Adventures in moulding.

Replicator

SG-1 Replicator

I’ve been wanting to give resin casting a try for quite a while now, and decided to start with something fairly simple that I’d need a lot of to get some practice in. The perfect thing was replicator blocks from Stargate SG-1. These are made from hundreds of little blocks, and a few people have these for sale on Shapeways. I ordered a few of them as originals, along with a starter moulding kit from Easy Composites. The kit is quite good, and comes with most things that you’ll need to do simple moulds. The only extra things that I ended up getting was some clay and mould release, but that was because I was going to be doing a two part mould.

This weekend's project.

Moulding and casting starter kit

It would be a waste of time going through the whole process of making moulds as there are plenty of tutorials and youtube videos on the various techniques. I just followed some of them, but I did learn a few things along the way.

Mold box built

Making a mould box

Base layer of clay ready

Base layer of clay in the box

This is the difficult part so far, making sure that the object is in place, and the seams are clean. Took a lot of work and will see how it comes out.

Pressed the blocks into the clay and made sure the edges were clean

Now just to wait for it to set, and then do the second part.

First half with the silicone poured in, waiting to set.

First part of mould done, eventually managed to dismantle the box I'd made. Note for next time, there is such a thing as too much hot glue.

First half set and deboxed

Clay removed and everything cleaned up, box remade, and second half of mould poured.

Reboxed. and second half poured.

So, first attempt didn't go too well. Did learn a lot tho. Need to come up with a better way to make the mould box (or don't use as much glue), don't make the keys too deep, more mould release when doing the second part of the mould, and make bigger pour entry points. May also join the pieces together with a sprue in the next attempt.

Right one turned out ok with a few air pockets. I ran out of resin on the left one.

With the mould done, I did my first attempt at casting. Whilst it didn’t turn out particularly well, it wasn’t the great big mess I was expecting. I hadn’t taken into account the amount of spillage when I poured into the mould, mainly due to the small entry point, so ran out of resin on the second block.

I’m going to remake the mould now, taking into account a few things that I learnt on the way, along with some tips from experts.

  • Make the mould box differently. I used acrylic and a hot glue gun which made it very hard to dismantle. I think I’ll use clay for my next one as I should have enough of it.
  • Do the base of the mould first, and press the parts into it before making the box round it. Was difficult to get in to make a clean seam.
  • Don’t make the key marks for the two moulds too deep. I did stupidly small deep holes first time, and it made it very hard to pull the mould apart, which leads to….
  • Use more release agent when pouring the second half of the mould.
  • Make the fill area bigger, and it needs vents to allow the air to come out. It has also been suggested to use an injection technique with a syringe to force the resin into the gaps.
  • Make more resin than I think. Its also hard to make small batches, so my next mould might incorporate all four blocks I got from shapeways.

If I get the next one working well enough, it’ll be a production line I think. By my calculations, I’ll need about 200 blocks to make a standard replicator. I’ve also ordered some metal powder to use in the moulds to give the finished blocks a metallic look, along with some black and dark grey pigment which will hopefully mean less painting of the finished product.

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R2D2 is all skin and bones

I recently got a nice parcel turn up at my door; my COM8B R2D2 frame. COM8 frames are one of the standard frames that are used by the R2 Builders club, with a number of different variations. I got the B, or budget, frame which is just a bare bones with nothing fancy to it.

A parcel is here Mmmm, packing peanuts! Shiny Aluminium

 

 

 

 

Assembly

The frame is really easy to assemble, as it is well machined and comes with some easy to follow instructions. It took less than an hour to put it all together, and at the end of it I had a nice looking frame. It also comes with handy mounting points for electronics. Some of the other features include a nice bracket for the dome motor, spring loaded to ensure a decent connection between the drive wheel or cog, and the dome. I’m just waiting for the charge bay panel to come through.

Assembled R2D2 frame

The next step was to work on the skins. I got these at the same time as I got the dome, and its been sitting gathering dust all this time. So far I’ve removed a few of the panels from the inner skins, but still have a lot more to cut out. Some of the seams are very thin, too thin for a hacksaw, so I have to be very careful with the cutting out. I may have to resort to the dremel to do these parts, but I’m loathe to do that as it could end up being very messy. There are some panels to remove from the front inner skin that aren’t pre-scored much like some of the inner dome was, so these need to be marked out and cut.

