A 180 ton household moulding machine suits medium PP buckets, storage boxes around 220 × 160 mm, casserole shells and mugs in sixes. With a 10% clamp reserve (a starting margin, not a rule), it holds about 388 to 582 cm² of conventional PP parts: one round part up to about 222 mm across at either PP factor, or about 272 mm near the lower one.
Large washing basins, big dustbins and multi-cavity thin-wall tubs are where it runs short. Clamp is the first filter. Shot size, opening stroke and lid shrinkage then decide which moulds belong on it, and the other articles in this series take those one at a time.
Key Takeaways
- Work out clamp from the part's footprint in the opening direction, the cavity count, any cold runner and the resin's tonnage factor.
- At PP factors of 2 to 3 US t/in², 180 t holds about 388 to 582 cm² of parts with a 10% reserve.
- Parts that fit only near a factor of 2 are trial jobs, not safe plans, until mould trials confirm the factor.
- Leaving a small mould at full tonnage adds no safety; it can crush vents, roll the parting line and crack blocks.
How Much Part Area Can 180 t of Clamp Hold?
About 388 cm² at a PP tonnage factor of 3 US t/in² and about 582 cm² at a factor of 2, both with a 10% reserve. Thin-wall work, at factors of 5 to 8, cuts the usable area to roughly 146 to 233 cm².
The method is set out by Jeremy Williams of RJG in Plastics Technology. Take the area of one part as seen from the direction the mould opens, subtract holes that pass through in that direction, multiply by the cavity count and add the cold-runner area. Multiply the total by a tonnage factor. He gives typical factors of 2 to 10 US t/in² and suggests 3 when you have nothing better.
For PP, an SPE Plastics Engineering article by A. Urbina puts the factor at 2 to 3, inside a span of 2 to 8 across resins, with polyethylene at the low end and polycarbonate toward the high end. Williams names melt flow, flow length, wall thickness and gate size, position and count as the variables that move it.
To work in metric, 1 US ton is 0.9072 t and 1 in² is 6.4516 cm², so 1 US t/in² is about 0.141 t/cm². With a hot runner the melt stays in the manifold, so only the cavities count toward the area.
Largest total projected area at 180 t, with a 10% reserve (a starting margin, not a rule)
| Tonnage factor (US t/in²) | Largest total area | Largest single round part |
|---|---|---|
| 2 (easy-flow PP) | 582 cm² | About 272 mm diameter |
| 3 (PP, cautious) | 388 cm² | About 222 mm diameter |
| 4 | 291 cm² | About 192 mm diameter |
| 5 (thin-wall, low end) | 233 cm² | About 172 mm diameter |
| 8 (thin-wall, high end) | 146 cm² | About 136 mm diameter |
Which Products Fit a 180 Ton Household Moulding Machine?
Medium buckets, boxes around 220 × 160 mm, casserole shells and six-cavity mug moulds fit at either PP factor. Larger buckets, basins, open-base baskets and small dustbins fit only if trials confirm a factor near 2. A single thin-wall tub fits only below the top of its range.
Example parts at 180 t (sizes assumed; one cavity unless stated; PP factor 2 to 3 US t/in², thin-wall 5 to 8; 10% reserve)
| Product group | Example part | Clamp needed | Fits 180 t? |
|---|---|---|---|
| Medium buckets | 220 mm rim | 118 to 176 t | Yes, at either factor |
| Larger buckets | 270 mm rim | 177 to 266 t | Only at a factor of about 2.0 |
| Tubs and basins | 260 mm round | 164 to 246 t | Only up to a factor of about 2.2 |
| Storage boxes | 220 × 160 mm | 109 to 163 t | Yes, at either factor |
| Storage boxes | 250 × 180 mm | 139 to 209 t | Only up to a factor of about 2.6 |
| Casserole shells | 220 mm round | 118 to 176 t | Yes, at either factor |
| Baskets | 320 × 220 mm, 30% open base | 152 to 229 t | Only up to a factor of about 2.4 |
| Small dustbins | 250 mm round top | 152 to 228 t | Only up to a factor of about 2.4 |
| Thin-wall tubs | 140 mm round | 119 to 190 t | Only up to a factor of about 7.6 |
For a bucket, tub or dustbin, the projected area is the outer rim circle, since the wall and base sit inside it. Handle lugs standing outside the rim add a little. In a basket, openings in the base run in the opening direction and come off the area, which is why a large basket can fit where a solid tray of the same size cannot.
