Just Another RepRap

Here’s a bit more progress that I made today. I finally got around to cutting the bed, circuit board holder, and other pieces out of MDF (medium density fibreboard).

I don’t have easy access to a plotter, so I needed to print the dxf file for the thick sheet template out on multiple pages and arrange them together correctly. I thought it would be easy to find software that did this, but I didn’t find anything easily at first. Eventually I found some shareware package for windows called CADViewX Lite, which had a demo called CAD Open in Word that let me open a dxf file and print it across multiple pages (with hash lines). It didn’t work as nicely as I’d have liked, but with a few measurements and careful alignments I was able to lay out the pages on the MDF and tape them down with single and double sided tape:

The MDF sheet I had was an unwieldy 2′ x 4′, so first I cut off the relevant area:

Many cuts with the jigsaw later, I’d cut out the five pieces (scotch taping the template down again to the newly cut sides as I went). I’ll drill the holes and jigsaw out the internal ovals later.

Here’s the bed that the Mendel will print on:

I also was cutting rod today. Here are the fully completed smooth rod pieces, which make up the X, Y, and Z axes:

Those were cut out of 3 original rods. In addition to the 3 original smooth rods, there are 9 threaded rods that need to be cut into many pieces. I was able to get through one of those today, resulting in 3 threaded rod pieces:

Unfortunately the cutting drains the rechargable battery on my Dremel like crazy. I went to the store looking for a spare rechargable battery (quite naively) and of course no one carries them locally. I considered buying a 2nd Dremel that was corded, but even if I can only cut 1-2 rods every 3 hours, I’ll still get them all done pretty quickly, so it didn’t seem worth it. (I may just do more cutting with a hack saw, but it’s a pain). I did order a spare battery online – it’ll probably arrive by the time my Mendel is fully completed.

Oh, one more off-topic thing.. Last week when I ordered some red and black wire for the power connections from sparkfun.com, I saw they had some stepper motors that looked to both be NEMA 17 and have more holding torque than the ones I’d purchased from makerbot.com (at least that’s what I thought after a quick calculation.. I might be wrong). We’ll see when they arrive – they were cheap enough that it won’t break me if I bought four extra steppers for nothing – I’ll find a home for them.

Next up – a lot more cutting of threaded rod, drilling holes in the MDF, more assembly of the X carriage, and a bunch of electronics work to redo the boards I have for Mendel.

Huzzah! There is good in the world. Progress continues.

In my previous post, I described how my place of work had asked for the MakerBot (which I was using as a RepStrap) back; it was originally made available to Chris and I as part of a “technology library”. I’d still had six pieces left to go (as it turns out, actually seven).

Good people came to the rescue. mccoyn built and sent me two z-leadscrew-base pieces and a z-motor-bracket:

Seeing those parts actually completed out of PLA, I’m greatly encouraged. My most recent attempts had all jammed up at some point during the long builds. I’ve told the next person that received the MakerBot that they need to rebuild the heater barrel assembly (this time actually using a new heater barrel and nozzle, because that seems to be completely gunked up), so maybe the original RepStrap will be able to print those parts out too someday – I hope never to find out, as I want to print those parts on my Mendel.

In parallel with mccoyn’s offer, I’d had a discussion with key people at work (I’ll omit names as I’m guessing they’d prefer that). Luckily I was able to thank the person responsible for ordering the MakerBot in the first place and setting up that technology library; hopefully I conveyed just how thankful I was for this. I also managed to get permission to have a few parts printed at work with a commercial Stratasys 3D printer. When it turned out that I actually had overlap between some of those parts and mccoyn’s pieces, I decided I’d use mccoyn’s and put the ones from work in the shoe box of spare parts (if not directly onto Chris’s Mendel, which will be the first set I start printing once I have my Mendel working, soon to be followed by a set for my brother Jon – who already has one piece. ).

Here’s an example of what the z-leadscrew-base printed on the Stratasys printer looked like (this was printed with ABS, and there was some support material used and washed away in a bath after):

I received offers from at least two other people privately to potentially supply me with pieces if I needed them (when they got their printer working). Thanks to all!

