Introduction: Learning Progressive Cavity Pump the 3d Printing Way

About: My name is Luis, I am from Barcelona and for the last years I've developed a curious obsession merging food and rapid prototyping. To have a unique and customized eating experience.

On my quest to print more types of food, I wanted to learn as many as possible different extruding mechanisms. At the same time, being a newbie at Pier9 I will be using this instructable as a soft start to use the 3d printers we have here (connex 500).

The goal is to print and test two different designs of progressive cavity pumps and hopefully get to learn some along the way.

Step 1: 3d Printing First Test

First tested pump is designed by emmett and is available on thingiverse. Printing with the Objet Connex 500, was easier than I could expect. Specially following the pier 9 basic user manual. First it felt weird not having control about the slicing process, the same way you do with FDM-RepRap printers (Slic3r, Cura, ...). But could not be happier with the result.

Cleaning the support is tedious but fun. I love the splashing machine.

Step 2: Testing Manual Pump

To test the first printed pump, I wanted to use three materials with different viscosity:

  • Water
  • Mashed potato puree
  • Peanut butter

Water was pumped properly (watch video). Cranking the pump push the water upwards.

Mashed potato puree it worked too. Although I encountered the first issue with this pump. It is a manual pump that pumps upwards. This means that the material being pushed need to be feed into the inlet of the pump (bottom). Water has no issue because it flows easily and refill the cavities. But mashed potato purée does not. Meaning that is hard to get a continuous flow without feeding the pump with more material. Also with purée things got messier. That is why we did not even try peanut butter. Knowing for sure it was going to be hard to clean.

Step 3: Second Printing Test

For our second and last printed pump I chose the Moineau stepper extruder by ttsalo. This is based in the previous pump but includes a stepper motor shaft connector to control the pump. This will allow us to test this pump in a closer 3d printing environment.

Assembling the extruder is easy. Maybe the only tricky park is to insert the motor coupler to the motor shaft through the pump cavity.

Step 4: Testing Moineau Stepper Motor Extruder

To test the extruder I connected the stepper motor to an Smothieboard that I had around. I little bit of an overkill but it worked.

First thing I tried was water. During the assembly process I already realized the stator was not as tight as the previous pump. So the results were not a surprise. In the video above you can see how the water could flow/leak without turning on the pump.

Afterwards I tested mashed purée. The consistency was similar to the previous test (thick). It was already hard to fill the pump because the purée did not flow, that is why I used the syringe in the picture to load it. As you can see in the second video the purée does not gets into the pump unless we apply pressure with the syringe. And since the pump is not sealed, it leaked around the syringe tip and through the motor shaft hole. A total mess to clean.

My guess is that this is the reason why the great people at Unfoldremix the design with luer lock connectors.

Willing to test the stepper motor extruder, we thin out the purée with tons of water until we got a thin melted-chocolate-like consistency. The third video shows the pump working. This time I was pouring the mix with a Pyrex measuring cup, no need for the pressure from the syringe. It worked, but it was a mess.

Step 5: Conclusions

This was my kicking off project during my AiR time at Pier 9. It has been great to learn how to use the printers and gain some experience with progressive cavity pumps.

Objet500 Connex printers are easy to use and have a great resolution, more than enough for the type of prints I do. Completely different from any other printer I used before, you do not need to worry about any slicing parameter, everything is set. Embedded support it is not hard, but boring, to clean. The power blasters add a layer of fun to it.

My only complain about it, is that as much as I love the precision and the quality of the prints, there is no food safe resin available. Meaning that any part that I print CAN NOT be in contact with food to be eaten. But that is not just a Objet issue, most of the printers share same drawback.

On the progressive cavity or moineau pump page, I just like it. Its a nice design that I want to experiment more with. I think the most challenging part relays on building the pump properly. Materials selection, accurate dimensions or getting a good seal between the stator and the rotor of the pump are some of the issues to overcome. Also special care needs to be taken to choose the right method to feed the mixtures into the pump. The technique used will also be highly depending on the consistency of the mixture. And if needed, provide a pressurized pump inlet (sealing the transmission from the motor to the stator too).

Overall a great a starting project here at Pier 9.