What a 150 ton household moulding machine can carry: largest total projected area across all cavities, with a 10% reserve (a starting margin, not a rule)
| Product group | Tonnage factor (US t/in²) | Largest total area at 150 t | What that can mean |
|---|---|---|---|
| PP storage boxes | 2 to 3 | 323 to 485 cm² | One 200 × 150 mm box (300 cm²) at either factor |
| PP casserole and thermoware shells | 2 to 3 | 323 to 485 cm² | One 200 mm round shell (314 cm²) at either factor |
| ABS casserole shells | 2 to 4 | 242 to 485 cm² | One 180 mm shell (254 cm²), but only up to a factor of 3 |
| Baskets with slots in the base | 2 to 3 | 323 to 485 cm² | A 260 × 180 mm basket with 35% open base (304 cm² net) at either factor |
| Solid serving trays | 2 to 3 | 323 to 485 cm² | One 240 × 170 mm tray (408 cm²), only near the lower factor |
| PP mugs and tumblers | 2 to 3 | 323 to 485 cm² | Four 85 mm mugs (227 cm²) at either factor; six (340 cm²) only near the lower |
| Thin-wall tubs and lids | 5 to 8 | 121 to 194 cm² | One 140 mm round lid (154 cm²), only at the lower factor |
A 150 ton household moulding machine suits PP storage boxes, casserole and thermoware shells, slotted baskets, mugs in fours and smaller trays. The limit is total projected area. With a 10% reserve, 150 t holds about 323 to 485 cm² of conventional PP work, but only about 121 to 194 cm² of thin-wall work.
That makes 150 t the size where single large houseware parts start to fit comfortably. Clamp is only the first check, though. Stroke, screw size and venting can still rule a mould out, and the other articles in this series cover each of them.
Key Takeaways
- Clamp needed is projected area, minus through-holes, times cavities, plus any cold runner, times a tonnage factor.
- At PP factors of 2 to 3 US t/in², 150 t holds about 323 to 485 cm² of parts with a 10% reserve.
- Slots in a basket base reduce projected area; slots in its side walls do not.
- For food-contact houseware, choose a PP grade the supplier lists as complying with IS 10910.
How Is the Clamp Force for a Houseware Mould Worked Out?
Find the area of one part as seen from the direction the mould opens, subtract through-holes in that direction, and multiply by the cavity count. Add the cold runner area, multiply by the resin's tonnage factor and add a reserve. That is the clamp the mould needs.
Jeremy Williams of RJG sets out this method in Plastics Technology. He gives typical factors of 2 to 10 US tons per square inch and recommends 3 when you have nothing better. A hot runner keeps its melt inside the manifold, so only the cavities count toward the area.
The factor moves with the part. Williams lists melt flow, flow length, wall thickness, gate location, gate size, gate count and resin volume as the things that shift it, so two PP parts with the same area can need noticeably different clamp.
For PP, an SPE Plastics Engineering article by A. Urbina puts the factor at 2 to 3 US t/in², within an overall range of 2 to 8 across materials. The same article suggests 400 bar of cavity pressure as a guide value when no other data exists.
Convert the units before you compare. One US ton is 0.9072 t and one square inch is 6.4516 cm², so 1 US t/in² equals about 0.141 t/cm². The 10% reserve used in this article is a starting margin, not a rule; trials on the actual mould can justify more or less.
Which Products Fit a 150 Ton Household Moulding Machine?
Single-cavity PP parts up to about 200 mm round, or 314 cm², fit at either PP factor. That covers storage boxes, casserole shells and slotted baskets. Small items such as mugs fit in multiples. Solid trays and large lids fit only near the lower factor, and thin-wall work is limited.
Baskets reward a careful drawing review. Openings in the base pass through in the direction the mould opens, so they come off the projected area. Slots in the side walls run at right angles to that direction, so they do not reduce the clamp, though they do add slides or shut-offs to the mould.
Lids deserve their own check. A lid can have a slightly larger footprint than the box it closes and a flatter, thinner section, so it can need more clamp than the box. Size the lid mould from its own drawing rather than assuming it matches the base.
