RepRap: Blog

The RepRap Child is heading for OSCON in Portland, Oregon (yes, I'm off to the US of A again). I'm presenting in the last session on Thursday afternoon and will probably set up an impromptu display in the foyer if I can get away with it, so pop in and say "Hi" if you're in the neighbourhood.

Vik :v)

Labels: oscon, reprap

Looks like we have a failure mode for PLA corner brackets. This picture shows a relatively recent bracket torn apart by the forces of fitting an 8mm rod into it and over-tightening one of the grub screws.

As you can see, the break is hardly a neat delamination, and the line of separation is at the apex of a teardrop-shaped hole. The corners also have little plastic in them, even after being squared off so they parted easily too.

As a temporary solution I am putting bolts through empty holes to hold things together. We'll see how it goes, but I think we may need to remove some of the unwanted honeycombing from the design and beef it up a little. I'm also installing the next one upside-down, so the apex of the teardrop is at the bottom of the bracket.

Vik :v)

Labels: corner bracket, failure, pla, reprap

The extruder clamp was missing from my pile of parts in the "complete" RepRap, so I've remedied that. Took about 12 hours to print in PLA. As you can see, the clamp grabs a 16mm PTFE rod very well even without the clamping screws. There is also a channel in the clamp to take a 4mm self-tapping screw with which I intend to further secure the PTFE.

I was short a few diagonal bracing brackets, but those are no problem and shouldn't take more than a couple of days to run off.

I'm now also short an X-axis flag 'cos I put a bench vice down on top of it...

Vik :v)

Labels: clamp, extruder, reprap

I've put a Z axis together using some ball-chain and 4 gears printed on my Darwin in PLA - I needed to fit a new motor anyway for testing with Arduino code. It appears that "4.5mm ball-chain" is a standard of some kind. It's a bit bigger than that normally used for keychains and biro bondage at the bank, but is I believe widely used by makers of window blinds and vents.

I have put the experimental ball-chain gear AoI files in the SVN on Sourceforge. You may need to re-scale the rim using AoI depending on how thick a line your RepRap/RepStrap extrudes. With mine the chain fits well up to about 110 degrees around, then gets too tight. Fortunately I only need 90 degrees, so that's OK.

Turning the motor by hand makes the platform go smoothly up and down. Now to build some drivers for it.

Vik :v)

Labels: ball, ball chain, chain, reprap

Lots of things got in the way of other things this week. I broke a couple of corner brackets and my PC now runs out of memory before it can print a new one. I've dragged a beefy laptop into the workshop to try over the weekend.

As part of this, due to an amazing piece of Yak Shaving, I have now committed the plywood RepRap files in SVG format to Sourceforge. They're not complete, and there is no changelog. So obviously, that needs to be fixed for a start!

The original 4mm ply design is there, my 4.4mm attempts so far are there, and an MDF-based design that's not very Darwin-compatible is in the development stages. I haven't tried printing that last one out on Ponoko yet, and it's only half complete.

But I'd really like to get the parts I've made on the real RepRap together into a working machine, so for the moment I've released these files in their incomplete state for the enthusiastic among you to tinker with. Enjoy.

Vik :v)

PS The brass cup for the metal extruder looks like it might be easily made by tapping into the end of a 3/4" or 1" brass piping endcap and bolting the barrel on.

Labels: plywood, reprap

We've been Slashdotted thanks to an article in ComputerWorld. A quick update on the state of play: I have now fabricated all the parts of the RepRap except the Z flag which is probably easier to just cut out of the side of a beer can. I've taken delivery of the steel rod for the frame, and the driver parts from Jaycar turned up this morning. So, all systems are go - except I have to be in Wellington for the next two days. The suspense is killing me!

GPL Note: Yes, we know the GPL doesn't cover hardware. That's why we're releasing hardware "In the spirit of" the GPL. We know about TAPR but it's not right for us at this point. It's complicated.

Vik :v)

Labels: full, parts, reprap, slashdot

The folks at Ponoko are being very patient with me and have run off a second attempt at getting the RepRap printed out on their laser cutting service. I'm not as good at this as Toby Borland who did the original lasercut conversion. Ponoko did their job fine; I goofed again, hence a few nibbled edges in the photo where parts almost fit together.

