A caterer asks for a quote on 500 ml rectangular containers, and the only free press is 180 t. Whether a 180 ton machine for food containers is the right choice depends on the wall. A reusable container with a 1.2 mm wall runs two cavities with clamp to spare. A thin-wall disposable version can need most of the clamp for one.
This article covers cavity count for containers, bowls and trays, what thin walls demand from the machine and the mould, resin grades, and the food-contact rules that apply in India.
Key Takeaways
- Thin walls raise the clamp per cavity: a published thin-wall range is 5 to 8 US t/in², against 3 to 5 for conventional moulding.
- Cooling time scales with the square of wall thickness, so halving the wall cuts cooling to about a quarter.
- FSSAI requires plastics in direct food contact to meet listed Indian Standards, such as IS 10910 for PP and IS 10146 for PE, with overall migration of no more than 60 mg/kg.
- Trays are clamp-hungry: a 300 × 200 mm tray in PP needs about 185 t even at the lowest factor.
How Many Cavities Can a 180 Ton Machine for Food Containers Run?
For a reusable PP container with a 1.2 mm wall and a 150 × 110 mm rim, two cavities need about 102 to 153 t with a 10% reserve, so 180 t holds them. Moulded thin-wall, the same container can need 128 to 204 t for one cavity.
The rim outline sets the projected area, because the mould sees the container from above. A 150 × 110 mm rim gives 165 cm² per cavity. The method, the unit conversion and the 10% reserve are explained in the applications article in this series.
Clamp needed for a container with a 150 × 110 mm rim on a hot runner, with a 10% reserve (a starting margin, not a rule)
| Wall type and factor | 1 cavity (165 cm²) | 2 cavities (330 cm²) | 4 cavities (660 cm²) |
|---|---|---|---|
| Reusable PP, 2 US t/in² | 51 t | 102 t | 204 t |
| Reusable PP, 3 US t/in² | 77 t | 153 t | 306 t |
| Thin wall, 5 US t/in² | 128 t | 255 t | 510 t |
| Thin wall, 8 US t/in² | 204 t | 408 t | 817 t |
Bowls behave like containers of the same rim size. A 150 mm round bowl has about 177 cm² of projected area, so two cavities in PP need about 164 t at the upper conventional factor. Trays are different. A 300 × 200 mm tray covers 600 cm² and needs about 185 t even at a factor of 2.
What Does Thin-Wall Moulding Demand From the Machine?
Speed, pressure and a stiff clamp. Thin-wall parts have flow length to wall ratios of about 100:1 to 200:1, can need injection pressures above 30,000 psi (about 2,068 bar), and fill in under one second at injection velocities above 3 in/s (76 mm/s).
These figures come from a PlasticsToday article by Gary Tremblay of Sabic Innovative Plastics. It says thin-wall machines tend to have accumulator-assisted clamps for fast movement and extra-thick platens, and it advises against adapting a conventional machine for the job.
The mould matters as much as the press. The article recommends steels harder than P-20, as many support pillars as will fit, venting on core and ejector pins, and, as a rule of thumb, double the ejector pins at twice the size, because thin walls shrink little and grip the core.
Wall thickness also sets output. RJG's guidance on cooling time says thickness is squared in the cooling equation, so a 0.6 mm wall needs about a quarter of the cooling of a 1.2 mm wall. RJG suggests adding about 20% to the calculated cooling timer as a safety factor.
Our view: if the order is for disposable thin-wall containers in volume, use a machine and mould built for thin-wall work. A general-purpose 180 t press is the better fit for reusable containers, bowls and lids with thicker walls, where it can run steadily without being pushed to its limits.
Which Resins and Food-Contact Rules Apply in India?
PP and HDPE both suit food containers. Under the FSSAI Packaging Regulations 2018, plastics in direct food contact must conform to listed Indian Standards, including IS 10910 for PP and IS 10146 for PE, and meet an overall migration limit of 60 mg/kg or 10 mg/dm².
Migration is tested to IS 9845, pigments must meet IS 9833, and food businesses need a certificate of conformity from an NABL-accredited lab for packaging in direct food contact. FSSAI allows recycled plastics in food contact only as and when it frames standards and guidelines for them.
Reliance's Repol H110MAS is one Indian PP homopolymer made for rigid packaging and houseware. Its data sheet lists an MFR of 11 g/10 min, a flexural modulus of 1,650 MPa, an HDT of 110 °C, compliance with IS 10910 for food contact and a mould temperature of 20 to 50 °C.
Grade and wall go together. A stiffer PP can let you thin the wall without the container bulging when filled, but every reduction raises the flow length to wall ratio and the factor you should size the clamp on.
What Should You Send Before Quoting a Food Container Job?
Send the container drawing with rim size, wall thickness and depth, the resin grade, the target cavity count and the monthly volume. With those, the clamp, shot and cooling checks can be run before anyone commits to a mould. See the 180 ton horizontal injection moulding machine page.
Frequently Asked Questions About Moulding Food Containers on 180 t
Can I use recycled PP for food containers in India?
Not freely. FSSAI allows recycled plastics in food contact only as and when it frames standards and guidelines for them, and the packaging must still meet the listed Indian Standards and migration limits. Check the current FSSAI position and your resin supplier's certification before you plan recycled content in any food-contact part.
What mould temperature suits PP food containers?
Follow the resin data sheet. For Repol H110MAS, Reliance lists a mould temperature of 20 to 50 °C and a melt temperature of 200 to 250 °C. A colder mould shortens cooling, but on a thin wall it can also freeze the flow front early and leave short shots at the far rim.
Why should lids and bodies be checked separately?
A lid is flat and wide, so its projected area can exceed the body's even though it weighs less. It also carries a sealing profile that must stay flat. Run the clamp and cooling calculation for the lid on its own, because the lid may be the part that limits the machine.
How does container depth affect the machine?
Depth adds no projected area, but it adds core length and opening stroke. A deep container must clear the core fully before it drops or is picked by a robot, so the opening must exceed about twice the depth plus a working clearance. Compare this with the stroke on the data sheet.
What causes warped trays and how is it fixed?
Uneven cooling and uneven packing. A large flat tray shrinks more where it is hotter or less packed, and the difference shows as bow or twist. Balanced cooling channels, a gate position that gives even flow and a stable mould temperature all help. A nucleated PP grade can also help keep shrinkage even.
Related Articles
- What Can You Make on a 180 Ton Injection Moulding Machine?
- When a Standard 180 Ton Machine Is Enough and When to Move Up
- Moulding Larger Electrical Housings on a 180 Ton Machine
Sources & References
- Food Safety and Standards Authority of India (FSSAI): Food Safety and Standards (Packaging) Regulations, 2018, compendium
- PlasticsToday, G. Tremblay (Sabic Innovative Plastics): Never too thin
- Reliance Industries: Repol H110MAS Technical Data Sheet
- RJG Inc.: How to Determine Injection Molding Cooling Time
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.
Limitation of Liability: Pratishna Engineers makes no representation or warranty, express or implied, regarding the completeness, accuracy or suitability of the information for any particular application. To the extent permitted by applicable law, Pratishna Engineers shall not be liable for any loss, damage, cost or consequence arising from reliance on or use of the information contained in this document. Final machine selection, configuration and application suitability should be confirmed with Pratishna Engineers based on complete and accurate project requirements.
