Sunday, August 15th 2010 - 1:05 PM

As I've been having lots of problems with the electronics of my laser I decided that a change was as good as a rest. As I can fire the laser I turned my attention to aligning the mirrors. Should be easy thought I. Seen loads of sites and explanations on how to do it but didn't seem to be quite as easy as I had envisaged. I could be me, perhaps I'm thick .
The paper or tape I used either set on fire or didn't give a clean burn mark which would act as a reference as I moved the axis. Anyhow, after what seemed like a lifetime and getting my coordination wrong and nearly burning myself I decided another method was on the books.
I already had a spirit level with an inbuilt low power visible laser, so I decided to use this.


I measured my laser tube at 59mm diameter, so I made a jig of the same diameter which would accept my laser. I made it long enough to rest on both supports. I also printed off some card targets of the same diameter as my mirrors. I put one of the targets in my static mirror and aligned my jig to hit the centre.

I then replaced the mirror and went on to the second mirror, repeating the process by adjusting the first mirror. I was able to work my way all the way round to the lens and the nozzle.
I was having particular problems with the full power laser exiting the nozzle hole. Inaccuracies were magnified to the extent that laser would not remain dead centre with the nozzle.
After replacing my jig with the laser tube I found that I only needed to adjust the rear tube support slightly to realign everything. I think this was due to a slight bend in my jig caused by a bent dowel. I wish I had done this from the start, it probably only took me 10 minutes to get it spot on.

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Sunday, August 1st 2010 - 5:28 PM

I had already assembled the X axis before I started the build forum so it may seem like I've jumped a bit, but I didn't want to take it apart to photograph the obvious. The laser tube, tube brackets, mirror holders, mirrors and laser head are identical to the build by "Willinaus" of Australia, so I haven't bothered going over the same details. I dealt with the same company and found them excellent. Everything arrived within 5 days of ordering and was unbroken.

I found that deciding where adjustments needed to be made in the machine for laser alignment was worth pondering over for a while. I made sure I could adjust my laser head vertically, which seems not to be the case in most machines. I did this so that the had was as close as possible to the track and hopefully I could work my way round from the tube. Some of the chinese laser I've seen seem to have them hanging out on a bracket, which I didn't like.

This photograph shows the adjustment in the flying mirror. I would have liked a micrometer adjustment but couldn't really afford the machining that would have been required. I wanted to keep costs to a minimum anyhow, hence the single bearings at the end of the shafts (simply supported). My other theory is "kiss", keep it simple stupid.

This photograph shows the Y axis drive. I was in two minds whether to have the motor in the centre of the shaft, directly driving the shaft. As I wanted a high resolution I went for a 3:1 drive from the motor. I also already had the motor which didn't have a shaft on both ends, so my mind was made up for me.
If you look carefully you will notice that the belt pulley is mounted on the end of the shaft. I realised that by not supporting the end I was going to induce a bending moment into the shaft at the bearing. This was a bit of a gamble with a 6mm shaft. I knew that the tension on the belt was quite low, but I am getting some bending so may have to use 10mm shafts at a later date.

This photograph shows the mounting for the static mirror at the laser. This adjustment is vertical only. The mirror holder assembly allows for some adjustment if it is not quite square. I adjusted to the required height using a digital vernier. Again if it's not quite square in the vertical, it can be adjusted with the holder. I would just like to point out how good these are. They are spring loaded and have lock nuts fitted.

I drilled a shed load of holes in the internal side panel to ensure the extractor wasn't trying to pull a vacuum instead of extracting like it should. I will be drilling some more in the right hand side of the machine adjacent to the electronics. This will ensure a good supply of cooling air. I will probably have to tape some up at a later date when I ge the extraction working.

Although my build has gone quite well up to date, I did have one problem. I could not get the X axis to run smoothly in the Y direction when I tightened everything up. I checked everything several times for squareness but the problem persisted. In the end I found that there was a very slight twist in the 50mm square tube I had used for the X axis. I had to install a shim between it and one of the linear bearing holders at one side to compensate. I realise that this will result in the laser head twisting also from one end to the other. Hopefully this will not cause a problem with such a small twist.

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Thursday, July 29th 2010 - 1:45 PM

Yes, I thought that myself. Will have to hope that I'm just imagining it. Have put a steel rule along it and it looks ok, but I can feel the linear bearings tightening up when I have the shaft in a certain orientation. I turn it 90 degrees and it disappears. This is almost certainly due to a slight bend in the shaft. I think I will replace it later as I can easily retract it.

