Laser cutting MDF

Last night BuildBrighton member Colleen tried laser cutting MDF for the first time on our laser cutter. The results were quite impressive. Cutting a single sheet of 3mm MDF at about 30mm/sec (we tend to stick with 16mm/sec for acrylic although it can be pushed to 20mm/sec) the only downside was the terrible smell and amount of smoke!

MDF doesn't half smoke when you laser cut it. Maybe it was the type of wood we were using - an 8' x 4' sheet from Wickes costs about�6. Not the "proper" laser-able MDF, just regular (cheap) stuff from a home supplies store. Despite the smoke, it's certainly a cheaper way of trying out designs than carving everything out of acrylic at �4/A4 sheet.

Colleen was making a simple jewelry stand for necklaces. Although originally using MDF just to make a prototype to see how the finished result would look, a quick coat of black acrylic paint, and it didn't look too bad at all - in fact, a coat of PVA glue and a dusting of glitter and it might look quite nice as it is!

(the later revision was made slightly longer and with hooks to stop the necklaces slipping off the stand when in use)

Necklace Stand

CNC linear rails testing

Down at BuildBrighton tonight, fellow PIC-programmers were in short supply, so with reluctance we had to crack open an Arduino Duemilanove and learn some crazy Arduino coding. It turns out it's not as difficult as it looks (but it does still make you feel a bit dirty).

To get things working, we just wanted to be able to turn a stepper motor clockwise and anti-clockwise. Here's the code we came up with:

int state=0;
int dir=0;

void setup(){
     pinMode(1, INPUT_PULLUP);
     pinMode(2, INPUT_PULLUP);
     pinMode(3, OUTPUT);
     pinMode(4, OUTPUT);
     pinMode(5, OUTPUT);
     pinMode(6, OUTPUT);

}

void loop(){
     //read the pushbutton value into a variable
     int inputVal1 = digitalRead(1);
     int inputVal2 = digitalRead(2);
     
     // Keep in mind the pullup means the pushbutton's
     // logic is inverted. It goes HIGH when it's open,
     // and LOW when it's pressed.
     if (inputVal1 == LOW) {
          // turn the motor clockwise
          dir=1;
     }else if(inputVal2 == LOW) {
          // turn the motor anticlockwise
          dir=-1;
     }else{
      // stop turning the motor
      dir=0;
     }
     
     if(dir!=0){
               // move the motor
               state+=dir;
               if(state<0){state=7;}
               if(state>7){state=0;}
               
               switch(state){
                     case 0:
                     // energise coil A
                     digitalWrite(3, HIGH);
                     digitalWrite(4, LOW);
                     digitalWrite(5, LOW);
                     digitalWrite(6, LOW);
                    
                     break;
                    
                     case 1:
                     // energise coils A+B
                     digitalWrite(3, HIGH);
                     digitalWrite(4, HIGH);
                     digitalWrite(5, LOW);
                     digitalWrite(6, LOW);
                     break;
                    
                     case 2:
                     // energise coil B
                     digitalWrite(3, LOW);
                     digitalWrite(4, HIGH);
                     digitalWrite(5, LOW);
                     digitalWrite(6, LOW);
                     break;
                    
                     case 3:
                     // energise coils B+C
                     digitalWrite(3, LOW);
                     digitalWrite(4, HIGH);
                     digitalWrite(5, HIGH);
                     digitalWrite(6, LOW);
                     break;
                    
                     case 4:
                     // energise coil C
                     digitalWrite(3, LOW);
                     digitalWrite(4, LOW);
                     digitalWrite(5, HIGH);
                     digitalWrite(6, LOW);
                     break;
                    
                     case 5:
                     // energise coils C+D
                     digitalWrite(3, LOW);
                     digitalWrite(4, LOW);
                     digitalWrite(5, HIGH);
                     digitalWrite(6, HIGH);
                     break;
                    
                     case 6:
                     // energise coil D
                     digitalWrite(3, LOW);
                     digitalWrite(4, LOW);
                     digitalWrite(5, LOW);
                     digitalWrite(6, HIGH);
                     break;
                                             
                     case 7:
                     // energise coils D+A
                     digitalWrite(3, HIGH);
                     digitalWrite(4, LOW);
                     digitalWrite(5, LOW);
                     digitalWrite(6, HIGH);
                     break;
                    
               }
               
               delay(1);
     }
     
}

It's a simple state machine - when the motor is turning clockwise, we energise the coils in sequence 1...2...3... etc, when running anti-clockwise we go 7...6...5.... etc

Doing this allows us to quickly and easily make the motor run by pulling an input pin low (pull-up resistors mean the inputs are always high with no input on them).

