Not what I thought I'd be posting about

...but it still qualifies as non-reprap related. :D

Earlier tonight Seppo and I built an Epic Workbench. Not one of those weedy things you might put a computer on, but something Indiana Jones could hide underneath to survive a nuclear blast. And we made it IN A CAVE! WITH A BOX OF SCRAPS! Okay, not really, but it was put together with stuff we found around the space.

Jeremy (of City Studios, the guy who leased us the space and will at some point use the rest of the warehouse) had a pile of modular office desks delivered to the warehouse a week or so ago; he'd got them for free from a decommissioned office or something. He also got a huge pile of 'junk' that came as part of the lot and was tossed out the back until it could be disposed of.

He said we could take whatever we wanted from that pile... which is a big deal because it's not junk at all. It's a large number of the modular partitioning frames and panels and such that are standard furniture for offices these days. In the dark, on treacherous ground I pulled out a couple of framework pieces and we discovered that they were each actually two frames bolted together that were *perfect* for making standing height workbenches.

An hour or so of work later, along with a couple of standard lengths of 2x4 and a sheet of ratty MDF that's been taking up space along one wall and we have the first of what will be quite a few brilliant standardised hackerspace workbenches. The MDF work surface is admittedly awful, and we'll probably replace it as soon as we can with a better specimen, but Seppo was eager to get an example finished and usable tonight, and it's perfectly serviceable (if you don't lose something down one of the larger holes :D)

We've found a few other treasures in the 'junk' pile so far, but those are going to be a surprise for later. And we've hardly scratched the surface of what is in there.

Greased Lightbox

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Catchup post!

Things have been a little busy of late, so I've been woefully behind on updates. Hackerspace Brisbane moved into new digs at Fortitude Valley; the new space is much larger than the old one and is starting to feel like home. Sadly for me I used to live 30 seconds walk away from here, but I moved away only a few months ago. ;_;

Anyway, moving in and getting everything set up (walls, internet, electricity, killingscaring off pigeons, reworking the rfid access) has taken a bunch of time away from the reprap. But not entirely!

The new stepper extruder has successfully replaced the old one, so no more griping about having to pull it apart every five minutes. It had consequences right the way down the line, however.

I threw together a temporary stepper driver using one of my easydrivers from my McWire mill. It can only supply a maximum of 750mA to the motor, which is borderline insufficient when running on 12V. When I mentioned this to Matt at one of the meetings, he dashed out to his car and pulled out a bunch of stepper control boards from some industrial printers he had recently dumpster dived. The chips (STK672-080) are through hole, properly documented online, and really beefy - up to 2.8A without a heatsink! I've built up a new driver board using one, but it is yet to be tested - the driver chip is unipolar, requiring me to run another two wires over the loom to the extruder. Makes me glad I didn't completely cut off those wires on the motor!

Initially I'd skipped putting springs on the bearing assembly, but the motor would get stuck unless I constantly supplied some extra torque with my fingers. Springs appear to be exorbitantly priced around here, so I went the DIY route and wound my own using music wire for pennies. The results aren't brilliantly pretty, but they work really well! The motor now only skips occasionally. Unfortunately it isn't a full solution, because the slightest extra friction on the filament stops it, so I need to monitor the filament feed. Hopefully the new driver will sort that out.

On the software side, the original reprap firmware has support for a stepper extruder, but there's a bug in it somewhere that causes the arduino to reset as soon as it is activated. That pretty much forced me over to the newer 5D firmware sooner than I'd expected, and 5D supposedly requires the Arduino to be replaced with a Atmega644-based Sanguino. They lie! 5D will run happily on a 328-based Duemilanove if you remove the directives preventing it from compiling; the *only* issue is that the compiled binary is larger than the older 168-based Arduinos can hold (about 20k) but the 328 has plenty of space left over.

I don't know if this is deliberate or just not given sufficient thought; the code blocks compilation for anything other than a 644, when it should just be blocking compilation for the 168 instead.

Once I moved over to the 5D firmware, I had to modify the g-code generation on the PC side to support the new 5D syntax. That was 'simply' a matter of enabling the Dimension plugin in Skeinforge. However, the result wasn't great; the subsequent prints all seemed to drive the Z axis WAY too fast even though Skeinforge was configured to allow only a maximum of 180mm/min in Z. Even the g-code output looked fine, as it correctly lowered the feed rate for the Z moves.

