• Fixing the Skew

    Once I had the build plate levelled and sticking , I had the luxury of being a bit more methodical about diagnosing the other issues. So of course, I printed out some funky vases..


    ..which served nothing to tell me what was wrong, but did show me that I really wasn’t going to get anything nice printed until I fixed it – there were gaps in the bottom, and the taller vase was funky on one side and almost flat on the other.

    My 3D mentor friend was kind enough to whip up a few shapes for me to test on, just a couple centimeters square in area. The shapes were fairly consistently skewed, especially on the perimeter:

    IMG_20130221_214843IMG_20130221_213801 IMG_20130221_205511 IMG_20130221_212623

    The best diagnosis I had was that the belts were loose. It took me a ridiculously long time to figure out how to tighten the belt, so let’s see if I can explain it a bit better.. Look at the motor that drives the belt. On the MBot Cube, there’s one for the x-axis mounted on the right side and it goes back and forth. The y-axis is mounted at the back of the right side, connected by a small belt. There are four screws holding each in place. You can unscrew the motors, pull them tight against the belt (as hard as you can), and then re-tighten the screws to hold them in place.

    When I tried this, things seemed to improve a little, but not completely. To see if I was on the right track, I loosened the belts. Happily, this did make it worse, specifically exaggerating the symptoms. In the example below, you can see the original prints on the left, after tightening in the top middle, and then after loosening on the left.


    At this point, my friend had the idea of checking the motors more specifically. Perhaps one of them wasn’t working properly? He had me go through the printer menu and enable the stepper motors. This is supposed to engage the motors and make it so that they don’t move when pushed. When I tried to move the extruder, though, the y-axis was most definitely jerking back and forth. I couldn’t see what was going on with it, so I took the entire motor off the assembly. Note: If you do this, make sure the printer’s power is off first.

    Once I just had the motor with its gear in my hand, it was easy to see that the gear was not solidly attached to the motor shaft. It required the tiniest hex key to tighten it, but once that was done it wasn’t moving a bit. With everything seemingly happy, I tried a print.. and hurrah! It worked! You can see the progression of test prints here:



    1. Default settings
    2. Tightened belts – slight improvement
    3. Loosened belts – more extreme symptoms
    4. Tightened again.. wasn’t as good as #2
    5. Tried yet again.. okay this isn’t working
    6. After fixing the motor’s gear
    7. Full solid print, dimensions almost perfectly even



    Pleased with my success, I tried the meeple and lucy the cat again:

    IMG_7144         IMG_7168


    No more holes, and lucy’s back was perfect. I’m still getting a weird texture on her front.. I don’t know what’s going on there, but I’m sure there are many more settings and upgrades to look at.


  • Doom of the Acrylic Build Plate

    I had sort of noticed that out of the box the acrylic build plate of the MBot Cube was a bit warped, but for whatever reason I dismissed it. I had been told that I should make sure it was level, so I tried to figure out how to do this. I hadn’t explored the menus on the printer itself yet, so I was looking through the ReplicatorG options instead. Happily, I found a script hiding in one of the menus “The Replicator Plate Leveling.gcode”. I’ve got a clone, so it should be fine, right? Right?!?


    I was surprised when I had to adjust the plate height quite a bit. Wasn’t it already sticking? Oh well, follow instructions. Seemed to be fairly level, despite the warp. Okay, start printing.

    Hmm, isn’t that really close to the extruder now? In fact, it’s dragging quite a bit. Is that the surface starting to melt?? Abort! ABORT!

    After a bit more fiddling and attempted prints, it was pretty clear: the acrylic build plate was doomed. A few grooves and potholes were melted into it, and it was quite obviously warped and wouldn’t level properly. It was impossible to test any of the other solutions, because nothing would print on that surface.


    I researched what my options were, and it sounded like the best solution was glass, heated or not. I found a relatively cheap option on eBay for a heated plate kit, but I figured in the meantime I’d look around for a local source of glass.. installing new electronics was not really my first choice.

    Many people were talking about borosilicate glass on the forums, since it’s supposed to withstand higher temperatures. When I spoke to various glass companies, however, I asked for something that could withstand the heat of the extruder (up to 250C), and they insisted I needed neoceram glass instead.. what’s used for fireplaces and such. That was going to cost me upwards of $100 for just a small piece, so I was losing enthusiasm fast. However, I read some more (that part is free, at least), and was (perhaps too easily) convinced that it really wasn’t all that important for it to be heat proof.. just completely flat. Fine, that I could do.

    It was difficult to find a glass supplier open at a time when I wasn’t at work, but Preston & Lieff (who are no longer located on Preston St, as google maps led me to believe) were open on a Saturday morning, so off I went. The guy I spoke to was baffled by my needs, but since I also seemed a bit baffled, he offered me a couple of 8″ x 8″ mirrors he had put aside for another customer who never picked them up. I thankfully accepted, and ran off to see whether they would work at all.

    I didn’t have any document clips large enough, and many people complained about those getting in the way anyway, so I attached the glass to my build plate with.. painter’s tape. Note: this is a bit dumb. It can’t possibly stay put for long. However, I was impatient and I still haven’t thought of a better solution. So here we go.

    Glass Plate

    The extra height also meant that I couldn’t screw down the leveling knobs far enough – the springs were too stiff. Since I knew the acrylic was never going to work for me again, I figured it wouldn’t be the end of the world to just extract the springs and cut them down to size. As a hack, it’s not too bad. Did the trick.

    This time I also used the correct leveling script, in the firmware of the printer. Clever how they put that right in there.. *sigh* Anyway, it worked out perfectly. My warping and nosedive extruder issues are over!

