Long overdue update.

August 18th, 2016

Well, it’s been a while since I wrote anything here. Not from lack of anything happening though! Lets see, I am still at Weta and still loving it. The things I get to work on and see are amazing. And mostly secret a lot of the time! Not sure what I am allowed to say I have worked on. Animatronics for films and various other things. I have to wait until these things come out then I can say what I did I guess. It’s great fun though and the stuff I am doing is a perfect match for my skill set. We do a lot of microcontroller stuff so I still do a lot of coding. Lots of hand making of things too. I knew one day all my silly projects over the years would be useful for something!

It’s going so well I have decided to give up on IT and just keep doing the animatronics thing for as long as that lasts. I sold my house in Auckland and bought a house here in Wellington in Miramar, close to work. Finally no mortgage which is great but I am on way less income so not a lot of money either! So much for my dream, no mortgage Orient Express trip (for now at least). But I earn enough to live comfortably so that’s all fine.

Been in my new house for about 4 months now and am just getting settled. I made this film to show people my new place in the world.

Sorry for the croaky voice, I had a bad cold.

So now I am almost settled I am thinking about getting back into my car projects. I have the Austin body to finish and the engine to build. And I would like to start on the Brooklands. I am now in contact with someone who has an original Brooklands and he is happy to help me with pictures and measurements of parts I am missing.  Mainly the engine/steering mounting brackets and some of the spring mounts and hangers. Will be good to get started on that. I have a parts list (for a Riley Nine, not a Brooklands) that I will go through and mark off what I have an figure out what I am missing.

I have the fireplace I am making but I will talk about that later. This post is about a new project, a laser cutter/3D printer/CNC type machine I am building.

In the film you can see a little project I was doing at work in my breaks and spare time. IT were throwing out a bunch of old PCs and parts. I managed to get a bunch of old DVD burners and pulled out the mechanisms and lasers. In a DVD burner the red laser is powerful to engrave things. This instructable inspired me and I basically did the same thing myself and made my own tiny laser engraver. I don’t have any need for one, we have several laser cutters at work I can use (we use them all the time) but I wanted to know how the machine worked. We also have at work a number of CNC machines they use for milling materials. They cut wood, metal and have an industrial robot arm used for cutting large blocks of polystyrene. I find them fascinating. I figured it would be fun to build my tiny machine to see how they work as the principles are the same as on a ‘real’ machine.

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In the end I kept blowing up the red lasers from the DVD drives. They are very finicky and even with the correct current limited driver for some reason mine kept dying on me. In the end I bought a 500mW blue laser module from Aliexpress. It is more powerful and comes complete with driver, heatsink, fan and so on. Given how well that tiny machine (working area of 36mm by 36mm!) works I thought why not build a bigger machine. What I really want to make is a laser cutter that I can use to cut out paper gaskets for my vintage cars. My plan is to build up a library of gaskets that I can then cut out as needed. So I started thinking about a bigger machine, something that can cut a A4 sized sheet (210mm x 297 mm).

There a lot of machines and designs about online if you look. Or complete kits you can buy and build. I prefer working things out for myself. In the end I decided on a machine build from aluminium using lead screws to move the axes. These you can find on Aliexpress such as these ones. You can find everything on Aliexpress. I’ve been using it a lot lately!

As well as laser cutting I was thinking it would be interesting to see if I could mount a small spindle on it and do light CNC type things. Mainly engraving PCBs. That would be very handy. Failing that just being able to plot resist onto boards, manually etch them but then use the machine to drill the holes would be good. To do that you need a Z axis as well as X and Y. You need to be able to lift and lower the cutting tool or drill or pen or whatever it is you have mounted on the machine. Since I was starting to think about adding a Z axis I began to think well, why not add a decent height Z axis and add an extruder and use the machine as a 3D printer. Feature creep, it’s not just for software!

So my simple laser cutter has become something of a multipurpose machine. In the end I got two sets of 400mm rails/screws for the X and Y axis and a 300mm set for the Z. That gives me a useable area of just over an A4 sheet in X and Y and with about 200mm of Z. That is comparable (actually a little larger) than most of the DIY 3D printers around.

I drew up my design in Inkscape. Now Inkscape is a 2D drawing program. I guess really I should be learning how to use a 3D program which I will need to design 3D printed parts! I have started playing with DesignSpark which you can get free from RS. Inkscape works great for doing any 2D designs for laser cutting though. But I designed the machine in 2D using old fashioned 3 view plans. By grouping parts of the drawing I can shift the moving parts around to check the limits of the machine and so on. That actually worked rather well.

laser cutter zx axis template

To test parts of the design I laser cut some of the parts from 3mm scraps of MDF. That allowed me to see how things could all fit together. I was able to power up the stepper motor to see how well things would move. I did notice a little problem with the design but I will come back to that in a minute.

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The main frame of the machine will be aluminium L section 40mm wide and 4mm thick. That will all be bolted together. The Y axis moves under a fixed gantry that holds the X axis. On the moving X axis is mounted the Z axis that moves up and down. The moving platforms for the axes are made from 3mm thick aluminium plate I scrounged from the scrap piles at work. One problem was how to cut it. To get it all nice I really should CNC cut it all. But I decided to do it all by hand. I cut the plate with a special blade in my jigsaw by hand. That worked very well. These days people are so quick to go for the modern ways but with patience and practice you can still do a lot of things by hand if you’re careful. After cutting I then linish the edges on my little home made linishing disc.

