PS Injection Molding
We mold Polystyrene (PS) (and compatible grades) for functional, structural and aesthetic parts — from low-volume bridge production to high-volume runs.
PS: Transparent, Rigid and Cheap — With a Brittleness Catch
Polystyrene delivers the highest stiffness-to-cost ratio in molding — and the transparency to match, with up to 1500×1000 mm parts and DIN-7168-m tolerances (https://firstmold.com/ps-injection-molding/). MOLDITQUICK molds GPPS and HIPS grades on its Sodick fleet under ISO9001 control.
High transparency — clear GPPS rivals acrylic for low-cost see-through parts; HIPS trades clarity for toughness.
Excellent stiffness and dimensional stability — parts hold their shape with predictable amorphous shrinkage.
Outstanding electrical insulation — PS is a standard dielectric for high-frequency and switchgear components.
Very low cost — one of the cheapest resins to mold, ideal for high-volume consumer and packaging parts.
Easy flow and fast cycles — fills thin walls and long flows; short cycles cut unit cost further.
Full colorability — transparent, translucent and opaque colors matched to Pantone/RAL with ΔE ≤ 1.0.
Proven in precision parts — high-end automotive lights and precision medical components molded with mold-flow-backed design (https://firstmold.com/ps-injection-molding/).
PS Processing Parameters We Control
Barrel, mold and shrinkage windows per published PS molding data (https://firstmold.com/ps-injection-molding/); drying per industry standard — verified in-house on Sodick presses under ISO9001 control.
| Parameter | Recommended Range | Why It Matters |
|---|---|---|
| Barrel temperature | 180–280 °C | Wide, forgiving window — PS flows freely; the upper end suits high-flow thin-wall parts. |
| Mold temperature | 20–70 °C | Cool molds give fast cycles; hotter molds improve surface gloss and weld-line strength. |
| Mold shrinkage | 0.4–0.7 % | Predictable amorphous shrinkage — cavity compensation keeps mating parts in tolerance. |
| Drying | Rarely needed (< 0.1 % absorption) | PS is not hygroscopic — resin can run straight from the hopper. |
| Wall thickness | 1.0–4 mm typical | Uniform walls prevent sink marks; thinner walls need higher flow grades. |
| Injection pressure | 70–140 MPa typical | Enough for thin walls; watch flash as PS flows easily at high pressure. |
PS Grades & Modified Compounds We Mold
The PS families FirstMold processes — including two-color and overmolding combinations (https://firstmold.com/ps-injection-molding/).
Common PS Defects — and How We Prevent Them
PS's main enemies are its own brittleness and easy flow; FirstMold's PS experience (https://firstmold.com/ps-injection-molding/) drives the controls below.
Molded-in stress plus PS's brittleness = surface micro-cracks around gates, inserts and snap-fits.
Uneven walls in a stiff, shrink-prone resin show sink on thick bosses and ribs.
Knit lines are weaker and more visible in PS than in most resins — cosmetic and structural risk.
PS flows so easily that worn parting lines or over-packing flash immediately.
Melt and mold windows are tuned for low orientation — stress cracks are prevented, not repaired.
Walls, ribs and bosses are balanced at DFM — no sink, no warp after ejection.
Gates positioned to keep knit lines out of visible and load-bearing zones, backed by mold-flow analysis.
Where PS Injection Molding Pays
Automotive
Lamp covers, glove-box parts, center-console elements, mirror housings and tail-light lenses (https://firstmold.com/ps-injection-molding/).
Consumer electronics
TV housings, printer parts, battery-pack housings, speaker housings and light-switch plates.
Daily goods
Cassette and storage cases, combs, pen barrels, cosmetic cases, transparent buttons, sunglass frames.
Medical & lab
Petri dishes, diagnostic housings, blister packs, IV-set components and safety shields.
Packaging
Transparent boxes, trays and display packaging in low-cost GPPS.
Electrical
High-frequency capacitors, switch plates and insulating components leveraging PS dielectric performance.
PS Design Rules We Enforce
- ✓PS shrinks 0.4–0.7 % — predictable amorphous shrink; compensate in cavity sizing and gate for uniform packing.
- ✓Keep wall thickness uniform — PS shows sink marks readily; ribs should run ≤ 60% of wall thickness.
- ✓Draft 1–2° minimum — PS is stiff and can crack or drag at ejection without draft.
- ✓Avoid sharp corners — fillet ≥ 0.5× wall thickness; PS brittleness makes notches a crack starter.
- ✓Gate to keep weld lines out of cosmetic and load-bearing zones — knit lines are weak points in PS.
- ✓For snap-fits and press-fits, use HIPS or specify impact-modified grades — GPPS does not yield.
- ✓Use high-flow grades for thin-wall and long-flow parts — PS freezes early in cold molds.
PS Injection Molding FAQ
- ✓Q: What's the difference between PS and HIPS? A: GPPS is crystal-clear but brittle; HIPS adds rubber for impact toughness at the cost of some clarity — the right pick depends on the part's abuse level.
- ✓Q: Can PS parts be transparent? A: Yes — GPPS transmits light well and is the low-cost choice for see-through parts; acrylic or PC only when optical quality or toughness demands more.
- ✓Q: Is PS safe for food contact? A: Food-contact PS grades are available per FDA 21 CFR for packaging and trays.
- ✓Q: Does PS need drying before molding? A: No — it absorbs under 0.1 % moisture, so it runs straight from the hopper, unlike ABS or PC.
- ✓Q: Why did my PS part crack in the field? A: Usually molded-in stress plus brittleness — gate, wall and snap-fit design are reviewed at DFM, and HIPS or impact grades are specified where loads exist.
- ✓Q: What tolerances can PS hold? A: DIN-7168-m standard with precision to ±0.05 mm — verified by first article and CMM (https://firstmold.com/ps-injection-molding/).
- ✓Q: What lead times apply? A: 7–12 days low volume, 25–30 days production, global shipping — with DFM and T1 samples included.
Related Capabilities
Explore the full range of MOLDITQUICK manufacturing services.