Skin test fit

For now I have drilled some of the mounting holes to attach the inner skin to the frame to give it a test fit. There are small 2mm gaps where the skins don’t meet, but from looking at other photos this is fairly standard and once the legs are on they hopefully won’t be noticed. I may end up filling them in a bit.

Test fit of front skins, both layers. Lots to cut out on both layers.

Test fit of inner rear skin. Need to cut out the rear door.

I’m just waiting for a nice day one weekend to finish the dome and do some cutting on the skins. Just a couple of holes to cut in dome, and a whole load of filing and sanding to make things fit properly. I have the hinges now so can start glueing those in and making the flaps work.

Slow progress, but it is at least progress

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Slicing my inner dome!

So, finally got some time on a weekend with nice weather to get outside with the inner dome and my Dremel. Whilst the dome set I got had a laser cut outer dome, the inner one was totally uncut. The aluminium domes come as an inner and outer to allow you to have the indent around each of the panels, and also lets you have a nice lip if you have the panels opening, which is something I want. Of course, this means lots of holes to cut. Any panels that are going to open have to be cut out, as well as all the holes for the lights and holo projectors (HP).

IMG_0182To start off with, all the holes were marked using the laser cut outer dome as a template. HP and light holes were to be the same size as the outer ones, but the opening panels need more of a lip. A tip I learnt from reading other builder’s logs was to use a large washer, and to put the marker pen in the center, then roll it around the edge of the opening. This gives you pretty much a perfect size for the lip. Next comes the scary part.

Cutting disc grave yard. They really don't last long, and some of the shattered. The larger ones broke in the center so were unusable.Cutting the dome! These things aren’t exactly cheap, and even worse they’re quite hard to come by, having to wait for runs to be done of them by the guys in the states. But, its got to be done so I got the Dremel and a whole bunch of fibreglass reinforced cutting discs for it. I needed a lot as the wear down extremely quickly. I went through over two dozen of them just on the dome. Thankfully I got plenty.

I found the easiest way to do it neatly was to do the large part of the cutting with the dremel, at least enough to make a cut a few cm long so that I could get the hacksaw into the hole. The hacksaw made a much cleaner cut with more control. The Dremel had a habit of biting in and running off a bit, which made some of the fine cuts a bit difficult. By far the hardest bits to do were the circles for which I ended up making a load of straight cuts through the center to form a star pattern, then gradually cut each of the prongs off. Once I had the main parts cut I attached all the cuts with a large file to take it to the lines I had drawn.

All the pie panels done now, along with the top HP. The metal on the spun domes is a fair bit thicker at the top. Just needs a load of filing and sanding to make smooth and safe.It took a good few hours to get through everything, but it was worth it. The holes are still a little rough and still need some sanding down with wet and dry. Also the circular holes all need to be made a little bigger. They were originally marked up to be the same size as the outer dome holes, but ideally they need to be at least a few mm bigger, especially the HPs. Another tip that I’ve found on the net is using a glass wine bottle to help with the sanding of the circular holes. Wrapping some wet and dry around the neck, you can sand in a circular motion to get an even hole.

Still left to do are the rear PSI holes, in both the inner and outer domes. It is the one outer hole that wasn’t pre-cut, so I need to be extra careful with the outer part. The current run of laser cut domes are a lot nicer, with the inner and outer ones laser cut and all just about ready to just polish and paint. Also, I think I’ve been fairly lucky with this dome, as a lot of people report having to cut the inner dome in half to get the inner and outer to fit together properly.

Finally got round to cutting some holes into R2's dome. He now has lights! :)Once the last PSI holes are cut I’ll be ready to bind the two domes together permanently, which is another scary one way step. I’m making sure I’ve as much done with them separate as possible to avoid damaging the outer dome with a slip of the Dremel. I still couldn’t resist having a test fit of the two domes and inserting some of the lighting. It looks pretty good.

Next main steps once its all bonded is to install the main radar eye which I’m hoping to bolt on to make it removable, and then I have to source a load of hinges which seem to be either very expensive, or hard to find.

All in all, a good weekend of work. I would’ve like to do more but due to losing an hour due to the clocks changing, an early morning call from work, and Mother’s Day, I didn’t have much time on the Sunday to do much. Fingers crossed for nice weather again next week to finish off the Dremel work outside. I might also make a start on the skins too.