The culprit was finally apprehended - in this case the 5D firmware. By default, the firmware is configured with a "Swish! Ultra-cool!" feature to accelerate the extruder head from it's current speed to each new speed that is supplied in the G-code - this allows the use of smaller motors like in the Mendel. Unfortunately, the acceleration includes moves on the Z axis! What would happen is the reprap would be moving the extruder head fast in XY and then try to decelerate *during* the Z move - starting at 2000mm/min and dropping to 180 at the end. But since 180 is the fastest that Z can do, almost the entire move was made far too fast. Obviously acceleration shouldn't be applied in this case!

I'm guessing that the reprap host software inserts explicit feedrate changes around Z moves that disables acceleration temporarily. Skeinforge doesn't. Disabling acceleration in the firmware and recompiling it fixed the problem.

I've now got the reprap printing ridiculously quickly - 40mm/s feed rates when doing infill (which makes the machine shake madly), and half that when doing outlines. That adds up to a massive win when printing objects that have large internal volumes, but not so much when it is all thin walls and details.

Now with a (mostly) working reprap, I was 'strongarmed' by Arjen into bringing it in to last week's Barcamp. I'd never been to one before, and I was looking forward to some of the talks that were scheduled. Alas! The machine proved so popular with attendees that I spent the entire day with the reprap in the common area printing and distributing nifty little HSBNE keyring tchotchkes. Maybe I'll just bring a video of it to the next one. ("No you don't!" I am told by multiple people :P) As the day progressed the print quality declined until the keyrings were no longer any good; the extruder wasn't laying down enough plastic, probably due to the weak extruder driver. But it will live again!

Sorry for the lack of photos; I've misplaced my camera's memory card. Will update when I find it. Coming up next - something not reprap related for the first time in a while!

Oil - the cause of, and solution to, all of life's problems.

Another week gone and there was not much to show for it. The extruder stopped working again, of course. No amount of fiddling with it would make it go for more than a layer or so of any print, which is really frustrating when one needs just one more print (ok, admittedly a pretty large one) to dump the extruder for good.

However I did solve some other niggling issues with the reprap. I figured out how to get a set square in between the X and Y axes and satisfactorily set them up perpendicular to each other; it worked really well until yesterday when there was a somewhat catastrophic failure and I had to go through the whole mess of disconnecting the X belts and realigning all over again. It *seems* to be robust now that it's back together, but I want to replace the bearing blocks that mount the X carriage onto the Y as they're extremely fiddly and will bind if they're done up too tight... or shed a bolt or two, go loose and bind anyway.

I also figured out a way of having the reprap itself tell me how much backlash there is in each axis. I modified the firmware so that it keeps track of how many steps it takes to move off an endstop - since there only needs to be one step's worth of actual movement away from an endstop to deactivate it, any extra must be backlash. I measured 5 steps of backlash on the X axis and 1 step on the Y axis, which seems to be about right; it comes out to 0.625mm on X and 0.125mm on Y. Plugging those values into Skeinforge's Lash module (well, half those values really) made a marked improvement... in the partial layers I could get out of the extruder, of course.

I noticed that the extruder seemed to have more trouble when the print head was in the middle of the bed as opposed to at the origin, which is closer to the spool and so the filament is pulled to the side less. I used a long bolt and a piece of acrylic with a couple of holes drilled in it to make a filament guide that sat a couple of inches above the extruder and ensured the filament was more vertical as it went into it. I also put some oil into a folded up Subway paper napkin and put it above the guide to oil the filament as it passed by.

Still no good. Gaah! Screw it, I'm just going to squirt heaps of oil (well, a few drops) directly into the top of the extruder. I don't care any more, and I've tried everything else.

Wait a second, that worked?

Two and a half hours later...

:D

Teething problems...

Things have not been all rosy in reprap land (what else is new?) The extruder started playing up again, and all the prints so far have come out elongated. The stretching isn't just in X or Y either, which would point to an easily addressed calibration problem - instead it was along the 45 degree line. There's only one explanation for that - my cartesian bot was a parallelogram ;_;

After some thought I figured out that I could move the belt on one end of the X carriage back by one tooth to change it's angle with respect to Y. This seems to have cured the lean mostly (although I might still move it back one more tooth) however circles are still coming out squished in X. And it's not a calibration issue, because a simple square comes out perfectly, and smaller circles are more strongly affected than larger ones.

