10 replies to this topic

[Karl Mitchell-Shead]

Hi all,

I am now running 3 consecutive mills, one large 5lb mill and two smaller 3lb gemrocks. Media as you know gets expensive and im considering buying a couple of kilo's of cylpebs.

So i am asking in your experiences / opinions what are the pro's / cons, advantages and disadvantages of ceramic and lead media for milling in various aspects of pyrotechnics?

Cheers in advance

Karl

Edited by Chief, 31 January 2010 - 10:56 PM.

[Night Owl]

Hi Karl

I run two mills and first used lead then changed to ceramic, I have quicker milled and faster BP with ceramic,
although my mills could not really take the weight of more than say 12x 20mm balls in one 1.5LB drum, I suspect a stronger mill would be best with lead.

Shell

Edited by shell shooter man, 31 January 2010 - 11:17 PM.

[digger]

I use ceramic media.

I have several different types. I don't use cyplebs as I have never been able to get them in a non sparking form. I used two types of ceramic, a standard 98% alumina which is great for powdering chems but sparks like crazy (just rub em together in a dark room and they light up (piezo luminescence)) and a non sparking variety which is great for larger mills as the density is lower than lead. But don't kid yourself it is still dense stuff, you will need allot. A 15 liter mill jar needs about 15Kg - 17Kg.

I don't know where you are buying it, but expect to pay in the region of £200 for a 25kg sack.

Obviously ceramic is great for powdering chems without contaminating them. Non sparking ceramic is good for BP, but probably best left to bigger mills unless you have a low powered mill. Lead is probably better for BP in the small mills that you are describing (far cheaper too if you buy scrap at 50p - £1 per kg).

[Karl Mitchell-Shead]

I currently use lead but am looking to try new media.

I have purchased 1 kg of 20mm cylpebs from Steve @ inoxia, i assume these are safe to mill BP with?

Piezo and luminescance from crystal energy fascinates me

[Steve]

The ceramic media we sell certainly doesn't spark under any conditions you will find in a ball mill. I have managed to get them to spark, but the speed and force they had to be struck together was quite extreme. If anyone thinks it would be useful, I may be able to set something up to measure the speed of impact required to spark.

I'll quote a bit from Lloyd E. Sponengurgh's book on milling regarding materials:

The material should be as heavy as possible, consistent with a hardness sufficient to do our grinding but not wear too rapidly. Burundum, Zirconia, High-density aluminium, and just plain, white porcelain balls are all heavy enough to grind pyrotechnic chemicals in ball sizes over 3/4" (19mm) in diameter, and jar sizes over 5" (127mm) in diameter. For smaller mills, or smaller balls, lead or steel balls should be used. Many pyros prefer lead balls, because they will not spark; but some fear that lead will wear off into material.

Lloyd's book really is the best if you want to learn a lot about milling.

[Karl Mitchell-Shead]

Excellent thanks Steve, look forward to it arriving in the next day or so

[maxman]

I might be being a bit thick here but when 3lb or 5lb mills are being reffered to what exactly is meant? I mean I thought the size of a jar was in litres? Do you mean the weight your machine is capable of turning constantly? If so how much BP is in a 51b mill? not 51lb I assume this includes media?

I use http://www.inoxia.co...product/72.aspx mill jar 1/2 full of 1/2" lead balls. I think the jar weighs abot 5kg without any BP (I say think because my scales only go to 3Kg and am to busy to empty and weigh) But 1/4 jar by volume is only 300g BP

Maxman

[cooperman435]

A lot of people confuse rock tumbler barrel weights with anything to do with ball milling.

The weight is what the tumbler is designed to roll on a constant basis, but this is exactly why they arent suitable for our aplication. The volume of media should occupy half the jar which will as far as I know always take it straight over the weight capability of the mill.

[maxman]

Yeah Phil, thats what I thought. The jar should be reffered to by its volume not weight. When I got that jar I measured 25% by volume in raw chems which is 300g then removed the chems and filled 50% with lead balls leaving 25% free space. I suppsose that makes mine about 11lb mill

While on the subject I would be wary of using any other media than lead to mill BP. Just take a look at the recent topic on passfire regarding a mill that went bang. It was the guys first time with ceramic media with a new large mill jar and a lifter bar.

Maxman

[cooperman435]

there is plenty of info on here giving pros and cons of lead and ceramic, my personal preference is lead due to availability, weight (meaning more efficiency I believe) and complete non sparking. Other swear by ceramic though.

[digger]

there is plenty of info on here giving pros and cons of lead and ceramic, my personal preference is lead due to availability, weight (meaning more efficiency I believe) and complete non sparking. Other swear by ceramic though.

I agree that there are advantages of both. Lead is good in smaller mills, however in larger mills I think ceramic wins as it is lighter.

Weight is not the be all and end all of efficiency. Impact force is proportional to the deceleration distance along with the mass. So don't forget lead will yield whereas ceramic will not, this effect becomes especially important when the particle size is small.

But I also agree with Maxman in being very careful on the choice of ceramic media (Steve's is good stuff). I have used ceramic for years with no problems, however my mill is run in the middle of a farmers field in a hole. So if I do blow up a mill no-one would be hurt, it would not even register as the local shotgun users will be louder.

Edited by digger, 01 February 2010 - 05:39 PM.