Cutting at last!

Its been quite a while since my last entry, but I've been busy. I have been trying to tweek the
electronics and hardware to overcome a few problems...

No.1 being a vibration or vibrations. Where do I start?
The worst direction was the Y axis. It was all over the place. During my initial cuts I got very disappointed. Pissed off even.
But I worked through a few options and it cutting fine now.

These are the points to be on the look out for-
1. Linear bearings work best in pairs and under load. Not alone and free running. I found there was quite a bit of play, not only between the bearing and housing but in the bearing itself.
So to counteract this issue I did this:

 There are bearing on the other side too.

2.Steppers vibrate at low speeds if not under load. My flying optic moved quite freely and was essentially no load on the motor.
- Imagine if you will, what is happening at low step rate -
As the stepper moves from one pole to the next, the mass of the rotor is accelerated around. Ideally, it stops dead in it new step position.
But no! it actually overshoots a little, only to be pulled back and eventually settle in its new position. This equals vibration.
It disappears at higher speeds as the rotor is caught in its overshoot position only to be pulled on by the next step.
So what can we do?
I believe... add load to the motor shaft(make a heavier flying optic) or reduce the current to the motor to the absolute minimum to move the FO.

3.fix the bearings on the flying optic.

4. Also microstep. I upped mine to 1/16 and it was a huge help.

 

I also upped my air pressure to 2 bar from a compressor. It made a huge difference to the cut depth. A Very noisy solution!

 To do: A water flow alarm. I'm working on that now. I will put up a post on that alone. Circuit etc. I managed to do a cut without the coolant water on at all. Crap! Probably 30 second or more.
Thankfully the laser survived.

And the lid with safety cut off switch to stop me burning my eyes.

Here's a couple of pics!

Shooting Down Satellites.

I did my first laser test today, with great success!
Here's what I've done over the last few days:
Laser mirrors fron a harddrive platter. I had my doubts but I thought, what do I have to loose? And I can report: it works!
I masking tapped both sides of a newly discected hard drisk, clamped between two sheets of Melemine chipboard and cut with a bimetal holesaw...carefully.

Here is a picture of the mirror on the plate from the top of the flying head.

I decided I need a visual referance that all the bits and pieces were switched on, pump, compressor, laser power supply and extraction(when ever I get around to that one!)
I spotted this switched splitter with neons in Tesco for €11.50 so I decided to go for it. It will save alot of wiring and switches.

For the cooling of the laser cutter I got a large tub from my local vet (Avondale Veteranary "A great place to get your balls cut off") I would think its at least 30 litres.
I decided to go mad and get electrical cable glands to try seal the tub all together, they are a very neat, sealed system for this kind of thing.

 

The pump I'm trying is a 10euro campervan water pump. It will pump at least 2.5m head. At 14lpm it should be plenty of flow to keep the 40watt laser cool. I got that pump on Ebay from the UK.

That jubalee clip, by the way is a stainless steel as it will be submerged.

Some progress(is better than none)

 Above is the new table I built for the cutter, nothing to explain here, I think the photo speaks for itself. Thats 1" ply on the top. I will build a cover eventually...

This is a shot of the controller in its case. An old computer case, at first I thought it would be way too large but now that I realise how many wires are going to be in there I'm glad.
In the box are:
2 motor drivers,
1 Leetro Controller
1 old DVD player power supply(24v for the Leetro board){Accross -12v to +12v. Not sure if thats a good idea but its working!}
1 36v power supply (for motors and air solenoid valve)
1 Neon panel switch.
                 

Flying head!

Today I finished the laser head. It was my first time doing threads internally and I'm delighted with the results!(don't forget you can do a slide show by clicking on the images)

The beginnings of this piece can be seen in an earlier post, so this is the continuation.
.
I'm going to test the ZNSE focal point with a red laser. I wonder if it is different from the focal point of the IR from the Co2 laser? Yes, I would say.
I think the images do a good job of explaining what i'm up to here so I'll keep this short.
The air assist fitting is 8mm tube diameter on a 1/8 bsp thread. Drilled and tapped.

Its difficult to see in this picture but the end of the middle tube is threaded externally at the end.

The thread I used is 24mm X 1mm. I learned how to thread off a video on youtube.(search "tublicain")
I decided to do air assist while I was at it.
I got a lovely 50.8mm focal lenght ZNSE lens off ebay. It is 20mm dia', so I cut a little sholder for it to sit on inside the nozzle.I'll put a thin washer/seal under it so as to protect the lens and seal the pressurised air from comming out the wrong place

The outlet for the air/laser is 2mm dia. I have no idea if this is too big or not. If anybody reading this has more information about what size it should be please leave a comment.

Mirror video

Here is a quick video of the first mirror alignment test. I think it looks promising...

Fantastic Laser Tube

Here is the lovely 40W laser tube. Chinese made and very beautiful. I love vacuum tube technology, in what ever form it comes. It is such an overt display of the incredible physics that are going on inside. Nowadays it all happens in SMDs or BGAs or some other little black blob of plastic.

 

So a brief description:

High reflector seems to be gold coated and the output coupler germanium. The electrodes I assume are nickle, judging from their colour and catalytic effect it would have.
Strangely the water cooling for the Ge is in a glass structure. I would have thought this fiddly bit of work would more easily be done in metal, not to mention the fact that glass is an insulator.

 

Anyway at this stage I trust the Chinese as the made most of the things I own!
As you may know this tube is: gas discharge tube in the centre surrounded by a water jacket which is itself surrounded by the gas reservoir. How the hell are these made? Respect to the crafts men and women involved.

So to mount the tube I needed its centre to be 115mm above the top of the frame. I have made two assumptions here (which normally turn out to be wrong...)
 1. There will be no vibration.
 2. I don't need triangulation.
 The tube is mounted on 6mm plates bolted to the top of the frame. The cradles are then on adjustable M8 threaded bar, to allow for virtical adjustment.
At this point I should mention that all these heights have been dictated by the mirror on the gantry... but that's another story.
Since this picture I have put some padding for the tube to rest in and centre itself correctly. I made allowances or that cutting the semicircle.

The Laser Flying Head.

This  is the start of the flying  head, it will eventually hold the ZNSE lens and have a compressed air supply connected and blowing out the bottom.

This post is the first stages of its construction. I'm learning a few things on this bit, threading on the lathe for one. Also Squashing the adjustable mirror mount on to the top of the 30mm square bar was interesting.

The image above shows the square bar drilled out to 20mm dia and the sliding tube to allow vertical focal point adjustment for cutting materials of different thicknesses. Or in my case, I'm not sure where the cutting surface is at all!

 The above pics show the end of the square bar chopped and flycut to a nice 45 degrees. The area of metal left is where the 5 elements of the adjustable mount had to fit. One trick which allowed this to squeeze in there was the spring fixings. A piece of M3 threaded rod is wound into the spring, obviously the handedness of the spring is important here. It really grips tight as it is under tension all the time.

So I drilled and tapped the locations in the body of the head and it was possible just to screw the springs in nice and neatly.

 

The rest of the mirror mount here is just as I've described in a previous post. One mistake I made in my marking out of these adjustable mounts is that the position is based on the front surface of the mirror that will be proud of the mount. Not the mount plate or the supporting bracket...

But luckily I went with 25mm mirrors so that should be enough room to allow for that mess up.

There will be a continuation of this part in a while. In the mean time I'm on to the laser tube mount.