 

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Inside Out

So, I seem to be building R2 in the reverse of how most people build their versions. Whilst I started with the dome due to finding a good deal, I’ve spent most of my time working on his internals and very little on the actual physical droid. Since my last post back in August regarding R2’s brain, I’ve done a lot of work on how everything will tie together to do the control. My current working idea is to have an i2c bus running throughout as R2’s central nervous system both sending out commands, and receiving feedback.R2D2_Electronics_Block_Diagram

The main control is still going to be a Raspberry Pi as this gives me much more range to do some interesting things later such as voice recognition, as well as letting me experiment with lots of different ways to actually control R2. I’m still thinking of using a PS3 controller as input, but also thinking of using a wii nunchuck is possible as a much smaller one to control simple operations.

The Pi will be linked via i2c to the various modules such as the servo controllers mentioned in my last post, with one in the dome and one in the body, and also to the lighting systems with Arduinos programmed to receive the signals to trigger various effects. I’m using BHD‘s Arduino code for the TeeCees lights in the dome at the moment, with just minor changes to accept the i2c signals. I may write something at a later date to do more dynamic light displays such as free form text messages to scroll across the RLD, but for now this is more than adequate.

Communication between the spinning dome and body will be through a 6 wire slip ring connector. 2 wires will be enough for the data signal, and then I will pair up the others to provide the power. I’ll probably have to go for two separate 5V supplies to the dome, one for electronics and one for servos as there will more than likely be a lot of noise coming over the servo power lines as they move.

PDUPower for all the electronics will come from a simple USB battery pack, which in turn will be plugged into the power distribution board I have designed. The PDU will take in a raw input from the sealed lead acid battery (or batteries) and produce clean 5v and 12v outputs, as well as a raw output direct to the speed controllers. The PDU also incorporates a few other features such as connectors for volt/amp meters that will be behind a panel on the front of R2, a voltage divider to allow the charge bay lights to function as a crude charge display for the batteries, and also a relay cut off for recharging R2. The last means that I can safely plug R2 into the charger (via an XLR connector), which will pull power going to the rest of the circuits. Lastly, there is the main power switch to kill power from the battery. There is a diode across the switch however which should allow any charge coming from the speed controllers to go back into the battery. This is a feature of the speed controllers to allow regenerative breaking.

The clean 12v will be used to power the audio amplifier. What is R2 without a few beeps and whistles?

I’m just waiting on the PCBs to come back from OSHPark, so I can try them out. Hopefully I managed to get most of it right and I haven’t seriously miscalculated the current draw from the batteries. I don’t want any tracks melting off the board!

Code wise, I’ve done quite a drastic rewrite of the controlling software to make it much more object oriented. Each different module (servos, audio, lights, etc.) is a module with a command keyword associated with it. This means adding new modules (LCD screen, extra lighting, drinks dispenser…) should be easy and just a case of creating a config file and possibly a class file if its a new type of module. All the code is available at github, along with the schematics and board diagrams of the PDU. The PDU is also available to get direct from OSHPark.

Fingers crossed I may be getting a few parts to build the actual droid with soon, including the feet, which means I now have to figure out a drive system for him. Mechanics isn’t exactly my strong suit, so should be interesting. 🙂

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Braaaaaaains!

So, whilst waiting for parts to turn up and paint to dry, I thought I’d make a start on the controls for R2. Simplest would be to just have the drive wheels, dome, and a couple of other bits controlled from a standard hobby RC controller. I’ve got a eight channel one and a few spare receivers so it would’ve been trivial to do that. However, I wanted something a bit more fancy. I’m wanting to have the panels on the dome to be controllable, as well as various controls for the main body panels, arms, fire extinguisher, etc.

My thoughts for this is to use a Raspberry Pi, along with a bunch of peripherals on an i2c bus. Adafruit do a nice i2c 16 channel servo board which a couple of should give enough channels to control everything I want. I will be putting one of these in the dome for all the various flaps, and another in the body for speed controllers and door mechanisms. Using a Pi will give me lots of power for doing controlling the servos and playing sounds, and hopefully I won’t need a real time OS. Future plans will involve voice recognition and maybe even facial recognition!

