The Disc Manufacturing Process

[JHern]

As an industrial designer, I design products and as disc golf nuts, I wish I could do my own disc ( the only thing missing is the cash to do the machined mold! I guess China might come to help there)...Also, I work with a special technical plasctic often called UHMW for Ultra-high-molecular-weight polyethylene and I always wonder if we could use the ultra resistant plastic as it can resist abrasion (its self lubricate), resist high and low temps and can be formed like Vibram disc (compression molding).

Sounds interesting, what does it feel like? Tacky? Is it significantly more dense?

Side note on the last video about Vibram manufacturing process, it's compression molding compare to injection molding.

Ah, forged vs. cast

Or maybe cut? I could also imagine a process of cutting a disc from a chunk of plastic with the right kind of initial geometry to avoid shrinkage artifacts and asymmetric residual stresses. Perhaps it could even be annealed somehow? That would probably be the most reliable and consistent method, although it might be a tad more expensive and time intensive.

For example, think about molding a lens-shape axi-symmetric chunk of plastic with mirror symmetry about the mid-plane, and set it aside for gradual cooling while still at elevated temperatures. The symmetry would translate into symmetric shrinkage after cooling out of the mold, reducing artifacts. Then cut a cylindrical chunk out of one side, to leave a flight plate and rim, and finish it with precision cutting tools to shape the nose. Et voila.

[JR]

Side note to a side note. That is the reason why Vibram needs to use so much lube and the chemical properties of the lube are probably such that it is hard to remove it quickly and why their grip improves a lot after using citrus wash or some such agent and warm water with lots of rinsing and rubbing. The difference in grip is major with this treatment.

JHern the method you suggest sounds expensive and time intensive from a commercial point of view. Production rate might me too slow to viable for anyone else bu a hobbyist that does not need to make a living out of making discs.

[JHern]

Here is an interesting discussion between Dave M and Dave D at the PDGA forum...

I'm not Dave D but have an opinion on why CE type plastic was discontinued by the polymer manufacturer (not by the molder Dave D at innova).
Typically injection molding companies in the US ( in order to make profit and be competitive) would want to be able to run parts as fast as possible, That particular type of TPU material took very long to set up. A disc made with current TPU ( champion, star, Evolution) usually takes about 40-60 seconds to be molded and demolded, where it is then set on a table for an additional 5 -6 minutes to cool.

We ran a similar style of plastic ( which we called nike spirits) that took nearly 3 minutes to set up,,,, meaning that at the end of an 8 hour shift instead of having 500 or so discs you would only have 160 ( thats if they were all good parts), and this particular type of urethane also produced lots of short shots ( bad parts) because it was also extremely difficult to mold through the .070 thick flight plate into a 1" triangular rim because of low flow rates. I heard from one innova molder that most of the CE discs were red, most likely do to the fact that the red colorant probably helped increase flow rates .

Since this material was so hard to mold ( not just by disc makers but most who used it) and often took up to 3 times as long to make a part, the polymer manufacturing company probably changed their formulation to be more competitive with the fast changing world of TPU development.

All in all there are about 40 different TPUs that could be used alone or blended together to produce HIGH END golf discs. I'd say the current Star discs are every bit as durable as the CE stuff and in my opinion are better engineered through formulations by Dave D to meet the requirements needed to achieve the right flex, surface feel (and whats most important,,,, )flight characteristic, for each specific model its molded.

does this sound accurate dave D?

I wish I could get a 40 sec cycle. Ours are more like 50-80 seconds. That particular plastic didn't take much more than 60 seconds, so it wasn't that, but I'm sure they had some reason or just couldn't make it anymore. We have manufacturer's changes in materials all the time that we don't want changed. Nothing we can do about it other than shop around for materials. Most of the slight mold changes we make are an effort to keep our discs flying or molding the same with the changing plastics. Also, there are many more urethane plastics than 40. When you add all the variations, it's well over 400. I know one manufacturer who has over 40, so it's a maze. The sales people you talk to trying to get suitable plastic don't know what they are talking about most of the time so the only way to find plastic is to get samples and test it. You can't trust the numbers or the sales people.

And you're right about the mixing to get the right flex, feel, and flight. Rarely do we use just one type of plastic for a run.

We have the ability to get custom made plastics and it still comes out wrong most of the time. A bit frustrating.

Here is a news blurb about Gateway's plastic supply...
http://www.plasticstoday.com/imm/articl ... putt-dough

Here is another story from Alliance, the supplier of Discraft plastic...
http://www.apstpe.com/TPU-makes-fast-gr ... e-Ultimate

Of course the above are plastics-supplier articles, so they don't talk about consistency issues.

Anyways, plastic supply is everything in the injection molding game, but plastic supply does not appear to be very reliable, at least according to all the information I've seen. This is the primary underlying reason for variations in disc runs. And when the plastic varies so much that you have to cut an entirely different mold to get an acceptable result for a new plastic supply, it is a big expense for the disc maker. If I were going into this business, I wouldn't use any supplier unless they could guarantee a supply of exactly the same plastic for decades.

