Solid Machined Delrin Finger Spool

[cool_hardware52]

explanation :

Delrin compound contains glass fibres .If plastic compound is correct moulded then these glass fibres are orientated in moulded space undamaged and in the full length.

If spool is cut out from moulded form then these fibres are orientated in moulding direction in rod . If we machine spool out of that rod then we cut these fibres and we broke interlacing of these fibres
so , we weaken the structure of the material.

Problem by moulding delrin is mold tool itself . It must be right designed : molten plastic has filled the mold from all sides at the same time before the start of plastic to solidify

AND

Spool from solid rod of delrin should be expensive

- that industrial plastic it is very expensive itself
- because it contains glass fibres ,machining tools have a lot of wear and tear
- cutting ( turning ) tool must be from artificial diamond (for serial production )
- there is a lot of waste from machining , but delrin is thermoplastic polymer material and could be recycled

Unfilled Acetal is the norm for machined parts. Most Acetal has no fibers, glass or any other.

The reason finger spools were originally machined from solid was the cost of the required mold. If you need 100,000 parts a $50,000 mold is cheap.

If you need 1000 parts a $50,000 mold is impractical.

This phenomena is common through out scuba. Items, often with a "tech" origin are first produced using "garage" methods because the diver needed something not available at the LDS, and then if the item becomes popular the claim is made that the "only right way" to produce them is the original small volume method. Finger Spools are classic example.

Regarding recycling; Acetal is a thermoplastic, but the realities are that "machining chips" or swarf from material removal processes are almost never recycled. Usually the machine tools used to cut the plastics are also used to cut many other materials including metals and the chance of contamination with cutting oils or metal chips is too high.


With a well designed mold a molded finger spool can be more robust than a machined one.

Tobin

 

[Lorenzoid]

Does anyone know who still makes spools that are machined from Delrin? It seems injection molding is the cheaper method and many manufacturers have moved that route.

I bought the Light Monkey spool. Halcyon is Delrin as well.

 

[lucca brassi]

Unfilled Acetal is the norm for machined parts. Most Acetal has no fibers, glass or any other.

IMO : Never saw unfilled plastic in product that is under mechanical load - just it makes no sense ?

In other sentences I agree with you .

 

[cool_hardware52]

IMO : Never saw unfilled plastic in product that is under mechanical load - just it makes no sense ?

In other sentences I agree with you .

Fiber filled plastics are often used for highly loaded applications, but straight unfilled Acetal is a strong, impact resistant engineering plastic. It's used routinely in demanding applications.

I've machined mountains of unfilled acetal for all sorts of parts. For example most canister light canister are unfilled acetal.

Tobin