Star sizing screens

[AdmiralDonSnider]

Excellent shells need excellent star uniformity. Excellent star uniformity requires the use of sizing screens, available at least in 0.5mm intervals, preferably in even more narrow ones.

 

Now where do you get those sizing screens?

 

Before someone recommends drilling one´s own, I must say that I´ve tried that with both stainless steel and aluminum. It´s a nightmare especially with small openings. The sheets deform, the holes have to be deburred, often shavings narrow the openings and spoil

size uniformity, not to forget the time required to make them... Well, they´re not the way to go, at least for me.

 

Now, where does one get these (laser or machine cut) for a reasonable prize (not the ridiculous one e.g. Wolter charges).

 

I´m currently using all kinds of perforated stuff, most intended to have no connection to pyro. But it´s hard to find the sizes you want...

 

 

[Ventsi]

Admiral, you might want to take a look at online metal shops in your area, or metal shops in general, they have what you are looking for at a price more than 10x less than Wolter.

 

Example: http://www.onlinemetals.com/merchant.cfm?id=1003&step=2&showunits=inches&sortby=od&top_cat=60

[Karlos]

Homemade separators: Made by hand drylling(drilling machine) in to aluminum plate.

http://img51.imageshack.us/img51/6259/sitat.jpg

http://pyrobin.com/files/sito.jpg

Work for maniacs.

[bbd4193]

Wolter Pyro tools has sizing screens http://www.wolterpyrotools.com/?page=cc_catg&cat=sieves

[apcqazwsx]

Now, where does one get these (laser or machine cut) for a reasonable prize (not the ridiculous one e.g. Wolter charges).

[mike_au]

Excellent star uniformity requires the use of sizing screens, available at least in 0.5mm intervals, preferably in even more narrow ones.

 

I've always liked the look of the sizing machines (Haven't gotten around to making on yet though). Two pieces of not quite parallel rod, one of them spinning. You feed your stars on at the end where the rods are closest together and they roll down until the gap between the rods is big enough for them to fall through. Your granularity depends on the angle of the rods and how many containers you use to catch the stars.

 

Is there any reason that screens are a better way to go?

[KruseMissile]

I've always liked the look of the sizing machines (Haven't gotten around to making on yet though). Two pieces of not quite parallel rod, one of them spinning. You feed your stars on at the end where the rods are closest together and they roll down until the gap between the rods is big enough for them to fall through. Your granularity depends on the angle of the rods and how many containers you use to catch the stars.

 

Is there any reason that screens are a better way to go?

 

 

The only problem with that is that its hard to get precision uniformity(you would literally need containers the size of the stars wanted all the way down the line) and you need to feed them in one by one. To me, its better to make your own(you only need a 12"x12") or buy them.

Brian

[Arthur]

I like the idea of two rods with tapering spacing. I'm also interested in fitting a star roller with one or two pick out rods. A stainless steel rod running helically into the drum again with the spacing tapered to pick out large stars and let smaller stars drop back.

 

The only way to make super precision stars is to weigh out the powder individually and press them in a power press. Trouble is that the press costs thousands and the tool for each size costs hundreds.

 

From finished and dried rolled stars what about hand weighing them and putting them into grades by weight range.

 

Search ebay for "Tablet Press" prices vary from £1000 to £50K but their only known use outside the licensed Pharmaceutical industry is illegal narcs.

[mike_au]

The only problem with that is that its hard to get precision uniformity(you would literally need containers the size of the stars wanted all the way down the line)

I don't understand what you mean, if you want 1mm precision and you want to use ice cream containers to catch the stars, then you align your rollers so that over about 15cm they diverge by 1mm. If you only want stars that are between 17.9mm and 18.2mm diameter then you arrange the rollers so at one side of the container they are 17.9mm apart and at the other side they are 18.2mm. On either side of the container you put some angle iron or a piece of pvc cut in half that runs the whole length of the rollers and catches any rejects.

 

you need to feed them in one by one.

I'm sure that with a little bit of messing about you could make a vibrating hopper or something that would feed them fairly reliably.

[AdmiralDonSnider]

Thanks mates for the suggestions.