I discovered what I believe to be the answer by watching the reprap doing the crosshatched infill on the large gear pictured at the top of this post. The left pattern in the diagram is what I should be seeing, but I was getting the right pattern instead. The bad pattern is being caused by backlash on the X axis. It might be caused by a loose grub screw on the X stepper drive shaft, or it might be a less easily corrected fault. Skeinforge has a backlash-mitigation option available; if I can't solve the problem mechanically, I'll solve it in software.

Speaking of Skeinforge, I'm slowly coming to grips with more of the obscure functions it provides. It's ridiculously powerful but it's hell trying to understand what each option actually does. Additionally, certain features are hidden in places that one wouldn't normally expect to find them. I finally found the option to shift the starting point of an object in the Multiply section - I just set it up to print one copy of the object, and I configured the other options there to automatically centre the object in the middle of the print bed. That solved the negative-axes problem once and for all.

And the extruder? I got fed up with it and tightened the springs down as far as they can sensibly go. And it stopped misbehaving. But I'm still going to replace it with a Wade's extruder as soon as possible. I've printed out a couple of parts for it already - hence the large gear :)

More prints!

More things printed! I printed a couple more minimugs today, one which failed part-way through, and one which completed essentially perfectly!

I also printed a whistle - which failed quite unexpectedly, squashed over to the left. It turns out that skeinforge happily works with objects that extend into the negative axes, and the whistle has a lanyard loop that extends into negative X. Each time the reprap tries to move into the negative region, it hits the endstops and the origin is reset, pushing subsequent layers to the right. We ended up with a straight lanyard hole and a curved whistle :P

I also attempted to print a classical 3d hypercube projection (two wireframe cubes joined at the corners) but that object started 10mm above the print bed! I need to find out if Skeinforge can recalculate the position of an object to put it's bounding box at (0,0,0), or if I need to write something myself.

(thanks to tj for the photo)

The post you've all been waiting for!

It's a minimug!

I've been completely stymied by the extruder ever since the last post. Everything else has been working fine, but the extruder would jam after less than one layer had been printed. Nothing I did seemed to help.

After many attempts, I gave up on the original extruder and started figuring out how to build a stepper extruder without being able to print it. I spent a couple of days building a version of the Mendel extruder multiple times in various 3d apps, finally trying out OpenSCAD and loving it. It's far better to code the relationship between objects once and then tweak variables to make changes than it is to keep doing the math by hand in a traditional 3D CAD app. I'll be using it from now on - and if you're a programmer, you should too!

Of course, a 3D model is only useful if it can be instantiated, and for this I dug out my McWire mill. Sure, it's never actually milled anything yet, but what better time to try it out? Unfortunately, I hit a problem in converting the model into a g-code toolpath for running the mill. It's a solved problem, so long as you're running windows and have paid for a commercial app... the free linux tools left much to be desired. I can get close to a decent toolpath using Skeinforge (which is supposedly capable of milling as well as printing use) but not close enough to convince me to run the mill with it yet.

Therefore, I put together a version of the crudestruder out of various crap I had lying about. Unfortunately it looks like the small NEMA 17 motors we have lying about the space aren't nearly strong enough to drive the filament without being geared down; so this attempt was a bust too.

I was planning on borrowing the geared mendel extruder parts from Buzz that we received from Adrian a couple of weeks ago, except they require the new smaller bearings I have none of. I raced out at 4pm today to go to Hobbyparts.com.au, which is the best local supplier - they close at 5pm and aren't open on the weekend, so it was a real rush... only to discover the huge traffic jam that already occupied the Pacific Motorway. No bearings (and hence no mendel extruder) for me this week!

I was forced to return to the original extruder - but I had learned a couple of things about it and the hot end this week. Buzz brought in a thermocouple which I was able to stick down into the molten PLA in the heater barrel, and it read around 165 degrees when the barrel thermistor read 190. That makes the PLA far more viscous and hard to extrude. Therefore I increased the temperature of the barrel to '210', making the PLA much more fluid.

