Thursday, 31 May 2012

Seek and ye shall find.

I had what I thought was a good idea, put a normal ink cartridge in the 3D printer, one with ink in and then see if it would print, that would rule out binder issues and perhaps I would get to see some printing. The printer's cartridges are based on Canon BC-20's and they simply decapitate them, remove the ink and wadding and glue a plastic screw top vial that has had its bottom cut off over the hole in the bottom of the cartridge. These vials have a screw cap which is compatible with the machine hose lines. I was given a bag of the vials so just hooked the lines to an empty one, it certainly proved that the binder pumps OK.  But alas still no joy, now I was getting errors, too many deprimes! This seems to be when the fluidic connection between the reservoir and nozzle is lost, seemed unlikely it was caused by the fresh out of the package ink cartridge. A guy on the forum suggested it might be the flex pcb type ribbon cable that runs to the cartridge so I took it off and had a look. And it seems it is definitely damaged.

This is the part that contacts with the cartridge. Now let's get all CSI on its ass, zoom in on sector D5.

And there is our problem, one of the tracks has broken and even peeled back, now give me a hard copy of that. But BladeRunner references aside the cable and I have a date under the stereo microscope with some very thin wire and a very small soldering iron. I'd better lay off the caffeine now! Fingers crossed this is the issue because I am so close now to printing something.

Spinnage is good for you

I managed to get the polygon mirror scanner rotating nicely, it was actually very simple once I convinced myself I had the right pin out. Then I tried to get the laser to fire up, this time it was a little harder because I only have printer service manuals to go by, I think I got the right connections but failed to get it to fire. I may have damaged the laser. Anyway it doesn't really matter as that laser is of the wrong wave length, would have been nice though.

Wednesday, 30 May 2012

Scanning based 3D printer

Talk on the diy_3d_printing_and_fabrication Yahoo group has turned recently towards the possibility of using the polygon scanning mirror and lenses from a laser printer to create a resin based 3D printer for large areas. The scanner scans a line with a laser and then you move the scanner to "develop" a layer, then repeat. Basically the same idea as a SLA or DLP based resin projector just a different method of imaging. A few guys have done this sort of thing to try and image PCBs directly in photoresist. The visible light curing resins that can be used in 3D printers may however work a lot better than the etch resist.

I have a Samsung laser printer with a perpetual paper pick up problem so decided to take it to bits to investigate. It is a pleasingly simple module, pictures now follow.

The scanning module as it is found in the printer, very possibly this is a part obtained from a 3rd party. It is a really neat sealed unit just waiting to be mounted into a machine.

The other side

At the bottom left we have the spinning mirror, at the top is the weird looking lens that corrects for the variation in distance from the mirror to the drum in the printer, probably does some focussing too, not sure.

This is a brushless motor controller by Rohm especially designed for polygon scanners. The control is very simple from what I have managed to work out, there is a clock to set the speed, a start/stop input and an output to say then the PLL has a lock (i.e. the speed is constant). Then power which is 24v (up to 36 but I suspect 24).

The optics consist of a collimator, a metal aperture and then a focussing lens with a long focal length. The mirror is very thin so perhaps the aperture stops stray reflections from other parts of the motor.

The collimator

The laser diode, a simple uncollimated source. At the very top you can also see a photodiode which is used to sync the control signals to the diode with the rotation of the mirror. The beam hits a small mirror at the other end of the correction lens and then shoots over to this sensor.

Should be quite easy to get a basic system up and running, I'll probably use the propeller microcontroller which should eat the task up but I will need a UV laser to do some real tests, not to mention some resin. And I have the Zcorp to finish! Argh, maybe tomorrow!

Progress slowing

Well I got the printer back together and it turned on again without incident, tried adding some powder and it spreads but not every time, sometimes the gantry just stopped. But I thought I would press on so after adding a little grease to the rails I set it to print. No joy, I got an error concerning the print cartridge and then the software running on the machine crashed. Today I put in another cartridge which I am sure is knackered and it started to go through the motions but no juice came out, then I got an error related to the serial buffer which may be because I am using a USB to serial converter but I have no idea. I think I have one normal ink cartridge that will fit so I may try this just to check the signals are getting through OK. I also have an old PC with a parallel port which I can try. Starting to lose some confidence I can get this going but must push through that, do things step by step and get in to the details

Spread em! The cover over the print section is removed here, as are the curtains the gantry pushes through.

