3D Printed Servo Valve

2016-07-06 09.47.14
Servo Valve

As I progress on my own rocket projects, I thought I would let everyone know what I have been up to lately. Juggling study and life can make things a bit slow but things are coming together for my test stand.

As part of this stand, I wanted some servo actuated valves for the pressurant and or vents etc. I was inspired by Rocket Moonlighting and his 3D printed valve holders so set about making my own.

I purchased servos and valves from  Aliexpress, of which are linked to below,
Servo – MG995, 15kg/cm torque at 6v
Valve – 1/4″ BSP SS Ball Valve

CAD Valve

I then drew the holder up in CAD and had it printed, I was lucky enough to find a model of the MG995 servo over at GrabCad which had the spline detail I needed in order to draw the connector from the servo to the valve.
As can be seen in the pictures below the whole thing is printed in 3 parts and held together with 6, 3mm bolts, keeping everything in place and rigid.

2016-07-06 09.47.25 2016-07-06 09.47.14

This particular valve had a grub screw holding the handle on so in the connector I had made, I made provisions for a 4mm grub screw to attach from either side for extra rigidity (you will need to tap this yourself). I was originally worried how a plastic shaft will hold up, so far it seems to be ok, although in the future I may print this part in metal, being so small it should not cost too much.

The video below shows the valve in action.

I was originally going to use these as vent valves for my rocket engine test stand but am undecided at the moment. Ideally, you want a normally open valve for this, so if there was to be an accident and power was lost, the valve would open and remain so venting the tanks.
I am also unsure of the valve seal material, I will have to pull apart one of the valves and check this, never the less they will still be put to use. I have a higher torque servo and larger valve that will be on the high-pressure side for the pressurization system, this will allow remote operation of the nitrogen/helium pressurant tank, the design will be the same as the above but slightly bigger to accommodate the valve.

My other idea is to use it on a flowmeter project, where I can accurately measure the elements of the rocket engine injector, this will be covered in another write up soon!

Injector flow testing apparatus.
Injector flow testing apparatus.

I have made the files and code available on Github, of which you can find them here.
Feel free to critique my design and especially my code (still learning), print your own and let me know how it turns out!.


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