We need to injection mould a plastic part to go into baking ovens at
300 Celcius (572 F). It would be better if it would function at 330 C
(626 F). At those temperatures it needs the physical strength of
copolymer polypropylene at room temperature. The current part (100 mm diameter,
phenolic resin) weighs 150 grams (5 oz). It presently costs USD
2.20.

We also need to mould a plain bush bearing able to carry 200 kg (440
lbs), size 1/2 ins dia x 1 1/2 ins long at the same temperatures.  We
currently use PTFE. Present cost USD 0.60.

1) What materials can we use? (Some cost increase possible, but not
too much).

2) How will the new materials compare to the existing phenolic and
PTFE from price and performance?

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Request for Question Clarification by jbf777-ga on 30 May 2003 10:01 PDT

Hello -

Can you disclose a little more information about this part?  Is it
insulated?  Under load?  Shape?

Thanks,

jbf777-ga
GA Researcher

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Clarification of Question by engineer84-ga on 30 May 2003 14:43 PDT

Part: Solid Phenolic wheel
Diameter x width (mm): 100x33
Capacity Vs. temp (mm@°C): 125@100°C, 100@250°C, 40@300°C
Width x bore (mm): 42x12

Image: http://www.fallshaw.com/hi_lo_temp/images/ht_dkt100.gif
The black wheel body is the Phenolic we're trying to replace, the
white plain bearing in the centre is the PTFE we're trying to replace.

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Request for Question Clarification by pafalafa-ga on 04 Jun 2003 07:53 PDT

Hello engineer84,

I've heard from three specialty injection molding companies now, and
they've each said the same thing -- phenolics are the material of
choice, and it would be extremely difficult to engineer a non-phenolic
replacement (difficult, but not necessarily impossible).

Each has also asked me:  Why?  What is the reason for looking for a
phenolic substitute.  If it is a matter of costs (which it doesn't
seem to be, from your question), you're unlikely to find a cheaper
substitute.  If there are performance issues, then these need to be
clarified, before anyone will respond with a specific recommendation
for a substitute.

Any additional information you can provide would be most helpful to
help pin down the answer to your question.

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Request for Question Clarification by jbf777-ga on 04 Jun 2003 08:18 PDT

Yes, I can attest to what Pafalafa is saying.  I've encountered the same thing.

jbf777-ga
GA Researcher

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Clarification of Question by engineer84-ga on 04 Jun 2003 17:25 PDT

Thanks guys,
Looking at the capacity vs temp numbers from my first clarification
(and I've fixed up the typo):
Capacity Vs. temp (kg@°C): 125kg@100°C, 100kg@250°C, 40kg@300°C
the phenolic is very weak up around the 300°C mark.
Phenolics generally get used when cast iron can't be (because cast
iron damages many floor types), but in hotter ovens (many of our
customers are operating at 330°C) the phenolic breaks down and the
wheel cracks.

... so we'd like to be able to supply a product that can function in a
330°C oven. We could handle a cost increase, but not too much (see
original question for our current costs). A summary of
price-performance for our options would allow us to progress.

[an innovative answer to the question might point us in the direction
of a more expensive high temperature material we could bond to a cast
iron centre as a tyre... this answer would have to first convince me
that no injection mould-able solution existed]

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Request for Question Clarification by pafalafa-ga on 05 Jun 2003 07:44 PDT

Hello.  Here's the latest feedback from one of the injection molders
I've been in touch with.  If you can provide the additional
information he is looking for, I believe they will be able to offer
some options for you, and I can put you in touch if that seems
advisable.  Here is what they need to know:

First, from a quotation standpoint can you give us an idea of annual
demand for the part.

Second, and more importantly from my vantage point, if the current
material is failing to perform at the conditions you mention, I need
to know something about
the current material and the mode of failure. There are not a lot of
plastic materials that have good long-term, or even short-term load
bearing capabilities at 300-330 C, so the list of options is going to
be
short and probably expensive. But we can avoid over specifying if you
can give us an idea of why the part is failing to perform as needed.

------------

My read on this is that he needs to know how the part is being used
(how long and how often it is exposed to high temps, what weights are
actually being carried, how long the piece lasts before failing, and
how, exactly it fails -- warps, buckles, cracks, explodes...?), and
any other info you can think to offer up.

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Request for Question Clarification by pafalafa-ga on 14 Jun 2003 14:37 PDT

Hello,

Just checking...are you still interested in having this question
researched?  If so, it would help tremendously if you could respond to
my earlier set of clarifying questions.

Thanks.

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Clarification of Question by engineer84-ga on 15 Jun 2003 22:41 PDT

Sorry about the delay there, guys - hectic couple of weeks and a
change of continent.

1) Volumes are approx 6000 a year (though they'd be higher with a
stronger product).

2) The wheels are used in a number of high temp applications, the
worst of them being long term use in baking ovens (say 16 hours/day @
300-330°C). At these temps the phenolic gets brittle, so the next hard
bump will shatter it (I'll get a more detailed description of the
modes of failure together and try to post it by tomorrow). The wheels
are generally on racks stacked full of parts - I'd like to be able to
maintain about 100kg per wheel at high temperature.

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Clarification of Question by engineer84-ga on 16 Jun 2003 22:47 PDT

Slightly more detail:
When tested at 300 degrees for 30 minutes the Phenolic wheels become
brittle and form surface cracks, wheel then shatters when impacted.
Most customer returns take place within the first 6 months of
operation and generally it only affects customers that use these
wheels at temp above 280°C.