Ok, so on to building. First, I spent an evening midweek figuring out exactly which items I had to order for wiring. Adrian’s excellent video illustration helped clear up any confusion I’d had about what went where. My spool of ribbon cable and lots of connectors will arrive probably around Monday, just in time to completely miss the weekend. That’s ok though, because I have a lot to do before I get to wiring.

First was cutting the metal rods and studding. I’ve put that off for a while, and just started on it last night. When I purchased the non-studded (smooth) rod for the X, Y, and Z axes, I went with A2 steel (even though I’d heard people say it was a pain to cut). It turns out it was relatively easy. A while back, in anticipation of this, I’d purchased a diamond cutting wheel for my Mendel for around $15 (maybe that’s overkill – I have no idea):

Here’s a quick video showing the sparks it created:

Before filing it down, here’s what it looked like after the cut:

I was supposed to cut it to 406mm (with a tolerance of +/- 1mm). I think I did pretty well:

The battery on my Dremmel needed recharging, so I was able to stop long enough to post this entry. Rather than building up a long post, I think I’ll just post this one now and follow up with more later. Another thing I’m doing this weekend is making an attempt at cutting out the MDF bed pieces with a jigsaw. There is a nice laser cutter at work that I might be able to talk someone into letting me use to cut pieces out of MDF, but it’d be nice if it was doable at home. Either way I bought a 2nd piece of MDF at Home Depot today after Emily and Alicia’s first-Saturday-of-the-month building time (this month they made a rain guage). But I digress.

More later. Once again, thanks mccoyn and unnamed person from work, both of which spent lots of time printing me pieces! I swear I’ll pay it forward!

Well, it’s been three and a half weeks since my last real description of any progress. In that two-posts-ago post I’d described the “crisis” of potentially losing the Makerbot before I was done printing pieces. As the circumstances of my last post pointed out to me rather harshly, that doesn’t really qualify as a crisis. Still, that issue was averted, as I was able to bring the Makerbot into work for the 3D printing class, then get it back out of the building.

Since that time, I’ve gone from having 20 pieces left to having 6 pieces left, but once again I’ve run out of time, as we received the expected request to return the Makerbot. I feel bad because it’s been in my possession almost 100% of the time, and Chris barely was able to use it (though he assures me he feels bad because he was able to enjoy actually having free time over the past few months while I did all of the hard learning for us, but I don’t know if I believe him. ). Being completely frustrated with constant extruder stall failures, I called Chris on Saturday and asked if he wanted to take the Makerbot for the few days that we have left, which he did.

Our hope had been to finish the parts for my Mendel, start printing parts for his Mendel with the Makerbot, then when my Mendel was assembled print half of his Mendel pieces with my Mendel to halve the print time. Instead it looks like we’ll be printing his entirely with my Mendel, once we find a way to get that done. As I said, we’re 6 pieces down (we still need the y-motor-bracket, z-motor-bracket, two z-leadscrew-base pieces, and two belt-split-jig-bracket-universal pieces). Maybe Chris will figure out something I’m missing on how to reduce friction enough to keep the extruder motor from stalling and he can actually print them out, but he’s dealing with the same machine I was, so I’m keeping my hopes in check.

Anyway, let me document more of the success I’d actually had during that time. As usual, pictures and video…

When I had twenty parts left, I tried printing one of the z-leadscrew-base parts out of PLA, but it failed. Here I was, 18 minutes into the destined-to-fail print:

..and here is a description of the failure:

So here let me take a second and describe what I’ve now learned about how to somewhat recover from a stalled extruder motor (at least temporarily). If you’re printing and the extruder motor stalls (meaning you’ve probably got some sort of jam beneath the extruder in the heater barrel or insulator), and you know it was supposed to be printing rather than just traveling (because the head is moving slower, or you’re on the perimeter where it’s supposed to be printing, etc), press the pause (||) button in replicatorg (DURING A TIME WHEN IT WAS SUPPOSED TO BE EXTRUDING, NOT JUST TRAVELING). I used to think the pause button was almost useless because it kept the extruder motor on, so you’d end up with some huge blob of plastic ruining your piece. However, in this case it works to your advantage. Now that the bed is paused, you can grab some pliers, grip the filament as hard as you can, and push it hard into the extruder (I used to attempt to do this while the bed was moving, which sometimes worked but more than often would push the nozzle into the piece itself, causing it to catch, miss steps, become misaligned, etc). If you push hard enough, eventually you’ll hear the stepper motor “catch”, as you added just enough pressure to move the motor past the threshold where it couldn’t push any more, and the motor will start up again. Plastic will start extruding, and you can click the pause button again to resume printing. Unfortunately this is a temporary fix, since whatever caused the jam is still probably there and it’ll jam up again soon. This can help though if you just spent 1 hour and 45 minutes of a 2 hour build watching it print fine, just to see it almost fail at the end.

