180 ton PET machine applications: product groups and the first check for each
| PET product | What matters most | First check on a 180 t machine |
|---|---|---|
| Heavier preforms for large-volume bottles | A large shot and a thick wall | Shot against the barrel, and the cycle the wall sets |
| Higher-cavity water and beverage bottle preforms | Low acetaldehyde, even weight across cavities | Mould width against the tie bars |
| Edible oil bottle preforms | Clarity, a food-contact grade, a neck that suits the closure | Cavity count and neck finish |
| Wide-mouth jar preforms for food and dry goods | Large neck diameter | Projected area per cavity, where clamp can become the limit |
| Thick-wall PETG cosmetic jar shells | Cooling time and sink marks | Cycle time and mould cooling |
| Glass-filled PET technical parts | Wear, drying and mould temperature | Screw and barrel suited to a filled resin |
The 180 ton PET machine applications that fit best are heavier preforms for large bottles, high-cavity water and beverage preform moulds, edible oil preforms and wide-mouth jar preforms, plus thick-wall PETG jars and some glass-filled PET parts. Bottle preform moulds are usually limited by shot, mould width and cycle. Wide jar preforms in high cavity counts are different: there, clamp becomes a real check.
This article sets out the product groups, how to check clamp for a preform mould, where jar preforms change the answer, and the Indian food-contact rules for PET bottles and jars.
Key Takeaways
- A 180 t PET machine suits work that outgrows a mid-size frame: heavier shots, more cavities or wider moulds.
- Clamp for a preform mould follows the widest cross-section of each cavity, usually the support ledge, times the cavity count and a cavity pressure.
- Projected area grows with the square of diameter, so an 80 mm jar ledge needs about 5.9 times the clamp of a 33 mm bottle ledge.
- Under the FSSAI Packaging Regulations, PET in food contact must conform to IS 12252, and packaged drinking water bottles need at least 85% transparency.
Which 180 Ton PET Machine Applications Fit Best?
Work that needs more shot, more cavities or a wider mould than a mid-size machine offers: heavy preforms for large bottles, high-cavity water preform moulds, edible oil preforms and wide-mouth jar preforms. A 180 t PET machine earns its place where the mould or the shot outgrows a smaller frame.
Large-volume bottle preforms bring their own shot, cooling and acetaldehyde questions, covered in the heavy preforms article in this series. How many cavities and what cycle a mould needs to meet a monthly order is worked through in the output planning article.
PETG jars and glass-filled PET parts are a different kind of job. A thick PETG jar wall sets a long cooling time, so cycle and sink marks decide the cost. Glass-filled PET is an engineering material that wears screws and runs a hot mould, so confirm the screw, barrel and mould temperature with your resin supplier first.
Our view: a 180 t PET machine is a volume machine. Buy it for a steady family of preforms on long runs, not for sample work and short batches, where a small shot in a large barrel stays hot for too long.
How Do You Check Clamp for a Preform Mould?
Multiply the projected area of one cavity by the number of cavities, add any cold-runner area, then multiply by a tonnage factor or cavity pressure. For a preform, the projected area is the circle of the widest diameter seen end-on, usually the support ledge below the thread.
The method comes from a Plastics Technology article by John Williams of RJG. A preform mould on a hot runner counts only the cavities, so there is no runner area to add. The length of the preform body does not count, because the clamp sees each cavity end-on.
Where you have no tonnage factor for your resin and wall, SPE's Plastics Engineering magazine gives a cavity pressure of 400 bar as a guide value. That is about 408 kg/cm², or 0.408 t for every square centimetre of projected area. Add a reserve, such as 10% (a starting margin, not a rule).
Do not answer a small figure by running the clamp at the machine maximum. The same RJG article warns that over-clamping can crush vents, roll the parting line and crack cavity blocks, and gives a case where a mould needing about 100 tons split its cavity block at 400 tons.
When Do Jar Preforms Make Clamp the Limit?
When the neck is wide and the cavity count is high. Area grows with the square of diameter, so an 80 mm jar ledge has about 5.9 times the area of a 33 mm bottle ledge. Eight such cavities can need the full clamp of a 180 t machine.
That changes the order of the checks. On a bottle preform mould, the mould width between the tie bars usually runs out before the clamp does. On a wide jar mould, work out the clamp first, then check mould size, because a cut in cavities may be needed for either reason.
Jar preforms also need a short stroke compared with long bottle preforms, which helps, but a wide core and neck splits still have to clear. The stroke and tie-bar checks are set out in the article in this series on when 180 t is enough.
Which Indian Rules Apply to PET Bottles and Jars?
If the bottle or jar will hold food, drinks or drinking water, the FSSAI Packaging Regulations 2018 apply. PET for food contact must conform to IS 12252, and bottles for packaged drinking water need a transparency of at least 85%. Edible oil and food jar buyers will ask for proof.
The regulations set an overall migration limit of 60 mg/kg or 10 mg/dm², tested to IS 9845, and require pigments to meet IS 9833. Food businesses need a certificate of conformity from an NABL-accredited lab for packaging in direct food contact, so keep resin lot records with every batch of preforms.
Recycled PET is a separate question. FSSAI allows recycled plastics in food contact only as and when it frames standards and guidelines for them, so check the current position before you plan rPET in a food preform.
What Should You Send to Check a PET Product on 180 t?
Send the preform or part drawing with weight, length, wall, neck finish and support-ledge diameter, the resin grade, the target cavity count and the monthly quantity. With those, clamp, mould size, stroke and shot can be checked together. See the 180 ton PET injection moulding machine page.
Frequently Asked Questions About PET Products on a 180 t Machine
Which diameter should I use for a preform's projected area?
Use the largest outer diameter the clamp sees end-on, which on most preforms is the support ledge below the thread. On jar preforms with a wide neck, take the widest point of the neck finish. Ask the mould maker to confirm the figure, since the steel around each cavity can matter for mould fit.
Is a 180 t PET machine suitable for PETG cosmetic jars?
It can be, where the jar size and cavity count fit the mould space and the shot sits well inside the barrel. PETG jars often have thick walls, so cooling time sets the cycle and sink marks set the quality. Plan mould cooling with the mould maker before deciding the cavity count.
Can a PET preform machine also mould glass-filled PET parts?
Possibly, but treat it as a separate application. Glass fibre wears screws, barrels and check valves faster, and filled PET runs a hotter mould than preforms. Confirm the screw and barrel metallurgy, mould temperature control and drying with your resin supplier and the machine supplier before you commit.
Do PET bottles for edible oil need food-contact compliance?
Yes. Edible oil is food, so the FSSAI Packaging Regulations apply to the bottle, including PET to IS 12252 and the migration limits. Your oil brand customer will need a certificate of conformity from an NABL-accredited lab, which depends on your resin, colourant and batch records.
Why not run small bottle preforms on a 180 t machine?
You can, but a light preform in a large barrel spends longer in the melt, which can raise acetaldehyde and IV loss. A larger frame also carries a higher base energy load. Small preforms in low cavity counts usually sit better on a smaller machine with a smaller screw.
Related Articles
- Heavy Preforms for Large-Volume Bottles on a 180 Ton Machine
- When the PET 180 Ton Is Enough and When to Move to 220 or 260 Ton
- Planning Preform Output: Cavities, Cycle Time and Drying Capacity
Sources & References
- Plastics Technology, J. Williams (RJG): Clamp Tonnage: More Is Better...Right?
- SPE Plastics Engineering, A. Urbina: Mastering Clamping Force Calculation
- 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.
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