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The design problem I had was that there is a little unwanted movement in the platforms that run on the rails. This comes from two places, the lead screw nut and the rails and bearings themselves. The rail sets from Aliexpress come with one brass nut per screw. With the nut mounted into it’s aluminium block and that all threaded onto the screw there was a little bit of movement in it. I fixed this by ordering extra nuts and making what’s called an anti-backlash nut. Instead of one nut you have two nuts separated by a spring. I simply added extra threaded holes for the second nut on the aluminium mounting block and inserted a spring into the middle of the block around the lead screw that pushes against the second nut. The screws holding this nut on are not done up tight but instead are left with a gap so the nut can move a little. I loctite the screws in place.

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This seems to work very well although it adds extra friction to the whole mechanism. The stepper seems to easily overcome that though.

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The other source of movement is the bearing blocks that run on the rails. They are not very wide so I found you could get some movement on the rail. In practice this would show up as twist on the moving platform. To counter this I have ordered extra bearings and will double them up. This helps a lot although you do lose a little travel (the same amount as the width of the bearing) on the axes. Having the rails spaced as far apart as possible will also help eliminate twist.

This twisting is what I think will prevent the machine being a good CNC cutting machine. With laser cutting and 3D printing there is no side loading on the moving bits as the tool (i.e the laser or the extruder) isn’t actually touching the workpiece. As soon as you have a spinning cutting tool you are trying to move into a material you are adding a lot of extra force to the bits you are trying to move. I think this is when you’ll start noticing deficiencies in the machine. I think drilling will be possible as the force is all up and down but I am not sure how well it will go when sideways cutting. I can only try and see!

To help with making the aluminium parts I laser cut cardboard templates and used them as cutting and drilling guides. I hand drilled all the holes on the drill press.

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That last plate is the one on the Z axis. Since I want to mount different things on it (laser, extruder, pen, spindle, etc) I am putting in many threaded holes so I can attach whatever I like. I will talk very nicely to Jordan at work and see if I can use his parallel arm air driven tapping machine to tap all the holes. These machines are brilliant and I wish I could have had one when I was drilling my Austin 7 crankcase to helicoil the studs into it!

Once those are done I can start assembling the Z and X axis parts and it should start making more sense how this machine will work. I am very new to this and I am sure I am making mistakes and there are better ways to build such a machine but this is a learning exercise so that’s OK.

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I random orbit sand the plates after drilling rather than countersinking the holes. I prefer the clean, sharp look it gives and countersinking also reduces the thickness available to put threads into.

The electronics for the machine are on the way. The mini laser engraver uses an Arduino running GRBL. That works great and allowed me to get my head around G-Code and how all that works. Not to be confused with G-Spots, something most engineers never have to deal with.

I already have an extruder (the bit that melts the plastic filament for 3D printing) as well as a feeder that forces the filament into the extruder. These I got off eBay along with extra nozzles in different sizes.

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Still coming are the main electronics, which consists of an Arduino Mega and a RAMPS board, as well as limit switches, cables and also a heated bed. 3D printing is much harder than laser cutting hence the need for upgraded electronics and all sorts of other paraphenalia. A laser just needs simple on/off commands which you can do in G-Code. The 3D printer has extruders to control with heaters and temperature feedback as well as feeders and heated beds and goodness knows what else.

I should say here I have never actually used a 3D printer or had any interest in them. I am a metalworker really. I prefer making things by hand in real materials! But working where I do I can see the uses of 3D printing. We use it all the time. So understanding how that all works is a good idea I think and for me the best way to learn is to do things for myself. I don’t know what I will actually use it for when I have it! Maybe I can 3D print small patterns to then cast in aluminium? 3D printed christmas presents for everyone this year?

The laser cutting should be much more useful. I could buy a bigger laser although I have successfully cut gaskets with the 500mW one I have. Oh, that’s one thing to note. In NZ there are now restrictions on high powered laser pointers. You can’t easily buy them and if you try to import one you need special permission and a valid reason. This is due to idiots pointing them at planes and so on. So before I bought my burning laser I contacted the Ministry of Health(!) to make sure it was OK for me to import a laser module. Apparently it only applies to laser pointers specifically. Actual high powered laser modules are no problem whatsoever!

Anyway, that’s where I am up to at the moment. It’s a bit rambling sorry, am out of practice with this blogging business. I will keep documenting the machine as I go. It could be a total failure but it is good to be out in the garage again making things. I am just starting to settle again. It was quite a move!

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Oh, and apologies for the bad photos. My old Canon Ixus camera died and I got a new one, a later model Canon thinking I could reuse the battery. But the bastards change the battery form factor between models so the batteries, even though they are actually the same, won’t fit the new model. And the new camera, an Ixus 175, is rubbish. The auto focus is really bad. Hence all the slightly out of focus photos. Next camera won’t be a Canon I think.

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