Weights and molds question...

[Amorybulldog]

Ok, here is a question that still has me stumped. How can you have the same mold have as much as 10 grams difference in the discs? It can't be bubbles in the plastic, at least not for champion line. It has to be something else. For example I got 4 or 5 discs from Innova, they were star cros: one was 172 the other was 160 I think. Got around 15 of the same discs from Discraft and they ranged from 167-177+. They look and feel the same but the weight is definitely different. How is that possible? Is the plastic used changed in density from one batch to the next? How can a 150 class even be the same disc with that much plastic not in the mold? I'm obviously a plastics/polymers idiot. Any insight on this is greatly appreciated.

[ERicJ]

Density of the plastic.

Extreme example: take a mold and fill it with Styrofoam and then another mold of the same shape and fill it with concrete. Both will have the same shape, but drastically different weights.

[gcoghill]

fill it with Styrofoam and then another mold of the same shape and fill it with concrete

However, in this case the mold is filled with the same material. I would have to think it would be a lot of extra work to have multiple batches of plastic made up for each gram weight.

I would think that it would just result from slight variations in the manufacturing process. But then again, that really doesn't seem like it would account for a 10 gram difference.

If indeed they are making different densities of plastic, I am curious how they go about doing so.

[Ryan P.]

I would think that just heating up the mold enough would make the plastic become less dense. I have thought about this too though. It basically seems to be that they pour different amounts of plastic into the mold, and then heat it up so they fill up the mold, and then let it dry. regardless of how much of the plastic is in the mold, it will fill up when it heats up. However, i don't know why they don't shrink a little when it cools down. But that's just what i've thought, and i have no expert opinion at all.

[gcoghill]

I sent an inquiry off to Discraft & Innova on this, we'll see what they have to say.

[garublador]

AFAIK they just use weighting agents. In other words they add stuff to the plastic to make it more dense.

[gcoghill]

Innova has this to say:

We adjust the mix and the production parameters to make different weights in the same mold.

Discraft suggested I look on the PDGA site, I think they misunderstood my question. I replied with more clarification.

Nice fast reply from both companies. Impressive, most impressive.

[garublador]

Also, from what I understand the weighing agents show up on x-ray so you should be prepared to explain what disc golf is whenver you fly with your discs in carry-on or expet your bag to be searched of you check them.

[ERicJ]

Also, from what I understand the weighing agents show up on x-ray so you should be prepared to explain what disc golf is whenver you fly with your discs in carry-on or expet your bag to be searched of you check them.
I've flown three times with discs so far, never a mention of it or a noted search.

ERic

[JR Stengele]

I have flown a lot, and sometimes they ask, and sometimes not. The key is making it easily accessible. I used to put my DG bag in my backpack and they got upset saying that it was if I was smuggling something. Now, I just use one bag. Usually I take my Innova travel bag that holds 11 discs plus a putter in the front and there are no questions asked. You never know so it is easier to be safe then sorry. You better believe I would put up a stink if they told me due to metal traces that I would have to leave it behind. = )

[djext1]

This is actually an interesting question that I guess I never really thought much about.


On the Gateway website here is a description on making putters, and putter 'flexibility'. it answers some of these questions I think:

http://www.gdstour.com/gateway_putter_flexibility.php

There are formulas that we use when, for example, shooting for a 4 (SuperSoft) and within in each class there is at least 1 polymer that is proprietary to that particular class. A Medium has a percentage of a talc-filled polypropylene (PP), a soft has a percentage of a regular PP, the SuperSoft has no PP and a Super-Stupid-Soft has no PP and a soft rubber thermoplastic vulcanizates (TPV) or thermoplastic elastomer (TPE) less than 70 A shore. (What does "70 A shore" mean?)

All recipes for production runs have 2 materials in common, a 90A shore TPV that is compounded with a mineral which is the “concentrate” that makes the discs heavy and a non mineral filled 80A shore TPV that weighs .93 that is the base.The concentrate weighs over 2.0 density and the target for a 175 putter would only be 1.4 density. PP weighs .90 and the talc filled pp weighs 1.7. The method of mixing each batch to get the right flex and weight is a very challenging task (a cross between math, science and art) and will always produce runs of discs in between the 2's,4's, 7's and 9's.

[Sean4287]

Maybe they add more plastic to the lip of the disc?

[Amorybulldog]

Sorry if I made your head hurt thinking about it. It makes sense that additives are used now. That would certainly explain a 10 gram difference in molds. Very interesting stuff.

Thanks for your input.