Tuesday, 29 May 2012

Random thoughts on 3D printer mechanics

While I was cleaning the Zcorp I started thinking about what it actually does and indeed what most 3D printers actually do. That is not very much really, I mean they do make things and are very cool but they don't tear through solid metal with multiple HP cutters and they don't get showered with abrasive sparks like CNC plasma cutters. Nope, most are almost office machines, they just move around a bit, not much load and not always that much speed. Mechanically these things should go on and on or at least what goes wrong should be pretty easy to repair. The real issues are in those little chips containing propriety code or things like the print heads which are very specific to the machine. I know if this machine had been DOA I could have done all the basic electronics myself with very little effort (things like the pumps and the build and powder bins etc etc) but the printer part? Not so much, not unless I cheated like I did on my own attempt to build a printer and that again leaves you locked in to another specific printer which they may only make for so long. This probably could be a post about property ownership and hackers wanting to be able to control every aspect of the gadgets that they own (unlike my ipad) but it won't because for me it is all about the worry that the thing I own will stop working and I won't be able to fix it. I hate not being able to fix it!

I have to wonder if a range of open source retrofit boards would be popular for these machines, this one was definitely going in the direction of the scrap yard and its PC based brain is almost certainly going to die long before its body does.

Looking like a real machine

 So this is the initial reason for the clean up, the "car wash" was really encrusted with powder and binder. But look a few minutes in hot water, a little tooth brush action and then a little more with a tooth pick and it is good to go, quite a transformation.

At the bottom you can see the squeegy that wipes the print head and above that a little box that makes a seal with it to stop it from drying out. That rocks in to place when the carriage hits the little button at the bottom right. If you need to clean this thing then you just need to disconnect the ribbon cable and the fluid lines from the printer assembly (the upright bit on the gantry) and then lift it off the machine. The car wash is held by a single screw but mine needed prising because it was glued in place with binder.

That looks a lot better doesn't it. The chute for the excess powder is removed in this picture for cleaning too and next to the hole you can also see I replaced the velcro strip. I think this is for cleaning the powder spreading roller. You can see at the back of the machine the "curtains" though which the gantry enters the build area, this keeps powder from the back of the machine, at least it did! It seems to be the braid that is used to protect cables laid flat with some soft plastic sheet inside. I should be able to source something similar to replace it.

And the Gantry all cleaned up. The main gantry went in the shower for cleaning, then I blew it dry with dry compressed air and oiled the bearings etc. Top left is the printer assembly, this just had to bee wiped carefully, not something to dunk really. I cleaned the linear rail, wiped the limit switch (on back of carriage) and not much else, will grease the ways at some point. Top right is the funky plastic thing that passes through the curtains, pointlessly complex design if you ask me. Reassembly should happen tomorrow night, maybe...

Monday, 28 May 2012

Lack of educayshon

Corrected the spelling of tomorrow in the title image. How embarrassing.

Clean up on isle 3

I decided to clean the "car wash" the part that wipes and stows the print head when not printing. The manual says remove and clean under the tap. I tried to remove it but it seemed that the entire printer section would need to be removed too. The manual does not say how to do this so I started unscrewing things and convinced myself that four bolts holding two plastic upright brackets would need to be removed. Turns out this was not the case, the print assembly can be lifted out of said brackets indeed you can see them in the photos below. But once out I could really just how dirty everything else was, not just coated in powder but hardened powder. I decided to remove the gantry, this was not very easy to do but was possible. I will try to document it when I put it back together to help others.

So here is the gantry with the print section removed, you can see a slot that it prints through and also the slot where the powder roller/spreader sits.

And another view, on the left is the powder chamber which is currently lowered and on the right the build area and the power chute which is connected to a vacuum system. I don't like the idea of the vacuum system because it is noisy, it would be better with a gravity system with just a slight negative air pressure IMHO, but what do I know at this stage.