Ok. So here’s a piece that printed extremely well – y-bearing-180-inner_2off:

By the way, every time I see that piece I think of this building in Boston:

I was about to bring the Makerbot in for the 3D printing class I mentioned two posts ago, and wanted to do a few ABS prints to remind myself what it was like (I’d been printing with PLA for so long that I’d forgotten what it was like). While PLA is excellent and wins in many categories, ABS does have its advantages too – one of which being that it extrudes in a closer-to-solid state that seems to allow you to print insanely fast with it. (However, don’t take my account as a source of any real information on this! I wouldn’t be surprised if some people have PLA printing super fast on their RepRaps, perhaps with modified extruders (or even the regular Mendel extruder).. or maybe speed doesn’t even enter into it).

Here is video of me printing the x-360-z-bearing-plate_2off piece in ABS, which I’d also attempted in PLA but I’m going with the ABS piece:

So I packed up the Makerbot (weeks ago), and brought it into work for the 3D printing class that I’d actually been looking forward to since around October. The talk was by Dr. Zoz Brooks, who you can see on the TV show “Prototype This!” on the Discovery channel. It was a great talk, and after in the hands on section we saw all of the hardware at work and I was able to show the Makerbot to everyone (along with all of the parts I’ve made for Mendel so far).

As I said above, I was able to take the Makerbot back home after that. Then Laurie threw me a surprise party for my 40th birthday. Two of the RepRap-related gifts that I got are visible in this picture: the PLA in the front from Cheryl, and the Terminator bobblehead on top from ChrisR. Chris’s public statement with the joke was something along the lines of “So Jeff talks to everyone about the RepRap, but he sometimes leaves out the best part of the whole thing – it’s a self replicating robot. The inevitable conclusion, of course, is that this will eventually lead to Skynet and the destruction of mankind. So this is to keep him honest and remind him of what he’s making.” (I disagree that I’ve ever left that part out, but why ruin a good joke).

Part creation continued.. Making two x-360-z-bearing-plate-mirror_2off pieces at once:

I made a much better z-axis-opto-spring than I had a month or so ago:

Comparing the two versions I made of the z-axis-opto-spring:

Again, as I said before, the default Makerbot ABS settings I’d grabbed from somewhere have the motors move extremely fast (maybe I’d slowed things down for PLA – I don’t remember). Here’s video of extremely fast printing of the y-bearing-360-outer-left_1off piece:

Here is a piece that might be unnecessary but I printed anyway, bed_height_spacer_31m:

And here’s another piece that might be unnecessary, but it was easy enough to print – x-cable-clamp_1off:

That’s it for successful parts.

Here’s video showing how incredibly beneficial it is to mount the extruder controller board above the plastruder, so you can see the idler wheel actually turn:

Here was a failed attempt to print a z-motor-bracket_1off out of ABS:

I’d gone through enough motor stalls that I was curious about what exactly the geared DC motor looked like inside, and before returning the Makerbot I figured it was worth taking a look. For anyone who’s interested, here’s what the inside of the motor looks like so you don’t have to open your own:

When taking the bearing off the shaft of the gearmotor, I realized that one side of the gear had actually broken off. In case it was adding resistance to the turning of the motor, I left it off.

Last two things.. First, the M6 nut on the heater barrel allows failure cases like this to live longer and remain undetected – here’s the heater barrel completely covered by plastic:

And finally, here’s the plastruder rebuilt by me (possibly for the last time, assuming I’m able to move onto my Mendel by somehow getting the last six parts I need):

The next thing I’ll do when I have free time is assemble more of the pieces I have (I should be able to complete the X axis, at the very least).

Six parts. So close, and yet so far.