Here's a video showing the motor in action:

Miniature CNC drilling machine x-axis carriage

We've had a bit of mixed success at Nerd Towers tonight.
Firstly, we wanted to get our x-axis working on the miniature drilling CNC machine. The y-axis (bed) is easy enough - it's just a plastic bed set on top of an Ikea drawer runner. The x-axis is altogether more difficult, as it's a gantry-based axis (to keep the size/footprint down).

In the spirit of making everything as cheaply and as repeatable as possible, we're using the same rack-and-pinion approach for our x-axis as we have done on the y.
Simply put, a long toothed edge will run along the top of the gantry, and the stepper motor mounted on top of the moving carriage will pull the carriage along by rotating a cog/pulley along the tooth-edged strip.

We've decided on this approach as once the parts are designed and proven to work, anyone with access to a laser cutter should be able to make the same thing from our drawings.
The only thing is, we've drawn most of the CNC by eye - so have no idea how far away from the rails or toothed edge our carriage is going to be. So the first thought was to make an adjustable carriage:

At the bottom of the picture you can see the side section of our carriage. By adjusting the bolts. the stepper motor (mounted on the top of the carriage section) could be moved closer to and further away from the toothed edge running along the top.
After bolting all this together, we found that not one single piece of this carriage had been designed properly so we started the whole thing again, this time with a slightly different approach - "guesstioneering"

It's a term coined one night at BuildBrighton and fits this approach perfectly.
Basically we make something based on a best guess, then whittle things down until they fit.....

This second carriage (in blue) was designed entirely by eye and with no reference to our frame! (if the frame doesn't fit, we can always tweak that, and the carriage together, until they line up and mesh together nicely!)
In this instance, the small cog on top of the stepper motor is neither high enough, nor close enough (laterally) to the toothed edge running along the top.
Instead of messing about measuring and re-measuring and cutting and re-cutting, we just decided to make our toothed edge have a bit more play in it. The idea being that we line it up with the carriage in place and just fix it down!

As we were cutting a new toothed section, we decided to go for a double-sided piece, with the cog on the stepper motor sitting between two rails. Hopefully, this will stop the motor from pushing away from the toothed edge and skipping steps....

The only thing now, of course, is that we need to make our gantry stands about 3mm higher and a little wider on one side (so they're asymmetrical) so that this new piece doesn't look like it's been cobbled together and just shoved on as an afterthought. (it has, but there's no need to advertise the fact!)

This new carriage moves along the rails quite nicely.
There's not much play and hopefully this double-rail approach will eliminate this altogether. Here's a quick photo to show the actual size of the gantry. It's really quite small -

So there we have it. A nice sliding gantry with a stepper motor mounted onto it. It's not quite working under it's own steam just yet, but we can't help but feel that we're getting a little bit closer!
Here's how the final thing will sort-of look in place over the y-axis bed. We may even go crazy and lose the lump of scrap wood for a nice piece of red acrylic. That's the kind of colour scheme that would make Robot Steve have a fit

Petanque score-keeping device

Many years ago, back on the old Nerd Club blog, we were playing about with Nokia phone screens and invented a digital score-keeping device. Originally it was a petanque score-keeper then morphed into two or three other things!

While over at the nerd cupboard last night, we were showing how the laser cutter works to a couple of friends from the local petanque club. Keen to demonstrate everything from design and drawing, importing into Newly Draw (the software that drives our LS3020 laser machine from HPC) and cutting, we came up with a simple, one-hour project: a petanque score-keeping device

It's basically two wheels spinning freely behind two cut-out windows. Each wheel still needs a sticker with the numbers 0 to 13 putting on it. We did think of engraving the numbers directly onto each wheel but they might not be easily readable when out on the terrain. 

