Wednesday, 30 July 2014

Homemade rotary tattoo gun from salvaged parts

Andrea has spent the last few weeks perfecting his homebrew tattoo gun, made from parts salvaged from most of the kind of equipment found around the hackspace. In particular, he found a simple servo-motor (from a large all-in-one printer/copier) and stripped off the encoder disk (sorry, CNC Paul, just didn't think to ask if it'd be any use to you!) and built a laser-cut frame around it.

The first design was made almost entirely "by-eye" and just happened to fit the components that made up the rest of the gun. After being dropped on the floor a couple of times, the flaws and weak points in the design soon became apparent, so a bigger, better, fancier design was put together.

The new design is not only made from super-awesome edge-light acrylic, and engraved with a cool retro-looking tattoo pattern itself, but extra bulk has been added around potential weak points.

The two pieces of acrylic are held together using M3 nuts and bolts. It's important that the nuts don't crush the acrylic, but maintain a nice, firm grip on it. So each bolt has no less than three nuts - one behind the head of the bolt, then another as a "spacer" and the third holds the acrylic tight up to the spacer bolt.

Using this arrangement, the nuts can be done up quite tightly, to grip the acrylic, without fear of the extra stress on the plastic causing it to bend and shatter under strain.
The handle (or grip) holding the needle is disposable, so a collar with grub-screw is used to attach this to the gun. And a simple rubber band applies enough pressure onto the needle to stop it flopping around as the rotary attachment drives it up and down, but without restricting its movement vertically.

The actual rotary head is an aluminium pulley, modified by adding an M3 bolt, slightly off-centre. The head of the tattoo-ing needle is connected to this, and as the motor spins, it causes the off-centre cam to drive the needle up and down, inside the grip.

Here's a video of the gun in action. Compared to the noisy clatter-clatter of a coil-based gun, this one is incredibly quiet.

The final result is quite impressive.

In operation, Andrea said that there was very little vibration compared to a coil-based gun. It's obviously much, much quieter, and there's also very little "splatter" while drawing lines. The lines are very precise and - apparently - "skin burn" is much less than when using a coil-gun.

The gun is also pretty handy at shading too. Using just a single colour ink, it takes a pretty decent gun to be able to create like a greyscale shading effect. Something which the rotary-junk-gun handled well too:

The crescent moon in this photo was completed in just a few minutes but proved, as a simple test, that the gun performs well as both a "liner" and a "shader".

Unsurprisingly, Andrea is quite pleased with the great performance from such a simple device - made relatively cheaply from a few parts lying around, that would otherwise have been confined to the tip.
Look out for more progress reports (and more members of the Nerd Club sporting new tattoos) in the coming weeks and months!

Sunday, 27 July 2014

Die cutting with a 20 ton hydraulic garage press

Nick from CustomStuff asked a favour - she's made us plenty of playing/gaming cards for prototype projects like non-RFID poker cards in the past - so it's only fair we helped out.

Having got a rush order in, and having problems with her own cutting setup, we were asked to produce about a hundred playing card boxes, with little more than a pre-made die and some pre-printed patterned (and laminated) A3 card. What we needed was a way of squashing the die into the card with enough force to cut where it needed cutting, and to crease where it needed creasing.

Our answer was to put into use a piece of equipment we've had hanging around for a long time (in Paul's living room since last Xmas, when he used it to emboss some handmade leather gifts). It's a 20 ton hydraulic hand-operated garage press.

It took a few goes to get the process just right, but eventually we managed to get a good, clean cut on just about every one!

The process was to place a 1" thick steel plate (thanks to CNC Paul) on the press, then a sheet of mdf as a cutting mat (a regular cutting mat is just too soft, as we found from experience!) then the laminated card on top of the mdf, the die (cutting side down) on the card, then a second 1" thick steel plate on top.
Those steel plates are pretty darned heavy - each one weighs over 20kg - no mean feat to lift on and off the cutting surface, every single time!

With the steel sandwich in place, the press is lowered onto the top steel plate. A good few pumps and there was a slight - but noticeable - click, as the blade cut into the card. For the first few attempts, we stopped at this point, but found that some boxes didn't cut all the way through, all the way around. So in future cuts, we placed the die such that the cutting point of the bottle was off-centre, and pumped the handle almost until it wouldn't go any futher (without too much effort).

The result was a perfectly cut (and creased) box outline, every time.