Apologies for posting such personal information amongst all of the RSS streams being read by so many, but I need to say this sooner rather than later.

My best friend Kevin died in a car crash yesterday morning. I can’t describe the sadness I feel. I’ve known him for over twenty years, and I will miss him more than can be expressed.

Over the past year he’d listened to more of my RepRap ramblings than anyone I know. He came up with a great idea for something fun thing to print on a RepRap, which he was going to share when I finished my Mendel. He designed software to create it, made incredible progress, and was just about done. Some day when I get my Mendel completed, I’ll share his creation.

Kev, I’m going to miss you buddy. I love you.

Kevin is survived by his wife Caroline and his son Charlie.  (Avoiding his last name to avoid spam). Caroline and Charlie, we love you so much, and I’m so sorry for our loss.

As the title of this post says, I made some more progress, I had another extruder failure, and then I had a huge, full blown crisis.

In order:

Progress. Here are some pictures of the Idler Bracket assembly:

Assembled Idler Bracket. This sits on one end of the X-axis. The four bearings allow the entire X axis to slide up and down along the Z axis. This piece holds/caps the two rods that make up the X axis.

Another view of the Idler Bracket assembly. The bearings on this side are for the belt that moves the X carriage left and right along the X axis.

Another view. The x-axis rods will go through the U-shaped space up against that plate.

View from the bottom of the Idler Bracket assembly.

I’d ordered some more ceramic tape so I could insulate the barrel again. I think that was a part of the problems I’d been having with PLA jamming up. I couldn’t make it as tall as it had been initially but I insulated at least part of the barrel:

Once that was on, I was able to print a few more parts correctly. By the way, I now print at 195C (using the ultimachine 4042D PLA.. I have some 4032D from makerbot.com but I haven’t used it yet).

x-vert-drive-side-plate-360-end_2off

This piece was horrible with PLA. I think I may go back to ABS for it and its similar siblings:

Horrible version of x-360-z-bearing-plate_2off. I will retry this piece with ABS.

So last weekend we met my parents for lunch at The Olive Garden. You know you’re too much into your RepRap work when you bring RepRap pieces and assemblies into the restaurant:

I tried printing this next piece 4-at-a-time with the Multiply plugin in Skeinforge at least twice until I gave up and did them each by hand. The difference in this case was night and day – it was a FAR better print as a one-off:

x-vert-drive-nut-trap_4off

Two x-vert-drive-nut-trap_4off's, with an M8 nut in place

A successfully trapped M8 nut, between two x-vert-drive-nut-trap_4off parts

So then at some point I wanted to finally get around to making the “thin-sheet” opto-endflag parts out of aluminum Coke cans. (Tangent warning) While I’m talking about opto-endstops, let me make my opinion clear on something. I’ve heard that Makerbot is no longer going to ship opto-endstop boards with their Makerbot kits because no one uses them. Well let me start out saying that I don’t use them on the Makerbot I’m using as a RepStrap, but I wanted to, and I certainly will be using them on my Mendel. They’re installed, just not being used. There are multiple reasons I don’t use them on the Makerbot:

1. The Popsicle stick slots on the Y carriage don’t line up with the opto-endstops on the side of the case, mounted correctly on the holes provided. Yes, I could line it up and drill the correct holes, but I didn’t. If this were my permanent machine, I might, if it weren’t for item #3 below.

2. The Z axis doesn’t even have a place for an endflag. You have to print your own out (which I did), mount it on the side (which I did), and hope that it doesn’t scrape up against the side of the wooden case and impede Z motion. Still, I have the printed one mounted on the table, but by design it’s not long enough to reach the endstop, so you’re supposed to put tape or something on the bottom. The one I printed out was ABS, so it’s warped, so I haven’t even bothered trying. Again – fixable, but this shouldn’t be something that people optionally do – it should work for everyone.

3. This is the biggest reason I haven’t bothered to get it all working: there are recurring stories of correctly mounted endstops not reacting well to events! I haven’t looked into those particular issues much because my endgame is a Mendel, but the stories say that the firmware doesn’t handle it well, etc.

