What a 180 ton container moulding machine can hold: largest projected area with a 10% reserve (a starting margin, not a rule)
| Tonnage factor (US t/in²) | Factor (t/cm²) | Typical case | Largest area | Round rim equivalent |
|---|---|---|---|---|
| 2 | 0.281 | PE or PP, easy flow, thicker walls | 582 cm² | 272 mm |
| 3 | 0.422 | PP upper end; common starting point | 388 cm² | 222 mm |
| 4 | 0.562 | Stiffer grades, longer flow | 291 cm² | 192 mm |
| 5 | 0.703 | Lower end of the thin-wall range | 233 cm² | 172 mm |
| 8 | 1.125 | Upper end of the thin-wall range | 145 cm² | 136 mm |
A 180 ton container moulding machine can run PP buckets up to about 4 litres, paint and grease tubs in three to five cavities, reusable food containers in two or three, thin-wall tubs in two to four, and dairy cups in three to six. The table shows the largest rim area each tonnage factor allows.
Container size alone does not settle it. Wall thickness moves the factor, depth moves the opening stroke, and the cavity count moves both clamp and shot.
Key Takeaways
- A container's projected area is its rim outline, so a 210 mm round rim gives about 346 cm² whatever the depth.
- At a factor of 3 US t/in² and a 10% reserve, 180 t holds about 388 cm²; at a thin-wall factor of 8, only about 145 cm².
- Rigid plastic packaging in India must contain at least 30% recycled material in 2025-26, rising to 60% by 2028-29, with exemptions where food rules restrict it.
- Depth, shot volume and cooling can limit a container job before clamp does, so check all of them for every mould.
How Do You Work Out What a 180 Ton Container Moulding Machine Can Hold?
Multiply projected area by a tonnage factor for the resin and wall. For a container, projected area is the rim outline as the mould sees it, times the cavity count, plus any cold runner. If the answer with a reserve stays under about 164 t, clamp is fine.
This method follows a Plastics Technology column by RJG trainer Jeremy Williams, which gives typical factors of 2 to 10 US tons per square inch and recommends 3 as a starting point. On a hot runner, only the cavities count. An SPE Plastics Engineering article by A. Urbina places PP at 2 to 3 and polyethylene at the low end of its 2 to 8 range.
The published factors are in US tons per square inch. One US t/in² is about 0.141 t/cm², so a factor of 3 becomes 0.422 t/cm². The 10% reserve used across this series is a starting margin, not a rule, and 180 t divided by 1.1 gives the 164 t working ceiling.
Thin walls change the factor more than anything else. The thin-wall article in this series explains why a published range of 5 to 8 US t/in² applies there, against 3 to 5 for conventional moulding.
Which Containers Fit, and in How Many Cavities?
On clamp alone, 180 t can carry one 4 litre bucket, three to five 1 kg tubs, two or three reusable 500 ml containers, two to four thin-wall 250 ml tubs or three to six 100 ml dairy cups. Each range spans the low and high factor.
Cavities a 180 t clamp can carry, by container (calculated, hot runner, 10% reserve)
| Container | Resin | Rim | Area per cavity | Cavities by clamp |
|---|---|---|---|---|
| 4 litre bucket | PP | 210 mm round | 346 cm² | 1 |
| 1 kg paint or grease tub | PP or HDPE | 120 mm round | 113 cm² | 3 to 5 (factor 3 to 2) |
| Reusable 500 ml container | PP | 150 × 110 mm | 165 cm² | 2 to 3 (factor 3 to 2) |
| Thin-wall 250 ml tub | PP | 85 mm round | 56.7 cm² | 2 to 4 (factor 8 to 5) |
| 100 ml dairy cup | PP or PS | 70 mm round | 38.5 cm² | 3 to 6 (factor 8 to 5) |
Grade choice follows the wall. For rigid packaging and houseware with conventional walls, Reliance's Repol H110MAS is a nucleated PP homopolymer with an MFR of 11 g/10 min and IS 10910 food-contact compliance. Thin-wall work calls for higher-flow grades, covered in the thin-wall article.