After removing a lot of screws, some of which were a nightmare to access (because I did it in the wrong order) I was able to remove the gantry, a few more screws and the white plastic part also came off, this part is shaped to go through a slot in the back of the machine formed from two pieces of plastic cable braid that act as a curtain and prevent powder from going into the back of the machine where the electrics reside.

And the underside complete with caked on powder. The whole lot will get a good wash and the bearings an oil. Should look good as new.

Sunday, 27 May 2012


It was a long shot and one which I would normally expect to fail. I took a trip to B&Q to see if they had any suitable O-rings. To my surprise and delight they had quite a few destined for plumbing applications. Plumbing is a bit old fashioned I suppose so the thickness's were imperial. 1/16th seemed to match and even the diameters seemed like they might work. I basically bought everything and spares, a cost only a fraction of the proper O-ring kit and even less than a new pump (400usd from zcorp).

But did they fit I hear you ask? Well yes, in fact the 8 piece 1/6th mixed o-ring set by Plumb sure had enough rings for two pumps. The pumps contain three O-rings, one on the non return valve which seemed fine, one on the piston (which was as loose as can be) and another that seals the assembly. I replaced the piston O-ring and it made a good seal but could still move in the groove to provide a valve action and it then started pumping but it also leaked so I replaced the body O-ring and all seems good. Fluid is flowing into the cartridge now, I am almost ready to print. Decided to try and clean a bit, may yet regret that.

Saturday, 26 May 2012

Getting blood from a stone

Well not quite but getting the binder from its bottle at the bottom of the machine all the way to the print head is proving a challenge. I've flushed most of the lines and found a blockage at the input to a filter and now it gets all the way to its little header tank but it shows no sign of going any further. The primer pump is not working, this is a solenoid operated metering pump by Valcor scientific (an SV560) I stripped it down and I think the o-rings are past it. Nothing in my kits will fit nor can be made to fit but looking on the yahoo group reveals a kit from the pump manufacturer is only 33usd, that's OK but it might take a while to come :( boo hoo but a chance to have a clean I guess.

Friday, 25 May 2012

So far so good

I picked up the Zcorp this morning, a hot drive to Stoke and back and an even hotter struggle with the machine out of the transit van I hired and up the drive. The seller was extremely helpful and loaded me with lots of extras I did not expect like bags for the powder vacuum system, powder and even a cool old school American vacuum cleaner to use when cleaning the machine and another few dozen bags for that too. He also showed me how to make my own print heads from an off the shelf Canon one, a plastic vial and some epoxy. He told me the problem with the machine was that it did not power up, this is normally a nice kind of problem to solve because it is probably some element of the power supply. He had tried a few things (mainly replacing everything he had a spare for) and suggested a few more things to try.

When I took the back of the Zcorp I was a little surprised by how much electronics actually faced me. I guess I forgot that printing is a fairly complicated task made to look easy by custom electronics normally, it also has a lot of gizmos to control and was built in the 90's. I checked the transformer that he had just replaced and it was working and there was power to the PC power supply that runs a standard PC motherboard but it was not turning on. He suggested it might be the power switch but that worked fine too. I ended up taking a large ISA board out of the motherboard so I could get access to the pins that normally connect to the controls on the front of a normal PC. These had a little interface board plugged in which I also removed. Shorting the relevant pins (after finding the manual for the MB online) caused it to spring in to life, the PC part at least.

But why wasn't the switch doing its thing? The little interface board was connected by a ribbon cable to another board that seems to manage the power supplies and connects to the power switch. But the connection to this board was odd, there was one less pin on the board than there was holes on the ribbon connector, you could therefore put it in two possible positions. Some continuity testing made me think it had been put in the wrong position and I was right. Moving it by a hole connected the power switch to the same pins I shorted. Now it booted, did a funny dance with the bins and started beeping. Enough for one night I think!

It is pretty odd, the pins on the right are the ones the ribbon connects to, the pins in the middle are not even used. Not very clear at all.

