Malcolm, this one's for you...

[Ryan .]

https://youtu.be/YwfKxbm2TK4

[Malcolm Napier]

Do you remember the first time that we met? It was at the Rising Sun on Silver Street at one of the first Hackspace meetings post Tom's garage. You managed to achieve a similar effect with a mains power metering devce that you had got from Maplin. And you were equally surprised that it happened. :-)

What is the conclusion? I think that I saw Richard start to point at something.

On Tuesday, 26 July 2016 23:24:15 UTC+1, Ryan wrote:

https://youtu.be/YwfKxbm2TK4

[Mark Hill]

Here's a still just after the white flash:

[Ryan .]

https://youtu.be/lpRwqwIFdG8

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[Malcolm Napier]

That looks like excellent progress - although the mystery of why all 3 power suplpies were dodgy remains.

Are you at rLab at present?

I was planing on coming down this evening - at around 1930h

[Richard Ibbotson]

We know that one was a broken Flyback transformer, a common failure. On the other two we have damaged bridge rectifiers and one a damaged power transistor. Replacements components on order, but actual cause may be elsewhere.

Sent via Richard's Phone

07871 256772

[Malcolm Napier]

Here are a few images of what Ryan and I got up to yesterday evening with the working PSU. Had I thought, I would have taken a few of the electonics at various stages of testing. The summary is:

We used some compressed air tubing to pipe water to and from the laser tube and fed the water to the tube direct from a tap and back to drain out of the sink. It is not distilled water but Ryan said it was OK!

We wired the repaired PSU direct to the tube (i.e. no other control electronics) to see if it would fire the tube - which it did - see hole in picture of test piece.....  (The optics seemed to be fairly well aligned so smoke from a plastic screwdriver handle placed underneath the lens was deemd a sufficient indicator.)

Then we wired the PSU back into the control panel on the laser (having checked out the mains wiring through to the switches and beyond). That enabled some more test firing via the control panel. As we hadn't moved the test piece between test shots we used the depth of the hole as a proxy for the effectiveness of the laser.  The hole was around 10mm deep - so not much wrong with the tube.

The next steps are:

Re-attach PSU properly to the mounting plate. The screws seem to be the wrong size?

Make good the wiring of sensor wire between tube and PSU

Find & fit decent water cooling and air pump

Address issue with belt & pulley

Clean chamber and mechanism

Soak test

[Richard Ibbotson]

Great progress

I don't know how far you want to go with it before passing to a Hackspace, but a few other things to consider.

 

May be worth adding a current meter. The power levels are controlled in software, but a useful indicator to limit laser current, and indicate when laser operating. They are under a fiver on ebay.

Add some interlocks.

Source a decent honeycomb bed, I did not look how Z axis is moved.

[Stuart Ward]

The sparks fly...

[Malcolm Napier]

Yes. You and Ryan have done a great job so far. Thanks.

The things that you suggest are all things that I would do if I were going to be using the cutter on a regular basis. However, I am very wary of scope creep and aware that it is ("another laser") taking up space in the rLab ground floor.

[Malcolm Napier]

I made it to rLab on Saturday morning (rather than Friday night as last predicted).

This Flikr Album shows some of the progress made.

Pictures 1-3 show the mounting of the PSU (which is still unsatisfactory) and tidying up of the wiring (particularly the "sensor/return" wire but also other wires that were disturbed along the way) . Picture 1 also shows the mains switches but doesn't show that they are much more securely mounted than before.

The PSU does not match the holes on the mounting board, so is not the original one. It is mainly held in place by a 8 x 3/4" pan head screw at the top right of the PSU as shown in the picture.There is a second screw of the same size inserted bottom left and acting as a peg to stop the PSU rotating. However, it needs a 10 x 3/4" pan head screw to bite into the backing board or maybe a 5mm set screw of similar length would do the job. I don't have either to hand but will order a small pack of 10 x 3/4" pan head screws from eBay tomorrow if no-one happens to volunteer that they have some and can spare 2 or 3.

Pictures 4 & 5 are for Richard - to answer a previous question about how z-height adjustment is achieved. The answer is a big knurled knob driving 4 lead screws via a toothed belt and the lead screw on which the knurled knob is mounted.

I had a look at the drive belt for the long axis - which I consider to be the x-axis but RDWorks/the machine controls might disagree. I haven't tried the controls yet. It was missing an M4 x 10 machine screw, nut and a couple of washers. I didn't have anything to hand but have shortened an M4 x 20 from my collection at home and set it aside, together with nuts and washers for next time that I am in.

I also got sick of moving bits of power supplies around and I worried that things might get lost/damaged - so I have put them "back together". Or at least put all the bits into the re-assembled cases. Along the way, I noticed that when the PCB is mounted in the case for PSU Model MYJG50W the test button appears to be permanently jammed on - which might be a cause of some problems for that PSU? When freed from the case the test button works fine.

