Since I’m interested in bigger things, so I’m looking into building bigger printers. (Anyone who wants to buy me a Stratasys can ask and I’ll give them the delivery address…) One option is to build a Mendel which has an envelope of 200mmx200mm. Another is to figure out how to put a print head on something really big, like a knee mill or a large CNC plasma table.

Here’s how I set it up: using Kapton tape, I attached a loop of nichrome wire to the underside of the platform. I also put the thermistor in an “average” spot away from the wire:

This connects using the A6 pin on the extruder, same as other boards, all of which are basically doing what Eberhard documented on his blog. For software, you’ll need to download and build the latest ReplicatorG and firmware from the makerbot github.

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The reason this matters is that it’s how the Cupcake monitors the temperature of the extruder. You want to be printing ABS at around 220C, but the smaller thermistor will “read low”, so the temperature reported back to the software is off. To get to the right temp, you have to fudge it and set it at 240, then make sure you change it to 240 anywhere in g code generated by software.

It’s easier, in my opinion, to just make/use a new ThermistorTable.cpp:

1. if you have access to a temperature probe that’s good up to around 260C, use the reprap thermistor page as a guide to making your own table.
2. follow the makerbot wiki instructions on upgrading your firmware to verify that the default software will build/install. If anything goes wrong, or this table doesn’t work for you, you need to be able to revert.
3. make a backup of the ThermistorTable.cpp file
4. copy the new table (found below) into ThermistorTable.cpp
5. rebuild and install just like you did with the default software

This is the table I’m using with a 1mm thermistor, I’m able to set the temp to 220C and print quite nicely.

#include "ThermistorTable.h"
// Thermistor
 lookup table for RepRap Temperature Sensor Boards (http://make.rrrf.org/ts)
// Made with createTemperatureLookup.py (http://svn.reprap.org/trunk/reprap/firmware/Arduino/utilities/createTemperatureLookup.py)
// ./createTemperatureLookup.py --r0=93700 --t0=24 --r1=0 --r2=4700 --beta=4881 --max-adc=1023
// r0: 93700
// t0: 24
// r1: 0
// r2: 4700
// beta: 4881
// max adc: 1023
#define NUMTEMPS 20
short temptable[NUMTEMPS][2] = {
   {1, 477},
   {54, 189},
   {107, 159},
   {160, 142},
   {213, 130},
   {266, 120},
   {319, 112},
   {372, 106},
   {425, 99},
   {478, 93},
   {531, 88},
   {584, 82},
   {637, 77},
   {690, 71},
   {743, 65},
   {796, 59},
   {849, 51},
   {902, 43},
   {955, 30},
   {1008, 4}
};

Here’s how I set it up: using Kapton tape, I attached a loop of nichrome wire to the underside of the platform. I also put the thermistor in an “average” spot away from the wire:

The big problem here is that the harness is not attached, so there’s no strain relief for where the wires are soldered to the thermistor and nichrome. Industrial hot glue doesn’t work, so I’m going to give heat-resistant epoxy a try next.

EDIT: Oops, completely forgot about how to hook it up! I’m using the A6 pin on the extruder, basically copying what Eberhard documented on his blog. For software, you’ll need to download and build the latest ReplicatorG and firmware from the makerbot github.

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If you’re considering a MakerBot Cupcake or other scratchbuilt,
open-source 3D printer for your home, read on. I’ve had one for several
weeks now and this is yet another entry about life with a first-gen,
home-scale 3D printer.

Location

It’s noisy. It smells. It’s like having a
mimeograph in your house. Yes, you can do a lot of useful things with
it and yes, it will generate a number of new and interesting smells and
sounds.

When I first set mine up, I had it on a hardwood floor in my
second-floor studio. While it was printing, I walked down stairs and
discovered it was about as loud downstairs as upstairs thanks to all the
vibrations being transmitted through the floor. I’ve since moved it to
the top of some shelves and will also add a rubber sheet under it to see
how that helps with the noise.

The steppers are noisy. Printing means that at least one, and often two going at the same time. How noisy are steppers? Well, people have performed songs using steppers, that’s how noisy they are.

Finally there’s the lovely smell of melting ABS. The MSDS for ABS isn’t
too terrifying, but I get tired of the smell after awhile. Plan on
having your MakerBot near a source of fresh air or other ventilation.

Oh, and solve all these location issues while keeping it next to the
computer you’re using to drive it, as you’ll be going between the two
quite a bit for the first few weeks.

Tools

There are a few tools that I’ve found handy to keep near the MakerBot. Handy enough that I’m buying “replacements” for where they used to live, because I’m tried of moving them back and
forth.