Lids need a separate check. A lid is often a few millimetres wider than its box and has a thinner, flatter section, so its mould can need more clamp than the box mould. The storage boxes article in this series covers lids, shrinkage and whether box and lid can share one mould.
Can a 180 t Machine Run Small Moulds Well?
Yes, if the mould covers enough of the tie-bar space and the clamp is set to what the mould needs. A mould covering less than about 70% of the distance between tie bars lets the platens bow, and full tonnage on a small mould can damage it.
The 70% figure is a rule of thumb from a Plastics Technology article on mounting moulds. Below it, the platens flex under clamp and the mould can flash at its centre; very small moulds can cause serious platen damage. Machine manuals usually give a minimum mould size, sometimes on a placard on the frame.
Over-clamping has its own cost. Williams describes a mould that needed about 100 tons but was clamped at the 400-ton machine maximum: the cavity block split in two places, at a cost upwards of $100,000. He also lists burns, short shots, crushed vents, a rolled parting line and broken inserts. Urbina adds that excess clamp can crack cylinder mounting plates and deform platens.
Our view: set the clamp for each mould from its calculated need plus the reserve, and never leave it at maximum by habit. A 110 t mould clamped at 180 t gains nothing and spends the extra force on its vents, parting line and the machine.
Which Resins and Food Rules Apply to These Products?
Impact copolymer PP suits buckets, baskets and parts that are dropped or carried full; homopolymer suits stiffer boxes and trays. Where a food business uses your tub or box as packaging, the resin must meet IS 10910 for PP and an NABL lab must certify conformity.
Those requirements come from the FSSAI Packaging Regulations, 2018. Schedule III lists the Indian Standards for plastics in food containers, including IS 10910 for PP, IS 10146 for PE and IS 10142 for PS. The overall migration limit is 60 mg/kg or 10 mg/dm², tested to IS 9845, and pigments must meet IS 9833.
For houseware sold to households rather than to food businesses, ask your buyer which standard they specify, and ask your resin supplier for a current compliance statement against IS 10910 before releasing a food-contact part.
What Should You Check Before Committing Moulds to 180 t?
List every mould planned for the first few years with its drawing, cavity count, runner type and resin. Run the clamp check at the upper factor, then check shot, stroke and mould size against the machine. See the 180 ton horizontal injection moulding machine page.
Frequently Asked Questions About a 180 Ton Household Moulding Machine
Can a 180 ton machine mould a full-size plastic chair?
No. A 450 × 450 mm footprint alone projects about 2,025 cm², several times the 388 to 582 cm² that 180 t can hold at PP factors with a reserve. Children's chairs and small step stools may fit, but check the projected area of the whole part, including legs and armrests, first.
Is a two-cavity mould a good idea at 180 t?
Only if both cavities and the runner fit at the upper factor. Two 160 mm round tubs project about 402 cm², which needs about 124 t at a PP factor of 2 and 187 t at 3. That makes it a trial job at 180 t, not a safe plan, before any runner is counted.
Does a hot runner let me add cavities at 180 t?
It removes the cold-runner area from the clamp sum and the runner weight from the shot, which helps. The cavities themselves still count in full. So a hot runner can turn a borderline mould into one that fits, but it cannot make room for a cavity whose own area exceeds the margin.
Can I mould ABS or HDPE houseware on the same machine?
Yes, but recalculate each mould for its own resin. Polyethylene sits at the low end of the tonnage factor range, so an HDPE part usually needs less clamp than the same part in ABS, which needs a higher factor than PP and must be dried before moulding. Check the drying time against your cycle and hopper size.
What if my product range grows after I buy?
Plan for the largest mould you expect in the next few years, not only the first one. If a planned part fits only near the lower factor, budget for mould trials or note it as a job for a larger machine. A second, smaller machine for small parts can suit better than oversizing one.
Related Articles
- Bucket Moulding on a 180 Ton Machine: Sizes, Shot Weight and Output
- Storage Boxes With Lids: Matching Shrinkage on a 180 Ton Machine
- 180 Ton Household vs Container Moulding Machine for Tubs and Containers
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
- Food Safety and Standards Authority of India (FSSAI): Food Safety and Standards (Packaging) Regulations, 2018, compendium
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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