Household vs container moulding machine at the same 180 t clamp: what each is built around (thin-wall figures from Tremblay, PlasticsToday; dry cycles from Catoen, MoldMaking Technology)
| Feature | Household type | Container (thin-wall) type | What it means for tubs |
|---|---|---|---|
| Screw and barrel | Larger screw, larger shot volume | Smaller barrel; shot at least about 40% of barrel | Small thin-wall shots sit too long in a big barrel |
| Injection pressure | Moderate, limited by the larger screw | Thin-wall work often above 2,068 bar (30,000 psi) | Thin walls freeze before they fill without it |
| Injection speed | Moderate | Fill under 1 s; 76 to 152 mm/s or more | Matters on long flow, thin wall |
| Clamp | Wide tie-bar space, long stroke and daylight | Fast, often accumulator-assisted; thick platens | Deep tubs need stroke; thin-wall needs speed |
| Dry cycle | 3 to 5 s | 1 to 2.5 s | Counts only on short cycles |
At the same 180 t, the household vs container moulding machine choice is about the injection unit and clamp speed, not the tonnage. Thick-walled washing tubs, deep storage tubs and buckets suit the household type. Thin-wall food and dairy tubs, whose flow path is long for their wall, suit the container type. The flow length to wall ratio tells you which group your tub is in.
Key Takeaways
- Below a flow length to wall ratio of about 150:1, fill risk is low and a household machine copes; thin-wall designs run at about 100:1 to 200:1.
- Thin-wall clamp factors of 5 to 8 US t/in² cut what 180 t can hold to roughly 146 to 233 cm² with a 10% reserve.
- Deep tubs need an opening stroke of at least 2.5 times part height before they need injection speed.
- Rigid packaging must carry 30% recycled content in 2025-26, rising to 60% by 2028-29, unless food rules restrict it.
What Separates the Two Machines at the Same Tonnage?
The injection unit and the clamp's speed. A container machine trades shot volume for pressure and speed, with a smaller barrel and a faster clamp. A household machine trades pressure for shot volume and mould space, with a larger screw, wider tie bars and a longer stroke.
Gary Tremblay of Sabic, writing in PlasticsToday, sets out what thin-wall work asks of a machine. Injection pressures typically exceed 30,000 psi, about 2,068 bar. Fill times are under one second and injection velocities run above 3 in/s (76 mm/s), with many jobs at 6 in/s (152 mm/s).
He describes thin-wall machines as tending to have accumulator-assisted clamps and extra-thick platens, with a tie-bar distance to platen thickness of 2:1 or less on better machines. They often carry a smaller barrel, and he puts the shot at no less than about 40% of barrel size. Adapting a conventional machine for thin-wall work is, in his words, "usually not a wise idea".
Screw diameter is where the trade shows. On the same injection unit, plastic pressure scales with one over the diameter squared and swept volume with the diameter squared. A 42 mm screw in place of a 52 mm one gives about 53% more pressure and about 35% less volume.
When Does the Household vs Container Moulding Machine Choice Matter?
When the tub's flow length to wall thickness ratio climbs toward thin-wall territory. Below about 150:1, the risk of sinks, short shots and dimensional problems is low and a household machine copes. Thin-wall designs run at about 100:1 to 200:1 and need more pressure and speed.
The 150:1 figure comes from Jeremy Williams of RJG in Plastics Technology, and the 100:1 to 200:1 band from Tremblay. Measure flow length from the gate along the longest path to the last point to fill, then divide by the nominal wall.
As an illustration, a 250 mm round tub, 150 mm deep with a 2.2 mm wall and a centre gate, has a flow path of about 275 mm and a ratio of about 125:1 (assumed sizes). A 500 ml food tub with a 0.7 mm wall, like the one in the worked example below, lands near 186:1.
Clamp moves with the ratio. Tremblay gives thin-wall clamp at 5 to 8 US t/in² against 3 to 5 for conventional moulding, so 180 t holds roughly 146 to 233 cm² of thin-wall parts with a 10% reserve (a starting margin, not a rule). The applications article in this series explains the clamp method.
Our view: if your tub's ratio is above about 150:1 and it will run for years, buy the machine for that tub. A household machine pushed to thin-wall pressures and speeds can make the part, but it runs at its limits on every shot.