I love the smell of ratchet straps in the morning (thank got for Lidl and there regular sales of them)

Wednesday, 23 May 2012

A small world

I love the internet. I posted to the diy_3d_printing_and_fabrication Yahoo group about my recent Zcorp acquisition and was almost immediately offered help to get it working plus a link to another Yahoo group about this exact printer the zcorp402. I was just accepted as a member and now have the service manuals which I found in their files section. Service manuals are like the holy grail when it comes to repair as you would expect.

New toy: Zcorp 3D printer

I'm wondering if my old Ebay addiction is coming back to haunt me. I just won this little beauty, a Zcorp 3D printer. It is based on inkjetting a binder into starch powder to build up a 3D model. I actually started trying to make one of these myself once: my attempts at a 3D printer but lost momentum. This one is not working but at £235 it is worth it just for the mechanics, if I get it working then that is great, otherwise I can probably put my own electronics on board. Printing in starch/plaster powder is not a patch on the resin based printer I just supported on Kickstarter except that the parts are perfectly supported by the powder. This should allow me to print CT data of bees that I collected some years ago directly. That was the original idea behind building my own actually.

There are two vats, one the build and one the powder, the gantry has a print head and a powder spreader. The powder vat piston goes up and the spreaders spreads the powder onto the build area, then it prints the binder and the build piston lowers and the process repeats. Simples!

Friday, 18 May 2012


Looks like my repair was successful as I was able to make some nice test cuts in 3mm steel, it really is like a knife through butter. Next I need to sort out a proper 30A connection so I can try cutting 12mm as an acid test.
 Amongst some welding practise you can see a little plasma cut face, there as a little slag on the cuts because of having to pierce but it knocks off.
 This is more like it, really nice cuts and a super finish, very little slag on the lower surface, with practise or better, CNC, this would be awesome.

Chrome browser tips

I am always surprised when I watch other people browse because they don't use some of the really handy features of the browser that make navigation much quicker, especially when manically researching using multiple tabs. The tips below also work on some other browsers.

1. Middle click to open a link in a new tab, i.e. press your roller, this is much quicker than right clicking and selecting open in new tab.
2. Close tabs with a middle click on the tab. You can do this even if you are not currently viewing the tab, its a quick way to get rid of tabs you are done with without losing your place.
3. Reorder tabs, you can simply drag them from side to side.
4. Pull a tab out of the browser, click on the tab and drag it, either into another instance of the browser or onto the desktop to become a new browser with only one tab. This is great for dual monitor systems. I think you can also drag them from Chrome to Firefox IIRC.
5. Middle click on the back button, this creates a new tab with the previous page loaded and the history so you can use the back button again from that tab, this is great if you want to go back AND keep looking at the page you just got to. Similarly you can right click on the back button and middle click on any of the links.
6. Right clicking on a tab gives some handy options as well.

Rectifiers in

My plan to install the new rectifiers in a twisted orientation to make up for the incorrect pin out worked. After cleaning the heatsink and the IGBT's with IPA to remove the heat transfer compound I applied fresh and reassembled. It turns on but makes a funny crackling sound, turns out this is normal according to some forum posts (one by a Hypertherm employee).

Tomorrow I hope to sort out a proper high amp socket so I can see if she cuts. Will also find out for sure if the softstart relays are switching because if not the NTC resistor is toast!

Almost there now, I hope!

Wednesday, 16 May 2012

S&G combination lock strip down

My combination lock arrived yesterday, a bit grubby inside so I stripped her down and gave it a bit of a clean. Need to sort out a mount for it  

 As delivered.
Stripped and cleaned.

Abort face palm

Looking at the underside of the PCB at a space where a rectifier should be made me think, hmm why don't I just stick a rectifier in there from this side, just to see if the beast will boot up.