I’m also wanting to do this as modularly as possible, so to this end my first bit of programming was a daemon to run that listens for commands and sends signals over i2c to the servo controllers. My thinking behind this is that I can write many different interfaces for controls, from a simple web/PHP interface for testing and such like, to another interface to translate bluetooth signals from a PS3 controller. I’ll also be able to write a scripting system to do preset motions.

IMG_0397_CR2_embedded_1

I’ve put the code for my R2 Control software up on github to keep track of changes and such like. If anyone else feels the urge to use it, or even contribute, they are more than welcome to. I’m no programmer, so I may be going down the wrong path for all this, but its a learning experience. The code seems to work pretty well for now, but still needs to be tested in R2. Theres still a couple of things I need to add before I start doing any of the other programs. Currently the servos will move as fast as possible to their new position so I need to add a loop in there to allow different speeds. I also need to add support for multiple i2c addresses. I should have these things coded in fairly soon hopefully, and once my hinges for the dome turn up I can start installing it all and testing.

 

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Polishing the dome

The R2 dome that I got actually consists of 2 domes, one to fit inside the other. The outer one comes pre laser cut to make things easier, with all the various panels held on by a small tab of metal. A quick run with a file or fine hacksaw makes them a doddle to remove. Both domes are produced by a method called metal spinning, which means they have ‘spin lines’ running around them. This doesn’t matter for the blank inner dome as it is mostly hidden, but the outer dome needs the lines polishing out of it to get the correct look. This is a lot of work with wet and dry paper, going from a pretty coarse grit, up to some really fine paper.

Starting with the 240 grit and a large bottle of water, giving the dome a good sand down will remove the spin lines and make the surface rough, but even. Moving up through the different grit ratings slowly (very slowly) smooths the surface over until you get to the 3000 grit. The side product of this is silver hands!

IMG_0171_CR2_embedded_1IMG_0176_CR2_embedded_1

It is all a slow and laborious process, but the end results are worth it. Whilst doing this work, the panels removed earlier needed painting, so a load of paper was laid out and the painting begun. I’ve been using Halfords car spray paints, starting with a grey primer to prep the surface, then a coat of Ford crystal blue, followed by Citroen poseidon blue, and finally a coat of laquer to protect it. It seems the trick is to do light coats, with a little bit of sanding in between with something like a 600 grit paper.

IMG_0148_CR2_embedded IMG_0170_CR2_embedded IMG_0179_CR2_embedded_1IMG_0385_CR2_embedded_1

The end results look really good. I applied a little too thick in a few places, but its all a learning experience for me. I’ve just got a little more polishing to do on the dome, and I need to mask off most of it to let me spray the ring around the bottom of it blue. The next stage is to start cutting the inner dome to allow the panels to open and things to come out. I’m a little apprehensive about doing it, but once I’ve started it it will be fine. But for now, a taster of how it will look:

IMG_0392_CR2_embedded_1 IMG_0395_CR2_embedded_1

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This is the droid you’re looking for.

Alright, so maybe a bit of a corny title, but I couldn’t resist.

So, at the end of May we had a trip to Milton Keynes for Collectomania. Besides meeting and getting autographs from Robert Llewellyn and Chris Judge, the other highlight was all the R2d2 droids that were running around. There was a whole collection of different astromech droids in varying states of the build process. Once I got home, and of course mentioned it to she who must be obeyed, I started looking at just how difficult these things were to build.

Initially I joined the main R2 builders club, which also has a yahoo group with lots of useful files and blueprints.The benefit of building an R2 over most other large props is the fact that there is such a large community of people who have already found most of the pitfalls. They also do runs of parts that might be beyond another builder’s skills or too expensive to produce in single units. Unfortunately, most of the talk and production is very America centric, but thankfully there is a very active UK builders group which I quickly signed up for.

After a few weeks of reading (and more reading) the forums I decided I would take the plunge. Mostly I will be keeping a picture log on Facebook and Google+, but will also write up occasionally on here.

I thought I’d first start with what I know, electronics. There are a set of PCBs available that handle all the dome lighting and runs from a single Arduino Pro Micro which gives a lot of power and flexibility. So, with the PCBs ordered, I jumped to eBay to get the rest of the components. Obviously, a lot of LEDs were needed so they were first, I needed a pro micro to run the system, and the other main component were MAX7219 chips. Now, if I was to source the chips from the UK they would have been in the order of ÂŁ9 each. eBay had them for a tenth of that price. These were pretty certainly cheap knock offs, but for that price I could order way more than needed and suffer a few DOA chips.