How Do Mould Size and Depth Change the Choice?
Deep or wide tubs need tie-bar space, opening stroke and daylight before they need speed. The mould should fit between the tie bars, the opening stroke should be at least 2.5 times the part height, and daylight must cover the mould thickness plus that stroke.
These checks come from Bruce Catoen's machine sizing article in MoldMaking Technology. Ideally the whole mould fits within the tie bars; at minimum the parts' projected area must, because platens can pull in near the tie bars and wear the parting line. On a toggle, maximum daylight is maximum shut height plus stroke; on a direct-piston clamp, it is minimum shut height plus maximum stroke.
Catoen gives dry cycles of 1 to 2.5 s for thin-wall machines against 3 to 5 s for others. On a 6 s thin-wall cycle, that gap is a large share of the cycle; on a 35 s tub cycle it barely registers. Clamp speed pays only where the cycle is short.
Which Packaging Rules Affect a Tub Moulder's Machine Choice?
Recycled-content rules for rigid packaging. Under the PWM (Amendment) Rules notified on 31 March 2026, rigid plastic packaging must 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.
Polymerupdate's summary of the amendment adds reuse targets for rigid packaging, a carry-forward of 2025-26 shortfalls for up to three years, and penalties of ₹10,000 to ₹15,00,000. Food tubs are the special case: FSSAI's packaging regulations allow recycled plastics for food only as and when FSSAI frames standards and guidelines for them.
Recycled content reaches the machine through residence time. Entec Polymers' guidance on recycled PP compounds gives a typical melt of about 199 to 227 °C, a maximum residence time of 5 minutes and a preference for cold runners, since small metal fragments can plug hot tips. A barrel sized to the shot keeps residence short; a large barrel running a small tub does not.
What Should You Send to Compare the Two?
Send the tub drawing with wall thickness, gate position and part weight, the cavity plan and the resin, including any recycled share. Flow ratio, clamp, shot and stroke together show which machine type fits. See the 180 ton horizontal injection moulding machine page.
Frequently Asked Questions About Household vs Container Moulding Machines
Can one 180 t machine run both buckets and thin-wall tubs?
It can, with compromises. A barrel big enough for buckets leaves a small thin-wall shot under 20% of capacity, where Bozzelli links long residence to degradation. A second barrel, which he notes can be swapped in under 30 minutes by a skilled operator, is one answer; a second machine is the other.
Is a container machine faster on every job?
No. Its advantage is fast injection and a short dry cycle, which count on short thin-wall cycles. On a thick-walled tub, cooling takes most of the cycle and the extra speed adds little. A thick, deep tub also needs the shot volume and mould space a household machine is built around.
Do thin-wall tubs need a hot runner?
Not always, but a hot runner can suit multi-cavity thin-wall moulds, because a cold runner adds projected area, shot weight and regrind. If the tub carries a high recycled share, note that recycled PP guidance from Entec Polymers prefers cold runners, since small metal fragments can plug hot tips.
Can a 180 t tub mould use in-mould labels?
Yes, if a robot can place a label in the mould every cycle. Labels are held by vacuum ports or by electrostatic charge; electrostatic holding needs a robot with end-of-arm tooling, a label magazine and a high-voltage supply. Allow for the robot's time inside the mould when you estimate the cycle.
What does a flow ratio of 150:1 mean in practice?
The melt travels 150 times the wall thickness from the gate to the farthest point. A 1.5 mm wall at that ratio allows a flow path of about 225 mm. Beyond it, filling needs more pressure and speed, so thicken the wall, add a gate or plan the part on a thin-wall machine.
Related Articles
- What Can You Make on a 180 Ton Household Moulding Machine?
- Bucket Moulding on a 180 Ton Machine: Sizes, Shot Weight and Output
- Storage Boxes With Lids: Matching Shrinkage on a 180 Ton Machine
Sources & References
- PlasticsToday, G. Tremblay (Sabic Innovative Plastics): Never too thin
- MoldMaking Technology, B. Catoen: Machine Sizing and Specification for Optimal Mold Performance, Part 1
- Polymerupdate, D. K. Jha: India eases plastic recycling regulations
- Entec Polymers: Processing ECHO Post-Industrial Recycled Polypropylene Compounds
Technical Disclaimer
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