The wheels will be held in place by a couple of tiny M3 bolts. Since the whole assembly will be glued together, there's no real need for a nut on the back (although reviewing the photos, that also means there was no need for us to cut a through-hole in the back of the device either!)

When made up, each device is about 8cm across and 3.5cm high. The perfect size for carrying around in your pocket, during a game of boules!


For anyone wanting to make one, here are the layout files:

Petanque score keeping device

Laser cutter LS3020 performing badly

While making some test pieces for our CNC drilling machine, we had a few problems with the laser cutter. It was nothing serious, except the cutter seemed to be losing power when cutting anything more than a simple few circles. We slowed the speed down from 20mm/sec to 10mm/sec and ramped up the power dial from 15mA to 20mA but to no avail - even making two passes didn't slice through a 3mm acrylic sheet.

The first thing that came to mind was mis-aligned mirrors. Unless the laser beam is correctly focussed, cutting power is only a fraction of maximum. But re-aligning mirrors is a real pain to get right - so before we messed about with that, we thought we'd give the old "turn-it-off-and-turn-it-on-again" approach a go.

Whenever we start using our laser cutter, the first thing we do is check for air bubbles in the laser tube.
Cutting with an air bubble can cause the tube to overheat and eventually crack or rupture. This is one thing we're quite paranoid about, so we always make sure there are no bubbles in the tube before starting!

A quick inspection of the tube and we found the problem.
There was a massive air bubble in the tube. But how did that get there?
It seems that our run-silent aquarium pump (supplied with the cutter to provide cooling water) wasn't in fact running.

To avoid getting bubbles in our water, we keep both the pump and the return pipe from the cutter fully submerged in water. This is great when everything is working - but when the pump stops running, there's no immediate indicator that the water isn't getting pumped round the laser tube.

Overheating (or cooling water that's got too warm) is another cause for power loss with a laser cutter. And that's exactly what was happening here. The laser tube wasn't getting any cooling water, and so just getting hotter and hotter!

We left the cutter switched off for about half an hour, then got the water pump up and running again (we didn't do it straight away, in case quickly cooling the glass laser tube caused it to crack). After leaving it for a few minutes, and checking that there were no more air bubbles in the glass tube, we fired up the laser.

It was soon cutting 3mm acrylic at 20mm/sec as usual as if nothing had ever gone wrong!
So just a word of warning to anyone suffering from poor performance - check your tube! We were lucky this time - an overheating tube can easily crack if you continue cutting with it;
it looks like we caught ours just in time. But we know to check our water pump is working, as well as getting rid of any and all air bubbles in the tube from time to time.

Laser cutter back working

It feels like it's taken months (in truth, it probably has) to find a new home for the Nerd Club down in Brighton (well, Hove Actually) and to get the laser cutter back up and running.
But today we made some solid progress. With a PC donated by Chris at BuildBrighton and some cheap extractor fan ducting from Wickes, we finally got our laser cutter up and running in it's new home.

Of course, the first test cuts should be something simple like a few circles in each corner of an acrylic sheet, testing the laser across the entirety of the cutting bed. We decided against this and went straight into a commissioned piece - some personalised coat hangers for children's clothing.

Baby Elvis has some really cool threads to wear, thanks to his grandma. Now he has some cool coat hangers to keep his awesome new shirts in pristine condition (at least until next feeding time!)

We're just thrilled to see the laser cutter working after such a long time.
Hopefully this will be the first of many jobs to put through it over the coming weeks.

Christmas clocks

It's beginning to look a lot like Christmas...... everywhere you go. Ok, it's not. I don't know what it is this year - the doom and gloom peddled on all the news channels, the recession, austerity measures or what - but it just doesn't feel Christmassy.

Maybe it's just because the weather is still quite mild and all the spring bulbs are popping up.
But there's something particularly un-Christmassy this year. There are a few lights about and a few shops have made a half-hearted nod towards Xmas, but in the main - and talking to other people, I'm not the only one - we're still waiting to be hit full in the face with Christmas Cheer.

Which is probably why I've left it so late to get making Xmas gifts this year. Normally, come December 1st, the first little door on the advent calendar gets opened and it's straight into maker-mode, planning and making for everyone. But for some reason, this year things have been left a little late.