After about 30 or so boxes, cutting performance fell slightly, with some corners of the box not cutting cleanly on every cut. This was fixed by replacing our mdf cutting mat. After cutting so many boxes, the mat started to fall apart in places.

A new piece of mdf, and cutting was as clean as the first time. After a few teething problems (and lifting a 20kg weight onto and off the press about a hundred times) we ended up with a stack of playing card boxes, each cut exactly, and each with crease lines in all the right places. It's nowhere near as quick as using a clicker press, and a lot more cumbersome, but we got through them all in just a few hours (maybe a bit more, including stopping for a brew and a chat in between every 10 sheets or so).

It was quite satisfying, not only to be able to return a favour, but to get such a successful result from something so crude and unlikely to work!

Tuesday, 22 July 2014

When did eBay turn into Maplin?

For years we've turned to eBay for cheap, low volume components. Quite often searching for something on Farnell or RS returns three or four of the same thing from a supplier on eBay (unless buying in suitably large volume).

But over the last six-to-eight months, we've been receiving fewer and fewer parcels at Nerd Towers from eBay, and more and more coming from "proper" online retailers. Here's just one example:

We're looking to prototype some simple kits for the up-and-coming Brighton Mini Maker Faire. These kits will be used to create simple motorised drag racers. As ever, habit suggests we hit eBay and see how cheaply we can get hold of the little hobby motors.

any number of variations on 3v motor, miniature motor, 5v motor, 9v motor and so on returned similar results; the cheapest being £1.43 per piece

the cheapest "hobby motors" are £1.59 each

Maybe there are cheaper miniature motors on eBay, but finding them is not easy. Or maybe they're not there. But according to the level of search we used, a miniature hobby motor costs about £1.50

So we were quite amazed to find exactly what we were looking for on the Rapid Electronics website for just 53 pence!

That makes the cost of eBay-purchased products three times the cost of buying them directly from a supplier! But it's not just on electrical items. It seems that sellers are now passing on their high sellers fees and making the exact same products on eBay more expensive than in their own online shops! for example, sell 0.8mm birch ply online. It comes in 9x11 inch sheets, available both in their eBay store, and directly from their website.

In the eBay store, each sheet costs £3.25. But in their own online store, each sheet costs just £2.85

It's long been a running joke that when you buy anything from Maplin, you have to pay the "Maplin Tax". This is the extra you get charged for being able to walk into the store and pick something up off the shelf (if they actually have what you want in stock) instead of waiting for next day delivery from your favourite online retailer.

But there's very little point in an "eBay Tax". There's no benefit buying something at a higher price from one online retailer than from another - better to buy direct from the seller, and let them keep all of the money spent at their online store, surely?

These days, we're finding we use eBay more to browse products, then look to source them elsewhere. Which is quite ironic, given that high-street retailers have been complaining that this is how customers shop in their bricks-and-motar stores - find something they like in-store, then go home and buy the same thing off eBay!

eBay used to be a fantastic world-wide marketplace, where you could reliably go and pick up pretty much anything, easily and cheaply. Yet these days, it's increasingly difficult to find exactly what you want from the eBay search results, meaning it's not easy - and the prices are noticeably more expensive than buying from other sources, so they're certainly not cheaper. 

Maplin is also neither of these things (even in-store it can be difficult to find what you what because of either the surly staff, or the fact that it's not in stock) but at least they have the advantage of being convenient. When you need a 22uF capacitor today, you can pop in and pick one up (albeit paying about 50 times its value). eBay is slowly turning into the online version of Maplin - but without the added benefit of being convenient!

Monday, 21 July 2014

Laser cut planks for Wild West 28mm terrain buildings

Here at Nerd Towers we love 28mm board gaming - and making up and painting the terrain as much as the miniature playing pieces and playing the games themselves.

A quick (but not-so-cheap) way of getting a really impressive looking gaming table up and running is through the use of laser-cut buildings, from companies such as or Sally4th etc. These buildings are, as often as not, lovely detailed, atmospheric pieces which look great when painted up.

The problem is, being familiar with laser cutting, and seeing how these buildings are made, they're a little bit "lacking" for many in the "Nerd Club Gaming Club". It's hard to say what it is, but scratch-built terrain, complete with little imperfections and slight errors always seem to have a little more "character" and (dare we say it) "realism".