Lids deserve their own line in the plan. A lid has the same rim outline as its container, so it needs similar clamp, but it is flatter and fills differently. A family mould that runs bodies and lids together must balance both, or one side flashes while the other short-fills.
Cavity count also has to suit the mould layout. Four round tubs fit a square pattern; six or eight cups need a longer mould. Check that the mould's outside size fits between the tie bars before you settle the cavity count on clamp alone.
What Limits a Container Job Besides Clamp?
Depth, shot and cooling. A deep bucket needs an opening stroke that clears the core and the part. A multi-cavity tub mould needs a shot that sits in a sensible share of the barrel. The thickest section, often the rim or the base, sets cooling and so output.
Shot share matters most on thin-wall work, where the right screw can decide whether the job runs at all. The screw article in this series compares a 40 mm and a 45 mm screw for that case. Output planning for cups and small tubs has its own article too.
Recycled content is now a planning item. PWM (Amendment) Rules notified on 31 March 2026 require rigid plastic packaging to contain at least 30% recycled material in 2025-26, rising to 60% by 2028-29, with exemptions where FSSAI and similar rules restrict recycled content. Paint and grease tubs are rigid packaging, so the targets can reach them; food containers may fall under the exemption.
Our view: if your container mix will include recycled PP, run your first trials with it, not with virgin resin. Melt flow and colour can vary from lot to lot, and a mould that only fills with virgin material has no margin for the rule.
What Should You Send Before Choosing a Container Machine?
Send each container drawing with rim size, depth and wall thickness, the resin grade, the share of recycled content you plan, the target cavity count and the monthly volume. With those, clamp, stroke, shot and cooling can all be checked before a mould is cut. See the 180 ton horizontal injection moulding machine page.
Frequently Asked Questions About 180 Ton Container Moulding
Can a 180 t machine mould a 10 litre bucket?
Not on clamp. A 10 litre bucket with a rim of about 290 mm has a projected area near 660 cm², which needs about 204 t even at a factor of 2 with a 10% reserve. Its depth also calls for a long opening stroke, so size the machine on both figures.
Is HDPE or PP better for paint and grease tubs?
Both are used. PP gives a stiffer wall for the same weight, while HDPE stays tougher in the cold and can resist some solvents and greases better. Check the fill product's compatibility at storage temperature, the drop test your customer runs and the tonnage factor of the grade you choose.
What is a stack mould and does it help on 180 t?
A stack mould has two parting faces back to back, so both levels share the same projected area against the clamp. It can roughly double cavities without doubling clamp, but it needs more opening stroke, more shot volume and a longer mould. Check the mould height and stroke before planning one.
How do bucket handle lugs affect the mould?
Lugs that hold the handle stand out from the side wall, so they can need side actions or collapsing cores in the mould. They also carry the full load of a filled bucket. Gate and pack the lug area well, and test pull-out strength on parts made with any recycled content you plan to use.
Does recycled PP change the moulding process?
It can. Recycled lots can vary in melt flow, colour and contamination, so fill pressure and cycle may shift between lots. Filter the melt where needed, track lot data and keep a process window wide enough to absorb the variation. Confirm recycled content rules for the end use before you start.
Related Articles
- Moulding Thin-Wall Food Containers on a 180 Ton Machine
- 40 mm or 45 mm Screw? Choosing for Thin-Wall Packaging
- Dairy Cups and Small Tubs: Output Planning on a 180 Ton Machine
Sources & References
- Plastics Technology, J. Williams (RJG): Clamp Tonnage: More Is Better...Right?
- SPE Plastics Engineering, A. Urbina: Mastering Clamping Force Calculation
- Polymerupdate, D. K. Jha: India eases plastic recycling regulations
- 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.
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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