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Cetak PlastikCetak PlastikPlastics Injection MoldingPlastics Injection Molding
Sejarah Plastik
Sifat Umum: tahan lama, keras, tangguh, ringan.
Jenis plastik: Thermoset
Contoh:
Polyester: lacquers, varnishes, perahu, furniture
Epoxy dan Resin: lem, coating untuk electrical circuits,composite: fiberglass baling-baling helicopter, perahu
Jenis plastik: Elastomer
Sifat Umum: thermoset, seperti sifat karet
Contoh:
Polyurethan: matras, cushion, insulation, mainan
Silicon: sarung tangan medis, masker, seal
Sifat Umum: suhu leleh rendah, lunak, flexible
Contoh:
Polyethylene: packaging, electrical insulation, milk and water bottles, packaging film
Polypropylene: carpet fibers, automotive bumpers, microwave containers, prosthetics
Polyvinyl chloride (PVC): electrical cables cover, credit cards, car instrument panels
Polystyrene: disposable spoons, forks, Styrofoam™Acrylics (PMMA: polymethyl methacrylate): paints, fake fur,
plexiglassPolyamide (nylon): textiles and fabrics, gears, bushing and
washers, bearingsPET (polyethylene terephthalate): bottles for acidic foods like juices,
food traysPTFE (polytetrafluoroethylene): non-stick coating, Gore-Tex™
(raincoats), dental floss
Jenis Plastik: Thermoplastik
Pengolahan plastik: Extrusion
pelletsopen cross-sections (channels) closed cross-sections (tubes, pipes) pelletsopen cross-sections (channels) closed cross-sections (tubes, pipes)
Pengolahan plastik: Blow molding
heated glass
3-piece mold
(a) The hollow piece of heated glass (parison)is first created by a blow mold(see text-book Fig 17.25)
(b) The mold is put together
(c) Plunger and hot air push theglass up
(d) Hot air blows the glass out towardsthe mold surface
(e) Mold comes apart, bottle is removed
heated glass
3-piece mold
(a) The hollow piece of heated glass (parison)is first created by a blow mold(see text-book Fig 17.25)
(b) The mold is put together
(c) Plunger and hot air push theglass up
(d) Hot air blows the glass out towardsthe mold surface
(e) Mold comes apart, bottle is removed
Pengolahan plastik: Thermoforming
Lembaran plastik Pemanasan (lunak) Dicetak sesuai bentuk
Vacuum thermoforming
Pengolahan plastik: Compression and Transfer Molding
• umumnya thermosetting polymer• mold dipanaskan dan ditutup dengan tekanan• Plastik mengalir kedalam rongga• perlu finishing
Peralatan makan, handel ketel, ski,Casing untuk circuit breaker, sol sepatu,fiber-reinforced composite
Pengolahan plastik: Compression and Transfer Molding
compression molding
transfer molding
(bentuk lebih rumit)
Pengolahan plastik: Injection Molding
- Paling banyak digunakan, penting, dan ekonomis.
Skematik Proses & MesinSkematik Proses & Mesin*
* Source: http://www.idsa-mp.org/proc/plastic/injection/injection_process.htm
*
Skematik mesin Injection molding thermoplastik
Pengaruh suhu mold dan tekanan Pengaruh suhu mold dan tekanan terhadap penyusutanterhadap penyusutan
0.030
0.000
0.0100.005
0.015
0.020
0.025
100 120 140 160 180 200 220 240
Mold Temperature (F)
LDPE PP
Nylon 6/6
PMMA
Acetal
Shri
nkag
e
0.030
0.000
0.010
0.005
0.015
0.020
0.025
Shri
nkag
e6000
800010000
1200014000
16000
Pressure on injection plunger (psi)
AcetalLDPE
Nylon 6/6
PP with flow
18000
PP across
flow
PMMA
Pengolahan Plastik: Injection Molding
Siklus operasi injection molding
[source: www.offshoresolutions.com] AVI [source: ylmf.com.hk]
Injection Molding: Bentuk/geometri Mold
Komponen utama:
mold pieces (menentukan bentuk/geometri produk), sprue, gates, runners, vents, ejection pins, cooling system
Injection Molding: 2-piece and 3-piece molds
Injection Molding: mold dengan core bergerak dan side-action cam - Bila bentuk/geometri ada undercuts
Part
Cavity
Core
Stripper plate
Komponen mold untukKomponen mold untukproduk cangkir plastikproduk cangkir plastik
Runner
Knob
Nozzle
Injection Molding: Perancangan injection mold
cup
parting line
parting plane
core
cavity
ejectionplate
runner
core
cavity
nozzle knob
cavity
core
(a) (b) (c) (d)
core
cavity
part
core
cavity
ejectionplate
core
cavity
ejectionplate
runner
core
cavityrunner
core
cavity
nozzle knob
cavity
core
nozzle knob
cavity
core
(a) (b) (c) (d)
core
cavity
part
core
cavity
core
cavity
part
gate
1. molding directions jumlah insert/cam yg dibutuhkan (bila ada)2. parting lines 3. parting planes dg memperlebar parting line (keluar)4. gating design dimana meletakkan gate5. multiple cavity mold menetapkan posisi dudukan komponen-
komponen6. runners: aliran plastik kedalam cavity7. sprue located: 8. functional parts of the mold
- ejection system: untuk melepas produk yg dicetak- systems to eject the solidified runners - alignment rods: untuk mempertahankan komponen
mold tetap segaris
Runner
Part
Cavity
Nozzle
Part
Cavity
Knob
Stripper plate
Runner
Part
Cavity
Nozzle
Runner
Part
Cavity
Nozzle
Runner
Part
Cavity
Nozzle
Part
Cavity
Knob
Stripper plate
Part
Cavity
Knob
Part
Cavity
Knob
Stripper plate
Runner
Part
Cavity
Nozzle
Runner
Part
Cavity
Nozzle
Perancangan injection mold : mold in action
[source: Lec notes, Prof T. Gutosky, MIT]
Perancangan injection mold : fitur-fitur umum
[source: www.idsa-mp.org]
(a) Shut-off hole:no side action required
(b) Latch:no side action required
(c) Angled Latch:Side action cam required
(a) Shut-off hole:no side action required
(b) Latch:no side action required
(c) Angled Latch:Side action cam required
Perancangan injection mold : fitur-fitur umum
Dasar perancangan produk injection molding
Dasar utama:(i) aliran plastik ke seluruh bagian cavity sebelum mengeras(ii) penyusutan plastik dalam lubang penyusut
Panduan (1) Usahakan penampang/ketebalan seragam seluruh bagian produk
How: use of ribs/gussets
[source: GE plastics: Injection Molding Design Guidelines]
Panduan (2) Hindari penampang yang tebal
[source: GE plastics: Injection Molding Design Guidelines]
Dasar perancangan produk injection molding
Panduan (3) Lokasi gate menunjukkan weld line
weld lines
* Source: http://www.idsa-mp.org/proc/plastic/injection/injection_design_7.htm
Dasar perancangan produk injection molding
Weld line, Sink markWeld line, Sink mark
* Source: http://www.idsa-mp.org/proc/plastic/injection/injection_design_7.htm
Weld line
Aliran kedalam Mold
Gate
Produk yg sudah jadi
Sink mark Perancangan ribs untuk meminimalkan sink mark