Back in November, I was helping Jason with his toy cars and lights controller. But since then, not much on the Xmas front. So last night I fired up the laser cutter and got designing some novelty clocks.
Most of the time was spent on the designing and drawing rather than the actual manufacture (which meant sending to the cutter, waiting a while, then some basic assembly afterwards) but the end results are quite pleasing:

[photo here]

Here are the design files should anyone fancy having a go -
Send the dxf to your laser cutter and carve out from your favourite coloured sheet of A4 acrylic (loaded in landscape).

Links to files:

• http://www.nerdclub.co.uk/files/numbers_clock1.dxf
• http://www.nerdclub.co.uk/files/numbers_clock1b.dxf

To finish the clock off (and mostly, to hide the clock movement from behind) I cut out some shapes from a second colour and fitted them inside some of the cut-outs from the main clock face. By turning the clock over they could simply be held in place with some tape. I used double-sided tape, then stuck a piece of card over the whole arrangement, to keep the shapes from falling out once the clock was on the wall.

[photo of reverse]


Here's a slightly different clock, requiring a little more assembly.
At first I wasn't too sure about the design but the more I look at it, the more it grows on me. At first I thought about making the smaller coloured numbers as inserts (so they mounted flush with the surrounding shapes) but now I think I prefer them as relief shapes, sitting on top of the basic number shape.

[photo of second clock]

I think it's the clear acrylic ring that makes this clock work so well. It means positioning the numbers is relatively easy (it would have been a nightmare trying to stick just the very edges of a few numbers to the centre disc to hold it all together) but when the clock is on the wall, the final effect is quite striking!

Here are the design files if you fancy making one of these yourself:

this is the clear acrylic ring that some of the numbers mount onto

with some clever layout, you can get all the numbers onto a single A4 sheet

optional extra - inset characters for the numbers 2,4, 6, 8, 10 and 12

Links to files:

• http://www.nerdclub.co.uk/files/numbers_clock2_circle.dxf
• http://www.nerdclub.co.uk/files/numbers_clock2_clear_ring.dxf
• http://www.nerdclub.co.uk/files/numbers_clock2_insets.dxf
• http://www.nerdclub.co.uk/files/numbers_clock2_numbers.dxf

Lastly, here's a simpler version of the second clock that requires much less assembly, designed smaller to fit on a single A4 sheet of acrylic (or wood or whatever you're making your clocks out of!)

this clock has all the numbers connected to make a single solid piece

using the previous clock as a base, this clock can also have raised numbers placed on top of the base design, or you can cut the inset figures out and use different coloured acrylic (wood, whatever) to fill the gaps

Links to files:
http://www.nerdclub.co.uk/files/clock1_single_piece.dxf
http://www.nerdclub.co.uk/files/clock1_with_insets.dxf
http://www.nerdclub.co.uk/files/clock1_inset_numbers.dxf

Delta robot and laser cutting

At another of our HackLlan meetings, and in preparation for the show-and-tell (provisionally booked for Sat 26th November, on the same day as the Llangollen Xmas Festival) we've had the laser cutter out, busy making and preparing a number of different projects.

First up is a simple three-servo delta-robot.
This robot will be programmed with a script to perform repetitive tasks such as pick up, move, release an object. There are no plans for any further  intelligence to be programmed into it at this stage - but perhaps could be used as a project for any follow-up workshop from the show-and-tell session.

The photo above shows the main structure with the servos mounted on it at 120 degree intervals. Slots were cut into a round disk, to allow the servo heads to move through 180 degrees, perpendicular to the base. The servos were lined up by placing their corners on top of some small cross-hairs etched into the base and stuck down with double-sided tape (in the final version we'll use permanent plastic cement, but for now we may need to move them around again as development continues!)

There are three legs, each made up of three lengths of acrylic.
The "hip" joint - the part that connects to the servo - is a single piece with a large circular head (for connecting to the servo horn). The lower part of the leg - from the "knee" to the ankle - is made up of two pieces connected either side of the top piece.

We're still thinking about how to make the joints, as the "ankle" joints need to free-moving in all axis directions. Someone suggested hobby-sized ball joints (like those found on remote control cars, helicopters etc). A cruder (but easier and cheaper) solution might be to simply use elastic bands to make the joints....

