Geared Peristaltic Quick-Fit Pump Extruder experiments

Even before my universal paste extruder, I have had it on my list to re-investigate the peristaltic pump at some point.

This was one of the last things I started for my 30 days of creation back in June #30DOC.

Many peristaltic pumps are already on Thingiverse, but none of them really jumped out at me, so I decided to design a geared version of the peristaltic pump for use on my Quick-fit X carriage.


My main aim for this project is to be able to pump and therefore extrude and print with cements, plasters, clays and super saturated sugar solutions, but small steps, first I need to get it working.

I was very aware that the tube is a really critical factor in any peristaltic pump, it can make or break a perfectly good design.

I had seen some designs that used quite inflexible plastic tubes and Motor's directly driving the pump mechanism, all leading to low performance and high torque requirements, that looked like a bad idea to me, so I decided from the outset to use Silicone tube and a herringbone gear set along with 4 bearings in an attempt to reduce pulsing of the pumped material to a very minimum.

My first prototype used a 6mm silicon tube with 4mm internal dimension, it was not as soft as I wanted, but was all that was available from my local aquarium shop.

The design went well but had one major flaw, it was almost impossible to assemble! I could not get the set of bearings in place while the tube was already inserted, and feeding in the tube afterwards was very tricky. 

Around this time I managed to get hold of some other silicone tubes from a model shop, these are normally used as fuel connections in RC models and aircraft.


The pink one was exactly what I was looking for, was soft, but with quite a think wall.

I revised the design dimensions to accommodate the new pink tube and split the top to make assembly possible - this has a lever on top so you can feed in the tube after the bearings are in place, then screw it together.

The second prototype assembled easily and to my surprise actually worked quite well.


It had one flaw, the lever wants to spring out, so the horizontal screw on the left hand side allows the tube to bulge out, it needs vertical pressure on the left hand side, the same as I did on the right.

Problem area for the V2 design.

In the video I'm holding the left hand side down, every now and again it pushes up releasing pressure on the tube, so the pump stops working. That's easily fixed in the next revision V3 below - 

Now you can assemble the pump easily and insert the tube when the gear and bearings are all fitted, then screw down the top clamp.

The tube is retained and fixed in place with this clamp, it uses a 4mm outer (2mm inner) PTFE tube as the nozzle.

Next steps are to attach a motor and work out the esteps then try to print something with some different materials!

I decided to release it now in the early development stages as I have a lot of things going on at the moment and may not be able to do much more on this until after the summer.

And as I type this, I'm exactly at this point with the development, so if you want to join me and maybe even beat me to getting it all working, head over to Thingiverse for the files to print one out and let me know how you get on!
And just to remind you it 's another thing designed to fit on my Quick-fit X-carriage.

Still lots of things yet to resolve with different materials and also if they are going to need to be under pressure to work at the viscosity you need to print out something?

Exciting? I think so, I have visions of a cement printer.... and maybe an unlimited supply of garden gnomes :)

Thanks for reading.

Rich.

P.S. - I also just started up a dedicated website for richrap.com - still early days but it'll grow over time, let me know what you would like to see on it! And I'm not going to stop blogging on here, just do more and more hopefully.