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3D Printed Peristaltic Pump

November 18, 2015
3D Printed Peristaltic Pump

Frank built a 3D Printed Peristaltic Pump designed to pump thick liquids at an easily controllable rate. It’s purpose is to pump blended food into a person’s feeding tube when they cannot physically eat.  His project came about when he went to visit his grandfather in China when his grandfather started radiotherapy to treat his esophagus cancer.

The first phase of the design was done on my aunt’s tablet using Onshape (a cloud based equivalent to SolidWorks) on China’s 4G cell network while in the hospital. When I went back to the USA I continued to work more in CAD since I had a printer to do trial and error. The 3D printing took three days, while the rest of the time was design, mechanical assembly, and circuitry.

Feeding my grandfather was challenging. We were squeezing blended food through ordinary syringes. Not only that, but the feeding rate had to be slow to keep my grandfather comfortable, not to mention it took a lot of strength to push the syringe. I wanted to make this easier for everybody. My grandmother does not have the strength to push the thick liquid through the syringe. So hence I decided to build a pump for them.

Frank Z 1

Frank Z 4

The design is relatively inexpensive compared to dedicated automated pumps. We had tried “turkey baster” style pumps, but found them limiting and inefficient. My grandfather was a doctor and a medic in the army. He didn’t want to take the nutrient IVs that are typically used. Instead, he wanted to keep his diet natural, and perhaps, keep his life as normal as possible- eating what the family ate, only blended.

The print is extra thick for durability, it is also printed at 100% infill. This presented thermodynamic challenges to be solved. The biggest challenge here is caused by the fact that the plastic is printed hot and then cools during the print. This means there’s some shrinkage, which causes bed adhesion problems (corners lifting during print, my new solution) and dimensional inaccuracies. The print also takes a long time. It took over 24 hours to print just one of the pieces.

3D printed Piece


I originally planned on sending off designs to my local 3D hubs, to start the printing earlier, but two hubs refused the job and one hub tried and it failed to print completely. If you look at some other peristaltic pump designs, half of them have no outer wall that the tube squeezes against. In contrast, this design has a very thick wall allowing the pump to pump thick liquids. The wall and rollers can squeeze together to ensure that the liquid does not flow backwards.

The motor is a gigantic motor with a gearbox that slows it down ridiculously, which also means it has a ridiculous amount of torque. I calculated about 25 pounds of torque at the radius of my rollers. I also designed and soldered a circuit to control this motor, which also involved writing firmware so that the speed and intervals of the motor can be controlled easily. Side note: scientific or medical peristaltic pumps typically use stepper motors instead, because it is possible to control the flow down to millilitre accuracy. My pump is much cheaper and doesn’t need such accuracy, because my grandfather really only needs to “clear his plate”.

Gearmotor attachment

There are six bearings – two bearings per roller. They are flanged, sealed and stainless steel. Their job is to squeeze the liquid through the tubing in the peristaltic pump. These bearings are supported by stainless steel binding posts. Using bearings, provides the pump with extra durability.  I’ve seen plenty of designs with just 3D printed rollers, I didn’t feel those would be durable enough.

Mechanical Parts:

  • DC brushed motor, with precision spur gear gearbox, 6V-12V operating voltage, 6mm D shaft, part 638222 on ServoCity or item number 1107 on Pololu
  • Actobotics brand 0.770″ set screw hub for 6mm shafts, part 545576 on Servo City
  • very flexible very soft tubing, 5mm OD, 3mm ID, FDA approved
  • barbed couplings for the tubing mentioned above, these hold the tube in place, FDA approved, 1/8 inch diameter is acceptable as well
  • 6x steel ball bearing, double shielded, 1/4 inch ID, 1/2 inch OD, used as the rollers
  • binding post, 1/4″ barrel diameter, #10 screw, 5/8 to 3/4 inch length, used as axles for the bearings
  • 4x #6-32 machine screw 1 inch long, holds the rotor to the hub
  • 6x M3 machine screw 0.5mm pitch 12mm long, holds the motor to the pump housing
  • 4x M4 nylon locking nut, to hold the pump housing together
  • 4x M4 machine screw 50mm long, to hold the pump housing together
  • 1x M4 screw with hex head cap 20mm long fully threaded, optional, used as an axle on the rotor, if you wanted to add a dust shield with another bearing
  • 1x M4 nylon locking nut, optional, to hold hex head cap screw mentioned above
  • 1x steel ball bearing, double shielded, flanged, with extended inner ring, 5/32 inch ID, 5/16 inch OD, optional, if you wanted to add a dust shield with another bearing
  • 1/8 inch thick clear polycarbonate sheet, optional, cut and drill into a dust shield
  • optionally use Loctite on the screws without nylon locking nuts

The Control Circuit:

I made the circuit “doing it live”, as in, it was not pre-planned, except I purchased a H-bridge motor drive from Pololu (a MAX14870 carrier board), and dug out a navigation switch (with forward, reverse, center click) to use as the user interface. The MCU is a ATmega328P because who doesn’t have a couple of these? Power supply is an ordinary 12V wall-wart capable of 3A. LM1117-5 is used as the 5V voltage regulator to bring the 12V down to 5V to power the MCU. Everything is soldered onto a small perfboard. All passive components are 0805 SMD sized. Wiring is done using 30 gauge kynar coated wire. Finally, it is wrapped in super wide clear heat-shrink tubing, along with a piece of paper (with instructions printed on). With my skills and experience, I can design, solder, and program a simple project like this in a day.

Once finished with the design he shipped the project off to his family back in China exactly two weeks after he arrived back to the USA.  (Talk about persistence and determination!)  Thanks to Frank Zhao for sharing his project with us!  For more information about his design please visit his blog.

The Control Circuit:

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