I’m currently building the Mantis – a little CNC router designed specifically to help create custom PCB’s. Actually, mine will look more like this.

I’m not convinced yet that this thing will be able to do PCB isolation routing, but I’m willing to give it a try. It’d make it much simpler to do one-off’s, instead of having to live with this:

But I’m not quite willing to dedicate an Arduino Mega and the UltiMaker electronics that is offered as option in the workshop. If you’re interested in 3D printing: the UltiMaker is derived from the RepRap and the MakerBot CupCake, as described here.

So instead of following everyone using the MPU-based approach, I’m going to re-use my parallel-port laptop running the EMC2 software, and let the laptop do all the work, instead of yet another dedicated board. I can always switch to a microcontroller setup later if this machine is practical enough to use it frequently. And if it doesn’t work out, my investment will have been relatively low.

There’s also a second reason for doing it this way: I’d like to build my own electronics for this CNC/3D stuff one day. I think there are better ways to do this sort of thing, more modular, more extensible, and more flexible (why not Ethernet? why not closed-loop servos?). But it wouldn’t be realistic to think I can take on that challenge as well, with everything else also going on at Jee Labs. So for now, the parallel-port shortcut will have to do.

Driving CNC stepper motors from a parallel port is a proven (but by now somewhat outdated) concept. Either way, it all ends up doing the same thing: executing the CNC world’s de-facto standard G-Code scripts.

You still need stepper motors, and stepper motor drivers, since a parallel port can only send out feeble 5V signals.

To save some time, I decided to try something a bit whacky by re-purposing an UltiMaker electronics board to hook up its motor drivers to the parallel port:

Lots of stuff on there I won’t need: heater control, extruder control, PWM…

Here’s a minimal setup, using just 3 stepper drivers and a little JeePlug board sitting on top of some extra headers on this board:

I patched a 5V regulator (plus LED) on there to feed the logic levels of the Pololu stepper drivers, and left everything else off, basically. Only thing left to do is wire up 7 signals + ground between the parallel-port breakout board and the JeePlug.

And then figure out the software side of things…

Finally found some time to fix the clogged extruder Mk4 I had on the CupCake. A new heater + extrusion head did the trick. Well, almost… watch the leaked blob of ABS on top of the extruder heat barrier:

As a result, the first part I printed did not contain enough material, and ended up too fragile for actual use. That’s part of a micro-lathe I’m printing for someone else, btw.

So I disassembled the extruder again, and replaced the PTFE rod with a new black one:

Yippie, now it’s working again. I’ve also upgraded to a heated build platform, which works great – no warping and the parts come off real easy, with raft and all:

Here’s a component from the Wade extruder which I’ll need for the Mendel:

Alas, not all is well yet. This was supposed to be the other half of that gearwheel pair:

Hmm, looks more like a cupcake to me…

The other nasty problem is that the main body of the Wade extruder I’m trying to build is too large for the CupCake. I can’t print it! Now I’ll either have to buy a complete extruder for the Mendel or find some other extruder which works with it. So as far as the next-generation “Mendel” is concerned, I still need to assemble the electronics and find some good extruder for it. Drat, it’s always those last 20% that bite…

Encouraged by some comments on yesterday’s post, I printed the same bracket again, laying on its side:

The horizontal base comes out ok (I cleaned up the hole):

Interestingly, the top of the bracket isn’t filled in, which is actually better:

The sides look much better as well:

(the Skeinforge settings aren’t perfect yet, layers could be mashed smoother together)

But wow – what a difference this makes! Thanks for the tip!

Here’s another object, a Geneva Wheel from Thingiverse:

Turning is not very smooth, had to cut off some plastic from the round shafts, but hey: it works!

PS. Don’t worry, I’m working most of my time on JeeNode stuff, hardware and software that is… ;)

I just had to try making a little mounting bracket for JeeNodes…

Here’s the design:

The design dimensions are 25 x 12 x 10.5 mm. It was created with OpenSCAD, which takes a description of the object and generates the solid model shown above:

Does it work? Can it be printed? Can it be used? Yeah, sort of…

Works for JeePlugs too, since all the boards have the same 21.1 mm width:

Took me three tries to get the sizes and the little ridge right (the middle one):

Pretty ugly stuff, when seen up close. But hey, that’s what pioneering looks like!

