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