So I did, and it works! The professional electronic engineer should avert his gaze now but for everyone else here is my temporary kludge:

I have a huge collection of these rectifiers, I think they are International Rectifier (oh yes it says on the side) and they will do about 25A. They were used in a project by Nottingham university on wind power, apparently the implementation was done by contractors in Scotland on site, it seems they did not realise that these devices are really designed for crimp terminals nor did they have a soldering iron big enough to solder them, so they just put the wire through the hole and soldered it back to itself with a little extra solder for good measure. Out of about 50 rectifiers I have not found one good joint! Not that this is a lot better, but....

It works!! At least it does not explode and not exploding is always good in electronic circles! I get the proper (yet wrong) rectifiers tomorrow and will mount them properly also replacing the thermal transfer compound on the IGBTs.

Thank F for that!!

Face palm

Put the board back with only one rectifier and no joy, then realised that they are not wired in parallel rather one for neutral and one for live, doh!

The plan

The original rectifiers sit off the board by quite a way and are then screwed to the heat-sink. This means there is a gap between the board and the rectifier. I'm hoping that I can bend the leads of another rectifier to fit. The original devices were Semikron SKB 51L16-W, which can do 29A forward current and are rated to 1600V.

The selection of leaded rectifiers available is not huge but I found a Vishay GBPC3512W which can handle 35A and 1200V. I lose a little on the voltage overhead but I suspect 1600V was overkill anyway. The package has a similar thickness but a different pin out. The following is what I plan:

It does not show that well but the general idea should be obvious, the twisted positions are the new rectifiers, twisting reduces the length of lead between the board and rectifier, much more and they probably would not be long enough, it still might be boarder line because of the stand off. I think I will turn some spacers to act as a jig when soldering and to ensure the right stand off. Will probably have to be split so I can remove them afterwards.

If this doesn't work then I may have to try and make some weird intermediate PCB from copper sheet, sounds like a recipe for disaster. While I wait for the rectifiers I'll check the rest of the board, I may even try "booting" from the remaining rectifier, if all else is well it should work and if it blows it shows the problem lies further in.

And in case it helps anyone this is the first draft of the first stages of the power supply where the problems have arisen (drawn in Diptrace).

Tuesday, 15 May 2012


Making some progress still, I started off by emailing Hypertherm, I heard they had really good customer service so I thought I would ask for some tips from tech support. Initially they did not seem to understand my request, "the power board might be faulty". So I explain that I know it is faulty but wonder if they might have an idea of the likely culprit that could cause this fault. I got this back: "We are not aware of any problem with the power board. You will need to replace it." OK so there is nothing wrong with the board I just need to replace it. To be honest I am not suprised they are not massively helpful, most companies are not interested in assisting repair.

So I move on and look at the schematics which are laid out to match the board which is nice but resemble spaghetti. With some help from a friend I redrew the first stages of the circuit so I could actually understand it and determined that the cause of the high current that was cooking the resistor was probably either the rectifier that produces rectified DC to the power factor correction inverter or a capacitor on the rectifiers output. Some resistance testing suggested the former. So I took the board off and this is what I found:

These are two bridge rectifiers that are wired in parallel, each can handle 30A so they should be more than OK for the 30A max input currents. But notice the small hole at the bottom right, yep it's fried!!!!

And wow, it blew a small hole out of the aluminium heat sink, impressive!!! I've now taken the rectifier off the board and have discovered the first real problem. It is no longer made and worse, the pin out is non standard!! It sits a fair way off the board so I have to hope I can find a way to make some sort of adapter for a new rectifier, we shall see. And lastly, a few photos of the insides for context:

Plasma progress

Well I replaced the resistor thing but it blows the fuse. That in itself is not a bad thing because I am trying to get it to start on a 13amp fuse and it probably should be on a 30 amp circuit however the flash that appeared close to the resistor was more worrying, do I really want it on a 30 amp circuit at this stage I wonder? The resistor is part of a soft start circuit, once the power supply gets up to speed a relay bypasses the resistor. The idea is to limit the initial in rush currents. I suspect that for some reason the bypass relays have not done their job and there has been welding current going through the resistor causing it to explode. But having said that even after the brief turn on it was pretty hot, and I have to wonder where the flash came from. It was probably wishful thinking to thing this would be easy!

Sunday, 13 May 2012

Tesla is the boss

A tesla valve. A oneway(ish) valve with no moving parts. 