I think it’s a shame that everyone doesn’t have an auto-homing device that uses the endstops at the beginning of each build to home itself and print correctly every single time. When we built this Makerbot we’d have installed the endstops and had it working (at least as well as the firmware allows) if we hadn’t read the line “It’s actually possible to run the Cupcake CNC with no endstops at all!” at 2:30am. The confusion surrounding the CAT5 cables and which pins to wire didn’t help much either. I’m looking forward to Mendel’s 3-endstop solution with correct homing behavior.  (at least I hope its behavior is correct! I haven’t checked recently).

But I digress. Like I said, I wanted to build my endstop flags, so I did:

Redrawing the templates to scale by hand was easier than getting the DXF file to print unscaled.

One coke can sacrificed its life, delivered me a delicious beverage, and produced 4 sets of opto endflags (3 spares each).

Here's the rest of the Coke can. These pieces don't get to live on forever in a RepRap.

Late Sunday, the Makerbot plastruder jammed again. This time it was plastic stuck in the acrylic that I just couldn’t get out. I took the plastruder apart, got the plastic out, flossed the gears for the hell of it, put it all back together, and then before reattaching the heater barrel assembly I figured I’d heat it up to let molten PLA drain out. Sigh. Something happened (don’t remember what), and eventually I had no temperature reading. I looked down and I’d pulled out one of the wires going to the still-intact thermistor (despite a pretty good crimp I thought). Damn.

Now though I was stuck with the problem that I had this M6 nut behind the metal retainer ring thing there, and it wouldn’t budge. So I couldn’t make room to get in there to unwind just the thermistor and the kapton tape around it. After enough fumbling trying to do that, I felt something give, and instinctively knew I’d just ruined the heater connection (and I had).

I stripped the heater barrel all the way down, again:

PTFE sure does flow.. you can see where the belt clamps were, and where it flowed around that.

Had to tear off that nice insulator that I'd just put on days before.

Full Blown Crisis

So, that wasn’t even the crisis.

Tuesday I go into work, and I’m sitting in a meeting. Chris (who built the Makerbot with me, and whose Mendel we’re building pieces for as soon as mine is done) handed me his phone. On it was an email from the secretary of the CTO where I work, telling us that there was a need for the Makerbot, and could we return it.

Ddddoooohhhhhhhhhhh…

By my count at that point I had 27 pieces left to print (I believe now that it’s actually 23, and probably really only 20, since I could get by without 3 of the pieces to space out circuit boards etc, and have the Mendel print its own final pieces, which would actually be pretty damned cool). The email mentioned something on January 27th, next Wednesday. That was 8 days away, and we had no idea when they wanted this back. Disaster! If I don’t have enough pieces to make the Mendel, then functionally I’m exactly where I was two months ago – without any exit strategy – no way to get the final pieces I need.

I experienced a good amount of panic that day. Yes, I’m sure after telling this story I could talk someone into letting me keep the Makerbot. My concern though was whether there was someone else in line for this, waiting this whole time. I didn’t want to have to risk the idea of someone else taking this Makerbot, which I’ve had to repair at least 7 times now in one fashion or another, and breaking it in a way that I couldn’t easily repair it from. I didn’t want someone else taking this away for 2+ months, leaving me with no way to finish my own printer (with which I could print other printers).

Looking further into the situation, it turns out the desire is to get the Makerbot for a 3D printing class being held next Wednesday. I’d actually been looking forward to that class already – I signed up a week or so ago, and I’d been looking forward to it since around the time that I started working here in October (it was on a schedule). Chris and I walked down and talked to the guy running this class. Thankfully, he just wants it in the class to show off, and he’s fine with us taking it back on Thursday. As it turns out, now I’ll be saying a few words about it in class! I’d been looking forward to the class for months, and as it turns out, the class had been looking forward to me. 

Of course, the Makerbot was still broken. This morning, I woke up at 7am, showered, got dressed for work, and headed down to the basement to rebuild the heater barrel assembly before work. I timed myself, for future reference (because for at least two days I dreaded the work of rebuilding the barrel – it’s just a pain). From a bare barrel to a Makerbot extruding PLA was 2 hours 45 minutes. Twenty of those at the start were just lining up the pieces I need. I decided to take a picture of that “heater barrel assembly kit” so I’d have a checklist for next time. Fumbling around looking for tools in the middle of a task like that is what makes it a variable length task to dread.