Of course, it wasn’t that straight forward. I didn’t realise just how close the LEDs were packed on the PCBs which meant I needed flangeless LEDs. Needless to say when I received the LEDs from eBay they had a flange on the dome which meant they would not fit. Hunting around in the forums, I found a possible source of LEDs from China that were definitely flangeless. So, re-order and wait.

Whilst I was waiting for the parts to turn up I hit a bit of luck. Probably the hardest main part to make myself was the dome. There are lots of different options for these, from aluminium to styrene or fibreglass. The runs for these are fairly infrequent, especially if you want a certain type of dome. I’d initially ruled out building my droid in aluminium due to cost and the fact I’ve never worked with metal before, but someone on the UK builders Facebook group mentioned they had a dome and a set of body skins available in aluminium. It was too good an opportunity to miss, so I bit the bullet and bought them. A couple of days later they turned up!

IMG_0136_CR2_embedded

This was scary, this was starting to be a large commitment. It is fun tho, so lets carry on!

 

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Solar!

Over the last couple of years I’ve been looking at the feasibility of  getting photovoltaic cells put on the roof of my house. I’ve only got a small amount of roof space seeing as I live in a mid terrace so wasn’t sure if I could get enough panels to make it worth while. A couple of months ago I decided to take the plunge and get a few quotes in. Unfortunately, this is where I met the main hurdle with the whole project. Despite emailing half a dozen companies, I only got two visits to give me a quote, and only one of those actually sent me a quote.

Thankfully I’d done enough research into the technology and rough costs so that I knew the quote I got back was a pretty typical price. The company also seemed to be pretty decent with some good reviews and a good web site. With all that in mind, I decided to go for it and accepted the quote. I was very impressed with how quickly things went. One of the requirements for getting the feed in tariff from the government is to get an Energy Performance Certificate (EPC) and within a few days I’d had the survey done for that and the certificate in my hands. Only a little over a week later the panels were installed, commissioned and my meter was running backwards.

 

Solar install

Solar install

So, what did I actually get installed? All together, 16 panels were squeezed onto my roof across two elevations with 8 on a west facing aspect and then 8 on the south facing which gave me 4kW in total. The installation is fairly straight forward and involves the two arrays of panels going into an inverter which feeds into the main circuit breaker panel. I’ve also installed a full monitoring system that keeps track of power consumed and solar power produced, which I’ll probably write about in another blog post.

The big question however is, is it all worth it? I haven’t been running them for long enough really to give a definitive answer, but from the calculations I’ve done I think the answer is a resounding yes. The feed in tariff is index linked, so will increase over the 20 year lifespan of the panels along with inflation, and it is highly unlikely that the price of electricity is going to go down, all of which means that I should have paid off the panels totally in under 8 years. I can see that number dropping quite a bit too as electric prices increase. Also, the feed in tariff runs for 20 years, but the panels should last even longer than that and are still 80+% efficient after the 20 year mark so should be providing free electricity for many years after the feed in tariff has finished. Over a 20 year period, the initial investment should see a return of over 12% which is so much more than any bank can offer.

If you can afford to get PV installed, I’d definitely recommend it. I’ve already seen a drastic drop in my electric usage and the money is much better installed on my roof than in the bank.

 

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K40-III Laser Review

In a few other blog entries, I described getting and modifying my laser cutter/engraver. You can read these here:

Frickin laser!

This post however is a review on the laser, as it comes from the eBay seller. I’ve broken it into a few sections, and pointed out where my experience has differed from other stories I’ve heard online.

Packaging and Delivery

So, the packaging wasn’t too bad. It was obviously shipped from China, and just redistributed from Portsmouth with no actual unpacking. The outer wooded crate was quite battered and falling apart, with lots of packing tape. Thankfully, inside the crate was lots of polystyrene, and the actual device was in good shape. The x/y carriage was secured with a bit of ribbon, and all electronics were well secured. Now, from various other blogs, I know this was very lucky for me as many other people complain of loose connections and missing screws. About the only complaint I have on the whole packaging front is the way the water cooling tubes were tied in knots. This put some rather bad kinks into the tubing which could restrict the water flow.