The ridge which holds the board doesn’t come out very clearly – the features are not yet a match for what the JeeCake 3D printer can do (or should it be the other way around?):

But despite appearances, this bracket is already surprisingly functional. Apart from the awful surface and rough shape, it’s a springy and very robust little piece of ABS plastic. It could easily be screwed down, and it would hold the board quite well.

Fascinating, it’ll be fun to see how this evolves over the next few years.

This is not what you might think it is:

I’ve been placing my headphone next to me on my desk for ages. There is of course never enough room on top, but plenty of spare room underneath:

So here’s my home-made headphone bracket:

Here’s the design, made with Sketchup:

I just picked a “2″ in a suitable font, re-sized it, “drilled” some holes in the base, and then “printed” it.

Piece of JeeCake!

PS. Given that CNC and 3D printing is not really the main focus of this weblog, I’ve set up a page on the wiki.

Update – design files added to Thingiverse.

Ok, one last post on the CupCake CNC trials before I get back to JeeNode stuff.

The raft is now very solidly stuck to the base:

This thing really sticks well, with plastic pushed down into the criss-cross grooves of the acrylic base. The trick is to place a plain paper sheet between the extruder head and the base, and to lower the Z axis until the paper slides away with just a tad of friction.

Unfortunately, the next problem comes up – as seen in this first Geneva Wheel trial:

It turns out that the next layer of the raft doesn’t stick well to the first one. I solved this by raising the default 230° setting to 240° for the raft.

Another serious problem was that there is a lot of plastic on the right end of the raft as the print nozzle paused (!) on each turn. And the second layer of the raft doesn’t extend all the way to the end. This was solved by adding three noise-suppressing 0.1 µF caps to the extruder motor and disconnecting all the end-stop optocouplers.

The object itself seems to come out fairly well, though there were some blobs of plastic around the nozzle during printing which clearly interfered with the X-Y motion at times.

Here are over a dozen more parts, printed using black ABS for a change:

These all came out ok, but note that even these small parts take 10..15 minutes to print – each.

The biggest remaining problem is “warping” – it’s causing over half my trials to fail:

This part failed to build (should have been 20 mm high), it slowly came off the base and started interfering more and more with the extruder nozzle. At some point the nozzle got stuck in fact. Note how the thickness of the part is completely uneven. This is caused by the ABS cooling down and shrinking a bit – slowly pulling itself off the raft (with considerable force). A heated baseplate seems to be the hack to solve this – but that will require a lot more tinkering.

Oh well. We’ll get there… eventually :)

Update – upgraded to ReplicatorG 0012 with Extruder firmware v1.8 and switched to Zach Hoeken’s thermistor settings (raft setting reverted to original 230°). The last change was to shine a halogen light on the platform and object, to heat it up a bit – this seems to get rid of just about all the warping, yeay!

It’s not as simple as it seems…

Well, the CupCake worked straight out of the box, which is of course fantastic. But printing does seem to have two tricky bits, called “extrusion” and “rafts”.

Here’s the printer making its third part:

What’s about to happen, is that the “raft” (that woven mat laid out on the bottom to hold the rest of the construction) is about to come off the base. In the above picture you can see two other problems: the raft itself coming apart, and a blob of plastic (front right) when the printer decided to pause for a few seconds, while the extruder kept pushing out plastic…

The problem seems to be that when the plastic cools down fully it becomes quite springy and rigid. Which is great for the final object, but causes trouble in keeping it stuck to the acrylic base. I suspect that the heated platform which people are experimenting with is to overcome this problem, by keeping the base slightly sticky for the duration of the build.

Or maybe a few wires extending further out from the raft would help, by “tacking down” the whole thing.

The other purpose of the raft is to even out the surface. In my case there is a slight difference in height across the base. I should probably try to get rid of that first.

Anyway, here are the objects made so far:

The meandering plastic retains its shape – that’s probably part of the magic behind all this.

PS. The stepper motors are noisy. I don’t think the software I’m using is micro-stepping right now.

Just got the missing part for the CupCake CNC 3D-printer in from MakerBot – partly their mistake, partly my mistake, long story… anyway – in the end they were extremely helpful in coming up with a good solution.

