Direct Drive Pastruder

by BenRockhold, published

Direct Drive Pastruder by BenRockhold Sep 28, 2012
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12069Views 1312Downloads Found in 3D Printer Extruders


This is a super-simple belt driven syringe-based extruder for viscous or non-newtonian fluids such as peanut butter. it uses the MakerBot MK6's 100oz-in stepper motor to provide the necessary force, and applies pressure to the syringe via the mechanical advantage of a belt based reduction. This potentially also increases the resolutuon of the steps/volume, but very little experimentation has been done with fine control of the flow rate.
This model was designed around scraps I happened to have laying around, but it works really well.
This extruder was co-designed with Scott Beibin in July 2012, specially for use in the Groucho Fractal Show - www.grouchofractal.com


Note: You may need to modify the SCAD to tightly fit your syringe.
The SCAD file relies on thing:19758 and on MCAD, https://github.com/elmom/MCAD
You will also need:
One high-torque stepper motor (for example http://www.anaheimautomation.com/products/stepper/stepper-motor-item.php?sID=69&pt=i&tID=75&cID=19 ), or scavenged from a MakerBot MK6 extruder
Four M3x10 bolts for mounting the motor
One 20mL syringe, with a 20mm OD
One M8 ID 26mm OD "skate" bearing
One large 5mm ID 16mm OD GT2 pulley
About 300mm of GT2 Belt (Cut to length as needed)
One 4mm ID 16mm OD bearing
One M4x15 to mount the bearing
Two M1x20 (probably) to mount the clamp
Assembly is easy, the pulley is attached to the motor, the motor is bolted to the main block, the belt is clamped on the right side, and then the idler is bolted to the block. The belt is fed into the pulley/idler and then the syringe and plunger pusher are mounted on top. The belt rests on top, kept under some small tension before use. I never designed a way to mount this to a printer (sorry) so I just zip-tied it down. It was a bit of a rushed job.
All I had to do for printing was tell Slic3r I had a 2mm nozzle and 16mm filament, as this best modeled my syringe. In addition, reversal must be totally disabled, or the pusher will fall off.

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Do you know where I could buy the M8 ID 26mm OD "skate" bearing?

It's pretty likely that I incorrectly measured the bearing diameter, as it looks like 22mm is the standard OD for these.
Here's the first Google Shopping hit for "skate bearing" in individual quantities: http://www.thebigbearingstore.com/servlet/the-1031/608-dsh-2RS-608-dsh-ZZ-Radial-Ball/Detail

The diameter doesn't matter much to the function of the device, except that the belt will end up at an angle instead of vertical, and maybe run against the plunger's body.

Okay that's what I figured but I just wanted to make sure. Thanks!

Were is the file for the pulley on the top of the syringe?

In the OpenSCAD file, it's the plungerpusher() function. I guess I never uploaded it separately as an STL, but it's easy to export.
-- Edit: I've gone and uploaded an STL I found in the directory I was using to develop this, two years ago. Should be whatever I used last, which is hopefully the working version!

You sir, are a gentleman and a scholar, and I take back all the bad things I've said about you. Thanks!