But this run also produced parts that DO fit together. We also managed to include 2 x 9mm MDF baseplates with cutouts for the wiping mechanism (no mechanism bits yet though) instead of just one in acrylic. I used the cutout space to print some test parts in that normally would require laminating. If they work, that'll save money and effort as you pay per cut and we can get the kit cost down further. I think we shaved US$40-50 off the previous run, and I hope to do the same again.



Most of the parts now have helpful little labels etched onto them, letting you know which tab fits in what slot. One of the more interesting set of goofs is that I accidentally told the laser to cut some lettering right through (and vice versa where some cut lines are only etched). So if you see lettering on the reverse of the cut sheets, you know it's a bad sign (marked in red on this photo, dropped sweet wrapper marked in blue). Maybe they parts will work if the 'D' and 'O' gaps are loaded with epoxy...

The ball-chain gears look like they'll work for 90 degrees of drive - just. I'll tweak them a bit more, and thicken the base of the gear teeth where the laser cut more than I thought it would. All being well, I'll be talking to the awfully nice Ponoko people in a week or so to run my third - and hopefully final - prototyping run. Meanwhile, I have what feels like a 1,000 piece 3D jigsaw to assemble and I have to correct the bits that don't fit!

Vik :v)

PS Missed the Y carriage out altogether Garrr!

Labels: ponoko, reprap

I've made an adaptor plate (it's in SVN) to allow single shaft stepper motors to be used on the Z axis. It's not a tricky part - you could hack it out of plywood or aluminium fairly easily if necessary. There are also slots in it to allow the mounting of smaller stepper motors, though I don't know yet if they'll turn the Z axis - we'll find out when I get the drivers for the Arduino stepper board.

The incarnation shown in the photo bends a little when fully stressed up, so I've thickened it by an extra mm since then.

Yes the corner bracket is fairly crappy, but the crappy side isn't used on the Z axis' corner so I'm using it anyway and saving myself another 7 hours of printing.

Vik :v)

Labels: adaptor, plate, reprap

I've upgraded to the latest code (SVN #1428 at time of writing), and rediscovered why we're turning the extruder on and off a lot. In this video we see the extruder nozzle go to my hand-made Meccano nose-wiper, nicely clean itself, then shoot off on the Y axis at X=0. After turning on its extruder feed, the nozzle builds up a nice thread of goopy plastic en route to where it really should be printing, and wipes it off on the workpiece. Charming.

Finally, after printing out a Y motor bracket looped with festive decorations, the RepRap software drove the Z axis back to zero, pushing the workpiece through the cooling fan and kindly lowered it again to show off the damage. Did someone say holiday? Oh, good.

Vik :v)

Labels: bad, nose, nozzle wipe, reprap

I've bought some "ball chain" or "beaded belt" from the local Mitre 10 hardware store for NZ$6.95 per metre. The balls on it are 4.60mm in diameter and have 1.80mm exposed length bars between them. I have plastic beaded belt of the same dimensions, so this is likely to be some kind of standard. Investigations continue, do clue us in.

I've designed a pulley (shown left) that can be fabricated on a RepRap - and made one. After a mechanical test, Adrian ran 4 off on the Strat. Note: Make one with a rim that lifts off in the future so I can fit the damn belt without resorting to violence.



Here is the video below showing them in operation. Note that the orange pulley under the bed in the lower left corner of the frame is rotating and that the old drive belt is not fitted. The red temporary join is a cable tie and is obviously not going to go smoothly around the corners. The chain is made from chromed brass, by the way.


To join the ends of the loop, I filed down the two terminating balls on the chain into approximate halves (measured with a badly-calibrated Mk I eyechrometer) while holding them in medical clamps. Then I held the clamps in a couple of angled vices so that the halves fitted together properly, finally soldering them together with a 30W soldering iron and highly toxic lead solder (yum). Better ideas welcomed! The joined chain is robust enough to turn the whole Z axis assembly with some enthusiasm. When I build the next RepRap the gears will go in the usual place.