I, personally, haven't played and enjoyed a video game since about 1989, when Jon Ritman and Bernie Drummond released Head over Heels on an affordable label. Not long after that came out, when I discovered that ZX Spectrums were not actually coded using a ZX Spectrum, I started writing my own software and simple games - and most computer games become exercises in moving sprites around a screen. I still don't play videogames, even 25 years later on, even after all the advances in technology. At the end of the day, I'd rather be making simple games than playing even the most immersive multi-player dungeon crawler.

Head over Heels - the last decent video game ever made?

And laser cut buildings on a board game terrain leave me cold for the same reason - rather than marvel at the periodic detail, things like finger joints and how the cutting kerf has been disguised catch my attention more than the model; I'm looking more at how it was put together, rather than enjoy the finished product.

And this is mostly, I feel, because most laser-cut buildings have very little construction needed - they're essentially flat-pack, prefabricated miniature houses. They have lots of large, flat surfaces, with some textures laser-engraved onto the surface to make them a little more interesting.

This is partly why we recently spent so much time hand-assembling a scratch-built roof for an Old West building from plasticard - to give the final model a little more texture and character. The problem with that approach was that it was really (really) time consuming. So we came up with a compromise of laser-cutting rows of slates and assembling them to create a textured roof, with overlapping tiles, but which took a fraction of the time to put together.

After successfully making our rows of roof tiles, we look the plastic-wooden-planking idea to the laser cutter to see how that would translate too. Instead of carving the card with a knife and then scratching woodgrain into the surface, we drew some slightly wobbly planks (to simulate them being warped and worn in the sun) and drew some free-hand lines over the surface (in Inkscrape) as grain.

(A variety of different worn/weathered planks; to create a straight edge, simply turn the plank upside down - so the wobbly bit is at the top - and overlap with another plank above. The two straight pieces at the bottom are for edging the sides of a "lapped plank" wall)

Our LS3020 laser cutter can etch and cut at the same time (or, rather, one immediately after the other) but the driver isn't as easy to use as the BuildBrighton white laser - you basically need to create a bitmap for etching (the woodgrain) and a vector image for the cut-lines. The NarlyDraw software that our LS3020 uses can only handle engraving from bitmaps, and cutting from vectors.

So this is where the fun starts:
It's easy to import a bitmap followed by a vector image, and line them up by eye. In fact, because our wood grain isn't critically placed, we could have done this. But we wanted to try out (and document) how to go about lining up the cut and etch images. So here goes....

Firstly, create the cut and etch drawing in Inkscape on two separate layers (one for the etching, one for the cutting). Place the etch layer above the cut layer, and make each layer visible and invisible, one at a time, to check that all the lines are on the correct layers!

Now draw a little cross (we used a 2mm x 2mm) and place it in the top left corner of one of the layers. Copy the entire cross and paste-in-place on the other layer. We now have a marker that we can use to align the two images in NarlyDraw. (If you're not confident of important the images to the same scale, you can always put another cross in the opposite, bottom-right corner, and use this as a guide to get both images to scale).

Hide everything except the etch layer, select everything and export the selection as a bitmap (Inkscrape exports to .png so we had to load this into Paint Shop Pro to turn it into a 1-bit bitmap: the one bit thing isn't necessary, but it's handy to do, to keep the file size down!) Now delete everything except the cut lines (or copy the cutlines and the cross to a new document) and save as .dxf.

With a .bmp (for etching) and a .dxf for cutting, simply import the two files into NewlyDraw, zoom in and make sure both layers line up on the same cross.

Lining up the cutting guide on both the etching and cutting layers. When both are perfectly lined up, the final result can be previewed easily in the NewlyDraw application

It was with some trepidation that we hit the "go" button, but shouldn't have worried!
NewlyDraw did a great job of etching the bitmap image first...

...before cutting out each plank from the surrounding wood:

Each set of planks takes only a couple of minutes to complete. They overlap nicely and sit quite flat, to create a realistic, weathered wooden wall for a shack or a shed

After a few of our sample offcut sheets had been fed through the laser cutter we had enough planks for the walls to build a small building

Another couple of goes through the laser cutter and we had plenty of roof tiles too

All that remains is to assemble a building using the bits and paint it up, so see whether the wood holds the grain pattern after a layer of acrylic has been applied and drybrushed  (etching it would be pointless otherwise!) or whether we need to use something more like an ink or a stain, and just keep the grain lines darker.

