I’ve been having fun printing with the various colors of ABS that MakerBot offers, but have always been somewhat envious of folks that have been printing successfully with PLA. I bought 5lb roll of the original 4032D that MakerBot sold, but ended up putting it on the shelf after reports from other operators that it was destroying their MK4 extruders.
Getting the new PLA printing was surprisingly easy, given the challenge of using a new extruder (which needed temperature, PID, and flow rate calibration) and it’s the first non-ABS plastic I’ve printed, so it will have different optimal printing temperatures and more.
I haven’t carefully calibrated the thermistor on my MK5, and I wasn’t sure of the right temperature to extrude PLA, so I started by setting the temperature to 180ºC and attempting to push some filament through by hand. I raised the temperature slowly until it became easy to push through by hand, around 195ºC. I had not yet locked down my PID settings, so I was getting some wild temperature swings. To be safe, I set the temp to 200ºC and started printing my favorite bottle opener from Thingiverse.
It turns out the flow rate for the MK5 is a lot higher than it was for the MK4. After putting down the raft, I was having trouble with the filament stripping inside the MK5 due to backpressure. Still, by paying attention to the print and tightening the thumbwheel whenever the filament slipped, I was able to get a completed bottle opener.
It was then that I noticed two things:
The top two layers of the object sagged deep into the honeycomb fill layers below, giving a terrible finish on top.
PLA has no give, so there was no way that a penny would fit into the slot. I have some nice bruises from trying to make it fit. :)
To fix the stripping and sagging problems, I figured that I should increase my Feedrate - the speed at which the platform moves to catch the extruded plastic. I figured that a too-low Feedrate would cause some back pressure when printing the raft (leading to stripping), and would contribute to sagging overhangs. I also guessed that the sagging is due in part to the high thermal mass of liquid PLA allowing it to sag before it cooled, so a lower extrusion temperature would let it solidify sooner, leading to less sagging. I still use skeinforge-0006, so these settings are in “raft.csv” (various temperatures) and “speed.csv” (Feedrate), respectively.
So, some calibration prints:
Starting with my first successful print in the upper-lefthand corner, with the temp of 200ºC and a feedrate of 26.5mm/s (which was working for my MK4), I slowly lowered my temp and increased feedrate. At 180ºC I had a failed print due to the PLA freezing up, so I am going to stick with 185ºC going forward. Increasing the feedrate by 25% immediately solved my filament stripping problem, but still left a pretty nasty top layer. Increasing beyond that smoothed out the top pretty well, and left clean enough slots that I could actually insert some coins, albeit dimes rather than pennies.
I may try increasing my feedrate further, but I found an odd result when going from 36.4375mm/s (slower, should have thicker walls) to 38.26mm/s (faster, should have thinner walls). Namely, they both seem like very solid objects, but the dime slid nicely into the slower-printed version using the edge of a desk, while I had to take a hammer to the faster-printed version, and actually ended up bending the dime rather than driving it into the plastic (PLA is tough stuff!). I would have expected the opposite.
Anyway, I hope these results are useful for some folks. I hope to improve my calibration a bit more, and trying out the MK5 with my old roll of PLA 4032D.
Actually, all sorts of new and exciting nonsense has happened to MakerBot #131.
I was excited to order get my MK5 Plastruder kit and join all of the cool people who have left the pinch-wheel and nichrome behind. Unfortunately, I ran into some problems early on, and after buying some cool thermocouple parts to try calibrating everything, finally determined that I had a bad thermistor.
Like many MakerBot owners, I feel compelled to help spread desktop 3D printing throughout the world. So, for the past several months, MakerBot #131 has been hard at work printing parts in 3D to make another 3D printer!
The Mendel is the second (and current) design for the RepRap project, whose goal is to create rapid-prototyping machines that can replicate themselves. As an Open Source Hardware project, everything about the Mendel’s design is available online via Subversion, from the mechanical parts to the electronics schematics, to the source code for the device and its host machine. Additionally, there is a fantastic community of very smart people who are constantly improving the design, trying new things, and helping others get their RepRaps working!
While the Mendel requires various hardware bits such as motors, electronics, nuts and bolts, etc., its structure is about 51% 3D-printed parts. This works out to about 98 individual pieces that need to be printed, and represents a huge number of printing hours.
To get started, I used a .zip file full of the 3D STL files for these parts that someone very nicely prepared and uploaded to the MakerBot Operators group. These files were from the 1.0 release of Mendel, so some of them ended up being out of date, and a few had issues that made them unprintable. Thankfully, another kind MakerBot operator uploaded a fully prepared set to Thingiverse, so I could go there for a replacement whenever I found a part that wouldn’t print.
Here, column N47 contains the "completeness" of the Mendel as a value of 0.0 - 1.0 in terms of number of hours printed so far divided by the expected number of hours total. This data could be used on an HTML page with an "update_mendel_progress" function by loading it with a script tag:
At any rate, after a lot of tweaking, many hair-raising moments, a required upgrade with the MakerBot Heated Build Platform v2.0, and hours and hours of printing, the parts were finally complete! I gave them to Matt Mets, a member of HackPittsburgh, and you can see the photos he took of the parts, above!
Despite some of the parts belonging to a slightly out-of-date design, Matt has been making progress on getting everything together!
CHDK’s remote USB trigger functionality works by detecting when it receives power over USB. This happens when two wires inside the USB mini-B cable are connected to power: the red wire gets 5 volts, and the black wire gets connected to ground.
Luckily, the extruder controller docs show two free digital pins, conveniently broken out with 5V and ground connections next to them. These are digital pins D9 and D10. According to the docs, they are intended for hooking up servo motors, but they would absolutely work for my purposes!
The layout for pins D9 and D10 goes (from left to right): I/O pin, 5V, ground. Since I wanted the data pin itself to provide the 5V, I chose to make a cable using a 3-pin piece of female header, soldering the red wire connecting to the I/O pin (on the left) and the black wire connecting to the ground pin (on the right). The center pin has no connection. You can see my “super fancy” cable on the left.
I know this post isn’t particularly about code, so stay tuned for the next parts of this series:
One problem with making time-lapse videos of MakerBot prints is the fact that the MakerBot works by moving the build platform (and therefore the object being built) around in the XY plane, resulting in an unwatchable blur.
It recently occurred to me that, since the MakerBot is such a hackable platform, I could probably make nice time-lapse videos by taking a picture of each layer. The idea is to have the MakerBot pose the object after each layer, and trigger a camera to take a snapshot.
Once CHDK was loaded and configured, I followed the USB Remote Cable instructions from the CHDK wiki. The basic idea is to set Enable Remote to on, and load a script that is ready to handle USB remote events. The one on the wiki page didn’t work as-is for me, presumably because my camera has half-shoot (i.e. focus and charge flash) and full-shoot (take picture) settings. Here is the result that worked for me:
As the script says, I now turn the camera on in record mode, disable the flash, and start the script. After that, the camera will automatically take a photo whenever I plug in the USB to my computer.
More from this series:
Part 1: Remote control camera with CHDK [YOU ARE HERE]