darknrgy's blog

MakerBot Cupcake CNC Build - It's Working!

The USB TTL Cable was delivered on a week day, so we burned some midnight oil to get things up and running. With the cable in place, we had zero difficulty connecting to the robot. Aside from a few direction reversals, everything worked perfectly!

Here is our robot actually doing something. The temperature of the extruder has been raised to 220C and we are ready to do some test extruding. 

 Here we are getting a nice clean extrusion - very little defects. Success!!!

 Installation of the extruder into the robot. 

 Makerbot Cupcake CNC Fully Assembled and Fully Functional, albeit so out of tune that it only prints spiderwebs. 

 Preparing for first print ever!!!

 aaaaand... spiderwebs. 

Getting the extrusion to stick to the build platform is the first big challenge. Along the way, we tried different temperatures and different pinch wheel tension. In feeding, pulling the thread back out, refeeding, pushing too hard, and generally yanking on shit, we ended up with a badly clogged and leaking extruder nozzle. I'll let Alan elaborate on his extruder deconstruction efforts (involves toaster oven) in a later post. In addition, he's going to talk a bit in detail about the various extruder tunings that got us mostly in business. 

Instead, I will bask in the glory of success of our first prints that did not look like spiderwebs and the corresponding action photography. 

 Holy Smokes an actual 20mm X 20mm cube.

 You see, we had so much trouble getting the extrusion to stick at first, that we devised our own heated build platform solution. This actually worked surprisingly well until we got annoyed with it and worked out the proper tuning that eliminated its need. 

 Making a huge mess...

 20mm X 20mm cube with dingleberry

 Sanded this one a bit

 One of my favorite photos. You can actually see the heated filament being deposited onto the object. 

 

 Part of our process was to meticulously document settings changes and results. This is only part of the notes. I've tweaked this in Lightroom to exaggerate the defects. There is quite a bit of variation even between prints without settings changes. Not a perfect machine, but we are very pleased with ourselves so far. 

 Looking down into the machine. 

Stay tuned for badly printed and generally useless plastic objects. 

Best. Project. Ever. 

MakerBot Cupcake CNC Build - Day 2

With the mechatronics in place, we proceeded to build the extruder and attempted to communicate with the machine. 

Extruder

Assembly is not as well documented here. The top component is the heating and extruding elements. Plastic filament is fed in from the left into the white plastic feeder. There is a hollow, threaded bolt on the inside, which the filament travels through. The extruder nozzle is far right and has a 0.5mm opening for the plastic to squeeze through. The threaded hollow bolt is wrapped with nichrome wire - around 6 inches and 6 ohms worth. The red leads feed power to the nichrome wires. Nichrome has a built in resistance, which means it will convert electricity directly to heat. The heating element is literally homemade. 

The bottom component is a thermistor and, together with the heating element, get liberally wrapped with insulation and heat proof tape. 

 

The thermistor touches the extruder nozzle directly. This is actually our first attempt at the nozzle. We ended up ripping it apart once it got clogged, and ended up assembling it slightly differently as you'll see later. 

I included this photo because I did this wrong. The blue color is because of a semitransparent tape and is meant to be peeled off BEFORE gluing it to the washer and putting tick marks ;).

The extruder is build with copious layers of acrylic.  

The extruder feeds plastic thread in through a "pinch drive". The red line is meant to show where the thread will run. The thread is pinched between the drive gear and the idler wheel and forced downward. This is where that new version of the drive wheel becomes important. The old style would mangle the thread without creating a lot of friction. The new one works MUCH better than the old. Again, here are the differences in thread characteristics: top is new drive, middle is old drive, and bottom is not processed. 

 

The mangled thread ends up not fitting through the plastic feeder tube. This is how we ended up with our first clog/rebuild, so don't do it like we did it. If you must use the old drive, keep the pressure light so that it does not mangle the thread. We also considered boring out the plastic feeder at one point, but the new drive makes it all better. 
 

 Electronics installed. The extruder is now fully assembled. 

 Aaaand it looks pretty bad ass. 

 

 Unfortunately, at this point we are stopped cold! Our buddy Jonathon tried as he might, but couldn't get his homemade USB TTL cable to play nice. Communication with the robot was not possible. A valiant effort though. We also tried various combinations of bad hacks and none of it worked. 