Which I had to try right away, of course ;)

After a bit of head scratching w.r.t. firmware versions and uploading, everything came together at last.

Here’s the first object getting printed at Jee Labs – whee this is fun:

After 8 minutes, it’s done and steps aside:

Mystery object…

After removing the “raft” and cutting off some loose ends:

So what is it? Oh, nothing spectacular really – it’s a Z-endstop for the machine itself. I figured that after us people doing so much to get it going, this machine might as well start working on improving itself right away…

I’m astonished by how well this first part came out. Very clean, very plastic’y, much sturdier than I expected.

All that’s left is to give this new beast a name – Jee3D? JeeCup? JeeCake? CuppaJeeno?

Spent a day with the family on assembling the CupCake CNC 3D-printer. Great fun!

Here’s where we are now:

The enclosure and all three axes have been assembled. As seen from the top:

Still remaining: the plastics extruder and the electronics – next week, hopefully!

Baby steps in CNC land, but still a milestone for me:

With a pencil, the worst that can happen is a broken tip. I’m not quite ready to put a Dremel on there, turning at 10′s of thousands of RPM, and chewing its way through anything that happens to be near it. Need to get the limit switches and the relay board going first, so it can be turned off under computer control. Besides, it’ll be noisy and get very dusty.

The red-black wire hanging down the “gantry” (yeah, new words every day) is for the limit switches, which have been glued in place but not yet hooked up. The switches have been connected in series, two per axis and using the Normally Closed pins so that the circuit gets broken when a limit switch trips. That way it will also act as stop signal when a wire gets pulled loose.

I’m still exploring, but I think I’ll call the longest axis (towards the camera) the X axis, and the sideways one the Y axis. Let’s just stick with Z for up and down ;)

The drawing is the standard demo built into EMC v2, and I had to move the paper during while drawing because it would have run off the edge otherwise:

Some oddities in there because the pencil is not rigidly attached to the tool holder, but basically it’s doing all the right things. And making funny sounds as the steppers go through curves such as for the “C” and the “S”. Can it draw an accurate rectangle? I hope to find out soon.

So now zee Jee Machine is writing on paper! Onwards!

The CNC router is coming together nicely. The controller board works so far, and so does the EMC software running on a Dell laptop:

Here’s the complete setup, next to the V90 (the electronics will go inside once finished):

And here’s the EMC 2.3.4 software, running under Linux (Ubuntu 8.04):

It just finished “doing” the demo, i.e. making the motors turn in lots of mysterious ways.

Some tech specs: the laptop has a worst-case real-time jitter of around 17600 nSec, which means the computer can send out up to 30,000 steps per second. I’m using quarter stepping, so that translates to 800 steps per rev, 4000 steps per inch, i.e. max about 7.5″ per second on the X and Y axes (which the motors can’t handle anyway – I may switch to 1/8th micro-stepping later). The system uses imperial units for the screws, so that’s what I’m sticking with, but I’ll probably do most designing in metric units. Resolution of the machine is about 0.006 mm for X & Y, and even higher for the Z axis. Don’t know about accuracy, repeatablity, and backlash yet – that’s where lots of tweaking will probably be required.

Next step is to mount the motors on the V90, and then go through all sorts of adjustments to make this thing move properly in all three axes. Oh, and hooking up the emergency button and the six limit switches.

And that’s just the CAM side of it all… CAD will be a completely different story!

First step to CNC was the mechanical assembly of the V90. Little to report here – it took an hour or two. Adjustment and tweaking will probably take a bit longer, once things start to move.

The next step was a bit more work – here’s the power supply + electronics stuff, mounted on some scrap wood. It was made flat enough to mount inside the V90, underneath the work area and X-axis (Y-axis?) slide:

At the top what this is all about: connections for three stepper motors and a strip to hook up limit switches and the emergency stop button.

The power brick in the bottom right supplies 5V to the parallel-port side of the RF-isolated breakout board and the opto-isolated relay board. That means the 24V @ 6.5A supply can’t ever reach the computer. It also avoids 1A current through the linear voltage regulator to supply the relays (i.e. 20W of heat, just to go from 24V to 5V).