Casserole and thermoware shells are wide, deep parts, and one cavity can use most of the clamp. In ABS, which can need a higher factor than PP, the usable diameter drops. The casseroles article in this series covers stroke and drying for these shells.
Our view: plan every mould on a 150 t machine at the upper factor for its resin, and treat any mould that fits only at the lower factor as a trial job. A tray that needs the last tonnes of clamp will flash when the melt runs a little hot.
Which Resins and Rules Matter for These Products?
PP homopolymer suits stiff parts such as trays and boxes, and impact copolymer suits parts that must survive drops, such as baskets and buckets. For anything in contact with food, pick a grade the supplier lists as complying with IS 10910, the Indian PP food-contact standard.
Reliance's Repol H110MAS is one example of a houseware grade. Its TDS describes a nucleated homopolymer for rigid packaging, furniture and houseware, with an MFR of 11 g/10 min, flexural modulus of 1,650 MPa and HDT of 110 °C. The sheet lists IS 10910 compliance and rules the grade out for single-use items banned under the PWM Rules.
Thin-wall tubs follow different rules. Gary Tremblay of Sabic, writing in PlasticsToday, puts thin-wall clamp at 5 to 8 US t/in² against 3 to 5 for conventional moulding, and describes adapting conventional machines for thin-wall work as usually unwise. Plan thin-wall programmes as a separate machine decision.
What Should You Prepare Before Choosing a Machine?
Collect the part drawings, cavity counts, runner type and resin grade for every mould planned for the first few years. Run the clamp check at the upper factor, then the stroke, screw and venting checks in this series. See the 150 ton horizontal injection moulding machine page.
Frequently Asked Questions About a 150 Ton Household Moulding Machine
Can a 150 ton machine mould plastic stools?
Not the seat of a full-size stool. A 300 mm round seat projects about 707 cm², which needs roughly 199 t at a PP factor of 2 before any reserve or legs are counted. Small step stools or children's stools may fit, but check the projected area of the whole part first.
Do slots in a basket reduce the clamp it needs?
Only slots that pass through in the direction the mould opens. Base openings come off the projected area, so a basket with an open base needs less clamp than a solid tray of the same size. Side-wall slots do not change the clamp, but they add mould complexity.
What happens if a mould needs more clamp than the machine has?
Melt pressure pushes the mould halves apart, and plastic escapes at the parting line as flash. The parts then need trimming and the parting line can wear. Reducing injection pressure to stop the flash often leads to short shots, so the real fix is fewer cavities or a larger machine.
Is the tonnage factor method accurate enough to buy a machine?
It is accurate enough for early sizing, which is its purpose. For a mould close to the limit, a mould-filling simulation or cavity pressure data from a similar part gives a better figure. Use the factor to shortlist the machine and simulation or trials to confirm the borderline moulds.
Is 150 t a sensible size for a mixed houseware range?
It can be, if your largest planned parts fit at the upper factor and your smallest shots still suit the screw. A range with large shells and tiny lids may be better split across two machines. The screw selection article in this series shows how to check the small-shot end.
Related Articles
- Casseroles and Thermoware Shells on a 150 Ton Machine
- 45 mm or 50 mm Screw? Choosing for Household Articles
- Baskets and Trays: Flow, Venting and Cycle Time on a 150 Ton Machine
Sources & References
- Plastics Technology, J. Williams (RJG): Clamp Tonnage: More Is Better...Right?
- SPE Plastics Engineering, A. Urbina: Mastering Clamping Force Calculation
- Reliance Industries: Repol H110MAS Technical Data Sheet
- PlasticsToday, G. Tremblay (Sabic Innovative Plastics): Never too thin
Technical Disclaimer
Disclaimer: The information provided in this document is for general informational and educational purposes only. It is based on technical references and industry information available at the time of preparation and may be subject to change. It does not constitute engineering, technical, commercial or professional advice, nor does it constitute a quotation, specification, warranty or contractual commitment by Pratishna Engineers.
Actual injection moulding machine and process requirements vary according to the component design, material, mould, production volume, machine configuration and operating conditions. The information, examples, calculations and recommendations provided should be independently evaluated and verified for the specific application before making any equipment, process or production decision. Information obtained from third-party sources remains subject to the accuracy and limitations of those sources.
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