I wonder how difficult it would be to set up a plastics synthesis operation, specifically tailored to disc production? If you could make your own plastic in house, you could have extremely precise control over the process, ensuring consistent results forever. Of course, it looks as if the best plastics are coming from BASF, 3M, etc., and are probably protected by patents up the wazoo, so one might be in danger of stumbling on legal obstacles (but maybe a settlement could be worked out, royalty payments made, and everybody's still happy?).

[JHern]

JHern the method you suggest sounds expensive and time intensive from a commercial point-of-view. Production rate might be too slow to be viable for anyone else but a hobbyist that does not need to make a living out of making discs.

Maybe, maybe not. There are precision robotic cutting tools out there that are quite amazing, although carving out a cavity in TPU might be tougher than usual...who knows? Technology can be pretty awesome and unexpected, especially in precision cutting. So a big down payment on the robotic cutting tool, which can handle a similar or shorter cycle time as the injection molded lens blank. I think it would be fun if it were possible to make custom discs using a method like this, since it would be much easier to fine tune and alter the flight characteristics, while the CAD input interfaced with a finite element solver could be programmed to calculate all the PDGA measures to ensure it falls within the specs. But to do this, we would have to start thinking "outside the mold" so to say.

[JR]

Or finding a suitable option machine wise. TPU is tough. They CNC steel but it takes months to make large parts and probably a day or more for a disc sized thing if it is complex in shape. But why not use it for softer plastics that is medium to base grade plastics? That might be viable manufacturing time wise and financially spread over enough discs. Which in a time of brick and mortar shops not having room for all manufacturers let alone discs in the market is getting harder and harder. Each year there are more than one new disc manufacturer. I'm not sure if the growth in players leaves enough demand for new companies. I think Innova reaps the benefits of growth mostly with Discraft gaining a little and the others probably not so much or in the case of European companies local sales.

One problem is supply of suitable plastic blocks and the excess carved out plastic. It costs to manufacture and recycle. Ideally you would return the ground/cut material to the supplier of the blocks who would make new blocks from that material.

Money talks and you can get large quantities of plastics cheaper per pound and if you had unlimited money you could buy years worth of plastic and custom manufacture it to perfection or reject the batch. It is a contract issue. Working together with the plastic manufacturer in an iterative process until the material is good enough is theoretically possible but it would probably cost big time. Then there is the added complexity of not only needing to deal with the plastic supplier but also the block manufacturer. It sounds more difficult than it might be worth. Let alone the pricing.

[JHern]

True enough. There are some dudes here in CA making discs out of wood, they are actually really nice and this would be a great way to experiment with the influence of shape on flight, but of course wood will never pass the flex test.

What if there was a tool that could cut, grind, and polish TPU the same way it does for wood? That would be ideal.

Anyways, thermoplastic injection molding seems to be the cheapest process by far, but it is prone to a great deal of sensitivity to plastic properties variations as well as operator dispersion. I wonder what the best way might be to break through this barrier, that's really what is holding the sport back in terms of equpiment.

[JR]

That machine should match the speed of injection molding machines too.

I would not wonder if TPU cutting and polishing machines already exist but how fast are they? They cut way harder materials and polish them given time with current CNC machines.

I had higher hopes for MVP using molds and liquid TPU. Theoretically with material that shrinks so little and hopefully the material lasting for a while there should have been no variations in the material. And the molds should determine the shape well because there is no heat applied. But i have not checked the recently linked video only read what they wrote here when they started.

I do not think the sport is being held back technologically it seems to be the other way around. There is need for limiting how far discs fly since so many courses have shrunk to too little demanding with current disc distance increases. The available land is a problem already and there are safety issues already. I do not believe that anyone that likes to play DG would stop just because discs are inconsistent and no sponsor would say no to sponsoring for that reason. I don't see how the equipment is holding back anyone. The largest gains for anyone would come from throwing better rather than switching discs. If added D was a requirement porous durable material flight plates might make the largest dent. And would likely cost a lot. And thorns would still pierce the flight plate easily no matter what kind of protective mesh was used most likely. Since all plastic flight plates get punctured too.

[JHern]

I had higher hopes for MVP using molds and liquid TPU. Theoretically with material that shrinks so little and hopefully the material lasting for a while there should have been no variations in the material. And the molds should determine the shape well because there is no heat applied. But i have not checked the recently linked video only read what they wrote here when they started.

That sounds highly promising. I know that thermoset plastics can also be used in some kinds of processes...kind of like an epoxy, in which 2 fluids react to make a tough solid. But I don't know of any particular kinds that would be suitable for discs.

I do not think the sport is being held back technologically...

While the distance potential of sport is not necessarily held back (PDGA rules already limit it), disc design, production, and QC is definitely held back. Consider that a disc design can be mathematically optimized to obtain a desired flight pattern with the least sensitivity to release errors for the best golf results, yet no manufacturer does this or even understands that it could be done. A disc could be mathematically modeled all the way from the formulation of the plastic, injection into the mold, shrinkage, stamping, and it's first throw and flight could be precisely predicted...but they have to entrust it to process engineers and pay them a salary, which is probably the biggest hurdle. Once they get to that point, there will be a noticeable jump in disc quality. No, you won't be able to throw farther, but you will be able to throw better golf scores with equipment that is precision-tuned for each purpose. Think of a perfectly stable disc that holds any line forever, and which is designed so that impacts don't alter the PLH. Or a disc that flexes or turns over slowly and controllably and predictably every time.