More laser cutting magic

In a desperate attempt to prove to a friend that our laser cutter (see, no longer the spanky new laser cutter - how long did that take?) is more than just a big "boy's toy" I had to find something useful to make with it.



Unfortunately, a kit of parts for a CNC pick-and-place machine (our next major project) is seen only as yet another "boy's toy" and doesn't count. Neither does anything involving gears, cogs, or PCB enclosures. Clocks only just count, but we've already made one of those, so need to come up with something else. Something that appeals to non-nerdy people.....



Here's what I came up with.

Funky vibrant herb markers.







No seriously, a range of herb markers in bright funky colours.

Not only do they brighten up the garden (useful if you're a crap gardener and all your flowers die off early) and serve a useful function (telling you what should be in place of that patch of bare soil) they're frost resistant and easy-wipe clean. The perfect "gardening solution".







The problem, of course, in designing the entire set of six in one laser cutting dxf file, is I've now got a spare five sets in various colours. And a whole load of little tiny acrylic letters! Look out for "funky vibrant herb markers" on eBay soon!

Laser cut solder paste stencils

Well, we've decided to give SMT a try again, for making our guitar PCBs. So the first thing to do is make an SMT version of our earlier (working) guitar board:

We tweaked it a bit - making some pads bigger and spacing a few out more. We also had problems with the first version of the board, connecting the guitar strings to the two rows of six pads at the top and bottom of the board. If we didn't take care soldering, the round pads would lift quite easily, so we've changed them slightly for this board.


This board was designed in ExpressPCB, printed to PDF using CutePDF then opened in Inkscape to flip it horizontally (mirrored) so the final transfer was the right way around - when you're working with through-hole components, you actually want the PCB to be mirrored on the underside so print it as you see it works fine. For SMT work, the image needs to be mirrored so that when it's transferred onto the copper board, it ends up the right-way around.

With our fancy new laser cutter (how longer before it stops being fancy and new, and just becomes "our laser cutter" I wonder?) we cut a stencil design into an acetate sheet. We won't do it again - acetate stinks! And it burns and browns and covers everything in a sticky goo. But here's the solder paste stencil we made anyway:



Maybe the stencil holes aren't fine enough, or maybe we didn't use it correctly, but after applying solder paste through the stencil, we just ended up with big blobs of paste on the board. Manually applying the paste with a small paintbrush may not give a better result, but is about ten times quicker to do!



So we cleaned the board off and applied the paste again using our tried-and-tested method with a small brush



Even with quite a large tip on our soldering iron we got quite satisfactory results. Simply touch the tip onto the pad to start the paste flowing. Any paste in the gaps between traces simply burns off (or flows onto a tinned pin). To be sure of a good contact, we touched the tip of the iron onto the pin to be soldered to make sure the solder doesn't just flow under it.

You may see solder on the bits of board between traces. On a professionally manufactured board, these bits would be covered with solder resist. This is where we just applied solder paste all over the pins then heated it to remove the bridges between traces. Obviously, where the solder paste settled on these "in-between bits" it's resulted in excess solder on the face of the board. We *could* have etched all this excess away and not bothered putting a "solid plane" between traces - but then the Ferric Chloride would take an age to etch the board fully.

Here's the finished board, with multi-core cables attached on one side.
It's not a complete working board, but we've proved that we can solder SMT components just as quickly (we're not going to say as easily!) as their through-hole counter-parts.



On a professionally manufactured board, with solder resist and only the pads exposed, soldering would be even easier - but we found hand-soldering SMT components onto a home-made board relatively straight forward (and pretty quick to do!)

In the example above, we tried two different types of wire - what we're calling "half-pitch" (0.025") IDE cable and "regular" 0.5" IDE cable. We thought that the bigger cable would be easier to solder to the board but thought we'd try the two side-by-side to compare them. Although the regular cable is easier to solder (the traces can be bigger and slightly wider spaced) it's also more likely to fail when working on a large number of boards - because each core is multi-stranded, you have to take great care when soldering as the strands can fan out and easily create bridging with the other contacts. The smaller cable is a bit more fiddly to work with, but because each core is solid, once it's in place, there should be no worries about bridging with other wires.