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Thursday, July 29th 2010 - 9:58 AM

The next few photographs show the attachment of the linear shaft assemblies. I used linear shafts because I already had the parts, but I think I would use slides as per the X axis if I was to make another. They seem more compact, allow full support and appear to run a little smoother, but this is just a personal thought. Although these linear shafts have never been thrown about, I'm sure there is a slight bend in one of them .





Although the T nut arrangement looks a little crude, I found it great for overcoming assembly and manufacturing tollerances.

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Tuesday, July 27th 2010 - 9:12 AM

I've now started the build in my workshop (garage). Unfortunately I already have a large CNC router which dominates the cental part of the available area. Because of this it makes distance photographs difficult/impossible.
The frame has been assembled and leveled but I didn't realise how far the floor was from being level. The adjustable feet only had 40mm of adjustment so I was forced to pack the back feet (what a great start) . The frame has been clad with 12mm MDF using M6 screws and 25mm repair washers so that I didn't crush the MDF. This has made the frame very stiff as I expected.
I've installed an IEC plug and breakout board at the right side of the machine and positioned the Y axis linear shafts.




Whilst pondering the extraction side of the job I realised I had a brand new cooker/hob extractor unit from my kitchen fitting days. I butchered this and managed to extract an adjustable speed centrifugal fan, a light and a micro switch. This should work great and is very compact. I had to install it into an enclosure which I attached to the left side of the machine.

The Y axis linear shafts were mounted to laser cut angle brackets so that they could be attached as modules along with the relevant bearings. This means that any adjustment would move all the relevant parts on that side (that's the theory anyhow). They have also been mounted using large "T" nuts underneath to give plenty of adjustment. Just realised I am limited to 5 attachments so will continue with my next post. I obtained the breakout board from a company called Routout Cnc a few years ago. I don't think that they do this item anymore, but they do one similar. http://www.routoutcnc.com

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Friday, July 23rd 2010 - 5:51 PM

23rd July 2010
My steelwork arrived from powder coating and all bolted together nicely. Did it in the garden as the weather was so nice ( unusual in the UK). All the rivet nuts(M6) were fitted at this stage which will allow the 12mm MDF panels to be bolted to the frame.
I'll now put it together in my garage, fit the panels (that will give it a lot more rigidity) and level everything up. I intentionally built it light-weight so that I would be able to assemble/disassemble it easily myself. This was a lesson learnt from when I built my CNC router. I think I was speaking an octave higher for about a week after assembling that.
Attachements...

This was the steelwork bolted together and rivet nuts fitted

This was the steelwork laid out before assembly.

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Thursday, July 22nd 2010 - 2:36 PM

Hi
My work area will be about 800mm x 700mm. If I had realised how long an 80w tube was going to be then I could have increased the X axis substantially. Should have done a bit more research before doing my design although I shouldn't imagine I will need an area much larger.
It's very difficult to get good quality router cutters below 3mm in the UK. All the ones I have tried never seem to last too long before they break. I do need a shank length of at least 10mm though for the work I do. I find that I need to reduce my feed to a very slow speed to avoid breaking them. Gave up in the end and stuck to 3mm.

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Wednesday, July 21st 2010 - 7:56 PM

Hi
I came across this site whilst researching information for building an homemade laser engraver/cutter. I have found it so helpful that I thought I would attempt to write a buildlog. I have never done this before so please be gentle with me.
I had already built a 4' x 6' CNC router so felt reasonably confident regarding the mechanics/controls. I used mach3 for this so intended to use it initially for my laser machine. Because there are no cutting loads on the cutter, this should be a lot easier build than my router. Just a big plotter I reckon and there is no Z axis to wory about
I manufacture wooden geared clocks but found that I was unable to make small gear wheels because of the minimum diameter of my cutting tools, about 3mm or 1/8". The laser should enable me to make small gears, although perhaps not as thick.

I have attached my some renderings of the design I have done in SolidWorks. The parts required for the chassis are currently being manufactured and powder coated. I have opted for an 80W tube, although at 1.6m, perhaps a little too long.
Anyhow too late now as I have received it from Coeltech in China (Ebay), along with the power supply, mirrors, mirror mounts, lens, cutting head, tube mounts. These all seem to be very good quality and I,m very impressed with them. They arrived in the UK 6 days after ordering them and nothing was broken.

As soon as the steelwork arrives I can get down to some serious assembly.

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