End stop switches, heat sink, and relay board have not yet been added / connected. Plus some power cable fasteners at the bottom, so they can’t be yanked loose.

All the high voltage is in one area at the bottom, to be covered by a shield. But even without the shield: all the exposed metal is recessed so it can’t be touched without sticking some sharp object in there – 220V scares me!

Heh, heh. Some crazy stuff is about to happen in the Jee Labs…

I’ve received a CNC router kit, i.e. the subtractive way to create 2D and 3D shapes. This one:

It’s one of the simplest CNC units available, from what I can tell. The work area is about 30 x 45 cm (A3).

Got various ideas to try out – from one-off pcb’s to front-panels. And more.

CNC routers can be very noisy and dusty, so this thing will be placed in a corner of the garage. A trusty ol’ Dell Inspiron 5000 laptop will sit next to it, running EMC and driving it all via the parallel port.

I’ve also ordered an extruder-type machine, i.e. the additive way to create 3D shapes. This one:

I don’t expect any of this to be a time saver – on the contrary, getting all the details right for CNC is going to take a huge amount of time and effort. But if it helps me try out ideas and explore new avenues, then so be it.

Yeah. Totally. Crazy. I know…

(Warning: this post is a digression into robotic tools…)

I’m still struggling with the assembly of JeeLinks: after 4 attempts, none of my boards work and each with different results – not good :(

The answer is probably to have SMD stencils made to apply the solder paste evenly and in precisely the right spot. Manual parts placement with a tweezer is tricky but it seems to work ok for me.

But I’m hesitant. Stencils add a considerable cost overhead to each pcb run, and I’d like to be able to do lots of prototype runs in the future.

The other way to do this is to automate. Unfortunately, SMD machines are expensive – even the manual-assist or “semi-automated” ones are in the multi-$1000 range. And I don’t really need a CNC router with extreme precision or a 50x50cm work area plus a full 3D Z-axis. I just need to deal with printed circuit boards of say 3x12cm and position them within 0.2mm or so. Plus a reasonably accurate automated solder paste dispenser.

Hm. Wait a minute. That’s essentially the range of a CD/DVD drive: the tray comes out about 12 cm, and the laser inside moves about 3 cm. Why not take apart an old CD drive and mount the laser motion system on top of the tray and perpendicular to it?

Here is an old Philips drive I still had, disassembled:

Here is the drive, “reorganized” to perform X/Y positioning, with both actuators at the opposite ends of their respective travel:

Here’s another one from AOpen:

A close-up with the laser platform turned and on top of the tray:

The motors in both drives create a smooth and not overly fast motion when driven by 1.5 .. 3V, but the tray motor from AOpen draws much more power (about 250 mA).

The main idea is that such a setup can move the laser platform over an area of 3x12cm. But instead of turning on the laser, some sort of pcb holder could be attached to it so that the board is positioned. Then, all I need is a syringe mounted in a fixed spot over this X/Y table and some move-down-and-dispense mechanism.

Voilá – a dirt cheap automated solder paste applicator for small PCBs!

Given that there is no sideways strain, I hope that the tray/X-axis positioner (which has some slack) can be made accurate enough for solder paste by spring-loading it. The laser/Y-axis accuracy should be ample without much effort.

One problem with both drives is that they use linear motors instead of stepping motors, so there is no easy way of figuring out the current X/Y position.

Hm again. Could we somehow accurately measure the position of the X/Y table? Adding quadrature encoders to both rotating shafts would solve it, but that means hacking the mechanism – which I’d rather not alter. Not to mention getting suitably small encoders.

So here’s a second idea: the X/Y table positions the pcb, but perhaps it could also move around a bit of graph paper, attached alongside the board. And then… maybe an optical mouse could be hacked to detect the changes? Though I don’t know how hackable optical mice are. Another option might be to use IR proximity sensors, but that’s pushing it and would require precise calibration.

The third issue is the solder paste dispenser. Some sort of syringe, with the plunger tied to a servo, perhaps?

There’s a second, simpler, use for such a system: a PCB inspection system. Just place a loupe or microscope on top and meander the board underneath it.

I’ve even got an old Ikea drawer to fit the entire thing into:

I know, I know, it’s crazy. But still… ideas are cheap, and so far my materials cost is zero!