We've yet to settle on a final design but whichever we choose, will probably be a compromise between easy of soldering and likelihood of failure - we want something that's easy to put together, but if we're likely to get a high failure rate, we'd be better off spending a bit more time on something a bit more fiddly, but be confident that it'll work once it's done!

Laser cutting magic clock

One of the great things I'm finding about having a laser cutter is just turning an idea into a product in a few hours. Such an opportunity presented itself this evening.

After playing petanque down on the seafront at the Brighton and Hove Petanque terrain, I got chatting to Ray - a longtime founder member and one-time president of the club. Ray is selling his house and soon moving to France, to spend his days drinking pastis and playing the game he loves, so it seemed a fitting to use my new-found skills to make some kind of memento - something that incorporates plastic and boules.

The obvious answer, of course is a set of child's plastic boules! The slightly less obvious answer (and the option we finally plumped for) is an all acrylic boules clock!



We had a sheet of A4 mirrored acrylic so quickly knocked up a design - drawn in Flash, exported as .wmf, then loaded into Inkscape and finally saved as a .dxf. This then allowed us to import the shape(s) into NewlyDraw, ready for cutting.
It seems like quite a faff but actually makes sense: you do all your drawing and editing in Flash (I personally love the Flash IDE for drawing!) then save the result as an image. You use Inkscape to prepare the file - no drawing here, but you can split shapes up, put them onto different layers, simplify splines etc. Then save as dxf and import into NewlyDraw. We just use NewlyDraw as the cutter driver - no messing about: load the dxf to cut shapes from, move the laser head to the start position and hit go. That's it!

Heres' the outline drawing


And here's a link to the dxf for cutting.
After assembling, we did hit a few snags, but only because we're still waiting for a delivery of various sized clock movements, so only had one movement to hand. It shouldn't have been a problem because it's on an acrylic-faced clock, but it didn't take long for the problems to start mounting up....

... firstly, with our clock consisting of a layer of 3mm mirrored acrylic on top of a base of 3mm blue opaque, we had a 6mm thick clock. That doesn't sound like much. But our clock movement was designed to fix to a 4mm or thinner face. So we had to re-cut the bit of the boule with the numbers 0-6, making the hole at the bottom wider, so that the clock movement attached onto to the blue layer only.

Then we spend ages getting the hole right for the hour (spiral) hand.
The clock movement was supposed to have a 5mm shaft. It took no less than five goes for use to find out that the hole needed for a snug fit is 4.7mm (we went 5mm, 4.9mm, 4.8mm - oh, this is going to take ages, let's skip a few and go for 4.5mm, oh that's a bit too small, what about 4.6mm, bugger it, if 4.7mm doesn't work, we'll have to give up and go to bed).

So what's with the weird spiral movement and peculiar numbering?
Well, of course, it's a petanque clock - so it's fitting that it should go from zero to thirteen (scoring in petanque goes up to 13, not 12). The spiral hand allows you to tell the time still, even though it's got these extra digits. If you think of the spiral hand as the hours and the short, straight hand as minutes, it's actually quite easy to read the time - in the example drawing above, the clock is reading half past three. Whichever number is covered by the spiral hand represents the hours, the minute hand works as normal. The photo, by the way, shows the time as 01:35am, which is what time it was when we finally finished making the first, working clock!

And the zero and thirteenth hours?
To be honest, it's best just to ignore them - they were only put there to make the clock look cool ;-)

Miniature instruments make a return

Using the invisible instrument idea, and the early DeskJam prototypes (originally developed for a concept for Mattel in Sept 2010) we're soon to launch a range of miniature, playable instruments.
After being turned down by Mattel - their target audience was 7-10 years olds, and the instruments had to be dumbed right down to the point of losing their impact - they were also presented to Ravensburger in Germany. They too loved the idea, but couldn't get the cost of production down to less than $4/unit (apparently this was to be able to sell them for $40 each!). So we've decided to hang the expense, and make the little instruments here at Nerd Towers.

The original DeskJam range included guitar and bass (both worked in the same way) a miniature synth and the original instrument that kicked it all off - some miniature usb drums. As we're no longer going ahead with DeskJam - there were two other companies involved in the original project, but all the electronics, firmware and software development was strictly our own work - we're building the entire range again from scratch.

