A 220 ton household moulding machine suits PP buckets and tubs up to about 245 mm across the rim, storage boxes around 260 × 180 mm and, near the low end of the PP range, 280 to 300 mm tubs, stool seats and laundry baskets with open bases. With a 10% reserve, 220 t holds about 474 to 711 cm² of conventional PP parts.
Clamp is the first filter, not the last. Mould width, opening stroke and shot size can each rule out a mould that the clamp would hold, so this article sets out what fits and then the checks that follow.
Key Takeaways
- Clamp needed is the projected area of the parts and any cold runner, times a tonnage factor, plus a reserve.
- At PP factors of 2 to 3 US t/in², 220 t covers about 474 to 711 cm² of parts with a 10% reserve.
- A box and its lid in one family mould can need over 300 t, even when each fits 220 t on its own.
- For houseware that touches food, pick a PP grade its supplier lists as complying with IS 10910.
How Do You Check Whether a Mould Fits 220 t?
Take the area of one part as seen from the opening direction, subtract through-holes, multiply by the cavities and add any cold runner. Multiply that total by the resin's tonnage factor and add a reserve. If the answer stays below 220 t, the clamp can hold the mould shut.
This is the method Jeremy Williams of RJG gives in Plastics Technology. His typical factors run from 2 to 10 US tons per square inch, with 3 as the starting point when you have no better data. With a hot runner, only the cavities count toward the area.
For PP, an SPE Plastics Engineering article by A. Urbina gives 2 to 3 US t/in². To work in metric, use 1 US t/in² = 0.1406 t/cm². The 10% reserve used here is a starting margin, not a rule. It leaves 200 t for the parts: 711 cm² at a factor of 2 and 474 cm² at 3.
The factor is not fixed for a resin. Williams lists melt flow, flow length, wall thickness, gate size, gate location, gate count and resin volume as things that move it. A thin tub filled from one centre gate over a long flow path sits higher in the range than a thick, short-flow part.
Which Products Fit a 220 Ton Household Moulding Machine?
Round PP parts up to about 245 mm across fit at either PP factor, which covers mid-size buckets, tubs and storage boxes. Parts up to about 300 mm across, such as larger tubs, stool seats and slotted laundry baskets, fit only when trials confirm a factor near 2.
Clamp needed per mould at PP factors of 2 to 3 US t/in², one cavity, sprue gated, with a 10% reserve (sizes are assumed for illustration)
| Product and size | Projected area | Clamp needed | Fit at 220 t |
|---|---|---|---|
| Storage box, 260 × 180 mm | 468 cm² | 145 to 217 t | Yes, at either factor |
| Bucket or tub, 240 mm rim | 452 cm² | 140 to 210 t | Yes, at either factor |
| Tub, 280 mm rim | 616 cm² | 191 to 286 t | Only near a factor of 2 |
| Stool seat, 300 mm round | 707 cm² | 219 to 328 t | At the limit, even at 2 |
| Laundry basket, 380 × 280 mm, 40% open base | 638 cm² | 198 to 296 t | Only near a factor of 2 |
| Solid tray, 350 × 250 mm | 875 cm² | 271 to 406 t | No |
Openings in a basket base pass through in the direction the mould opens, so they come off the projected area. Slots in the side walls do not reduce clamp. A solid tray has no such relief, which is why the tray in the table needs more clamp than the larger slotted basket.
Our view: plan every PP mould on a 220 t machine at a factor of 3, and treat any mould that fits only near 2 as a trial job before you commit to it. A tub that needs the last tonnes of clamp will flash as soon as the melt runs a little hot.
What Else Can Rule a Mould Out at 220 t?
Mould width, mould height, opening stroke and shot size. A wide mould may not pass between the tie bars, a deep part may not clear its core, and a heavy part may need more barrel than the machine carries. Check all four before ordering steel.
Small moulds are a risk too. A Plastics Technology article on mounting moulds, by P. Witaszek and co-authors, gives a rule of thumb that the mould should cover at least 70% of the distance between the tie bars. Smaller moulds let the platens bow under clamp, which shows up as flash in the centre of the mould.
Opening stroke and daylight for deep parts are covered in the deep moulds article in this series. Shot and barrel sizing for heavy buckets are worked through in the buckets and tubs article.
Over-clamping is not a safe fallback. Williams describes a mould that needed about 100 tons being clamped at a 400-ton machine maximum; the cavity block split in two places. Set clamp from the calculation, not from the top of the machine's range.
Which PP Grades and Indian Rules Apply to Household Articles?
Use PP homopolymer for stiff boxes and trays, and impact copolymer for buckets, tubs and baskets that get dropped. For anything that touches food, choose a grade whose supplier lists compliance with IS 10910, the Indian standard for PP in food contact applications.
Reliance's Repol H110MAS is one homopolymer example. Its TDS lists houseware among its uses, with an MFR of 11 g/10 min, flexural modulus of 1,650 MPa, HDT of 110 °C and IS 10910 compliance. Its notched Izod of 30 J/m at 23 °C suits stiff parts better than parts dropped full.
Recycled content is the other rule to track. Rigid plastic packaging in India now carries minimum recycled-content targets, and the recycled PP article in this series covers which household parts they reach and how to run recycled grades.
What Should You Send Before Choosing a Machine?
Send part drawings, cavity counts, runner type and resin grade for each mould you plan to run, with boxes and lids as separate drawings. Each mould can then be checked at a factor of 3 first, then for width, stroke and shot. See the 220 ton horizontal injection moulding machine page.
Frequently Asked Questions About a 220 Ton Household Moulding Machine
Can a 220 ton machine mould a plastic chair?
Not a full-size chair. A chair's seat and back together project far more than 711 cm², the most 220 t can hold at a PP factor of 2 with a 10% reserve. Stool seats up to about 300 mm across sit right at that limit, so treat them as trial jobs on this size.
Why can a lid need more clamp than its box?
A lid can be slightly larger in outline than the box it closes, and its flat, thin section can push the tonnage factor up. In the worked example, the lid needs about 159 to 238 t against 145 to 217 t for the box. Size each mould from its own drawing, never by assumption.
Is a 220 t machine too big for small houseware parts?
It can be. A small shot on a large barrel stays in the heat for many cycles, and a large machine running a small part uses more energy per part than it needs. If much of your range is mugs and small lids, a smaller machine for those can free the 220 t for buckets and tubs.
Can two buckets run in one mould on 220 t?
Two buckets with 200 mm rims project about 628 cm² together, which needs about 194 t at a PP factor of 2 and 292 t at 3, with a 10% reserve. That fits only if trials confirm a low factor, and the wider two-cavity mould must also pass between the tie bars.
Should you trust a tonnage factor for a borderline mould?
For early sizing, yes. For a mould that fits only near the bottom of the range, use mould-filling simulation or cavity pressure data from a similar part. The factor shortlists the machine; simulation and trials confirm the moulds that sit close to the 220 t limit before you order steel.
Related Articles
- Larger Buckets and Tubs on a 220 Ton Machine
- Deep Houseware Moulds: Daylight and Ejector Stroke on a 220 Ton Machine
- Using Recycled PP on a 220 Ton Household Machine
Sources & References
- Plastics Technology, J. Williams (RJG): Clamp Tonnage: More Is Better...Right?
- SPE Plastics Engineering, A. Urbina: Mastering Clamping Force Calculation
- Plastics Technology, P. Witaszek, J. Klees, J. Fattori, E. Di Siro, J. Bozzelli: How to Mount an Injection Mold (June 2017)
- Reliance Industries: Repol H110MAS Technical Data Sheet
Technical Disclaimer
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