injection molds/extrusion

You must see sample parts... before signing off the tooling.

There are good tool makers in China but you need to vet them carefully and be very exact with drawings spec's sign off etc.

Most tools do need adjustment but is critical that finishes, tolerances and any high precision areas are specified .

What we usually do is to machine trial parts out of plastic or ABS and give it to the customer to be tested. until we are sure what the customer needs and to solve teething problems. The tool is then made and production can start. The customer usually also orders some of the development parts for urgent sales. (at a higher cost of course)

I work with a company in latin america for both manufacturing and injection molds Send me an Email with your contact info and I will pass it on . very very cost effective. ellisd@comcast.net

Does this company also do profile extruding?

Any serious plastics professional will tell you that there are three major considerations in assemblies of injection molded and extruded parts - particularly when they are going to be used together with other mating parts, and sold anonymously through distribution into 'Construction' - especially with warranty related questions in the background. You don't mention number of cavities and general mold design criteria so without specifics it would be difficult to 'direct' you on the injection molding portion at this early point. Consistent, clear and written communication should be your watchword. Depending of which of these following items you NEED, it WILL change the way one would think about design and tool up of either plastic process, and the resulting 'tweaks' needed on tooling -

1) Dimensions (critical, control, reference)

2) Aesthetics (critical, control, reference surfaces)

3) Physicals (flammability, electrical, impact, UV, reactivity with other parts etc)

As a senior member in the Society of Plastics Engineers and successful Product Manager mating injection molded and extruded assemblies for many years in construction related industries sold through distribution, here are a few general thoughts to consider (assuming you have the DESIGN issues take care of):

a) photostereolithography - for $1500 or so you can have sample parts made to dimension for critical assembly fits, including undercuts, blind holes etc. Bet on the final injection molded parts being closer to print (caveat - a poorly or improperly packed, voided, or stress-molded-in part can 'hit the numbers' and still be a poorly performing part in application - see Aesthetics and Physicals) and then have some examples of the extrusion produced with high and low critical tolerances produced by p- as above and submitted by your extruder. In nearly 30 years have not found more than about a half dozen with more than 3-4 CRITICAL dimensions for assembly with molded parts. On the other hand - a major item to think about during the contract review process would be what OTHER mating parts does your system need to match up with? It may be that one of the parts is not yet fully developed in how it relates to them . . .

b) understand what you NEED in terms of the big three - one of the three is always easy to produce at 'rate and weight'; two of three is more difficult and probably will affect production rates, all three will nearly always affect production and discard rates and therefore your final delivered price.

c) insist that your sample parts be produced from the actual production tooling at PRODUCTION rates from PRODUCTION material - nothing creates more availability to market headaches than to submit your sample assemblies for further consideration (aka electrical, UV, or smoke/flame) only to find out that the sample parts were made from a general purpose or utility grade of material that does not include your special needs - self extinguishing, impact or notched IZOD capability, UV characteristics, static dissipative qualities, biocides, fungicides etc.

d) work with a house that has their own in-house wire capability for the extrusion tooling. It is much less costly to open up or remake the extrusion tooling than the injection molding tooling - probably on the order of 6-10 to one. Ask to see examples of their tooling and their tool storage area. Notice how they keep the unused tooling on the shelf - cleaned and measured, shiny and production ready or rusty, filled with plastic and unkempt against the day someone might reorder? A number of houses will quote inexpensive flat plate tooling, but be wary of the how these tools work over multiple lots of raw materials which can and do change - particularly if your spec a 'utility grade' of material.

e) be at least a little paranoid; Trust, but Verify. For every one of the good plastic outfits out there, there are some who won't measure up beyond the sample parts. Look for a house that has some sort of quality policy (with or without the ISO moniker), with sample retains on less than perfect quality parts used year to year to maintain quality outputs, and written records of past production runs including retained information back to incoming raw materials and supplier raw materials certifications if possible etc.

f) get it in writing; material specs, quality and production records - ask to attend and help fill out a 'Contract Review' - answering the couple dozen critical questions that a good processor needs answers to to 'help them help you' is a critical set of meetings. Some sales people can actually act in this 'Product Management' role; and unfortunately many can't.

g) ask for and be prepared to get enough samples to have engineering testing done on the resulting samples - and do it

A well run project process has additional nuances of course, but these should give you a good grounding. Good luck with your project.

Jim Wilson

Jim,

I thank you very much for your time and input.However I would like to speak to you further regarding this project if at all possible.

Thanks again,

Mike

Hi.

There are several items you should verify:

1. for both extrusion and injection molding, a first article inspection (FAI) is a standard metric, the number of key dimensions that affect quality should be verified. So first all dimensions are measured at the high and low limits of the process, then key dimensions (pick no more than 5) should be measured through a statisitcally significant number (guessing say 32 samples) all dimensions must be inside tolerance.

2. tweaks to the mold to achieve process stability are a norm and nothing to worry about if they are truely to achieve process stability and are trending towards that. If the tweaks are just to get it to run then there is cause to worry.

3. when I purchase molds or machines I do what is called an FAT (factory acceptance test) It is a protocol, basic rules of engagement, the tool or machine must run 98% uptime at rate, must not have greater than 2% unplanned downtime (stuff that breaks) and produce no more than 2% rejects including start up samples.

If that is achieved I release up to 80% of the money.

4. After it is in production complete the same test called SAT (Site Acceptance Test), is now at the molder's plant, must run 24 hrs with at least two lots of resin preferably one at a low melt point and one at a high to assure it is stable throught out.

5. Typically molds are made out of hard materials, cores and cavities tend not to be hardened after mfg. you should be ok relative to rework from a hardness perspective, the worry here however is the finish and the tolerances, polishing or surface modifications remove steel and add plastic.

I have a little company in NH that can help with specifications and run off protocols,

www.jumpstartmfgllc.com

We are one of best tooling and injection molding factory in China.You can give me you requirement by email: xinlaibj@126.com I would answer soon.

Thanks,

Tony