Software

The software is the worst part of this device, which is why I threw it away as soon as I’d tested the machine was working. That being said, I can give a few observations from my short lived interaction with it. First off the software is very much Chinese with very basic translations. If you haven’t got the Chinese localisations installed on your computer, then the install process will show lots of strange characters, not that it will be much better unless you can read Chinese. This means installing the software is pretty much blind.

If you manage to stagger through the install process, you’re presented with a whole wealth of configuration options, drop downs, and a big canvas area. At this point, I managed to get one of the example files loaded and the laser tested. After that I didn’t really use the software again. I do know you can import Corel Draw pictures, and possibly even get a plugin of Corel Draw. There are lots of videos on using the software, and if you don’t want to customise the machine, you’re best off watching them.

Laser

Once again, from reading other blogs, I believe that I was rather lucky in that the test fire worked first time. Many other people have to go through an alignment process of tweaking the mirrors or even actually moving the whole laser tube. I can see why they would have these issues as this whole machine isn’t what I’d call well built. Lots of rough edges and no real finish to it in any way, but you get what you pay for. The extractor unit is very basic, and the slot for it is not a good fit. It is well worth taping it into place to get a better seal, and hence better suction to extract the fumes. For cooling you get supplied with a small aquarium pump which needs submerging in a bucket of distilled water to keep the laser cool.

The main area with the x/y axis is actually not too bad, with it all running quite smoothly. The x axis is very slightly out of alignment, which is something I still have to correct, but overall I’m fairly impressed with this. The axis are controlled by standard stepper motors, with endstops being hall effect sensors. The main drawback however is that the cutting area isn’t sealed, so the extractor doesn’t work as well as it should do.

Safety

I think this deserves a section all to itself. This device is built with absolutely no safety features at all. The laser can be running with the lid open to allow people to put their hand in the (invisible) beam of the laser, there are no interlocks either to stop the laser if the water isn’t flowing or the extractor fan fails. I could see no fuses at all within the electronics enclosure, and from one blog I read it was pointed out that some short circuits could put 20kV through to the control panel. Also, the cutting area is not sealed from the electronics area either, so fumes can easily pass through and escape.

Summary

You get what you pay for. This is a very cheap (for laser cutters) machine, with no regard to build quality or safety. If you want to get a laser cutter that works out of the box for commercial reasons, then spend three times more and get something better. That being said, if this is for someone who is technically adept and has experience in cartesian robots such as Reprap or other CNC machines, and wants something to experiment with, this could be a good purchase. My other posts describe what needs to be done to get this working to an acceptable standard, and it will cost a bit more money. I’ve probably spend another 50% on top of the original cost to get it working properly with safety features. If you do go down that route, then this can turn out to be a nice little machine for a hobby or hackspace. Once tuned and tweaked, cutting materials up to 5mm may be possible.

I’m pretty happy with it, and it was a good way to experiment with laser cutters without spending thousands of pounds. I am already thinking about going the entire homebrew route for my next one, if this turns out to be useful for me.

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Upgraded Laser CNC

Last week I took delivery of a nice laser CNC engraver/cutter. This was a very cheap chinese machine, model number K40-III. When I got it, I knew the controller and the machine itself were very limited but there was an open hardware project call LaOS that I hoped would solve some of the issues. Couple that with a bit of my own customisation, hopefully I am going to end up with a fairly decent machine, for a lot less than a commercial model. I’m not the first to attempt this, as these machines are very common on eBay. I haven’t seen any success stories on my browsing so hopefully I will be the first.

I’m not going to put all the details on here, as I am updating the project wiki so its all in one place. This is going to be more of a log of what I do, so if you want the nitty gritty details, take a look at the wiki page for this machine.

So, on with the log. After making sure it was all in working order, the next job was to figure out what all the connections did, and what to do with them. Starting with a load of photos, I started to trawl the net. The controller board I knew was a chinese model, so punching the numbers off the silk screen into Google I managed to find a pdf with the technical details. One drawback, it was all in chinese! Thankfully Google translate came to the rescue and gave me enough details, coupled with details on the Laos wiki about other laser machines, to know what each of the connectors did. The other part that needed tracing was the power supply. Thankfully this turned out to be a simple case of checking continuity between the pins and the components on the control panel. After all this investigation, I knew how the stepper motors, the endstops, the control panel, and the power were connected.

