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www.TK560.com Vacuum Forming, Movie Prop, Sci-fi and GIjOE Forum
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spacephrawg Novice
Joined: 02 Jul 2010 Posts: 42
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Posted: Wed Jul 28, 2010 12:47 pm Post subject: do you design molds differently for different plastics? |
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I'm thinking of Lexan vs. ABS. I have no idea what the diff would be as far as mold construction goes. The prototype mold would be MDF as has been recommended to me but the production tool would be aluminum. Can you advise? thank you, and thank you for fielding my n00b questions! _________________ please pardon my apparent newbie ignorance! |
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MicroCast Newbie
Joined: 09 Sep 2011 Posts: 5 Location: Ontario, Canada
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Posted: Wed Sep 28, 2011 1:06 pm Post subject: Re: do you design molds differently for different plastics? |
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spacephrawg wrote: | I'm thinking of Lexan vs. ABS. I have no idea what the diff would be as far as mold construction goes. The prototype mold would be MDF as has been recommended to me but the production tool would be aluminum. Can you advise? thank you, and thank you for fielding my n00b questions! |
Hi ya.. I know this post is a little late but I'm new here too so I'm reading over past post...
I believe you would choose your plastic to best suit your end use & cost. For example. If I want to pull stepping stone molds for casting concrete I would go with ABS from .080 and up. If I wanted to cast candy or chocolate I would use a FDA approved food plastic like PETG .020 and up. If I want to produce cheap limited use molds for plaster or resin casting and prototyping I would use cheap HIPS.
I've never used Lexon /Polycarbonate and the only thing I know about it is it's high price.
Aluminum is the best tooling you can have but you really need to justify the cost. You don't need a aluminum tool unless your pulling rapid cycles all day long.
Hope this helps. Below are some facts from my plastic product sheet I use myself.
ABS --Hard, rigid amorphous thermoplastic with good impact strength and weather resistance. It contains
a rubber content which gives it an improved impact resistance. Available with different textures and
fi nishes in a range of thickness. Needs drying. Available in Fire Retardant and UV stabilised grades.
FormabilityGood – forms to a high defi nition.
HygroscopicYes – pre drying required at approx 80° (1 hour
per mm)
StrengthGood – High Impact
Shrinkage Rates0.3 – 0.8%
AvailabilityFrom stock
Solvent/ FillerMethyl Ethyl Ketene (MEK), Toluene and Dichloromethane
Solvent will make fi ller paste.
Finishing/ MachiningMachines well with Circular Saws, Routers and
Band saws– takes all sprays.
Can be Guillotined and Roller cut.
ClearNot Available
ColoursBlack / White / Grey and limited colours.
ApplicationsLuggage, Caravan Parts, Vehicular Parts, Sanitary
Parts, Electrical Enclosures.
PriceMedium
LEXON/P.C. -- Hard, rigid clear amorphous material with high impact resistance and good fire rating. Self extinguishing.
Requires high forming temperatures. Needs drying. Excellent clarity. Similar properties to Acrylic.
Finishing/ MachiningGood for screen printing. Good machine qualities.
Can be ultrasonically welded, drilled and
tapped. Takes spray.
ClearYes
ColoursTranslucent and solid colours. Opal and diffuser
patterns. Available in a variety of embossed textures.
ApplicationsLight diffusers, Signs, Machine Guards, Aircraft
trim, Skylights, Riot Shields, Guards and Visors
PriceExpensive
FormabilityGood
HygroscopicYes – Drying temperature 90° C. 1mm – 1 hr. 3mm
– 4hrs. 4mm – 10hrs.
StrengthVery good impact strength
Shrinkage Rate0.6 – 0.8%
AvailabilityFrom stock
Solvent/ FillerBetween PC components Dichloromethane or
MEK solvent. Care must be taken with solvents
as PC is a stress sensitive material and can be
adversely affected by the solvents at its weak
points. Most proprietary adhesives can be used
to join PC with metal, glass and wood. |
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