I am hoping to acquire the original air pump and water pump at some stage soon, hopefully Tuesday evening. Once we have those, we can do some more serious testing.  . 

[Malcolm Napier]

Nearly a month has gone by and I have finally managed to fix the belt on the x-axis as best I can. This is not for want of trying.

I have also experimented with some cleaning stuff for the gooey residue that gets left after the laser cutter is used but will report on that in a separate post.

I am not convinced that the combination of the design of x-axis drive and the components used allow for the optimal alignment of the belt. However, it is assembled and tensioned and it will work as far as I can tell. The plan is for the laser to leave rLab for its new home (Surrey & Hampshire Hackspace) over the coming weekend.  

So I am wondering if anyone (i.e. Ryan or possibly Richard I) will have time to test out if the x-axis works OK before then?

I can't see the point in doing any more than that (e.g. fitting the air pump, water pump & water chiller or any interlocks) until the laser is in its new home.

Regards,
Malcolm

[Jonathan Hall]

Hi I'm Jon from RML, and I'm mostly responsible for the dismantling of the x axis tensioner at Richmond, but also buying the spare belt and 'gearwheel' that you should have received with the cutter. We concluded that the original aluminium belt tensioner was wobbling and that this was caused by the failure of the brass axle due to wear, and the failure of the bearings within/between. I think it needs a new axle turning, and then new 9mm bearings should fit into the new gearwheel (IIRC that's what I spec'ed it to be drilled for).  I was using the laser for engraving scale brickwork on buildings for a model railway layout, and the wobbly x axis was causing problems with alignment across the work piece (brick courses didn't line up).

We were just about to get a new axle turned from steel when the power supply failed, and failed, and failed.. and then a member bought a new cutter instead...

I may yet end up joining Reading Hackspace - my employer is moving us from Egham, to just off the Basingstoke Road, so I'm probably moving to South Reading sometime in 2018?

Jon

[Malcolm Napier]

Hi Jon,

Thank you. That is very useful information.

The laser heads of towards it's new home in Guildford tomorrow, via a staging post in Camberley.

I will be back on the case in late September, when I return from holiday.

I might pick your brains further at that stage. I am hoping the setup is sufficiently functional to allow us to test that we are not going to get another PSU failure, in the near term. But I will examine the tensioner unit further.

And you know where we are as and when you make it to South Reading. :-)

[Mark Hanford]

Hi all,

I'm the one currently stashing the cutter until we have our space ready for it - we can't wait to get it going! I've not done anything with it yet apart from a bit of cleanup, and sorting out some bits'n'bobs for the reservoir and bench etc.

Thanks for the cutter and all the help I'll no doubt be looking for :)

Mark Hanford

Director, SH Makerspace

[Ryan .]

Mark, no worries! 

If you want a hand getting it running, speak to one of our members Alex Gibson, he expressed an interest in learning about laser maintenance last night.

R

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[Mark Hanford]

Have you found anywhere particularly good for getting acrylic and plywood stock from? Or is it just a case of hunting about on eBay to see what's a good price at the time?

M

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[Ryan .]

Kitronik, a few others, eBay if the price is right.

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[Alex Gibson]

HLN supplies - let me know if you want to order there, and we can combine postage costs, with an rLab order and/or for my business

Tapped on my mobile phone.

[Richard Ibbotson]

What happened with spare/broken PSU and bridges/ transistors/ dummy load ? Do we still need to fix other PSU ?

[Mark Hanford]

These were with the cutter when Malcolm dropped it off at mine, and he took them back with him - I assume they'll turn up once he's back from holiday.

[Malcolm Napier]

They are currently in a box at my house.

I was hoping to do (some of) the repairs under supervision once I return to the UK.

I have removed the resistors from the acrylic and was intending to discuss and implement a more compact solution.

I would also like to tidy up the control potentiometer and power connector arrangement to replace the insulating tape.

[Malcolm Napier]

Also, well done Mark. That looks really shiny.

:-)

[Mark Hanford]

Hi folks, apologies for the repost, but I think I posted this in the wrong thread last time ☺️

We've managed to get everything hooked up now, and mechanically things seem sound. Does anyone have any idea if the control panel should give an indication if the water flow sensor is stuck? We're not getting any life out of the "pulse" button, regardless of power levels, but the 'test' button on the PSU does generate a pulse. I think the alignment may be slightly off, as we are getting a crescent-shaped hole in the test piece. Here's a picture of the test firing results http://i.imgur.com/PM3mT8w.jpg
If anyone is interested, I'm documenting as we go on the forum: https://shm-forum.org.uk/t/laser-cutter-refurbishment/254