Here are the tools/pieces I use:

Heater barrel assembly building kit/checklist

As it turns out I only missed two tools – regular wire strippers, and a small pair of scissors to snip the kapton tape.

In no particular rush, it took me a ridiculous 72 minutes just to get the right length of nichrome wire connected to two wires, crimped, covered in solder for the hell of it, and wrapped in kapton tape.

At the end, I once again had a working extruder:

Extruding again! Woohoo!

So now the challenge is to either finish the remaining 20 pieces before next Tuesday morning (when I have to bring the Makerbot into work), or to make sure I get the Makerbot back after both classes on Thursday afternoon. I’d had a vague hope of finishing the printed parts by my birthday (January 25th, this Monday), but at this point I don’t think I’m gonna make it. But at least the Makerbot is working again!

The countdown continues! 33 pieces left to print!! (out of 106)

(To the impatient – make sure you at least see the last video in this post, but really, you should be reading/watching all of it. )

Before I was able to print out any more pieces I had to try rectifying this extruder-stops-extruding-PLA problem. Since my last blog post I’d discovered that sometimes I could just twist (rotate) the filament to get the motor to catch, instead of just pushing down hard. I also noticed that it seemed like my pushing/twisting would only be effective if the motor was about to change state. For example, I might push/twist like crazy with no luck, until it went to circle a vertical hole, at which point it would always catch. I think that when the motor fails to push for some reason (blockage, non-melted piece, covered nozzle, whatever) it “shuts off” for the rest of that command (I don’t know the extruder board firmware/hardware or the details of the extruder motor enough to validate this observation.. anyone?).

So now twisting is a part of my concern. Even with a lazy susan, PLA coils up something awful, which has to be putting rotational torque on the filament while in the extruder. So one thought I had was that maybe the teeth were dug in but then the piece twisted in some way that it couldn’t grip it anymore. (doesn’t make too much sense but the thought persisted).

So, I took apart the plastruder again and moved the idler wheel even closer to the teeth, not even using the metal spacer (I figured the spacer was made for 3mm filament, and the ultimachine PLA seems to be 2.8mm (that’s from memory, trust my earlier blog posts if they contradict that measurement)).

That helped. I think. It didn’t eliminate the problem, but it does seem less frequent.

What I also did was floss out the teeth on the extruder motor gear.. They certainly had some plastic stuck in there.

Flossing out black ABS from the extruder teeth

Flossing out barely visible PLA (to the left of the pick) from the extruder teeth

My guess though is that that was never really the problem. If the caked teeth had been unable to grip filament, then I should have always heard the motor running but never actually pushing out plastic. Instead, I hear NOTHING when it has this problem. This again lends towards the idea of some kind of jam/blockage/other-motor-resistance (causing the motor to shut down until the next command).

Here’s a video where I try to document/record/illustrate the problem where the extruder motor stops even trying to push. You have to turn the sound way up and try to ignore the sound of the motor of the X and Y axes, and instead listen for the shhhhhhh shhhhh shhhhhh sound of the extruder motor:

Without any actual knowledge of the situation, I’m secretly hoping that the stepper-motor-driven Mendel extruder handles this problem better, but I have no idea whether it’s actually better or worse.

Next, for lack of a better place to put it, here’s a complete non sequitur: possibly the most exciting RepRap video ever recorded:

Assuming you’ve recovered from the exitement of that video, let’s continue. Ok.. So I was able to make some new parts.. There was this one, from the end of that last video:

x-180-z-bearing-plate_2off

..and then I got brave and tried using the Skeinforge Multiply filter to make more than one of the same part, with somewhat acceptable levels of success:

x-bar-clamp-m3_6off, done with Multiply

Here’s another part, which would be almost impossible to print in ABS without a heated bed or heated chamber:

Printing x-end-bracket_2off with PLA

Two instances of x-end-bracket_2off, both missing some plastic at the highest levels in those bars

A picture of all of the pieces I’ve printed since the last blog post:

The most recently printed pieces to my Mendel RepRap

Of those, here was my favorite:

x-vert-drive-side-plate-180-end_2off. When I see this piece I think of Halo 3 and Forge, as if that were a staircase leading to a ledge.