    Glass may be completely flat, but it’s also completely smooth. Getting anything to stick to it was really frustrating. Thanks to the wonderful forums again, I found that a combination of acetone/plastic slurry (dissolve a few pieces of failed prints into a jar of acetone) painted onto the plate and then sprayed with Garnier Fructis extra hold hairspray worked wonders. It’s not completely perfect, and I recommend printing things that aren’t too long and thin, but it allowed me to get on with diagnosing the other problems.


  • First Prints

    Being excited about simply having a 3D printer at my disposal, my first few prints were not particularly scientific or methodical in choice. I printed off a bunch of things I thought were relatively simple in shape, as well as a few requests from friends and family. The results were.. less than ideal. I had at least fixed the shuddering issue: my friend informed me that I was trying to print _way_ too fast. I changed the feedrate from something like 100 down to only 20, and the travel feedrate to 40. I fiddled with the extruder temperature quite a bit, ranging from 220C to 240C. My best results were around 235C for the red, and 228C for the green. Apparently it’s quite common for different colours to have different preferences for temperature, but unfortunately the manufacturers don’t give any suggestions along those lines. It’s all a matter of trial and error.


    This meeple was printed at 2x scale, and showed many holes and weird offsets.


    The barrel-monkey cookie cutter turned out probably the best, considering it was at least functional. However, it showed similar holes in the base of it.


    Lucy the cat had a nice smooth texture on one side, but had very thin and wispy lines on her chest, leaving a gaping hole (I printed her with no infill).


    The cat from my first print was slightly less messy, but still had the same holes issues.


    My Dad requested this trilego piece in particular because he was interested in the idea of custom-shaped things that are compatible with Legos. Unfortunately, due to the weird offsets, this piece was not at all compatible with Legos.

    I went to a few different forums to see if there was anyone out there who could shed some light on my problems. I got the best responses on the MakerBot google group and the Reprap forums.

    Theories included:

    • I needed to level my build plate – this is also known as tramming. If the first layer is messed up, it can affect the rest of the model badly. It can also cause some issues with the plastic sticking to the build plate.
    • Trapesoidal prints indicate that the X-axis is not square to the frame (I’m not sure this was the case at all)
    • The extruder wasn’t extruding regularly. To test this, I needed to use ReplicatorG to extrude a known amount of filament (e.g. 50mm) and measure it. To solve it, there are various software and hardware solutions.
    • The drive pulleys / belts could be loose.
    • Lack of heated build plate might be an issue.

    Leveling the build plate seemed simplest to do, so that’s where I started. Unfortunately, this ended up being very stressful..

  • Meet the MBot Cube


    My printer is the MBot Cube dual extrusion 3D printer, sold from mbot3d.com. It is a clone of the open-source MakerBot Replicator, allowed by their copyright terms. You can check out the specs in more detail on MBot’s site (if you can wade through the Engrish), but the important things to me were:

    • Dual extrusion (allows for multi-colour prints or support material in a dissolvable material)
    • Large print bed (20cm x 20cm x 20cm)
    • Good resolution (0.1mm to 0.3mm layer thickness)
    • Works with both ABS and PLA
    • Ships fully assembled (no fiddling with kits – good for a beginner)
    • Very reasonable price, including shipping

    I knew that I was taking a risk getting something from China since there were few reviews of this particular printer and getting support from them might be difficult, but I was encouraged to go ahead with it by a friend who already owns a Replicator and could guide me through troubleshooting if necessary. With a limited budget, this seemed like the best option for getting something I would be happy with for a while.

    MBot was very good about responding to my initial queries by email about the details of their printer, and the fabrication time and shipping estimate was very accurate. I received my order within about 4-5 weeks, with a shipping cost of about $200 and duties fee of ~$26. Pretty much everything I needed to get started was included in the box. It came with the following items:

    • The printer!
    • Hex key for the larger hex screws
    • SD card
    • Metal scraper to remove prints
    • Two spindles of 1kg each ABS filament
    • Power cable for some other country standard.. but if you have a standard computer/printer power cable it can be switched in easily.

    The filament that was included was not in any colour I had chosen, just random. I ended up with a translucent red and a bright green. At least I don’t feel bad messing up prints in those colours!

    I found the links for the software on the MBot site didn’t work for me, so I just googled that version of the software. Be warned: do not try to use the latest version of ReplicatorG, it won’t work with the installed firmware. The method to upgrade the firmware through ReplicatorG is also a complete pain in the ass and likely won’t work either. Save yourself a headache at first and just use the older ReplicatorG software. Theoretically, there is a method for updating the firmware more directly, but I haven’t tested that out yet.

    Before printing anything, I needed to get the filament loaded. I didn’t know at the time that there are functions in the firmware to do this, so I attached the printer by USB cable and used the ReplicatorG software to first back out the filament nibs that were shipped with the printer and then feed in the new colours. You can see in the picture above the partially black curlicue of green filament as a result of switching the colours.

    I also tried printing through the USB cable, but this was an exercise in frustration as it would often time out. My friend explained to me that this is a result of packets being lost due to USB being unreliable, so I switched to printing from the SD card. Happily, I have an SD card reader on my laptop that simplifies that process.

    The first thing I tried to print was a cat, which you can find on Thingiverse. As you can see below (click to embiggen), it’s a recognizable cat, but not particularly detailed or pretty. I was fairly happy that out of the box it could do this well. The acrylic build platform seemed to stick to the plastic well, and it was easy to remove the print when it finished (more on this later…).


    Problems I saw right away:

    • There were holes in the cat
    • The plastic looked messy and not sticking to itself
    • The printer shuddered like crazy as it printed

    Next up.. my various experiments in diagnosing the problems and improving print quality!

    If you have any questions about this printer or any of the issues mentioned in this post, please don’t hesitate to drop me a line.