I also found a significant amount of friction in the extruder where the filament first enters it - there's a long section that the filament has to pass through before it gets to the drive screw, and it's perfectly straight. Unlike the filament, which has a significant curve to it. Disassembly (aaargh), lots of filing (aaargh) and some oil (eh) helped prevent the filament from jamming in that area. The oil also made the filament path far more transparent, improving visibility in the entire extruder.

Finally, the gearing at the top of the extruder wasn't correct - this being the first version of the rapman extruder, it placed the motor too far away from the drive screw gear, so that the gears would regularly skip teeth when the required force went up. I filed out the holes for the motor, tilted it, and drilled a new bolt hole for the motor at the gear end, which keeps the motor gear much closer to the drive gear. Now it no longer skips, regardless of the drive resistance.

And suddenly the extruder came good!

Now I need to go back into Skeinforge and start tweaking. It placed a ridiculous amount of inter-layer cooling time into the minimug gcode, the cooling movements on the bottom ten layers or so also significantly damaged the outer perimeter of those layers. Fixing that should speed up printing by about 5 times or so. Also, I don't think the minimug completely finished; it got somewhere close and then stopped, oozing a large blob onto the mug and causing the gcode uploader to spazz out a bit. I've heard about spurious serial corruption from other people, so that may be the culprit. Reducing the amount of useless gcode movements, and using one of the newer firmwares with checksumming should help. Finally, the aspect ratio of the minimug is off, as I have yet to properly calibrate the steps/mm values for the three axes.

Mo' hacking, mo' problems.

Not a lot of progress to show unfortunately, just lots more fixing. Fixed the extruder, fixed the Z belt (which had bloody well better not come apart again now that Buzz has sewn the damn thing together) fixed the entire X assembly, fixed the extruder AGAIN. The biggest problem now is actually getting the extruder pulling filament reliably, as PLA is quite hard and tends to resist the drive thread. I've sharpened the threads with a hacksaw, and will be testing it out today.

I'm also fiddling with Skeinforge instead of the reprap host - far more complicated, but it looks like it'll give me the output I want. More importantly, it gives me a great preview of the generated layers so I know what I should be seeing on the print bed.

The mendel parts from Adrian Bowyer have just arrived at the hackerspace, and they look amazing. I'll be happy if I get parts even half that good.

First pri... oh.

Here you go - a really poor rendition of the minimug.

The reprap is essentially finished; it's now just a matter of finding all the little things that fail in the middle of a print and getting them nailed down. The X and Y axes were swapped so that the prints aren't mirrored. The Z and (now) Y belts were significantly tightened. The PSU was replaced after the old one went BANG and FLASH and stopped working when I added the Z stepper driver for the first time. A bunch of nuts had threadlocker put on them - some before they came off in the middle of a print... and some after. Yet another crack in an acrylic piece (although Buzz wasn't to know how fragile the stuff is...) The list keeps expanding.

We now have a filament spool made from junk and hot glue. And some appreciation of just how much more annoying a tangle is when it's in a filament that can't be arbitrarily bent and twisted. :P

Also, the stepper drivers now no longer overheat, after a liberal application of giant random heatsinks.

All hail our new giant random heatsink overlords.

Launch the goo!

It took some doing, but the reprap is finally squirting plastic.

A lot of faffing about with the firmware and the thermistor started reading approximately the right temperature, so I could start testing the hot end. Unfortunately I soon discovered that the thermistor would short out when it got above about 130 degrees, and start reading 255 permanently until it cooled down and I fiddled with the leads. Since the short appeared to be somewhere in the thermal epoxy I ended up digging away at it to try and expose more of the thermistor leads... and broke one in the process. Oh no! Some more digging and I was able to expose enough of the broken lead to solder back to it. After that the thermistor started behaving reliably. Yet another bullet dodged! Then we had a bit of trouble getting the hot end to heat up enough, so Buzz wrapped some fire blanket around the hot end to insulate it a bit, and finally the hot end was working well.

And the smell? It gave off a bit, but only enough to notice it and not enough to act like mustard gas now that the control loop is closed - thank god.

I sent the G-codes to start the extruder motor... and watched as the machine stubbornly refused to activate it. Aargh! A couple of hours of hardware testing didn't get me or Buzz anywhere, so I had to come back after a nights sleep to attack the firmware code and find out what was happening. Turns out that the firmware defaults to an extrusion speed of ZERO, and will faithfully turn on the extruder motor at that speed - the reprap host software isn't explicitly setting the speed. Changing the extruder speed manually to 255 before turning it on got it going immediately.