After all this messing about with laser cutters and trying out different approaches to etching and cutting on the same piece, it was actually quite late when we finished last night; so the build and paint begins in earnest this evening!

Sunday, 20 July 2014

Laser cut slates for 28mm terrain roofs

After getting the laser cutter up and running at the new Nerd Club home in the Boiler Room Studios, we threw some simple designs at it and had it carving out roof shingles from some 1mm birchwood laser-ply at an impressive 32mm/sec, at just 15mA.

After the nightmare that has been the BuildBrighton laser cutter in recent weeks, it was really nice to just load up a file, hit go and have some super-intricate parts drop out of the cutting bed!
We've cut a mixture of "regular" and "irregular" rows of slates and even without the cutting and swapping around we expected to have to do, got some nice-looking roof panels pretty easily

We'll have to design and cut some ridge tiles, but the overall effect is far better than a laser-etched plank of 2mm mdf - and something we're looking forward to putting on our Wild West buildings.

Sunday, 13 July 2014

UV exposure unit ready for fitting

About six weeks or so ago we pulled apart some UV acrylic nail art lamps with a view to creating an exposure unit for fixing images onto silkscreens (and for fixing solder mask to etched pcbs).

The project stalled for a while due to a number of things, but having recently got the laser cutter working, and successfully getting the CNC router to move about (albeit not exactly drawing shapes yet) we've been inspired to spend a bit more time kitting the unit out with stuff that "just works" so it's on hand, ready to be used, as the need arises.

With this in mind, we spent some time last night getting the UV exposure unit finished - well, the electrics for it, anyway

The controls are all wired up and at the minute we're running the whole thing straight off the mains. All that remains now is to line the bottom of the tray with reflective foil (to hopefully reduce any chance of "striping" as the unit won't actually sit very low down on the underside of the desktop). Once it's installed in our large desk we'll put a relay switch inline with the power supply, so we can control the exposure time using a homebrew digital timer (of course, made from a PIC and a max7219 and some 7 segment LEDs!)

Just to make sure nothing had got damaged during the rewiring, we powered it up to see that it all still worked. Amazingly, it did.

It was only afterwards we realised that had it gone horribly wrong, none of us actually knew were the fuse box is, in the Boiler Room Studios - we could have been left in the pitch dark, feeling pretty stupid. Thankfully it just worked; but we'll make sure we know where the fuses are before we do anything else with mains wiring - just in case......

Friday, 11 July 2014

HPC LS3020 laser cutter up and running again!

A while back we secured a unit in a shared studio in Hove, for making messy things and generally doing the kind of things that are likely to either upset the family home or the neighbours (laser cutting, CNC routing, screen printing etc.)

Our LS3020 laser cutter from HPC has been in storage for a long time -maybe about 12 months or so - and it was to great delight that we got it connected up and working again last night.

Given the amount of hassle the laser cutter at BuildBrighton has caused in recent months, we were terrified that the mirrors might need realigning, the cutting lens could be damaged... any number of things that could have gone wrong with it, as it's been dragged around a few different places and never actually tried out, for a long time.

Amazingly, we switched on the old PC that was driving it last time, plugged everything in and hit "go". It cut our 3mm acrylic sheet at 15mA and at 16mm/sec, straight through, first time!

Because Nick, Charlie and Paul were also at the unit during the first test, they each got a yellow nameplate. The cuts are spot on - no beam spreading or half-cut lines; the cuts are nice and "tight" and well focussed. Some of the pieces needed pushing from the sheet - not because they were badly cut, but because the cutting was so precise, the parts had to be lifted exactly vertically to get them to come away.

Sometimes, on the BuildBrighton laser, everything falls away from the sheet as it's lifted off the cutting bed. While this is encouraging (at least the laser manages to get all the way through the material) sometimes it's only after two or three passes. And that means that sometimes the cuts are wider than they would normally be. Not only were all our cuts cleanly through the entire material, the cuts were so tight that the pieces were a little bit "squeaky" as they were removed from the sheet. At 16mm/sec we erred on the side of caution - there's a chance that we might even get away with cutting at a faster rate.

But for now, we're just thrilled that we have a working laser cutter once more. Admittedly, the extractor wasn't connected up properly during the test cut, and the studio did smell a bit like pear drops for a while, but as soon as that's all plumbed in, we'll be super-productive, laser cutting night and day, no doubt (for a while, at least!)