Anyways, for the modern manufacturer, the question isn't about whether or not the sport is held back, the question is how to increase market share and make the kinds of products that do exist even better. Innova has a jump on everyone because they've made so many different molds and they've tried so many different designs, they have a large library of empirical knowledge to stand on, and a large sales catalog (i.e., it is an excellent bet that any player can find multiple Innova molds that they like to throw, and which they find useful in their golf game). This gives them a huge leg up on everyone else, and only Discraft has come close to offering such variety. And then they are still doing cool new stuff, like Blizzard plastic, which proves that working on innova-tion can still pay off. New start-ups have to focus on producing only those kinds of discs which are perceived as being the most popular, they don't have the financial resources to buy hundreds of molds and blanket the market. They must pick and choose their way into the market, and it takes a while before they can fill all the slots in a bag with their molds.

[JR]

At least blunter primo discs won't deform in the PLH normally. I'm not so sure that design alone can make speed 13 and over discs maintain PLH indefinitely. That would slow down the wear a lot and it might not be financially sensible for any manufacturer to pursue that. Some discs do already hold their lines to the ground.

[isobar]

Has anyone tried using a 3D printer to make a few discs and see how they work? I know they aren't cheap, however I believe for someone looking to develop a disc, it would be cheaper to run a few samples in a 3D printer and see how they feel. I don't know exactly what plastic resin most printers use though, it might be too hard to use for discs.

[JR]

The material cost is that of a few bought discs so for prototyping the cost is not prohibitive if you can get your mitts on a printer and have the schematics in a format that the printer understands. I'd imagine the end result would be hard and slick. You could make a mold too and pour liquid polyurethane into it but at least some of those are super carcinogenic and allergenic so all manner of protective gear is a must not just recommended.

[JHern]

Has anyone tried using a 3D printer to make a few discs and see how they work? I know they aren't cheap, however I believe for someone looking to develop a disc, it would be cheaper to run a few samples in a 3D printer and see how they feel. I don't know exactly what plastic resin most printers use though, it might be too hard to use for discs.

This is an excellent suggestion. While the plastic that is used in the 3D printer might not be ideal for throwing, it would at least allow you to assess the aerodynamical properties and how they trade off with mold shape, which is ultimately what we're after. In other words, the 3D printed disc could be put directly into a small wind tunnel (a research grade tunnel that goes to 80 MPH could be built for ~$10K), and the aerodynamical forces and moments could be measured directly. The wind tunnel measurements will then allow you to assess the flight characteristics precisely using the kind of simulations that myself and others already do.

In fact, we wouldn't even need a 3D printer, a high precision robotic (CNC) lathe would be just fine, since we're producing axisymmetric discs. Just input the CAD profile of the disc, set the tolerance, and let the machine go to work. Just found one for sale on ebay for $2K...
http://www.ebay.com/itm/Amera-Seiki-TC- ... 19d881024d

Note that, to cut the proper mold, you would need to get a consistent blend of plastic, measure its shrinkage characteristics precisely, and then reverse engineer the mold shape that would produce the desired disc shape using plastic shrinkage calculation software (e.g., finite element analysis).

So for less money that the cost of producing one $20K steel mold, you could buy all the equipment you would ever need to be able to reverse engineer disc designs, and obtain the best possible designs. You could even use mathematical analysis to optimize mold shapes for various characteristics:
1) A desired rim depth and width, such that the grip is comfortable for the thrower.
2) A mold shape whose flight characteristics are least affected by plastic variation, yielding the maximum intrinsic consistency.
3) Etc., the list of possibilities are endless.

Of course, you would also need to hire somebody who understands all of this, which would cost a bit more. But maybe some of us would be willing to do it for a small fee on a limited basis, to make it more affordable, like a consultancy type of arrangement.

[JR]

Some years ago i saw people write here that some companies have gotten mold made from steel for 5K and aluminum way less 2-3K range. And aluminum molds last max 5000 discs. I have no idea about steel longevity.

[JHern]

Some years ago i saw people write here that some companies have gotten mold made from steel for 5K and aluminum way less 2-3K range. And aluminum molds last max 5000 discs. I have no idea about steel longevity.

It depends on where you make it, whether you use union shops, etc.. My cousin is a union machinist, been working in that field for decades, and says a good quality mold will run more than $10K. Either way, it's in the same ballpark as the cost of the CNC lathe+wind tunnel that would permit the disc manufacturer to make the best discs possible...

...a consultancy disc design shop could be setup to handle the entire process, from designing the mold, securing the plastic supply, to getting the mold machined. Of course, at that point, they might as well pick up a couple of plastic injection molding machines and make discs themselves.

[MrScoopa]

I know first hand that 3D printers have been used to make test discs. The only negative stated was they were fragile, no full rips(too much grip pressure), and field throws only for the softer landings.