Setting the heater on to 190 degrees and starting the extruder motor gave me some nice little blobs of goo, which I then stretched out by moving the head most of the way across the print bed. And then the X-axis stopped moving - turns out that the shaft coupling on the stepper had worked it's way loose, and I ended up having to disassemble it to realign and tighten the grub screw down hard(-ish) again. There's only so far I can do that without ripping the acrylic coupling apart, so I might have to get in there with some superglue or epoxy if it comes loose again.

Speaking of the steppers, there's something of a heat problem with them. The steppers themselves get very hot, which isn't too big a problem (and I have a couple of random CPU heatsinks stuck to them now) but the stepper drivers get even hotter, which is. The heatsinks aren't sufficient to keep the chips cool, and when they get too hot (i.e. ten seconds after power on) they start sending lots of random steps to the motors. I've got a fan set up, but it's only able to keep the X and Y drivers cool. Before I finally start the Z axis up, I need to sort out a much better heatsinking solution for all three driver boards.

First Movement!

Unfortunately it was hard into one end of the Z carriage and broke off the opto flag. Yay! :S

Something weird is going on between the firmware and the host software - with the firmware in test mode I can get it to move both directions no problem, but when I'm using the firmware proper things only move one way.

I also discovered that passive cooling isn't sufficient for the stepper drivers; when the chip gets hot enough it starts sending spurious steps to the motor. Blowing on it was enough to get it to stop. I repurposed the extruder fan as a driver cooling fan, only to have the sinking realisation that Buzz nicked the molex connector off the end a while back... so I had to find another one to replace it. *sigh*

Off camping for a few days, so no progress until early next week. Cya!

Edit: just figured out my movement problem - it's what will happen if the endstop is being read with the wrong sense. Now I won't be obsessing over it all weekend!

Even ridiculously closer now!

The wiring is basically done; really all that's left is to level the print bed. But I also need to recheck every distance to make sure the whole thing is still square, and check every board individually to make sure they're wired up okay.

The wiring was a pain, though - I was particularly short on wire that was thick enough to handle the high currents that could be going to the steppers and heater coil, so in the end every one of them used a different type and colour of wire to every other one. Sigh. Cable ties are liberally applied in an attempt to keep the ratsnest under control.

The wiring to the moving carriage at the top is all tied to a loop of the PLA filament, which is springy enough to keep it out of the way. I had to superglue a bit of scrap acrylic to the x carriage to provide somewhere to cable tie the filament to; I'm fairly confident it'll be robust enough. Also, every wire to the extruder head has some kind of connector in-line before being attached to the guide filament; hopefully this will let me detach the entire head without too much fuss in the future. When it inevitably goes kablooie.

Oh, so close!

Not much left to do now! Mostly just wiring the X carriage and fine tuning the Z axis, followed by putting thread locker on some important nuts.

Rapman assembly part 9

There's not much left to do on the cartesian bot now. I have to mount the Y stepper motor (on the top frontmost corner), one Y drive belt and the X drive belt.

The Z belt took a couple of attempts and a fair bit of fiddling to successfully splice the ends together; the second photo shows the jig I threw together using scrap acrylic and some polymorph. That attempt failed because I tried to do the splice whilst the belt was under tension - whoops.

The last attempt was also nearly a disaster when I discovered that the belt went the wrong way around one of the diagonal rods; I ended up having to completely remove the rod to get the belt where it was supposed to go. And then completely disassemble the belt tensioner that was on that rod, because it was impossible to realign the rod with my measurement jig while it was still on there.

The tensioner is a bit of a problem, because the belt doesn't have enough slack to fit it in the appropriate place! I ended up having to remove some of the nuts in the tensioner to reduce it's profile, and I spliced the belt together with a two tooth gap instead of just a one tooth gap to make it a little looser... and the tensioner barely fits. I don't have enough spare belt to make a replacement Z loop - in fact, I seem to only just have enough belt for the remaining belts with no spare left over. So it's probably just as well I made the Z belt as tight as it is!

Dear god, it smells like death!