Car part design = WTF

I spent a good part of today helping a friend fix the central locking on his car. It turned out to be a dry joint on a PCB in the locking module itself. Because of this the system though the door was open all the time and because of that it refused to operate the central locking for the rest of the car, cue a long walk around to the passenger side everything he came to lock up.

The actual repair took about 30 seconds and a bit of Google time researching the issue however we spent almost half a day getting at the locking mechanism, removing trim panels, wrestling with wiring looms. And when we finally liberated the lock it was hard to tell which end was which. It looked as if it was a space ship or had been designed by genetic algorithms or a room full of monkeys, I could simply not imagine any logic that would lead to this design. I really wonder how they come up with them. Are they given a space in which they must force a part like this? Is it form following function? Is it design for manufacture? I just don't know.

Saturday, 12 May 2012

Fruits of my labour

So this is what I ended up making in the workshop last weekend, an adapter so I can use a proper saddle on my exercise bike, the old one was like a bench with no room for my thighs to move up and down. This one is still quite uncomfortable but my butt should soon toughen up and hopefully I will reduce the gravitational pressure now I have removed all excuses stopping me from using it.

Hmm plasma

I have a super special secret idea for a CNC plasma cutter but my plasma cutter is a bit of a wimp, an ancient Hypertherm 380 which can only cut 3mm max properly. Looking at better machines today made me realise why I have such a wimpy machine. A Hypertherm Powermax45, which is the daddy, and will cut 12mm steel is a whopping £1756 inc VAT. So I had a look on Ebay, you know, just in case, and found one available that was not working, some disk shape part had blown and the supplier would only offer to change the board out for £500.  Well as the guy said he had it for sale elsewhere I gave him a call and we negotiated a price. Given the torch itself is a £350 spare I could not expect to pay peanuts but I think it was fair. I'll divulge the amount when (if?) I get it working! I could not resist going to pick it up straight away so had an enjoyable drive to Richmond in London where I met him at the edge of the Thames in the pitch black. This is not as bad as it sounds as he lives in the middle of the river on a boat, a very nice chap he was too!

So here it is:

Its actually smaller than my old one and possibly lighter, that's progress for you! And here is at least one of the reasons it is not working:

The supplier would not even look at replacing the parts on the board which is a shame because I put this into Google and found out immediately that it is a 10ohm circuit protection thermistor by Ametherm. I just ordered a couple from Farnell for around £3.50 each. If this is all that is wrong then I will be a very happy bunny indeed but we shall see, maybe tomorrow, bum it's Saturday tomorrow :(

Thursday, 10 May 2012

3D printer now live on kickstarter

The printer I mentioned earlier is now live on kickstarter. I've actually bought a suitable projector through my work to build one from scratch to use in my "proper" research but I believe in this project so much I have decided to back the project personally so will be getting one of the complete kits when available for use in The Littlest Workshop.

I could probably build something using the surplus parts I have for far less money so why have I decided to go down this route? If you look at commercial machines the one area they vary is in the means of release of the part from the bottom of the build vat, others build from the top down to avoid this issue. Michael has found a solution that avoids current patents and has then made it public, he also intends to make the project open source.

This in my mind is quite selfless, it is likely that in a short period of time there will be a myriad of people jumping on the band wagon, this will surely include the big players. This means that his decision possibly limits the future of his venture, however he is not fazed and clearly just wants people to have printers to play with. The upshot is that the copy cats and big players will drive down prices and future generations will not only be cheap compared to current commercial offerings but genuinely affordable.

So I feel I want to support his noble cause and the fact I get a tried and test 3D printer out of it is a real bonus. As for the projector I still have at work, I am sure I can make use of that, perhaps an ultra high resolution printer using high quality parts or perhaps I will investigate some more usual printing ideas I have.

Monday, 7 May 2012

Back in the workshop

I've not been in my workshop proper for a while really, it needs a good sort out and to be honest I need more space or at least a lot of work, something I am not so keen on in rented accommodation. But in any case being able to see the bench is a good start.

