Chinese Laser cutter issue

Hi guys! I'm pretty desperate. As it is with chinese laser cutters it's impossible to find someone who can fix it for you so I thought I'll give this forum a try. So I got this 50 W laser cutter from China on ebay (photo attached) and it was cutting fine until a few days ago when it started to cut a little bit out of focus so I thought the mirrors needed realigning. So I did, and now it seems that the mirrors are aligned and centred but the laser doesn't cut, just lightly engraves where it should be cutting. Have you guys experience that? Do you know what the problem is and how to fix it? Thanks in advance for your help.

... what's the actual "life-time"?

This cheapish chinese glass-tubes are often sealed/glued with the wrong glue, so the "lifetime" of the gas mixture can be below 100 hours, until the output power noticeably decreases ...

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Viktor
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Call for the project "garbage-free seas" - [reprap.org]

When my arrived the mirrors and lens were filthy.
Can't say from previous use but like the thing was stored open in an old warehouse for years.
After setting all up and some tests I decided to align the mirrors properly - this gave a little bit more power.
But after cleaning the optics I had to actually decrease my previous power levels so I won't overburn.

Then there is the power supply....
They are universal supplies, so they can often power more than just a 50W tube.
This means without a real laser power meter you are always guessing and it is possible to burn the tube out early with too high power levels.
Having said that, build quality is far below any known standards, so I might pay off to open the device and follow all cables.
I have seen cases with the power supply cable for the tube being wrapped around the contacts and the blank ends left to arc onto the case - this way the laser will never get the power it needs.
Same story for the holes in the case, the cables just goe unprotected over the metal, so if you see bad signs insulate the cable in the affected area.

Well, they said the lifetime if used frequently, should be around a year. I only had it for 4 moths and use it only every now and then. The most annoying thing about it is that you can't find anyone anywhere who could come around and have a look at it.

The only thing you basically can do is try to find a replacement power supply or a way to accurately measure the output of the existing one.
Sure the tube might be a lemon but if you spend a few hundret bucks for a replacement and find out it still won't work because of the power supply....

Are you sure you aligned the mirrors properly? Because it sounds like (assuming your tube and power supply are fine) you might possibly be blocking some of the laser energy before it exits the lens (i.e. the beam is hitting the sidewalls of the mirror holders/lens nozzle). Have you looked at the laser tube (wear safety glasses!) while it is firing to see if you have a strong pink beam?

On a related issue, everyone with these types of lasers (I have a 50W eBay laser, the Shenhui SH-G350) should install an ammeter if their machine didn't come with one. I bought this one, which goes from 0-30ma.

[www.amazon.com]

It shows you 2 important things:
1. If your power supply is working (at least if it is supplying the proper amperage, I guess the high voltage components could still be non-functional).
2. The amount of power being fed to your laser tube. All tubes have a maximum amperage that they should not exceed. Many/most of these Chinese lasers overdrive the tube to claim a higher wattage rating, which can dramatically shorten the tube life.

See this thread for how to install and for some other improvements that can be made to these machines.

[www.cnczone.com]

-robertk925

Have you contacted the seller about this?

Robbin....................................................................................................................................................................... laser pointer

Edited 1 time(s). Last edit at 03/12/2016 09:59AM by robbinsleep.

Had some fun Skype time with a friend from Germany and he got himself a china clone last year.
Thank god from a "local" online seller, so he was covered by the full DE warranty laws.
After we had some good talks about basically everything we came back to our toys and he told me that so far his laser tube had to be replaced by the seller 2 times.
The first failed within weeks and was only used at a max of 30% power.
The second failed some hours after installation, again only on low power.
His last replacement is going strong now for over 9 months but he claims it is a totally different model.
The previous ones all came from china and had nothing readable on them in regards to power output or current ratings.
Number 3 is a US model with all the bells and whistles on the labels.
The glass is thicker, the connections for the tubes stronger and with quick release fittings, no comparison to the stuff the machine came with.

On a side note I read that cheap laser tubes from asia are often refurbished units that just got a new gas filling but no new optics.
Could be another explanation why so many china tubes are just sealed with silicone...