The hot end of the extruder is a spiral of nichrome wire wrapped around a piece of brass tube, smothered in fire cement and shrouded in a piece of copper tube.

Well, it would have been fire cement except Buzz had a small amount of high-temperature epoxy available instead. Which was nice because it cures by itself in an hour instead of requiring a couple of days or a trip to an oven.

What wasn't so nice was what happened when I fired up the heating element. Fire cement would have happily taken the abuse, but instead the epoxy emitted incredibly foul smelling smoke. At this point I don't actually have the temperature control loop in place, so I probably exceeded the epoxy's max temp (260C, which isn't much above our desired working temp). The rest of the afternoon was pretty miserable, waiting for the smell to dissipate. People walking past the windows started coughing, including Paul - and he was smoking at the time! Even after the smell had abated from the room, I still had it clinging to the skin on my hands and suffered whenever they got too close to my nose.

The hot end is still in working order, thankfully; but I'm leaving it till the very end of the build before doing anything more with it...

Rapman assembly part 7

I've been in a Red Queens Race with this damn thing for the past few days (running as fast as possible just to stay in the same place) and it's only now that I have some true progress to show off.

I spent a lot of time on the extruder; it looks the same but it runs much more smoothly now. The gears that were slipping are much improved, and I learned a considerable amount about how to fine-tune the spring-loaded bearing. When you tighten the spring bolts too far it acts like they aren't tightened enough, but the real solution is to back them off. I originally had them done right up, which did nothing but grind the reaction washer on the other side of the extruder and eventually force it out of place. After replacing the washer (backwards, as one side is now badly gouged) and releasing the spring bolts it came good.

I was forced to remove the top frame from the cartesian bot and disassemble it a few days ago, so I spent a long time getting everything perfectly aligned before trying to reassemble it. I made a measuring jig out of a long strip of acrylic with rod-sized holes at the appropriate distances, and it's been far more accurate for getting the frames perfectly sized than the original sizing bars that came with the kit. Once I reassembled the full frame and put another couple of holes in the jig it made setting the diagonal tie bars effortless.

Unfortunately I discovered after the top frame was on that one of the opto-endstops was on the wrong bar! There was a short panic as I contemplated disassembling the top frame AGAIN - the only way to move the endstop - but thankfully it was possible to rearrange things so that it's only slightly different to the instructions, but all the endstops can still do their job. A big sigh of relief there, I must say!


Tonight Buzz and Andrew were also at the hackerspace, and Buzz decided to MacGyver a stepper-driven extruder from a large stepper he had in his bag, along with a bunch of scrap acrylic from my rapman kit. It works amazingly well for something thrown together in a couple of hours! It's a bit large and ungainly to fit on my rapman, but a bit more work and it'll plonk straight onto his repstrap. It was also a good test of my stepper drivers, as we watched a piece of ABS filament go back and forth, and back and forth, and back and forth...

Rapman assembly part 6

Progress is slowing as I get closer to the end. Things don't just need to be assembled anymore; it's all 'align this perfectly' and 'file this to exactly the right size'.

Case in point is the extruder, which I've got the top half assembled here. It's already been disassembled, filed, and reassembled once; and I'll be doing that again tomorrow. As things stand it does work; I've applied power to the motor and had a piece of PLA filament move through it. Unfortunately the top gear linkage slips at one point each rotation and I've need to figure out how to fix it.

I also need to disassemble the frame to a large extent; all those rods that I cleaned have now got a nice new layer of rust on them that I need to remove again. Gah! Hopefully a layer of 3in1 oil will keep them from rusting again (and the lubrication can't hurt.)

I also have to fix another crack that showed up in a corner block whilst I was trying to square the frame. That job will be easier once the frame is rebuilt; I'm making various sizing jigs out of a long piece of scrap acrylic I had lying around to use together with the two that came in the kit.

Rapman assembly part 5

Here's what I did today; sorting out the diagonal tie rods and attempting to get the whole thing square. Haven't even nearly succeeded yet; a tape measure really isn't the best tool for the job. I have to dig into my post-move boxes and see if I can find my long straight edge.

I also discovered that the instructions suddenly end just before explaining how to set up the Y drive assembly. Tut tut. I've got enough info and photos from the reprap forums to get by, thankfully.