Something I picked up a few months back from Ikea was a plastic CD/DVD organizer thing (INREDA). The moment I saw it I knew what I could use it for. Organizing my small tool draw, works pretty well. I think you can buy things for exactly this purpose but I am not sure they will stand impatient draw slamming like this one.

It would also be excellent for sorting endmills, reamers and drills etc. Perhaps with some little squares of foam as seperators if needed.

The clear bench inspired me to finally mount my Milwaukee Portaband saw on the stand I got for it last summer. I have some pretty good excuses for not getting this done sooner but it really only took 10 minutes. The stand is by Swag off road and it works well. I need to get a new blade for the saw though, I picked it up on Ebay and you could ride "bare arsed to London" on the supplied blade as my Dad used to say. The only downsides of the stand are the shipping and I am also not a fan of the big logos in the side. If it is strong enough even with all these cuts then I have to wonder why all that materials is there in the first place. He has now update the design and it comes in three pieces, that should reduce the shipping as volume is a factor. You can also get a simpler stand that is just the top section which you clamp in a vice.

Cuts in 10mm Ali were really accurate despite the blunt blade.

Cheese dreams

This post should be filed directly under the "for shits and giggles" category (shouldn't they all). It struck me that keys, even those with security keyways are susceptible from copying and you can even buy/make proper key copying systems from high tech keyway scanning cutters to clay and low melting point allow.

But what would Maguyver do? While thinking these thoughts I was enjoying a few Babybel cheeses, they come in a wax coating which is much softer than candle wax. Hmm.

1. The left over wax from the Babybels, note the nice "Damascus" finish caused by the inner white wax and the outer red. 2. The wax was melted in some tin foil boats with a hot air gun. I put it in the freezer to harden and make it easier to remove the foil. 3. I wrapped it in cling film (food wrap) to act as a barrier because once at room temp it is really soft and sticky. 4/5. The impressions left by the key after squeezing the two halves onto it. 6. The result cast in epoxy, it was far from perfect, the process could work but you need to put the wax into boxes so that it is constrained when you press the halves onto the key, also good for registration of the mould halves. An alternative for registration with this method is a couple of ball bearings pressed into the wax beside the key when impressioned.

Does it open a lock? I have no idea, I accidentally made it for a lock I broke, doh!

Saturday, 5 May 2012

Exciting times in 3D printing

3D printers that build up models by setting UV curable resins with lasers, layer by layer are one of the oldest types of 3D printer, however, they are still one of the most expensive. Several years ago someone hit upon the idea of using projectors to cure resin selectively, the paper I read used a UV light source and an industrial LCD. LCDs however don't really like UV very much at least bog standard ones filter a lot of it.

Texas instruments then came up with their DLP micro mirror projectors which image using an array of tiny mirrors. These too can be affected by UV but at least do pass it. Several companies now produce printers based on this technology.

The printers are simple in principle, a light source with a decent UV content (a projector bulb has plenty) and a DLP projector and then some means of moving a build platform up and down. You have two options when building, you can build from the top of a vat of resin and move the build platform down or you can build through the transparent bottom of a vat and move the built platform upwards. The latter method is simpler in many ways but you can have problems with your part sticking to the vat bottom either through adhesion or the vacuum forces created as the part is lifted from the vat bottom (try lifting a piece of glass off another directly upwards).

A few amateurs have had a go at making this type of printer and have had good success, this one in particular is really amazing and has already produced excellent results. He hopes to make a low cost kit in the near future, check out his Facebook page for more info:

A render of the production model, the real thing looks as good (or it will with once anodized)

The prototype machine making a lovely model of the Eiffel tower.

New toy

I just picked up this bad boy on Ebay. A Sargent and Greenleaf 6730 combination lock. The better S&G locks have a little knob on them which you turn when you are ready to open and this prevents any manipulation but this one allows the classic stethoscope wielding activities from the movies. Of course in reality you don't bother with a stethoscope and it normally requires a good couple of hours of graph drawing and wiggling. I only know the theory, this will be my first chance to actually try, at least when it arrives. Maybe tomorrow?