RIP homemade USB TTL that didn't work :'(

Make sure you get your Magical USB TTL Cable on the same day you're going to build your robot unless you're satisfied with just looking at your robot. 

MakerBot Cupcake CNC Build - Day 1

We've laid out most of the parts here. We ended up using a second desk just for tools and each had our own little work space. Worked great for parallel building. Most of the X/Y stage parts are foreground. 

 

Tiny neodymium magnets about 5mm cubed make up the platform latch. These little magnets will launch across the room if you're not careful. 

 

Y Stage Assembly

 

 

  

 

 

 

X Stage Assembly

 X Stage Stepper Motor and idler wheel installed

Y Stage in place, but not fully mounted. You can start to imagine how this works...

X/Y Stage fully assembled! As the belt is moved by the motor, the Y stage moves left and right.   

Build platform adapter mounted. The neodymium magnets will hold the build platform onto this adapter. 

Outer Shell

Here we have the circuit boards laid out. 

 Circuit boards mounted and Alan assembles the outer shell. 

 There is a slight burnt wood smell from the laser cutting that takes me back to my Dad's woodshop. 

 The final pieces are being assembled on the outer shell. Power supply also has its own base plate. 

 Here the outer shell is fully assembled and power supply installed. 

Z Stage Assembly

Parts are laid out for Z Stage assembly

 Stepper motor, Z-Rods, idler pullies

 The entire system turns, causing the vertical rods to rotate. The build platform rides on nuts threaded by the vertical rods. This makes the build platform ride up and down at your beckon. 

 Fingers becoming sufficiently hosed from work more appropriate for factory worker children. 

FINAL ASSEMBLY

 X/Y Stage taking position. Skipped a step here where we installed the horizontal slider rods. It is now starting to look like a robot. 

 From here you can imagine how it works. The X/Y stage provides movement in two dimensions along a plane horizontal to the table. When the extruder is installed, it will ride up and down along the vertical Z-Rods by sitting on those nuts you can see in the middle of the rod. 

 

 Getting most of our cabling hooked up. It's hard to see, but the extruder platform is mounted here as well. 

 

 Work it 

MakerBot Cupcake CNC Build Introduction

 Cupcake CNC partially assembled

A buddy Alan and I decided to build a cool robot. Alan ponied up for the Cupcake CNC Basic Kit by MakerBot and I tooled up and provided a workspace. Special thanks to my girlfriend Jeannie for enduring many days of melting plastic, solder fumes, and a distinct lack of dining table. 

The Cupcake CNC machine is an amazing, open source 3D printer. It works by heating and depositing plastic layers upon subsequent layers to build any object you can imagine that would fit into the size of about a cupcake. There is a large community of object designers as well as a large community backing for the open source machine hardware and all software. You can even download the original CAD files to make your own machine parts if you have a laser cutter. 3D objects can be built in any number of 3d programs and exported directly to your face. Neat. 

A couple things to note if you decide to build this bastard. 

1. BUY THE DAMN USB TTL CABLE. We had some decent EE experience and we were not able to homemade a cable. Without the cable, you will do nothing except wait for overnight parcel. And you will pay a lot of money for it and this will cause depression until it arrives. Then you will be happy. 

2. You will need a few more tools than it says you need because of a few manufacturing defects. I recommend a drill and assorted bits, and a dremel capable of cutting through metal screws. Wire cutters, soldering equipment, multimeter, magic hands, heat gun, toaster oven. You know, typical household goods. 

3. The kit comes with 10 pin headers and rainbow cables. THESE SUCK. Unless you have the special tool to make them, but even then I recommend finding them prebuilt on digikey or, if you're in the bay area, head over to Weird Stuff. Actually, just go there anyway. Isles and isles of surplus electronics. We loaded up on those cables and I think we paid dollars. 

4. Get the Mk5 Drive Gear Upgrade Kit if it is not already part of the kit. The old drive gear is not designed to bite into the plastic thread so there is no happy balance between tightening the grip and disfiguring the plastic past a point where it will feed through the rest of the extruder. The following photo illustrates the problem:

top is new drive wheel (mk5), middle is mangled by old drive wheel, bottom is unprocessed 

Most of all, you will need patience and perseverance. This is a lovely kit with a big reward, but it takes quite a bit of time before you print your first Hello World Cube that doesn't look like a cobweb.