Team:Rotterdam HR/Hardware Peristaltic Pump
Peristaltic Pump
Hardware: Peristaltic Pump
The idea
To accurately pump the produced gas out of the system, we needed a peristaltic pump. We decided to design and 3d print it ourselves. How hard could it be? Apparently, quite difficult. Read on to see how we did it.
What is a peristaltic pump?
A peristaltic pump is a pump that 
can pump a gas or fluid, without being in direct contact with it. Is moves
this fluid or gas with a peristaltic motion. This motion is achieved by closing a part of the hose with a ball
bearing, and moving this ball bearing in a circular motion in the direction of the desired flow direction. A
peristaltic pump needs at least two ball bearings on opposite end to guarantee an even flow rate. When the ball
bearing moves it shifts the closed part of the hose toward the desired flow direction and thereby creating a
vacuum behind it. This vacuum will displace the gas or fluid and make it flow.
Version 1
We decided on using a stepper motor, because they 
are very accurate. This would allow us to accurately pump a
specific volume of gas out of the system. But we figured a stepper motor alone wouldn’t be able to produce enough
force to make the pump. So, we first designed a planetary reduction drive to reduce the speed by four times,
thereby increasing the force by four time. Next, we searched for a suitable silicone hose to use in our pump. We
eventually found a relatively cheap hose with a outer diameter (OD) of 4 mm and an inner diameter (ID) of 2 mm.
Using these specifications, we started designing the pump.
Version 2
Because of some ordering problems, we were not able to get the hose we specified earlier. We also found out that the study of Biology and Medical Lab research has been stockpiling these kinds of hoses for years (thanks for not telling us sooner), so we used one of their hoses. This one had an OD of 5 mm, and an ID of 1 mm. This meant we needed to completely redesign the pump.
Version 3
Now that we redesigned the pump to fit the hose, 
things should work, right? No, because the motor, even with the
gearbox, wasn’t strong enough. So for this version, we designed a second gearbox that fits on top of the first,
and reduces the speed by another four times. These two gearboxes work together to create 16 times the amount of
force the motor produces.
Version 4
Now that the hose fits, 
and the motor is powerful enough, it just has to work now doesn’t it? Wrong again, this
time it pulled the hose through the pump. But, it did work occasionally. So for this version, we redesigned the
pump so the cavity in which the hose is placed is shaped exactly like the hose. This should restrain its
movement.
but still couldn’t hold the hose reliably. To fix this, we
designed a separate clamp that keeps the hose from moving.