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.

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.

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.

A lost camera, found again.

I have been working away the last few days without taking any pic's. So now, as I found my camera again, there is a bit of progress to be shown.
First here is a picture of the frame of the cutter itself. I was just laying it out to see the size and make a few decisions! Again the size being dictated by the belt length.(by the way, if you click any of the pictures, a larger sized slideshow should come up, nice!)

You can see the first of the X axis' supported rails here. The other is the gantry rail temporarily. I cut the box section with the bandsaw and finished it with the flycutter on the lathe. I really like the fly cutter, it such a lovely finish. Great for butt joints.

Below is the linear bearing and belt setup for the gantry. The "belt through the hole" idea is from the LightObject design. A nice space saving idea.

It allows gubbins to be directly above the bearing and belt. The clamping plate setup is the same as the gantry. One fixed and one adjustable.

In the picture above you can see the bolt holes for the motor mount and the access for the linear bearing bolts. Mine is off to the side a bit, due to the fact the I had to bolt the bearing and spacer on from above.
Here is a wide of the gantry minus the rail, motor etc.

Just tonight I finished drilling the 8, 22mm holes in the bearing blocks for the X axis belts. Each hole took 8  different sized drill bits. Spotter, centering bit, 4mm, 7mm 11mm 13mm 16mm 20mm 22mm. It makes it time consuming but the way the hole is still in the right place at the end makes worth while. More on that in the next post.

Clamping plates 15 3m.

In this post, clamping plates and gantry assembly and other very very interesting things.
Lets start with blurry picture.

 The point I was trying to illustrate was the bevelling of the edges of the slots. I wanted the belt to sit in as deeply as possible, so the corners had to go. The piece of Al. above 10x10x50mm with the slots being 1.6mm wide 1.5 deep and 19mm long. On 3mm centres to match the belt...
I cut it on my CNC. I cut at .6mm per pass 100mm/min with 3in1 as cutting fluid.
Once I was happy that it was working I went ahead and cut the other 5.

I'll chop them up with a slot saw on the lathe.
Here is the slide on the gantry. The linear bearing arrived! I did notice that you must tighten the two grub screws in them to fix the bearing into the mount.

The belt clamp on the left is fixed and on the right is adjustable to tighten the belt.

A Hard Case to Crack

Good progress today. Linear rail for gantry drilled and tapped and gantry motor mount made!
I'll start with the motor mount as its very straight forward and need little explaining.
Here is a pic!

Its 6mm thick. I had to put it in the 4 jaw chuck on the lathe to cut the big hole.Drilled the 4 holes to 4.2mm and tapped M5. I've yet to drill the holes to mount on the gantry. I need to get the linear bearing first...

But the big thing today was the supported rail for the gantry.

 I'm going to go into a bit of detail here because

 it was a pain to get this done untill I got the knack!

 (and this might help someone trying the same thing)

In this project I'm using 16mm linear rails. They are case hardened, which means no drilling into the surface.
But...below the surface is normal mild steel! So I can work that easily if I can just get to it!
If your drills or taps touch the hardened steel the will snap.
So follow the steps below and your laughing!

1. Mark your drilling points with a permanent marker (don't bother trying to scribe a mark at this stage).

2. With an angle grinder, grind the spots you've marked. Be careful, try to stay inside your support width, 8mm in my case. The point here is to get the centre of the cut to be through the case hardening.

Here is the first cut

3. Remeasure, scribe and centre punch your drilling points.

 4. Get a tile drill at least 2mm larger that the thread diameter of your tie down bolts. M6 in my case so I'm drilling with an 8mm here. Naturally you want to use lubericant of some type here... an interesting side note, normally these drills are used for tiles and glass and water is the lubericant. But I have a suspition that the water is a coolant not a lubericant.

I noticed that it wasn't untill the oil I was using was pushed out of the drills path did it start cutting properly.

5. Drill with the tile drill untill you are at least 1mm larger than you tap diameter. So I drilled in to 7mm or so!
Now you can go ahead with a nornal tapping drill size as you are throught he case hardening...

 6. Once you've done one hole, go and tap it!
      You see the gap between the tap and the case hardened steel.

 Now scew in a short length of threaded bar. This will help ensure all the other holes are on the same axis!

7. Go ahead and drill the other holes. Tile drill then tapping drill always using the threaded bar as a guide to the alignment.

When you have all that done mark and drill the U channel. It will all line up... and you get:

Lovely.