The only difficult part was how to control the laser. This is a bit I struggled with as the documentation for the LaOS project is still being written, and there seemed to be multiple ways to control the laser. One of the power supply connectors allowed me to fire the laser, which was great for testing, but it didn’t honour the laser enable/disable button which I would rather leave in place and active. There was also another connector pin that was labelled as Laser, which in theory will control turning the laser on and off from the controller board. Experimentation will be needed I think.

With this knowledge in hand, I purchased a LaOS PCB, along with the PCB for the i2c LCD addon, and started putting the electronics together. Again, due to the project wiki being fairly new, and the team behind it being very small, it wasn’t quite as easy as other projects I’ve encountered such as RepRap. I’m fairly confident this will change over time, and I know I’ll be going through the wiki adding information once I’ve got it all working.

Once the electronics were constructed and ready, I unplugged the old controller, plugged in the new one, loaded up a test firmware and turned it on. I rather quickly encountered my first problem. A total school boy error of putting the wrong voltage capacitor on the board meant it blew up in my face… literally. Still, no harm was done to either the board or myself, apart from a bit of an adrenaline rush. I quickly swapped out the old capacitor with a newer one of the correct voltage and plugged it all in again. Nothing blew up this time, and I could confirm that all the voltages seemed correct. Next step was to try some of the motors and end stops. Moving the head back and forth showed that both home position endstops were working fine thankfully, and were inverted so that they turned off when homed. I guess its safer that way, and it told me I needed to set that up in the configuration.

Happy that things seemed fine, I put the real firmware onto the board and fired it all up. Success… kind of! The X axis homed nicely, but the Y axis sat and juddered in place. After a few posts on the forums, and a lot of messing with config files, and checking of connections, finally it homed to the correct position. With that seeming to work, I fired up the interface software called visicut, and tried to send a few test files to the machine. Well, things moved, but not exactly in the right way. Still, better than nothing and I was fairly certain that it was all down to settings in the config file. I was beginning to understand that the config file is the hardest part of setting it all up, but finally after a lot more tweaking of the file, I had both axis moving in the correct way and the correct amount.

Next came the laser. In some ways, I was dreading this. So far I’d been messing with things I knew about from building a couple of reprap machines, namely stepper motors and pololu stepper drivers. I was fairly confident if I blew either of these things, then I could fix or replace them. The laser was something totally new. However, from reading the documentation, and putting a multimeter onto the connection marked L on the PSU, I was fairly certain all I needed to do to active the laser was to pull the L pin down to ground. All this took was a single wire from L to one of the Laser On pins on the LaOS board, and the other Laser On pin I simply tied to a handy ground point (ie, the screw terminal on the board that came from the PSU ground).

With a little bit of trepidation, I powered up the printer and started visicut. I loaded a simple rectangle file to test with, and hit the execute button. A nice little rectangle was cut out of the test bit of card! Wow, that was easy! To say I was happy would be a little bit of an understatement. I quickly grabbed a bit of acrylic I’d got to test with and fired up inkscape to draw something. I only wanted something simple, so I decided to try and engrave my name into the acrylic, so a quick click on the text button, and I typed my name in. Up to the extensions menu, and select Lasercut Path and the image I created was loaded up in visicut. A click on engrave, and execute, and my name was being etched into the acrylic! It turned out rather nicely! 🙂

Frickin laser!

All in all, I’m very happy. I got a cheap machine off eBay with a lot of limitations and with the help of an Open Source hardware project, I’ve turned it into a networked laser CNC machine. It is still limited in the strength of the laser and the bed size, but I now feel confident enough that if I end up using it a lot, I can get a higher end cutter and convert that.

I’ve still got a way to go yet on this project. The CUPS driver isn’t working properly, so I’m relying on using visicut to do the actually printing work, but that isn’t too bad as it is a pretty easy to use program. I also need to put PWM onto the laser output so that the controller board can vary the laser cutting power itself. Lastly, there is the i2c LCD module to get working. For some reason if I plug the module in, the controller board won’t boot properly, but I haven’t done any investigation yet to find the reasons. Oh, and I think a few safety measures are needed such as a water flow sensor and lid sensor which deactivate the laser in the case of anything not working… better safe than sorry!

 

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