Propellant Extrusion

[Larry W]

Has anyone had any success trying to form grains via extrusion on a small scale? Say with a kitchen aid sausage stuffer with a die etc. I am interested especially for the smaller grains 29, 38 that are harder to work with individually.

[MClark]

I was involved with make literally tons of propellant on a Werner Pfleiderer ZSK-58E compounder/extruder. More on topic we made R&D grains from double base grains on a small 2" bore ram extruder.
The issue with the process is with the binders we normally use the mix must be VERY thick so it will not slump while curing. We did a lot of PVC binder mixes and they come out of the machine cured and rigid.
Grains would need to be inhibited on OD unless a ID/OD burn is desired. It could be used to extrude into tubes.

The WP extruder we used is "dismantled" and is not longer in operation.

Mark

[bobkrech]

The uncured propellant is not usually viscous enough to maintain a shape and curing times range from hours to days. None of the manufacturers use extrusion in their propellant processing, so IMO extrusion is not appropriate for the hobby rocket motor grain product, and a sausage extruder would not be appropriate in any case.

This a research topic not suitable for the open forum, so please register for access to the research forum where we can continue the conversation.

Bob

[Larry W]

Thank you mark and bob I will register. I was concidering using it to fill say a24-48 inch casting tube with core and inhibitor. Then possibly maintaining the coring rod in tension while subjecting the grain length under slight pressure with end caps while curing.

[tbonerocketeer]

None of the manufacturers use extrusion in their propellant processing

Bob

Pretty sure Loki does.

[Buckeyegator]

I know for sure that Gorilla does.

Terry

[ClayD]

Having made an extruder, and mixed a few pounds of propellant, I dont think I would combine the two...

Larry, i would suggest something like this... it would also vacuum process your grains so that you dont have bubbles induced by the screw/ram - die process....( yealds a higher density-- which increases isp... I THINK)

http://www.rimworld.com/nassarocketr...ast/index.html

[JDcluster]

I hear AT does. The thing is: you have to get your propellant down to the consistency of toothpaste in order for it work.



JD

[butalane]

Pretty sure Loki does.

They didn't when Jeff owned it, they weren't even vaccum casting.

I hear AT does. The thing is: you have to get your propellant down to the consistency of toothpaste in order for it work.



JD

I think you guys are confusing vacuum casting through a slit plate and extrusion.

http://en.wikipedia.org/wiki/Extrusion

Vacuum casting via a slit plate/casting bell is pretty common in the industry on all scales. Slit sizing can be difficult and poses a number of problems. Clay's link explains it pretty well.

[Buckeyegator]

Butalane:

I think you may have the proper definition and process.

Terry

[ClayD]

instead of a hopper, i would probably use some 4" or 6" PVC pipe, the machine a cylinder to "squeegy" the propellant down....

I think this would talk me into casting directly into my cases with a liner installed... since the end you would be doing this, to the casting tube, would be fairly similar distances for the same diameters of cases..


i wonder how you keep the propellant from being pulled between the cylinder wall and the casting tube???

I really wish there was some more in depth resources out there on what has been done, and how to do it on a hobby level...

[tbonerocketeer]

They didn't when Jeff owned it, they weren't even vaccum casting.

It was in the assets when I looked into buying it. They vacuum mix though.

[butalane]

instead of a hopper, i would probably use some 4" or 6" PVC pipe, the machine a cylinder to "squeegy" the propellant down....

I think this would talk me into casting directly into my cases with a liner installed... since the end you would be doing this, to the casting tube, would be fairly similar distances for the same diameters of cases..


i wonder how you keep the propellant from being pulled between the cylinder wall and the casting tube???

I really wish there was some more in depth resources out there on what has been done, and how to do it on a hobby level...

Vacuum casting is usually done in a "bell" into which the case is placed. Leaking propellant isnt any more of a consideration that casting at atm as there is no gradient on either side of the case.

Most hobbiests dont vacuum cast because its tedious and not always adaptable to all propellants. Slit plate sizing ishard as well.

Unless youre trying to squeeze the last bit of impulse out of your formula, there wre other ways to increase performance first.