During thermal processing, ABS plastic fumes are not a very good thing to be breathing in. Most ABS plastic MSDS (Material Safety Data Sheet) warn that “Thermal processing fumes may cause irritation to the eyes, skin and respiratory tract and in cases of severe overexposure, nausea and headache”. So, one of the very first things I printed was a fume extractor to send the fumes outside.
Finished print of Suction Adapter
To make this fume extractor, I decided to modify a very old “squirrel cage” type blower fan that I had. So, with the help of my trusty calipers, I created some adapters in Solidworks that would allow 1″ and 3″ diameter hose to connect to the suction and blower ends of the fan.
Suction Adapter
The prints came out pretty nice, but I have improved a lot on the print quality since then. They are rock solid, with a 4mm wall thickness, and the cone is at a 35° taper so support material is not required.
Two Suction Adapters
I printed out two adapters because this blower fan was actually two sided, powered by one motor. The initial idea was one fan would be the fume extractor for my large machine and the other would be the fume extractor for my Fab@Home.
Suction Adapters Mounted on Blower Fan
The AC motor is in the center and the suction adapters attach to the two “squirrel cage” blowers with #4-40 screws. 1″ flexible hose attaches to the smaller end of the suction adapter, sealed with hot glue. This 1″ hose brings fumes from the vicinity of the print head nozzle.
After calibrating the max speeds of the stepper motors, the first test print was an encoder mount that allows the RepRap magnetic rotary encoder board v1.0 to clamp onto the extruder drive motor
Encoder Mount
There are recessed spaces for a #4-40 screw and nut so the part can be clamped around the motor body. With this mount, the board is positioned exactly so the AS5040 chip is directly over the rear drive shaft. A small magnet is then attached to the rear drive shaft. (Note: These pictures display an earlier version of this part without its 4 mounting screw holes in the top for the board. The last picture in this post shows the board mounted into the final version of the part with the 4 screw mounting holes.)
Close up
The first layer is yellow because that was what color was in the heater barrel before I put the natural colored plastic in.
Backside
Mounts onto the Extruder Drive motor
It fits quite securely, and the part has a nice surface finish as well. Now the the tricky part is getting it to work with the extruder board firmware. (The above image shows the encoder board before any components were soldered.)
From my first few prints, I noticed that some vertical walls in the parts were not perfectly planar. The image below is a good example of this. This is the result of the nozzle not returning to the exact same X and Y coordinate on every layer.
Since I had anti-backlash nuts on the ACME screws, lead screw backlash was not the problem. The problem I found was that the X and Y stepper motors were being run too fast and were thus skipping steps. This resulted in the X and Y axes not returning to the same exact position on each layer, hence the above image. After some speed calibration, I resolved this by setting the motors’ max speed at a point where they would not skip any steps. This max speed was set in Skeinforge. Unfortunately with Skeinforge, it sets all axes to this max speed. The Z axis needs to move much slower than the X and Y because it has to lift the entire Z stage. You can set a max speed in the machines.xml file in ReplicatorG, but it does not seem to obey this on its own. A M105 command needs to be inserted at the beginning of every g-code file, which prevents the motors from exceeding the max speed that is set in machines.xml.
3/8"-8 2 Start ACME lead screw
3/8″-12 ACME screw is a little slow, only traveling .083in [2.11mm] per motor revolution. I decided to change the X and Y axes to 3/8-8 2-start ACME screws which provides travel of .25in [6.35] per motor revolution, significantly increasing print speed. Now I run my machine at 20 mm/s in the X and Y axes, and 5 mm/s in the Z axis.