The first instrument in our new range of instruments is the guitar.
We're working on a range of guitar shapes and styles, but each will basically consist of the same set of components: a touch-sensitive neck for selecting the chord/riff to play, and a set of touch-sensitive strings, which the user can strum to trigger the sound(s). For anyone reading the blog a few weeks back and wondering why the topics had jumped around to include multiple touch sensitive inputs, things should become clearer from hereon in...

The first thing we did was create a multi-layered guitar shape.
For the main guitar body, we're working with two layers of 5mm acrylic - into which we've cut a void to give a 10mm deep space for the electronics:



The front and back are cut from 3mm coloured opaque acrylic (this laser cutter has been soooo handy!) and a scratchplate made from some 1mm HIPS. This super-thin material is just right for the scratchplate (3mm acrylic is far too thick) and means that when we introduce some 3mm thick pickups, they stand proud by just the right amount - just like a real guitar!



Finally the layers are all assembled and the final guitar is starting to take shape:



The channel along the neck is for the touch-sensitive board. PCB pins will be inserted onto the "back" (non-copper) side of some copper clad board, and soldered to the etched front. To allow space for the soldered pins, we needed to keep a channel running along the length of the neck.

So it's off to the cupboard to dig out some Ferric Chloride and to get etching. Finally, it feels great to be making PCBs again - and this time, the end product is ready and waiting to be populated with some tried-and-tested electronics. This is one project that might actually get finished within a reasonable timeframe....

Laser splash back

A few weeks ago we tried cutting some miniature guitar shapes from MDF with mixed results. At best it could be described as a partial success. With our swanky new LS3020 laser cutter, however, cutting such shapes is a doddle!

Like most laser cutter users, we've had to spend some time with different materials of different thicknesses and types, finding out which settings to use for the best cut rate.

For 5mm acrylic, we're cutting 15mA at about 8mm/sec.
For 3mm acrylic, we're using 15mA and cutting at about 18mm/sec.

These values give an incredible performance, far better than we'd hoped, especially considering how slow and difficult the laser cutter at BuildBrighton has been. We've tried cutting slower, with less power, and faster with more power - but 15/18 gives a nice balance between speed and power use (apparently, cutting with less power makes the CO2 tube last longer; I guess it's a matter of time before we find out how true this is!)

However, whatever speed/power settings we use, we're getting a bit of what can only be described as "splashback" on the reverse of each piece. It's more obvious on some cuts than others, but on the back of some pieces, the pattern of the honeycomb bed can be seen in relief. It's particularly noticeable when cutting black acrylic:



After removing the protective film, small pits can be seen on the back and on the edges of the piece:



Yet the "front" face of each piece is cut perfectly, with a smooth, straight polished edge:



We've had conflicting advice on how to correct this - some people say a faster cut with more power gives a better finish. Some people have told us that we need to turn down the power and cut more slowly. In our experience, both approaches still create this "crazing" on the back. Maybe it's something to do with the bed. Maybe it's time to put in another appearance on the LaserScript forums to see what advice any other users can give. Those guys have been so helpful and supportive getting us up and running - we can't be the only people to have experienced this problem. Other than this little niggle, we're absolutely thrilled with the laser cutter and can't wait to start making "proper" stuff with it!

First shapes off the laser cutter

While waiting for a delivery of acrylic sheets (ok, it was only ordered a few hours ago and it's Sunday evening!) we've been playing about with the few sheets of clear plastic we got with the cutter, to find out which settings work best for us.

We found that cutting at 15mA, 20mm/sec works really well for 3mm acrylic.
Any slower and the beam reflects off the honeycomb bed and pits the reverse of the plastic. Any faster and the beam doesn't always cut all the way through on the tight corners of intricate shapes.



Here are some example logos for a new shop opening soon; it's called NIX and offers an outlet for cottage industries and artisans. The idea is really simple. For a fixed monthly fee, you get a shelf on which you can display and sell your wares.