And here's what Buzz (assisted later on by Doug) did today. The driver boards are all nicely mounted on a sheet of cardboard, wired together and tested with a basic Reprap Gen 2 firmware on the Arduino. Sadly no 5D firmware for us until I get everything working and can look into replacing the dc motor extruder with a stepper driven one instead.

The ATX power supply I'd modified to use for the Rapman somehow died since the last time I fired it up a few days ago - which bugs me no end since I had pretty much used it non stop since 2001; it was the most robust PSU I've ever had. :(

Rapman assembly part 4

WORSHIP THE CUBE!

*ahem*

It's been a couple of days since my last post, mostly filled with "Disassemble... File... Reassemble... Repeat".

It kinda got to me (Disassemble - dead! No disassemble!) and so I took a day off.

I got the Z rods and X carriage finally moving smoothly (...ish), pulled all the top corner blocks apart and reassembled them (with filing in the middle, bah) and put together the top frame. I also built the parts for the Y drive assembly, which are pictured underneath the frame.

I managed at one point to cut the tip of my left index finger with a stanley knife, and it has been stinging ever since. One day I'll learn my lesson!

Eventually Andrew (who had been around all day) left, after I said I'd wait until another day to put the top frame on - and then I insanely went ahead and did it by myself. More filing (AAAH) and a rather ill-advised bump with a fist and the vertical rods slotted in where they were supposed to go... whereupon I discovered I had incorrectly reassembled one of the corner blocks (AAAAAAAH!) Another half an hour and a partial disassembly of the block in-situ and everything was as it should be.

Rapman assembly part 3

A bit more progress today, although it looks more impressive than it is. The frame is finally taking shape, although there's a lot more fiddling to do before the Z rods shown here move smoothly :(

I am having trouble with the X carriage binding a bit at one end of it's travel; until that is sorted I can't assemble the top half of the frame.

I'm also at a loss as to what to do with the Z belt - it needs to be a continuous loop, but I only have a cut length instead. So I have to join it somehow, and I can't find any reference as to how to do it properly. Thankfully the X and Y belts don't have to be continuous, as the ends are clamped to their respective carriages.

Edit: I just got pointed at http://reprap.org/bin/view/Main/AssemblingDarwinMachinery#Z_belt which explains how to splice a belt. While I don't have a belt splicer jig, it shouldn't be hard to make one out of polymorph.

Rapman assembly part 2

More parts assembled! Here are the eight corner blocks (one attached to the stepper) and the four Z rods. On the left end of each rod is the platform attachment assembly, and on the right side are the belt-driven gears.

Annoyingly, a bunch of the parts were only lasered through about 3/4 of the way through, and so I spent ages abusing a flathead screwdriver to try and break them apart, along with a heck of a lot of filing. :(

The good news is I had help today - Doug dropped by in the afternoon and was a massive help for several hours. Thanks Doug!

Rapman assembly part 1

A couple of years ago a bunch of people (including myself) here in Brisbane pooled their funds to buy a Reprap kit... and then never found the time to put it together. Oops.

Anyway, since I currently have oodles of free time I've taken over Hackerspace Brisbane the past few days and started assembling it.

It's taking forever going really well! I have all the electronics (early version Gen 2 RRRF boards as they were bought back in 2008) and the majority of the X carriage assembly put together. The carriage itself doesn't yet slide freely enough on the rails for me to completely assemble it, but I think I'll leave it for a while and move on to the corner blocks tomorrow.

One of the pieces was broken during delivery and I broke another piece or two trying to get some of the holes cleared where the laser didn't cut deep enough. So I whipped up a batch of acrylic cement last night ready for me to do field repairs. The cement is just acrylic chips (of which there are plenty left over once the reprap pieces are removed from the sheet) dissolved in acetone. Put the chips and just enough acetone to cover them in a container that won't itself melt in the solvent, seal the container and leave it for several hours. The acrylic doesn't so much dissolve as slowly soften as the solvent infiltrates the material. Once it's gooey enough you can smear some of it between the broken pieces and clamp them together. After leaving the piece for a couple of hours to let the acetone evaporate completely the resultant piece is as strong as if it had never been broken in the first place!

I did say I'd taken over the space, didn't I? :) We should probably clean up the other desk so I can spread across it too so we have some space for anyone else coming on Tuesday night...