Labels: ball chain, beaded belt, drive, gear, reprap

I had an idea in the bath. To feed the filament, all we need are two ratcheted holes and a solenoid to drive them apart and bring them together. No gears or rotary bearings would be required, and we'd have absolute control over filament driving.

I built this working prototype from two bottle tops, one aluminium and one steel 'cos that's what I could find without having to dive into the kitchen rubbish bag. I drilled a central 2.5mm hole through in the direction I wanted the filament to go (out the top) and cut 4 radial slots out of the hole with a sharp knife about 7mm long. The aluminium one is far too soft. Move them together, filament moves forward. Move them apart or let a compression spring do it for you, filament stays put.

We can change the distance driven, change the timing, and vary the power of the solenoid to change driving pressures. A spring or split washer on top might help even things out.

A similar system might step beaded belts.

Hold on to a static filament and you can step along it...

I shall simultaneously celebrate this idea and obtain another ratcheting component.

Vik :v)

Labels: driver, fliament, ratchet, reprap

I have something to do while my RepRap is out of action. Toby Borland has done a wonderful design of the RepRap which is meant to be cut on 4mm plywood. He has kindly released the
source, and I've converted an early version of it to the EPS format used by Ponoko on their laser cutting and vending service. We're putting the files up there for free use; we're not taking a cut. Ahah.

I've put up the plywood parts separately to the thick acrylic bed; I'll experiment with a 9mm MDF base but it might be too thin. Toby has since sent me some fixes for the plywood parts - already in EPS format - which I'll work in and scale according to how well the first batch of Ponoko parts fit. The files need optimising to reduce the cutting cost (mostly removing double-cut lines) too. Until that's done, the design should be regarded as pre-alpha and non-functional. As it stands, the ply seems to be slightly thicker than 4mm, so a lot of parts don't fit together properly. Oh yeah, I did muck up the scaling in a few places too - mostly ones that matter!

Prepare for strike two, and props to Ponoko for their support.

Vik :v)

Labels: laser, plywood, ponoko, reprap

One of the frustrating things about developing the RepRap is the need to focus on making it actually replicate. I've had a few great ideas about RepRap pass me by for this reason, so I thought I'd better document them.

1. Make it print braille. In theory, easy. In practice, it needs someone to convert braille into STL (mistakenly called SVG earlier by torpid author).

2. A spooling device driver for the RepRap GUI. If we can produce pre-processed files, a much simpler production program is needed. This would allow RepRap to be driven by primitive controllers, PDAs and the OLPC.

3. A Logo turtle driver for RepRap. Logo is well understood in the educational sector, and runs on the OLPC. It would enable novel fabrication techniques to be developed by the young and inquisitive.

Pick it up and run with it, folks.

Vik :v)

Labels: braille, logo, reprap, stl, turtle

My LCD screen is starting to return to a less blue shade after enduring a stream of classic Anglo-Saxon last night. The cause of this was the crashing of the GUI software with an Out of Memory error about 98% of the way through the biggest part of the RepRap - the carriage.

I knew things were not going well. Garbage collects were happening with increasing frequency. I'd run the job to a nullcartesian device first to make sure it would print - probably best to close and restart given the current state of play.

I had "top" running, so I know it was all Java. No other applications of any consequence going on a 2GB machine.


Now the good news: Though technically incomplete, on inspection the part appears quite functional. There are some big blobs on it where the extruder was left running in garbage collects (should we force a GC at the end of a layer? Can we, or will Java "know better"?), but these will soon succumb to my trusty Dremmel tool. I believe I can now start work on the X axis assembly, the first phase of mechanical construction in our instructions. Yeah, looks like the picture on the left :) I leant on the X motor bracket and cracked it, but clear epoxy cures all ills.

Vik :v)

Labels: carriage, reprap

Need I say more?

Well, yes. The pads definitely stopped the corners curling. One pad didn't print (dodgy patch on baseboard most likely) and that corner started lifting. Not having superglue to hand after Oz, I put a dab of hot-melt glue on that corner to anchor it down, and that stopped the curl nicely.

The mounting slots for the smaller motors are a little short, but I've fixed the STL file and uploaded it. I'll just hold this one on place with some cunning wire-bending.

