140 ton vs 180 ton injection moulding machine: largest projected area and 90 mm cups per mould, 10% reserve (a starting margin, not a rule)
| Tonnage factor (US t/in²) | Area at 140 t | Area at 180 t | 90 mm cups at 140 t | 90 mm cups at 180 t |
|---|---|---|---|---|
| 3 (conventional wall) | 302 cm² | 388 cm² | 4 | 6 |
| 5 (low end of thin-wall) | 181 cm² | 233 cm² | 2 | 3 |
| 8 (high end of thin-wall) | 113 cm² | 146 cm² | 1 | 2 |
For thin-wall cups and small tubs, a 180 t clamp holds about 29% more projected area than 140 t, which at thin-wall factors is roughly one more 90 mm cup per mould. That can matter, but it is not the first question. Thin walls are filled by injection speed and pressure, so check those before tonnage.
Cup counts in the table use the rim circle, 63.6 cm² for a 90 mm cup, and round down.
Key Takeaways
- Thin-wall designs have flow length to thickness ratios of about 100:1 to 200:1 and can need 5 to 8 US t/in² of clamp, against 3 to 5 for conventional parts.
- Injection speed, pressure and fill time decide whether a thin cup fills; tonnage only holds the mould shut.
- A bigger frame raises the minimum mould size too. A small cup mould should still cover about 70% of the tie-bar distance.
- Food-contact cups and tubs in India must use resins that meet FSSAI's listed standards, with overall migration limited to 60 mg/kg.
What Makes a Cup or Tub Thin-Wall?
A part is thin-wall when its flow length is about 100 to 200 times its wall thickness. A 0.6 mm cup with 110 mm of flow sits near 180:1. There, filling needs far higher pressure and speed than conventional moulding, and the clamp needs more force per square centimetre.
That definition comes from a PlasticsToday article by G. Tremblay of Sabic Innovative Plastics. He puts thin-wall clamp needs at 5 to 8 US t/in², against 3 to 5 for conventional parts, and injection pressures typically above 30,000 psi, which is about 2,068 bar or 2,109 kg/cm².
Resin matters as much as the machine. The article says thin-wall resins need high flow and must withstand shear heating of 50,000 s⁻¹ or more. A general moulding grade that runs a thick lid well may burn or short-fill in a thin cup.
Which Matters More for Thin Walls, Tonnage or Injection Speed?
Injection speed and pressure matter more. Thin-wall jobs fill in under a second, with injection velocities above 76 mm/s and many at 152 mm/s. A clamp of any size cannot rescue a cup that freezes before it fills, so compare the injection unit first.
Tremblay's article adds that thin-wall machines tend to have accumulator-assisted clamps, extra-thick platens and, on better machines, a tie-bar distance to platen thickness ratio of 2:1 or less. He calls adapting a conventional machine to thin-wall work usually not a wise idea.
The barrel matters too. He suggests the shot should be at least 40% of barrel size, because too large a barrel may not give the pressure boost and lets resin degrade. Control resolution counts: he lists 0.01 s on time and 1 bar on pressure as targets.
Then the dry cycle. MoldMaking Technology's Bruce Catoen gives 1 to 2.5 s as ideal for thin-wall, fast-cycling work. On a cup cycle of a few seconds, a slow mould movement can cost more output than any clamp difference.
How Does a 140 Ton vs 180 Ton Injection Moulding Machine Compare for Cups?
At thin-wall factors, 140 t carries about one or two 90 mm cups and 180 t about two or three. For small tubs the gain is similar in area. If your cavity count fits 140 t at the high factor, the bigger clamp only buys unneeded reserve.
The frame can work against you. A Plastics Technology mould-setting guide 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, which can flash the mould's centre. A two-cavity cup mould on a larger frame can fall short of that line.
Mould build also changes with thin walls. Tremblay recommends harder steels than P-20, thicker plates, many support pillars, vents on core and ejector pins, and larger cooling lines. Size the mould's plates and pillars for the clamp the job needs, then check the frame.
Our view is clear: choose by injection unit first, cavity count second and tonnage third. A 180 t frame with a slow injection unit makes fewer good cups than a 140 t frame with the right one.
Which Food Rules Apply to Cups and Tubs in India?
FSSAI's Packaging Regulations, 2018 require plastics in food contact to meet listed Indian Standards, such as IS 10910 for PP and IS 10142 for polystyrene. Overall migration is limited to 60 mg/kg, or 10 mg/dm², tested to IS 9845, with specific limits for several metals.
Printed cups bring more rules: pigments must meet IS 9833 and printing inks IS 15495. Food businesses need a certificate of conformity from an NABL lab for packaging in direct contact. Recycled plastics can be used for food only as and when FSSAI frames standards for them. Recycled-content targets under the plastic waste rules are covered in the applications article in this series.
What Should You Send to Choose Between 140 t and 180 t?
Send the cup or tub drawing, wall thickness and flow length, resin grade and MFR, part weight, cavities, the mould's outside size and shut height, any in-mould labelling, and your target output. With those, fill rate, pressure, clamp and mould fit can be checked on both sizes. See the 140 ton container injection moulding machine page.
Frequently Asked Questions About 140 Ton vs 180 Ton Machines for Thin-Wall Packaging
Can a 140 ton machine make a 500 ml thin-wall tub?
Possibly in one cavity. A tub with a 140 cm² footprint needs about 108 to 173 t with a 10% reserve at thin-wall factors of 5 to 8, so 140 t covers the lower part of that range. Injection speed, shot share and the mould's flow ratio decide whether it fills.
Is PP or PS better for thin-wall cups?
Both are used for cups. PP is tougher and suits hot fill and microwave use, while PS is stiff and clear but more brittle. FSSAI lists IS 10910 for PP and IS 10142 for PS in food contact. Choose with the filler, since sealing and stacking needs can decide it.
Does in-mould labelling change the machine choice?
It can. IML adds a robot that places labels in the open mould, so mould-open time and the machine's interface for automation matter. Labels must also be printed with inks that meet IS 15495 for food packaging. Plan the robot, label magazine and guarding with the machine, not afterwards.
Why do thin-wall cups crack at the gate?
Possible causes include high shear at a small gate, a melt that is too cold, over-packing, or a resin without enough flow for the wall. Thin-wall resins need to withstand very high shear rates. Check gate size, melt temperature and hold pressure, and confirm the grade is meant for thin-wall work.
Will a bigger clamp fix short shots in thin cups?
No. A short shot means the melt froze before the cavity filled, which is a speed, pressure, temperature or venting problem. Extra clamp only holds the mould shut. Raising clamp on a short-filling mould can crush vents and make the short shot worse, so look at the injection side first.
Related Articles
- What Can You Make on a 140 Ton Container Moulding Machine?
- Cap and Closure Production on a 140 Ton Machine: Cavities and Cycle Time
- Single-Screw Machines for Closures: Why a 35 mm Screw Suits Light Shots
Sources & References
- PlasticsToday, G. Tremblay (Sabic Innovative Plastics): Never too thin (Oct 2007)
- MoldMaking Technology, B. Catoen: Machine Sizing and Specification for Optimal Mold Performance, Part 1 (Aug 2025)
- Plastics Technology, P. Witaszek, J. Klees, J. Fattori, E. Di Siro, J. Bozzelli: How to Mount an Injection Mold (June 2017)
- Food Safety and Standards Authority of India: Food Safety and Standards (Packaging) Regulations, 2018, compendium
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