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.

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.

Adjustable mirror mount, The first.

 

This is the first one I'm making and it is for the gantry, which seems to dictate a few different heights on other parts of the machine.

I mostly copied this design from mirror mounts I saw for sale on Ebay. The plate with the mirror attached is pulled tight against the thumbscrews by a pair of springs. It all pivots on a ball bearing.

 

I decides to go with 25mm diameter mirrors because it allowed for the best chance of alignment to happen at all!

I started by using a 1" hole saw to cut the recess for the mirror to sit in. I just cut 2mm or so in to the 6mm thick aluminium.
Then I drilled out the rest of the material to a 22mm hole. It wandered all over the place as can be seen from the back view. Not too big a deal in this case, just looks poor.
For the ball bearing hole and thumb screw holes I used the cone of a centreing drill. it gives a chatter free conical hole, unlike a counter sink in my drill press.
Perhaps not the best cone angle.
I'm using a 6.5?mm dia ball bearing here. It was just one I had lying/rolling around. It seems okay.

The adjusting screws are M4 by .5, the fine version of the standard M4 thread. I did so because I read someone giving out about a similar set-up which was using a standard thread here and it was very difficult to get an accurate adjustment with it.(this was on a commercial, cheapo Chinese laser cutter.)

I cut the springs from a long spring I had and bent the loops up. They work well. 4mm dia with wire of .9mm I think.They are held in place with TIG filler rod pins.
I made the thumb screws on the lathe. Turned from 6mm brass rod, down to M4 by .5!(with a die). I should have faced off, then centre drilled the ends of the bar before I started, as I need to put a small ball bearing into the end of the thumb screw to stop it biting into the aluminium.

The mirror will be held in place with a ring held in with three M3 socket heads. To be cut on my router from 2mm aluminium sheet.

Leetro Machine Controller Arrival!

I splashed out when I saw a Leetro laser cutter machine controller for sale on eBay.
It's one of these!
I was origanally going to try to botch my way through it with Mach2/3. But I saw this and decided it was too good an opertunity to pass.

I have had some success in past using a diode laser on my CNC and using the 0.0016 as my cutting depth and using the direction pin as digital on/off for the laser. The process is detailed elsewhere on the web and a search will bring it up so I won't explain here. Worth looking into to play around with a diode laser on a cnc router.

Not another project!

I have been thinking about making a CNC laser cutter for a while now and was inspired to start when I saw this laser cutter XY set up.
Its simplicity of design is what struck me and the fact that its made of fairly standard components.
So thats the design I'm going to follow morealess.
I'm keeping this blog as a record for myself as much as for anyone else who might want to look in!

On my shopping list so far are:

3X16mm open linear bearings (Ebay, china.)
3m 16mm round rod/shaft to suit above.( Reliance bearings JFK Ind Est, Dublin.)
4m 50X50X3mm Aluminium box section. (Miko Metals, Cork)
500mm 80X80X8 L angle.(Miko Metals, Cork)
2m 25X50X3mm Aluminium box section.(Healey's JFK Ind Est, Dublin)
6 3m24-15 timing pulleys (Rotate Ltd, Dublin Ind Est)
3 1800mm 3m-15 Timing belts (Poly-belt, USA, Internet)
4 flexable shaft couplers (Ebay, China)
2 Steppers(1 I have from a photocopier, 1 probably from Hobbycnc, USA)
Misc bolts!
Laser 40watt plus power supply (Ebay no doubt)
Mirrors (Dont know yet)
Mirror mounts (Dont know yet)
Cutter head (Dont know yet)

There will be plenty of photos along the way too...