80W Chinese Laser Cutter Commissioning

Tell us about your projects. Update us regularly.
Post Reply
User avatar
seaton
Master Maker
Posts: 222
Joined: Tue Jun 24, 2014 11:41 am
Location: Bunbury, WA
Contact:

80W Chinese Laser Cutter Commissioning

Post by seaton » Mon Nov 21, 2016 12:12 pm

New 80W Chinese Laser cutter arrived last week from eBay...took approximately a week and a half to be shipped from Sydney, Jo my partner purchased it for her business and (cough cough) other maker activities :D. So yesterday I got a chance to set things up and commission it.

This thing was very well packed and the nice courier actually unpacked it and helped her move it inside the house where its temporary home is until new Shed is build.

Looks like installed tube is actually rated at 70W with peak power at 80W . Not really surprised with this as it happened to Paul with his 60W and I was sort of expecting it. I'll decide if its worth pursuing further with seller as probably not worth the hassle, although I haven't given any feedback as yet so still may have some leverage.

Image

First thing was to remove all the grease on the rails which was layed on pretty thick. There was also quite a bit of swarf floating around in the bottom of the various compartments, sop removed all that too.

Image

Image

Image

All peripheral equipment was hooked up and tested i.e. water pump for tube cooling, air assist and extraction fan then powered up. Language is in Chinese I know Paul sent me instructions of what he did to get english menu, but I didn't have my computer handy so just browsed through each menu until I could read english and enabled it. This worked and now all readable and could perform motion tests which were all straight forward and all worked as it should.

Next was cleaning the optics, all optics were in bad need of cleaning, from the photos you can see the initial state of them before and after cleaning with a bit of isopropyl on cotton buds.

2nd Mirror Before:
Image

After:
Image

Focal Lens Before:
Image

After:
Image

The rest were much like these so won't bore you with their pictures.

Once optics cleaned now the fun part of alignment, I suspected that these should be factory aligned....how wrong I was. The did have it roughly aligned, even had the 1st mirror stand in back to front so I couldn't adjust mirror height easily as you can see in the first picture how far off the initial alignment was like on the first mirror, well it was a similar story on the rest.

Alignment procedure was to stick some masking tape over the optics as the beam is not visible and set power to lowest it can fire, in my case 12% seemed to work pretty well. I quickly learned after the first couple of test fires I need a few layers of tape as I had to clean the optics again where it burnt through with a single ms pulse at 12%.

Image

Image

From the burn mark you can then see where the beam is in relation to the optics and so mirror is adjusted accordingly to get beam fairly central to the first mirror.

Alignment as shipped 1st Mirror
Image

Adjusted
Image

Then same process for the next two mirrors except the alignment needs to be performed on each of the Axis both near and far, i.e. move the Y Axis closest to the tube, do test fire and then move Y Axis to its extent and do another test fire, then make adjustment then rinse and repeat. This process ensures the beam is perpendicular along each axis under alignment. Here you can see the progressive alignment in the mirrors adjustments of the 2nd mirror in relation to the 3rd mirror aka Moving Head (X-Axis).

Image

Final Mirror on the X Axis was the hardest as for the life of me I couldn't get it aligned and central to the mirror. This mirror is the moving head mirror which directs the beam to the focal lens and out the nozzle onto the workpiece. I aligned as best as I could albeit a little high and proceeded to test nozzle alignment which was central to the exit nozzle so I though was good to go, however I found that the beam hitting the work piece was skewed to the right.....i.e. if you sit facing the head the beam should be hitting right below it along the beam axis, well this was to the right about 5mm so I tried to manually adjust the head mirror, I managed to pull it back under but from redoing a nozzle test I found it to be hitting the side of the nozzle and more than likely reducing exit power considerable. This skew is being caused by the beam not hitting the focal lens centrally and hence the optics will bend the light.

After a lot of head scratching I reviewed the entire optical path to see how it could be adjusted as it looked like the entire beam needed to go down so that I could get it central on the head mirror (was currently high) My answer to the problem appears in the form of a lock nut below the Laser Tube. I thought Id give it a go and loosen then adjust it down. success the beam dropped, After checking all the path alignment again all was good except for the exit nozzle was off, this made sense as is now hitting optics fairly centrally and so after a small head mirror adjustment I my beam was central and hitting directly under the head!!!

I will post some more photos of the my test fires and alignment shortly to show how I could see the beam path of my cuts through this adjustment process.

Anyway very happy with the initial results and definitely shows that the Chinese laser cutters need a fire bit of cleaning and adjustment before putting into service.

User avatar
seaton
Master Maker
Posts: 222
Joined: Tue Jun 24, 2014 11:41 am
Location: Bunbury, WA
Contact:

Re: 80W Chinese Laser Cutter Commissioning

Post by seaton » Mon Dec 05, 2016 4:54 pm

Over the weekend I installed a beam combiner

A beam combiner is used to combine visible red laser pointer with the main beam so the red dot appears on the surface of your work and can see where its login to cut. The Chinese laser cutters come with a laser pointer connected to the head and adjusted so the dot aligns with the centre of the beam, problem is its height specific so if you change your focus distance then this dot is out and will need re-adjusting. However the the dot via the beam combiner is always in lien with ether beam (in theory) .

I wanted to install my beam combiner right out of the tube and before the first mirror so any losses are minimised, apparently one of the downside to the beam combiner is you loose some beam power as the main beam does have to pass through an extra element. As I don't have a power meter at the moment I'm taking the work of others and appears to be < 1% loss.


However... as you can see there is not enough room with the tube and 1st mirror.

Image

To see if I had any "wiggle" room with my tube I removed the HV cover end, this end is where the High voltage connects to the tube and judging by the length of the cover and the tube I had plenty of room to move the tube along.

Image

Heres a photo of complete tube with camera held high above my head so I could fit everything in (my back is too the wall) Don't let the photo fool you, the tube is approx 120mm diameter and ~1200mm in length

Image

overhead view with combiner installed between tube and 1st mirror minus the laser pointer which gets installed perpendicular to the beam.

Image

after installation I wanted to re-check alignment and just so happened I came across some decent acrylic 25mm thick block during the week for just the purpose of beam alignment, and I mentioned the process it in my original post, however I only had some 3mm acrylic. so I could only get the angle of the beam roughly aligned.

Here is the first pulse test and as you can see the beam profile of the cut is slightly skewed to the right, what this means is that anything cut with will have a slight sloping edge on it. Power @ 40%, I also realised that I hadn't set correct focus height. not really a problem for the beam angle just won't give me correct depth.

Image

Finally after aligning I have a straight beam, I've also posted some vision of the test with the beam correctly aligned on youtube, apologies about the quality, it was much better on my phone. Power is still set to 40% and doesn't have a problem getting all the way though the 25mm acrylic.

Image

https://youtu.be/pn3d9MSHPdc

Stephen...

Post Reply