Reference on plastic parts manufacturing

[Tunalover]

Can anyone suggest a good technical reference on plastic part manufacturing including materials selection and various manufacturing methods? I need to know much more about plastic part design and manufacturing. Thanks in advance for your suggestions.

Howard Bruce Jackson
Senior Mechanical Design Engineer


Tunalover

 

[MikeHalloran]

SPI publishes a huge volume of material.
Most of it is fairly pricey, and there's certainly useful stuff in there somewhere. The volume of material actually makes it hard to find what you want.

For free, you can inquire of every plastic resin manufacturer you can find. They are all extremely interested in getting you up to speed, and using their products with unbounded success. To that end, they provide excellent engineering and/or design handbooks, nowadays as pdf files, but you may be able to find printed material to fill a bookshelf or six.

Of course, having material organized by resin or by brand makes it harder to select among the various resins and brands, one task for which the SPI material may be more useful.

Also, if your outfit is already dealing with plastic fabricators or molders, it would be a good idea to get acquainted with them. Spend a day with each, learning what they do, how they do it, and see some of their challenges firsthand.

If you are really going at this cold, do some destructive examination and comparative anatomy on things like disposable razors and toothpaste pumps. Then try to design something yourself. Maybe like a piece of a carburetor. Most molders are hot rodders, so will understand carburetors for a few more years. Take your detailed design for a carburetor part (or whatever) to a couple of molders, and take notes about what they say after they stop laughing.





Mike Halloran
Pembroke Pines, FL, USA

 

[Tunalover]

Thanks Mike!


Tunalover

 

[KENAT]

Like Mike implies some vendors have design guides on their websites etc.

E.g. our RIM vendor has this

http://www.premoldcorp.com/design-guide-download/

These guys have design guides on a number of rapid prototyping processes aw well as 'injection molding'

http://www.solidconcepts.com/resources/design-guidelines/injection-molding-design-guidelines/

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[Tunalover]

Thanks Kenat. I know there always is the prerogative of getting with the plastic fabricators. That is always the BEST source of information but what I'm looking for are general design guidelines for various fabrication methods that would apply to ALL fabricators. Maybe a textbook or handbook of some kind...


Tunalover

 

[KENAT]

Well, a general 'design for manufacture' text book would have more than the breadth you're looking for - but will probably be woefully lacking in details.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[MikeHalloran]

The rules don't apply to all molders.

My friend Siggy, now sadly not available for consultation, specialized in low volume injection molding, using molds mostly made of aluminum plates, with no draft, manually removable pins to make holes, and steel for the odd fine detail. His molding machine was simple, and part ejection involved disassembling the mold from around the part. ... with an impact wrench. ... in a carefully choreographed dance of assemble, clamp the mold in the machine, inject, removed the mold to the bench, disassemble, repeat, in order to provide part consistency.

Siggy put a red mark on every feature that I had carefully provided on the first drawing I sent him. I had to remove the draft and the clever half holes and such.

My point is that in injection molding especially, you have to be a partner with your supplier in order to get the results you want. Many, maybe most, molders are self-taught, clever, arrogant in a good way, and busy enough to not really need your business. They each do everything in their own way, so molds don't really interchange among molders, even though you technically own them and could move them.
If a Supply Chain Manager gets involved in the procurement of molded parts, you might as well close the doors, because you will shortly be out of business.

So, I repeat, if your outfit is now doing business with molders, you need to personally visit them and get acquainted.



Mike Halloran
Pembroke Pines, FL, USA

 

[Tunalover]

Mike,
I always partner with the fabricators. But I am also generally not empowered to choose suppliers. I am generally told to design parts loosely enough that many molders could deliver them. However, there are always molders that are favored for the time being and those are the ones I work with to review designs for manufacturability. Sometimes I send a print out to more than one molder for review and comment.

Tunalover