What a 260 ton household moulding machine can hold: clamp per mould at PP factors of 2 to 3 US t/in², one cavity, sprue gated, 10% reserve (sizes assumed for illustration)
| Product and size | Projected area | Clamp needed | Fit at 260 t |
|---|---|---|---|
| Bucket or tub, 260 mm rim | 531 cm² | 164 to 246 t | Yes, at either factor |
| Storage box, 280 × 190 mm | 532 cm² | 165 to 247 t | Yes, at either factor |
| Round dustbin, 300 mm rim | 707 cm² | 219 to 328 t | Only near a factor of 2 |
| Laundry basket, 400 × 300 mm, 40% open base | 720 cm² | 223 to 334 t | Only near a factor of 2 |
| Large storage box, 330 × 230 mm | 759 cm² | 235 to 352 t | Only near a factor of 2 |
| Solid tray, 350 × 250 mm | 875 cm² | 271 to 406 t | No |
A 260 ton household moulding machine comfortably holds round PP parts up to about 267 mm across and boxes of about 530 cm², and, when trials confirm a low factor, dustbins, stool seats, laundry baskets and large boxes up to about 840 cm². That range comes from 260 t less a 10% reserve, divided by PP's tonnage factor.
The table is a clamp check only. Height, flatness and cycle time decide many large household parts, and each has its own article in this series.
Key Takeaways
- With a 10% reserve, 260 t holds about 560 cm² of PP parts at a factor of 3 and about 840 cm² at 2.
- Dustbins, laundry baskets and large boxes fit 260 t only when trials confirm a factor near 2.
- Two 200 mm buckets in one mould need about 201 t at a factor of 2 and fit up to a factor of about 2.6.
- For food-contact houseware, use a PP grade whose supplier lists compliance with IS 10910.
How Do You Work Out Whether a Part Fits 260 t?
Find the part's area seen from the direction the mould opens, remove through-holes, multiply by the cavity count and add the cold runner. Multiply by a tonnage factor for the resin and add a reserve. A result below 260 t means the clamp can hold the mould.
Jeremy Williams of RJG describes this method in Plastics Technology and recommends a factor of 3 US tons per square inch when nothing better is known, within a typical span of 2 to 10. Only cavities count with a hot runner, because the melt in the manifold never presses on the parting line.
For PP, A. Urbina's SPE Plastics Engineering article gives 2 to 3 US t/in². In metric, 1 US t/in² is about 0.1406 t/cm². This article holds back 10% of the clamp as a starting margin, not a rule, which leaves about 236 t for the parts at 260 t.
Divide 236 t by 0.281 t/cm², the factor of 2, and the limit is about 840 cm². At a factor of 3, 0.422 t/cm², it is about 560 cm². Melt flow, flow length, wall thickness and gating move the real factor, so a thin part filled through one gate sits higher than a thick, short-flow one.
Which Products Fit a 260 Ton Household Moulding Machine?
Buckets, tubs and boxes up to about 530 cm² fit at either PP factor. Round dustbins, stool seats, slotted laundry baskets and storage boxes up to about 840 cm² fit only near a factor of 2. Solid trays larger than that need a bigger clamp, whatever the resin.
The step from 220 t to 260 t adds about 18% more clamp, which moves dustbins with 300 mm rims and large storage boxes from impossible to possible, but only at the low end of the PP range. Plan those moulds with trials on the actual part before cutting final steel.
Multi-cavity moulds open another route. Two 200 mm buckets per shot need about 201 t at a factor of 2, as the worked example shows, which can double output from one mould when the buckets are small enough. The barrel must then carry two parts per shot as well.
Our view: at 260 t, put the large, single-cavity parts on the machine and keep two-cavity moulds for parts that fit comfortably at a factor of 3. A two-cavity mould that only fits at 2 gives you twice the parts and twice the flash when the melt runs hot.
Where Does a 260 t Machine Run Short?
On height, flatness and mould size. Tall dustbins need more opening stroke than a mid-size machine may offer, large flat trays warp unless wall and cooling are balanced, and big moulds must still fit between the tie bars. Check each before you confirm a product for 260 t.
Bruce Catoen's guide to machine sizing in MoldMaking Technology says the parts' projected area should sit fully inside the tie bars, because platens can pull in near them and wear the parting line. Ideally the whole mould fits within them. Wide box and basket moulds reach this limit early.
Clamping harder is not the answer for a mould that flashes. An SPE Plastics Engineering article warns that excess clamp force can crack hydraulic cylinder mounting plates, deform platens and fracture the machine frame. Stroke, flatness and cycle time are covered in the dustbins, flat trays and pump flow articles in this series.
Which PP Grades and Indian Standards Apply?
Homopolymer PP suits stiff boxes, trays and lids; impact copolymer suits dustbins, buckets and baskets that are dropped or stacked. For anything that touches food, choose a grade listed against IS 10910, the Indian standard for PP in food contact, and ask for the compliance certificate.
Reliance's Repol H110MAS is one example of a nucleated homopolymer for houseware. Its TDS gives an MFR of 11 g/10 min, flexural modulus of 1,650 MPa, HDT of 110 °C, IS 10910 compliance and BIS designation IS 10951-1-MBL-C, and rules it out for single-use items banned under the PWM Rules.
What Should You Send Before Choosing a Machine?
Send drawings with footprint, height, wall thickness and part weight for each mould, the resin grade and the cavity count you want. The clamp check comes first at a factor of 3, then stroke, flatness and mould size. See the 260 ton horizontal injection moulding machine page.
Frequently Asked Questions About a 260 Ton Household Moulding Machine
Is 260 t enough for a full-size plastic chair?
No. A full-size chair projects well beyond 840 cm², the most 260 t can hold at a PP factor of 2 with a 10% reserve. Stool seats around 300 mm across and small children's chairs may fit, but check the whole part's projected area, legs and back included, before planning a chair mould.
What does 40 t more clamp add over a 220 t machine?
About 18% more projected area at the same factor. In practice that lets 300 mm round dustbins, stool seats and some large storage boxes fit at a factor near 2, where a 220 t machine sits at or beyond its limit. Height and stroke still need checking separately.
Can lids for dustbins and boxes share the 260 t machine?
They can, as separate moulds. A lid has the same or slightly larger outline than its base, so it needs similar clamp but far less stroke. Running lids and bases on one machine means mould changes, so balance changeover time against the quantities each part needs.
How do I find the real tonnage factor for my part?
Run the mould on trial and reduce clamp in steps while watching the parting line for flash, or use mould-filling simulation and cavity pressure data from a similar part. The lowest clamp that runs flash-free, plus your reserve, gives the real requirement for that mould.
Does a hot runner let more parts fit on 260 t?
It can. With a hot runner, only the cavities count toward projected area, because the melt in the manifold does not press on the parting line. On a two-cavity mould with a large cold runner, removing the runner area can be enough to bring the mould within 260 t.
Related Articles
- Dustbins and Large Storage Boxes on a 260 Ton Machine
- Large Flat Trays Without Warp on a 260 Ton Machine
- Pump Flow and Cycle Time on Large Household Machines
Sources & References
- Plastics Technology, J. Williams (RJG): Clamp Tonnage: More Is Better...Right?
- SPE Plastics Engineering, A. Urbina: Mastering Clamping Force Calculation
- MoldMaking Technology, B. Catoen: Machine Sizing and Specification for Optimal Mold Performance, Part 1
- Reliance Industries: Repol H110MAS Technical Data Sheet
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.
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