Laser-C11.aspx). I don't have any affiliation with Light Object and have not bought anything from them but have them bookmarked as a potential supplier.

Regards
Khalid