While printing parts, I also assembled more of my x-carriage. I was able to fit the M4 hex nuts into their recessed holes (despite the poor construction of the x-carriage-upper piece I’d printed) by using a soldering iron to just push them into the plastic (which worked amazingly well). That let me attach four bearings to the upper piece, and bolt it to the lower piece.

x-carriage assembled (upper and lower parts connected, with belt clips, bearings, and fasteners), sans extruder.

Another view of the x-carriage

A particularly cool view can be seen here, where you see how the carriage mates with one of the two parallel bars that the x-carriage slides on along the X axis. Note the three bearings in the front of the picture as well as the three bearings way in the back. One of the smooth bars slides through all of those bearings.

This tunnel is where one of the smooth bars goes through. See how bearings from three sides limit Y translation, Z translation, Y rotation, and Z rotation.

On the other side of the carriage is the four bearings that go with the 2nd rod, which keep the entire carriage from rotating around the X axis formed by the first rod:

These bearings on the opposite side prevent rotation around the X axis, which in combination with the bearings from the other side restrict motion to only translation along the X axis.

And here are two good shots of those snug-in-their-melt-assisted-holes trapped M4 hex nuts:

A view of the trapped hex nuts that I massaged into their poorly-built hex-shaped holes with a soldering iron

More soldering-iron-helped trapped hex nuts

And of course, finally, video:

Thirty three more pieces left!

“Aagghh!!!” That’s one way to describe the past few days (Friday through Sunday) of my RepRap experience.

PLA has been an extreme pain. My first sign of major problems was in trying to print the z-tensioner piece out of PLA. This looks like a relatively easy piece to print, but my first two attempts failed. The first was some random unattended mistake:

The second though showed the problem I’ve been wrestling with all weekend. Check out the top part of the print in these pictures:

At some point the extruder stops extruding, and if I’m not there to correct it (by pressing hard on the filament and/or turning it etc), then it will leave the rest of the build unfinished. More on that below.

So I put that piece on hold, and tried printing the x-180-z-bearing plate, and that’s when the heater barrel pushed out (again!):

Frustrated, I went to the store. The good news is I bought a lazy susan for the PLA supply, and lots of that Scotch Blue Painters tape (#2090) that Adrian mentioned in August (the tape works awesome.. but I’m getting ahead of myself). Having either a spool or a lazy susan really is important with PLA, because twisting becomes a serious problem. It still doesn’t feel solved. If you buy a lazy susan, go with a large one; I wrestled with a $5 difference (I was at Target and had a choice between a $13.59 11″ or a $18.79 16″), and mistakenly picked the 11″. The spool of PLA had measured about 10″ before, but then it unwinds and actually started getting stuck in between the rotating part beneath it. I put a piece of cardboard beneath it for now, but I’ll probably go return it and get the larger one. [Update: Laurie's so awesome - she's returning it for me while at Target tonight]

Back to the pain. I had to disassemble the plastruder to get the PLA filament out (actually, I only went as far as unscrewing the bolt holding the large acrylic wheel, which I keep hoping was the cause of my later problems, but that’s a false hope because as I described above, I had the problem before touching the plastruder). Here was what the filament looked like:

So. I needed a new PTFE insulator. I’d told myself that next time I made one, I’d make a bunch. So that gave me the excuse to create a centering jig for the PTFE rods, leading to this video:

Great, I made four PTFE insulators, and put three in a ziplock bag for use in the probably-not-too-far-future. Then there was just the matter of heating up the heater barrel to get any PLA blockages out. Except that’s when I realized that the heater wire connection had broken, and I had to completely redo my heater barrel, all the way down to putting on new nichrome wire. (At least the thermistor was still working!)

I rebuilt the barrel, and this time put an M6 nut on to keep the barrel from pushing out of the PTFE so easily. Unfortunately it’s not a thin nut, so it uses up more of the barrel. It also acts as a heat sink. All of these things to through my mind when trying to diagnose the PLA jamming problem (maybe the heat sink makes for a cold area in the barrel which solidifies liquid PLA), but again, I keep forgetting that I had the problem BEFORE rebuilding the barrel. Writing this stuff down sure helps.

