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Star plates vs. gang pumps for smaller stars, pressure used for plates


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#1 mabuse00

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Posted 13 September 2020 - 07:43 AM

One question in advance, concerning starplates:

That might depend on the composition/binder and wetness ect. , but just to have some numbers for calculations:

 

What is in your opinion the pressure range for proper, hardbreak resistant pressed stars?

I found numbers between 1500 and 2xxx psi on the composition.

 

Woodysrocks offers some nice starplates, stating the small and medium ones are suited for 1 and 2tons respectively, by rough calculation that would mean some 1000psi on the comp.

 

Do you have an opinion on that?

In this case I have some 8-12mm stars in mind. The ones I used to make using syringes, causing blisters on my hands and lots of cursing... ;)

 

 

Second question:

In general, what do you think of gang pumps?

Your're likely never get the same pressure on your stars, and using other means than the force of ones hand I expect them to be damaged rather easily (true? Just my thoughts...).

 

 

Third question:

I had some nice applications for microstars in my mind - that means crackling, but also colours.

Something like 3mm would be my choice. Cutting with a screen is not my way, I just dont like it.

So - the solution should be either a gang pump or a special star plate...

Rather on the large side with dragon eggs, but using some kind of spacer system to limit their length to small disks/pellets.

Using a non NC composition.

 

This is just some brainstorming activity right know, what are your thoughts on that?


Edited by mabuse00, 13 September 2020 - 07:45 AM.


#2 WSM

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Posted 13 September 2020 - 09:37 AM

One question in advance, concerning starplates:

That might depend on the composition/binder and wetness ect. , but just to have some numbers for calculations:

What is in your opinion the pressure range for proper, hardbreak resistant pressed stars?

I found numbers between 1500 and 2xxx psi on the composition.

Woodysrocks offers some nice starplates, stating the small and medium ones are suited for 1 and 2tons respectively, by rough calculation that would mean some 1000psi on the comp.

Do you have an opinion on that?

In this case I have some 8-12mm stars in mind. The ones I used to make using syringes, causing blisters on my hands and lots of cursing... ;)

Second question:

In general, what do you think of gang pumps?

Your're likely never get the same pressure on your stars, and using other means than the force of ones hand I expect them to be damaged rather easily (true? Just my thoughts...).

Third question:

I had some nice applications for microstars in my mind - that means crackling, but also colours.

Something like 3mm would be my choice. Cutting with a screen is not my way, I just dont like it.

So - the solution should be either a gang pump or a special star plate...

Rather on the large side with dragon eggs, but using some kind of spacer system to limit their length to small disks/pellets.

Using a non NC composition.

This is just some brainstorming activity right know, what are your thoughts on that?

 

I'l share my opinions on those items I have experience in/with.

 

As for star pumps, water bound stars are easier to clean the tools up after use. I won't bore you with the nightmare of trying to un-stick a close fitting star pump after solvent bound star composition dried in it (gluing it very tightly together  :o  :(  :angry:). I'm sure the same problem with a star plate would be exponentially worse (and oh so expensive)!

 

I haven't used star plates with a press yet, so I can't comment there.

 

Gang pumps are great for small batches of stars where the tedium of single star pumping is wearing on your nerves and hands, AND you don't need industrial quantities of stars. IF your stars tend to crumble, consider a harder binding system (something that binds and dries harder, preferably water based if you're pumping them). I've heard glowing reports from hobbyists using star-pol. Possibly mixing various water based binders can give the high binding strength you're looking for; obviously plenty of experimentation may be called for.

 

Some pyrotechnists have used phenolic resin with denatured alcohol to achieve very hard binding. The scheme involving heat curing (with a small percentage of hexamine added to the resin) might work very well as long as you clean your tools immediately after pressing and before curing the stars or comets (and avoid taking long breaks during the process). 

 

Lastly, I've had success rolling small (~3mm) strobe cores for color changing stars, on small seed or shot. Though rolling stars can be very tedious (until they're 1/4" and larger), the uniformity of sizes achieved once your skills are honed make the process VERY effective. Ten zillion workers in the Orient can't be wrong... :blink:  :rolleyes:

 

Good luck and keep plugging along  :D.

 

WSM B)


Edited by WSM, 13 September 2020 - 09:43 AM.


#3 Carbon796

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Posted 13 September 2020 - 04:49 PM

I pretty much only use star plates and pumps.Binders; SGRS the majority of the time. For Colors, cut/pumped.Then dex, usually for more traditional charcoal based comets for cylinder shells. And sometimes Phenolic, also for pumped colors.

Acrossed the board I use 500psi on the comp. From 1/4" stars to 4" comets. And I'll hand ram up to 1-1/4". Don't have any star strength problems.

Micro stars can probably be made similar to polverone or forte nitro. As long as perfect sizing isnt necessary. But, close/similar sizing is good enough. Just adjust your screen sizing to match your needs.

#4 BetICouldMake1

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Posted 14 September 2020 - 08:19 AM

When making stars there's generally an inverse relationship between pressure and moisture. I think anything above 1500 psi is excessive for pumping stars. I usually pump stars at 1000-1500psi on the comp, but I've gone lower with extra moisture. I've pumped 3/4 stars using just body weight with around 12% water. In my press I would only use 5-6% water. I have used Woody's medium size star plates in a 1 ton arbor press with something like 10-12% water and it worked well. Really you just need enough pressure to consolidate the star so it holds together when ejected, the binder does most of the work in terms of hardness and durability once dry.  

 

I prefer dextrin to sgrs for pumping most compositions. It's a bit easier to clean up and it seems pump more cleanly; less sticking to the pins/plate. 

 

Gang pumps are nice but can be tiring to use and, in my experience, are harder to clean, more particular about getting the moisture content just right, and will produce less consistently sized stars. If you're bulk filling it's fine, but if you're planning to stack them in a shell it can be an issue since the ends sometimes round off and the heights are not identical as they are using a star plate. 

 

For making micro stars I'd say your best bet is either rolling or cutting. If you don't want to screen cut for whatever reason you could just roll out a patty and cut them with a knife as you normally would. Filling the holes in a 3mm star plate would not be fun. 



#5 mabuse00

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Posted 14 September 2020 - 08:53 AM

Thank you for your opinions :)

 

Well, indeed I also plan to use alcoholic binders, I did so with star pumps and had more or less trouble, depending on the composition...

I never got stars in really hard quality with hand pressure and dextrine - but using PVB my stars could qualify as amour piercing bullets.

 

I must add that in most cases I'm doing mineature kidsplay size stuff.

No working by the bucket here. But I like consistency, and perfection.

 

A small starplate seems to fit my needs. At least for the medium size.

 

 

Filling the holes in a 3mm star plate would not be fun

Your probably right. Somehow I still like it better...

 

 

 

 

What do you think of POM parts, like those from woodysrocks?

The idea of having one part taking the bulk of wear, beeing replacable is interesting to me.


Edited by mabuse00, 14 September 2020 - 08:55 AM.


#6 Bensmith

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Posted 14 September 2020 - 09:08 AM

It's been previously mentioned, but with less pressure, more moisture is needed. More pressure and less moisture is needed. I like 2,000psi on the comp and around 5% moisture with either SGRS or Dextrin. But, you can easily use small star plates with 10-15% moisture and a small 1 ton arbor press. Checkout the setup available from cannonfuse.com (I know the guy that makes 'em... ha ha). 1/4", 3/8" & 1/2" plates designed to work with a 1 ton arbor press. Grab the accessory package that contains the fill plate, pressing plate and extraction plate. You'll be good to go. 






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