Injection molding is a manufacturing process where plastic is forced into a mold cavity under pressure. A mold cavity is essentially a negative of the part being produced. The cavity is filled with plastic, and the plastic changes phase to a solid, resulting in a positive. Typically injection pressures range from 5000 to 20,000 psi. Because of the high pressures involved, the mold must be clamped shut during injection and cooling. Clamping forces are measured in tons.
Courtesy of Fleming Plastic Equipment, an extract from their ancillary equipment catalogue.
AAS Methacrylate-acrylic-styren PEEK Polyaryletherketone ABS Acrylonitrile-butadiene-styrene PEI Polyetherimide ACM Acrylic acid ester rubber PEO, PEOX Polyethylene oxide ADC Allyl diglycol carbonate PEPA Polyester block amides AES Acrylonitrile-ethylene- propylene-styrene PEP Polyethylene-propylene AMMA Acrylonitrile-methyl methacrylate PES Polyester sulphone ANM Acrylic acid ester rubber PET, PETP Polyethylene terephthalate APP Atactic polypropylene PETG Polyethylene terephthalate, glycol comonomer ASA Acrylonitrile-styrene-acrylic ester PF Phenol formaldehyde AXS Acrylonitrile-styrene- terpolymers PFA Perfluoro alkoxy alkaline BR Cis-1, 4-polybutadiene rubber PFEP Polytetrafluorethylene- perfluoro-propylene BS Butadiene-styrene rubber PFF Phenol-furfural CA Cellulose acetate PI Polyimide CAB Cellulose acetate-butyrate PIB Polyisobutylene CAP Celluose acetate propionate PIBI Butyl rubber CF Cresol formaldehyde PIR Polyisocyanate CHR Epichlorhydrine PMCA Polymethyl - chloroacrylate CMC Carboxymethyl cellulose PMI Polymethacryloimide CN Cellulose nitrate PMP Poly- 4 -methylpentene-1 CP Cellulose propionate POM Polyoxymethylene, polyacetal CPE Chlorinated polyethylene (correctly:PEC) PP Polypropylene CPVC Chlorinated polyvinylchloride (correctly:PVCC) PPC Chlorinated polypropylene CR Chloroprene rubber PPMS Polyparamethylstyrene CS Casein PPO(S) Polyphenylene oxide (styrene) CSM Chlorosulfonated polyethylene PPOX Polypropylene oxide CTA Cellulose triacetate PPS Polyphenylene sulfide DAP Diallyl phthalate PPSU Polyphenylene sulfone EC Ethyl cellulose PS Polystyrene ECB Ethylene-cop-bitumen PSB Styrene butadiene rubber ECTFE Ethylene-chlorotrifluoro- ethylene PSU Polysulfone EEA Ethylene-ethylacrylate PTFE Polytetrafluorethylene EMA Ethylene-methacrylic acid PTP Polyterephthalates EP Epoxy epoxide PUR Polyurethane EPDM Ethylene-propylene teropolymer rubber PVAC Polyvinyl acetate EPM Ethylene-propylene rubber PVAL Polyvinyl alcohol EPS Expanded polystyrene PVB Polyvinyl butyral ETFE Ethylene-tetrafluroethylene PVC Polyvinyl chloride EVA, EVAC Ethylene-vinyl acetate PVCA Polyvinyl chloride-acetate FEP Perfluoro ethylene-propylene PVCC Chlorinated polyvinyl chloride FF Furan formaldehyde PVDC Polyvinylidene chloride GR-I Butyl rubber PVDF Polyvinylidene fluoride GR-N Nitrile rubber PVFM Polyvinyl formal GR-S Styrene-butadiene rubber PVK Polyvinyl carbazole IIR Butyl rubber PVP Polyvinyl pyrrolidone IPDI Isophorone diisocyanate RF Resorcin formaldehyde IR Cis-1, 4-polyisoprene rubber SAN Styrene-acylonitrile MBS Methylmethacrylate- butadiene- styrene SB Styrene-butadiene MC Methyl cellulose SBR Styrene-butadiene rubber MDI Diphenylmethane diisocyanate SI Silicone plastics MF Melamine formaldehyde Si Silicone rubber MMA Methylmethacrylate SMA Styrene-maleic anhydride MPF Melamine-phenol- formaldehyde SMS Styrene - methylstyrene NBR Nitrile rubber SRP Styrene-rubber-plastics NC Cellulose nitrate TAC Triallylcyanurate NR Natural rubber TFA Fluor-alkoxy-terpolymer PA Polyamide (nylon) TDI Toluyl diisocyanate PAA Polyacrylic acid TMDI Trimethyl-hexamethylene diisocyanate PAI Poly-amideimide TPU Thermoplastic polyurethane PAK Polyester alkyd TPX Polymethylpentene PAN Polyacrylonitrile UF Urea formaldehyde PB Polybutene-l UP Unsaturated polyester PBAN Polybutadiene-acrylonitrile VAC Vinyl acetate PBS Polybutadiene-styrene VC Vinyl chloride PBTP Polybutylene therephthalate VCE Vinyl chloride-ethylene PC Polycarbonate VCEVA Vinyl chloride-ethylene- vinyl acetate PCD Polycarbodiimide VCOA Vinyl chloride-octylacrylate PCTFE Polymonochlorotri fluoroethylene VCVAC Vinyl chloride-vinyl acetate PDAP Polydiallyl phthalate VCVDL Vinyl chloride-vinylidene chloride PE Polyethylene VF Vulcanized fibre PEC Chlorinated polyethylene
However, in real life nothing is square and we are continually confronted with a multitude of shapes. Products that are unique to each industry will go through various stresses, strains and impact scenarios. Heat, sunlight and colour can also add complexity let alone the number of components that will need to interact synergistically.
Improved impact strength and physical properties.
Improved dimensional stability.
Improved high temperature stability.
Ease of processing.
Thinner wall sections.
Superior structural properties.
Giving rise to LFT being used in items traditionally made from SFT through to various metals.
Being able to identify high stress locations in a part and using modelling to predict how the fibres will orientate has allowed the design of parts with thinner walls to enable functionality, reduce weight and to improve overall performance primarily through:
Tailoring the fibre orientation in the direction of critical stresses.
Tailoring fibre content to the strength and stiffness required.
Tailoring melt flow in the mould to achieve desired fibre orientation and moving weld lines to areas of low stress.
Employing low shear moulding processes with generously sized runners and gates.
And utilising FEA and MFA analysis to design and test in the initial stages before tool construction begins.
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