So now that it was re-wired, I heated it up and pulled out the semi-molten PLA..

I put it in the plastruder, mounted it back in the MakerBot (forgetting to put on any hose clamps), and started a test extrusion, which worked for a short amount of time. Then, total dismay.. I saw PLA leaking out near the nut:

Pulled it all out, tightened the nut like crazy, put two hose clamps on, and put it all back together.

Finally I had a working RepStrap again.

Then I went to print. The test extrusion at the beginning almost always fails; either PLA doesn’t come out, or it comes out and curls up and clings to the heater barrel like spray cheese on a ritz cracker, or I push the filament down by hand super hard and it eventually catches. After pressing down until a good base of the x-carriage-lower piece was laid out, I had a promising print going:

Success, kind of?

Then, I went through around 3-5 attempts of printing the x-carriage-upper piece go to above that. Each one failed ultimately because the extruder stopped extruding. I’m no longer convinced it’s a blockage (or that it’s always a blockage – I could have overlapping problems). I think that the extruder isn’t able to grip the filament well sometimes. I tried reversing the extruder after one of those times to examine the filament and look for a worn off part that it couldn’t grip, but I couldn’t find anything conclusive (although maybe that time it was a blockage instead). Aagghh. So one thing I did is I recompiled the 1.6 extruder firmware and changed the motor reverse speed to 0, so it wouldn’t do the reverse-the-motor-to-prevent-ooze trick (the thought being that maybe melted PLA was being pulled back up to an area that was cool and it solidified). That didn’t fix it.

So out of my frustration printing that piece, I felt the need to cheer myself up, and I decided to assemble my first pieces together!

That was enough motivation for one more try Sunday night to get a working x-carriage-upper piece printed. It was not easy. Basically 2.5 hours of babysitting and being a human-powered extruder motor assist.

A video I call “Lowered Expectations”:

There ya go. So, PLA = lots of pain, but it’s a way to actually get non-warping pieces without a heated bed (which at some point I’ll revisit). I’m psyched that I was able to make it far enough to actually assemble something. That x-carriage-upper piece is so messy that almost none of the captive nut areas work, so it’ll be interesting to see if I can actually use it, but I’m hopeful. Of course, I’d rather have a reliable printing process that I could walk away from and print another one that worked!

Technically, I’ve started assembly of my Mendel! Woohoo!

Check it out!

I printed the good one at 225C, 255 extruder speed, rotated so it’s correct (on it’s back).

The YouTube compression doesn’t quite do the piece justice, so here are some pics.

First, here are some early attempts:

Upper left is ABS printed vertically, upper right is ABS printed flat on its side, lower left is the my first PLA attempt (235C, 210extrspeed), lower right is my second PLA attempt (240C, 255extrspeed)

Then I lowered the temperature to 225C, and kept extrspeed at 255:

225C, 255 extrspeed. Looks good, but inside of recessed area is a bit rough.

Then I printed one more, this time rotated on its side, at 225C with an extrusion speed of 255 (edited the gcode file by hand). This final piece can be seen on the right in this next pic of all of the PLA attempts so far:

4 PLA attempts. The one on the far right is the excellent one.

Again, the one on the right is the best one. Printed on its side, 225C, 255 extrspeed.

Here are a few more pics of the beautiful piece. It feels like either something you’d expect from a super expensive 3D printer, or something you’d expect from outer space. Superman’s fortress of solitude comes to mind:

One last comparison shot – the piece on top in this next picture is the 225C printed vertically, and the piece below is the 225C rotated to print horizontally.

Looking around my work bench, not including any of the items in these pics, I count at least five other attempts that failed in ABS because of warping. PLA worked great, with no heated bed, and no raft. I did run into some problems where the extruder stopped printing because of some internal jam or backing up (guess), but I was able to fix that by setting the temp to 240 and extruding for a while.

Moving on to other pieces now.

Quick post. So Sunday night I had time to take out the supply of PLA (Polylactic acid, a clear biodegradable plastic that won’t warp like ABS) and give it a shot. I didn’t have any of the temperatures down right (temperature was 235C, extruder speed was 210), so it didn’t come out great, but here was my first attempt:

Might get to work on it again later tonight after everyone falls asleep – we’ll see.