• dykes or wire cutters: useful for getting a nice clean cut on the ABS filament single-edge
• razor scraper: if you’re using acrylic platforms, this makes it much easier to get the raft off.
• small (~15cm) ruler for adjusting/aligning the Z-axis after you crash the head.

Software

I’m focused on OSX right now, but some of these packages are available on those platforms and may have different issues.

The biggest issue I’m facing on OSX is Intel vs. PowerPC. It seems that the python builds for these two platforms aren’t “bug compatible” across the two different architectures. Skeinforge, the primary tool used by the greater reprap community for converting STL to g code functions differently on the different architectures. My plan had been to dedicate my old PowerPC G5 to running the MakerBot and some scanners, but currently I have to keep my Intel MacBook nearby in order to run skeinforge.

One of the handier tools if you’re using OSX is
Other than that, things have been going fairly well. Blender turns out to be very powerful, but it’s not only non-intuitive, it’s counter-intuitive in places. Do a bunch of the tutorials and get used to the idea that a “unit” in Blender is “1mm” on the printer.

Printing

Almost every problem I had was due to not getting the extruder to the right temperature for ABS. The supplier changed parts on the MakerBot crew and nobody noticed until too late, so some of us got “the tiny thermistor” (about 1mm wide) that reads higher than the normal thermistor people were using. After some fiddling around with a temperature probe, I made a new source file for the build, you can find it on the makerbot group.

Once I nailed the temperature, it was time to do something about alignment/adjustment. I tightened the belts as snug as possible then trammed my build platform (more on that in a future post). The final step will be to go to a heated platform, as this seems to yield large prints that don’t warp.

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Assembly

I bought the “Deluxe” kit for $950 that comes with pre-soldered boards, tools, and pretty much everything you need to get up and printing. Mine was missing a couple of random bits I was able to find in my spares box — a header here, a screw of the right length there, but otherwise everything was in order and neatly packed. It was US$ 200 more than the “regular” kit, but the time saved sourcing parts and soldering chips was well worth it to me. There were a couple of times I needed a small screwdriver to pry/move something, but I did most of the assembly with the hex keys and box wrenches included in the Deluxe kit.

The instructions weren’t always perfect. I had to print them out (long story) and discovered that all of the images in my printout were reversed left/right. At a few points the text was right and the photos were wrong or vice-versa. Still, my experience fabbing and working with kitbuilds made it pretty easy to finish the kit in a few evenings.

Testing

This is where I had (and still have) the most problems, mostly due to my MakerBot controller being a Mac G5/PowerPC.

One of the more important free tools — skeinforge — has problems on PowerPC due to the default Python install being wonky. Someone on an Intel Mac would tell me to “do foo”, I’d “do foo”, and it would fail, so we’d go around about whether or not I was “doing foo” properly. After switching to my MacBook (Intel) for testing, most of the software issues went away and I was able to design/print some test objects.

General Usage

My SolidWorks Student Edition expired the week before my MakerBot showed up, so it’s off to the world of free software for modeling. Learning Blender is a bit difficult after using SolidWorks and the free version of SketchUp is not very powerful past simple geometries. Compounding the problems is again, the G5 I’m trying to use as my server. Reading the Blender FAQ it appears that a G5 with a big monitor can be problematic due to memory issues. Switching my display from “millions” to “thousands” of colors and closing most of my other apps has made it crash much less than before.

It seems to me that the UI for ReplicatorG was branched pretty early from the Arduino world — some of the painful bugs of early Arduino days still exist in ReplicatorG. In particular, do not turn off your Makerbot while the ReplicatorG control panel is open. I’ve hung my G5 several times this way.

Design Notes

A few things I’ve learned in my first few designs and test prints

Small holes are hard. I tried to make a 3mm hole in a 1cm thick drive wheel and ended up drilling it out. When you’re making an object, remember that the print head resolution is much lower than what you see on screen. (If you’re used to lasercutters and Stratasys machines, it’s like going from .3mm technical pencils to kid’s crayons. :-)

Learn to dial in your raft while it starts to print. I’ve ruined several prints because the raft wasn’t firmly embedded in the print surface from start to finish. After a few layers, the raft would start to peel off the surface and the print would be ruined.

Learn g-code. You might want to verify or change the code generated by skeinforge. In my case, I started adding a M01statement after the first movement to build the raft to verify that the raft would actually be on the print surface. I also had to go through and edit the temp settings at various places to account for my personal cupcake’s printing requirements.

Get a cheap caliper, even a flimsy plastic one is better than a ruler for measuring things down to ~1mm. I’m making a housing for an LCD display and the art-store $10 plastic caliper is as good as my Starrett for the resolution the Cupcake can print.

That’s all for now, will post more as I learn more.

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