Obviously these would look much better in coloured and/or opaque acrylic, but they're just test pieces to see what the laser cutter can do. And so far, the results are pretty impressive!

line drawing exported as dxf for importing into NewlyDraw

Here's the original business logo, to compare the results to:

Cutting at last!

After a few false starts, and a nervous first try, we're finally cutting stuff with our new LS3020 laser cutter! The tiny bubbles problem apparently is quite common with new tubes, and a few capfuls of Milton sterilising fluid soon sorted them out (thanks guys on the LaserScript forums for the tip!)

So now we're safely(?!) cutting acrylic with the laser, it's time to get familiar with the NewlyDraw software and find out which power and speed settings work best with which materials.

At the minute, we're trying on clear 3mm acrylic.
The laser cutter is whizzing little 10mm circles out no problem, at about 12mA. Now we just need to find out what all these settings in the software actually do!

After selecting the items to cut out and from the file menu, hitting ENGRAVE, the following dialogue appears. From here you can jog the head around or set it to it's origin (we found that -80,0 put us in a good starting point, at the top left of the sheet of acrylic) and even choose optimum cutting paths (more on that later, we're still trying to walk, let alone sprint off into the distance!)



After hitting "start engrave" a second dialogue appears



This has more of the same - a second chance to jog the head around - and some speed/power settings. We're not quite sure which of these relates to what: whether the speed setting is for jogging the head, or for cutting. To date, changing these values doesn't really make much difference: the laser head goes off on it's merry way, making short work of the 3mm acrylic, no matter what speed/power settings we put into this second screen. We're guessing that these need to be changed somewhere else, and we're probably giving it too much juice or not moving as quickly as we could, for the given power level or something.
Either way, it's another visit to the LaserScript forums to double-check we're doing everything right. It's exciting having a laser cutter. And a little bit scary!

Laser cutter from HPC

It's been a busy couple of weeks, with "real life" taking over for a while (always the case, as summer approaches, family holidays are arranged, lots of doubling up at work covering for colleagues who are lucky enough to take their holidays before the schools break up and so on).

As work on the touch-sensitive range of instruments stalled, due to cutting problems, we decided to take the plunge and make a heavy investment. In fact, we're making quite a few BIG investments at the minute, the least of which is taking out a lease on a shop to sell homewares, home-made goods and generally supporting the whole maker/cottage industries that are slowly but surely growing throughout the UK. As well as buying stock in, I've got a crazy idea about selling make-it-yourself kits and pre-assembled "geeky gadgets". And the first range of products? Yup. Miniature instruments.

So making them from MDF seems difficult due to the limitations of the CNC, what's the alternative? Acrylic of course! You can see where this is heading....

...HPC in Halifax supply laser cutters. And we're the proud owners of a shiny new LS3020 machine. We spent the day up there recently and saw one in action. It was amazing - blasting through 6mm acrylic in a single pass with no problems, cutting mdf, laser ply, and even solid maple, all 6mm thick, in a single pass at varying speeds (the slowest at around 8mm/sec cut 4 layers for an entire guitar in just a few minutes). Exciting stuff!

After getting everything set up and following the instructions and advice very closely, we're almost ready to cut. The only thing is, this is an expensive bit of kit, and very easy to get wrong (and break �150 CO2 tubes apparently). So we're a bit nervous of actually firing the thing up on our own!
The thing is, the CO2 tube had some air bubbles in it even after the machine had been switched on (with the water pump running) for about half an hour. We got rid of the big bubbles that had collected at either end, by tipping the machine then pinching the water inlet pipe for a second or two and releasing (returning the machine to horizontal). This worked really well for getting rid of the "air locks" in the tube.
completely air bubble free water jacket around the CO2 tube

The worry thing is that the main part of the tube has a lot of little tiny weeny bubbles along its length.

smaller than the bubbles in a Wispa bar, are these anything to worry about?

We've tried all manner of stopping and starting the water flow, tipping the machine, leaving it to rest, turning it off and going for a walk, switching it on and moving it around. It doesn't matter what we do, those little tiny bubbles don't want to go! The question is - can we run the machine with these little bubbles? Do they matter that much? Not knowing enough about it, we're frightened to fire the machine up fully and try cutting, just in case the tube gets busted. That'd be a real bummer. The machine's only a few days old; we don't want to break it before we get started!