Next, the carriage.

Vik :v)

Labels: bracket, motor, reprap

A mini-milestone for you RepRap-watchers. Ed and myself have now fabricated half the V1.0 RepRap's parts, if you count them by type (i.e. we have 8 corner brackets but that only counts as one "part" even if I've only made one).

On the left is the latest batch of parts: X and Y axis Opto Flags, a couple of X Belt Clamps and a Z Studding Tie. I think the flags are the most delicate objects I've made, and appear to be approaching the limits for our current software's resolution.

Vik :v)

Labels: flag, half, parts, reprap

Being allowed to present RepRap at LinuxConf 2008 was wonderful, and thanks to all for the encouragement I got that really belongs with the RepRap team. So many new ideas, and very little time spent on repairs all considering.

One that stood out was the idea of using RepRap to print braille, and to make relief maps with textured surfaces to assist the blind.

I contacted the OLPC project to see if they would cooperate on ensuring an OLPC can drive the RepRap. Currently our software won't fit, and the OLPC is essentially python-driven so a re-write or novel way of printing the CAD files might well be necessary as things stand.

Finally, I've been porting Toby Borland's plywood RepRap files to Ponoko's upload format and I think I've got something that should print. Whether one can actually assemble what comes out remains to be seen. The parts cost for RP'd parts, gears & base is in the region of USD$350 and you can download the source. I say again, it's not quite perfected yet.

My Darwin has been chugging along while I work, having a little difficulty with the Z axis after its return from Oz. Perhaps I was just lucky before, but now the Z axis rubs on parts of the base. Being me, I've bashed holes to allow clearance for the nuts.

Here are three Y bearing housings, recently printed. One is marked with a break and is dud, the other two were printed after Adrian's recent accidental sqrt() bugfix. I now have 3 of them, and have manufactured bearings. Bearings look a little short on infill - OK, very short - but seem functional. I've just done another corner bracket (3 to go) and the next part is: Replacement Y axis flag.

Vik :v)

Labels: braille, lca, linuxconf, olpc, ponoko, reprap

Here's the Bed Corner mounted up with springs & nuts on a piece of studding. On the bottom of the studding I've stuck 2 Diagonal Tie Brackets. The top one - from Steve's no-overhang STL - is printed using the new software and has not been manually tidied (though I did have to warm up the retaining nut to get it in), the bottom one was done with last month's software and has been tidied. Adrian's latest fixes have made quite an improvement in quality, I'm sure you'll all agree.

Sadly, printing Corner Brackets in fine detail seems to cause a new bug so no more of them for a little while. But I'm off to Wellington in a few days anyway, and I'll be taking Darwin with me.

Please ignore mess at "dirty" end of bench...

Vik :v)

Labels: output, reprap

It took me 3 goes. One cable pulled, and a stuck filament roll; but I got it printed in the end. Thanks to Steve for helping with the STL file. The object took 5.8 hours to print in PLA using Darwin hardware and Adrian's latest fixes. It has really picked up steam now and the quality has improved as the nozzle moves faster - as predicted.

No hint of curling on this part either.

If you look inside the holes on the left, you can see some stringing, but it is now more like annoying cobwebs than a barrier that needs drilling out with a cordless drill. Just as well - I did stick an 8mm drill bit in my hand last time.



Here's the view from above, with a clearer view of the stringing. The thick stuff is caused by a plotting error we're looking into, and the fine, spider-web stuff is what the more persistent stringing issue now looks like.

I've tried to bend the part, and it doesn't break despite the plastic flow being a little low, so we should be good to give it a go in a real Darwin.

Vik :v)

Labels: bed, corner, darwin, pla, reprap

Here's a quick video of Kate and I testing our copy of Adrian's Paste Extruder prototype. We've loaded it up with 50ml water and excessive pumping.

Adrian has also made some beta firmware that we hope to get out there soon, using the PIC16F648A CPU. I've stuck it in my Darwin and seem to be able to make things extrude.

Darwin now has a snug carry-case, and I hope to test it out on a trip to Wellington in the near future.

Vik :v)

Labels: paste extruder, reprap, squirt, water