 

Karlos, the Admiral has always admired your sizing screens as seen on Pyrobin :-). Large screens may be somewhat easier to realize, but the 2,5mm one I tried lately was just Uhmm.

 

I did some more research about star sizing and must admit that I misconcepted the technique assuming that people use screens with very close intervals to size stars as they size powders.

 

Instead the rolling workers choose one screen at the desired final diameter and bring up all the stars of the batch to a size where they are held in the openings (not sitting on them). The key in this process is repeated screening, followed by careful growing of what passed the mesh. This method doesn´t require close interval screens, just a few at the desired sizes.

[Mumbles]

For very small holes, like 2.5mm, wouldn't it be easier to just use mesh screen? I know some people who use mesh screen for sizing all stars up to about 12mm. Welded wire mesh is pretty consistent and wont budge like woven mesh. Even woven cloth is fine if you're just sifting, though not quite as accurate.

[AdmiralDonSnider]

Yes, mesh screen has been recommended to me. Unfortunately there aren´t too much sizes available if you look for coarse ones; pyro supplies carry screens but usually something like 4 and 10 mesh, with nothing in between. It´s hard to get a good narrow set.

 

I too found that woven mesh tends to deform and slip.

[Mumbles]

You know, I'm not even sure if the ones I saw for screening were woven now that I think about it. They have welded wire cloth with the over-under woven look. Most pyro suppliers carry screens primarily for screening and sifting chemicals. I don't know how common using them to size stars is, but it works.

 

Another thing to think about would be drilling holes in plastic containers. I've seen that done too. It's a little easier to clean up any extra burrs and drill through.

[dagabu]

You know, I'm not even sure if the ones I saw for screening were woven now that I think about it. They have welded wire cloth with the over-under woven look. Most pyro suppliers carry screens primarily for screening and sifting chemicals. I don't know how common using them to size stars is, but it works.

 

Another thing to think about would be drilling holes in plastic containers. I've seen that done too. It's a little easier to clean up any extra burrs and drill through.

 

Harbor freight has step drills for a great price, they will work well for drilling your own and the next step works to deburr the hole. They also have stepless bits.

[FrankRizzo]

Harbor freight has step drills for a great price, they will work well for drilling your own and the next step works to deburr the hole. They also have stepless bits.

 

That's what I used as well. I had a bunch of bucket bottoms that I'd removed the top portions from to make bucket screens. I put a small piece of wood in the notch of the step drill to use as a stop at the correct diameter I wanted, then drilled half of each bucket bottom in a Swiss cheese pattern for a few common sizes of stars. Any over sized holes (there were a few as I messed with the depth stop) were masked off with tape, and filled with hot glue.

[mumpyro]

Hey guys, I'm new here, I normally hang out on passfire but I have star sizing screens if anyone is looking for them. They are MUCH cheaper than the ones offered by Wolter. They are made from standard 5 gallon buckets using the bottom 3.5". The screens are all cut out on a CNC machine in 21 different sizes from 3/32" up to 1 1/8". I recognize a few members here that have purchased them and up until now I have only been advertising them on passfire so as to not get swamped with requests. We are coming up on our busy season for building pyro and wanted to get as many screens out of before then as possible. MM sizes are currently not available, sorry. The holes are cut to a tolerance of .01 or less for the micro to medium sizes and a tolerance of .02 or less on the larger sizes. The buckets are .1" thick on the bottom so will hold up very well.

I have a lot of sizes in stock, but depending on order backups, it could take up to two weeks to get orders processed and shipped. I am running a discount on them in single and kit versions for another two weeks, once the sale is over, the prices of screens will be going up until after the 4th of July and may not be available until the PGI convention in Fargo. Whatever buckets and kits are in listed in stock when you add them to the cart is what I will have available for sale.

http://www.mumpyro.com/tools/screenset.jpg

 

If you are interested, check them out at http://www.mumpyro.com/tools I have been selling these since October of 2010 and have sold over 500 of them with no complaints so far.

Edited March 11, 2011 by mumpyro

[dagabu]

I can attest to Mumpyro's craftsmanship, you will be surprised at the quality and precise detail. I believe that these screens are an essential part of the serious pyros tool set. They also stack making sorting a breeze!

[Algenco]

Great to see you here!!

 

I have the basic set and they are great, quality workmanship