PET products on a 125 ton machine include narrow-neck preforms for water, soft drink, edible oil, FMCG and pharma bottles, and wide-mouth jar preforms of up to about 72 mm across in four-cavity moulds, or about 101 mm in two-cavity moulds. Those jar limits come from the clamp. For narrow necks the clamp is not the constraint; shot volume, cycle time and mould width set the cavity count.
The extra 25 t over a 100 t machine mostly widens the range of jars you can run. It does less for light water preforms, which never came close to the clamp limit in the first place.
Key Takeaways
- With a 10% reserve and an assumed PET factor of 5 US t/in², 125 t covers about 162 cm² of projected area.
- That allows a 72 mm jar preform in four cavities, 83 mm in three or 101 mm in two.
- A narrow-neck preform with a 33 mm support ring could run 18 cavities by clamp alone, so other limits arrive first.
- Bottle-grade PET is sold by end use, so choose the grade with the bottler before the mould is designed.
How Much Projected Area Does 125 t Hold for PET?
About 162 cm², using a 10% reserve and an assumed tonnage factor of 5 US t/in² for PET. Projected area is the circle at each preform's widest point, times the number of cavities. With a hot runner, only the cavities count toward that total.
The method comes from Jeremy Williams of RJG, writing in Plastics Technology: projected area of one part, times cavities, plus any cold runner, times a tonnage factor. He starts at 3 US tons per square inch where no better figure is known, and lists factors from 2 to 10 depending on the resin and part.
The factor of 5 used here is an assumption, taken from the top of the 3 to 5 range that Glenn Tremblay of Sabic gives for conventional moulding in PlasticsToday. In metric that is 0.703 t/cm². The 10% reserve is a starting margin, not a rule, and leaves about 113.6 t of the 125 t for the cavities.
Check your machine's rated clamp force on its specification sheet before using these numbers. A machine sold by a round tonnage can have a rated figure slightly different from the name, and the limits move in proportion.
Which PET Products on a 125 Ton Machine Fit Best?
Narrow-neck preforms for still water, soft drinks, edible oil, hair oil, disinfectants and pharma bottles fit with clamp to spare. Wide-mouth jar preforms are where 125 t earns its place: four cavities up to about 72 mm, or two up to about 101 mm, fit inside the clamp.
Largest round preform per cavity count at 125 t (factor 5 US t/in², 10% reserve, hot runner; assumptions for illustration)
| Cavities in the mould | Area per cavity | Largest diameter at the widest point |
|---|---|---|
| 2 | 80.8 cm² | About 101 mm |
| 3 | 53.9 cm² | About 83 mm |
| 4 | 40.4 cm² | About 72 mm |
| 6 | 26.9 cm² | About 59 mm |
| 8 | 20.2 cm² | About 51 mm |
Resin choice follows the product. Reliance's Relpet listing on UL Prospector names separate bottle grades for still water, aerated drinks, hot-fill juices and isotonic drinks, and a general grade for foods, FMCG containers and pharmaceuticals. Agree the grade with your customer first, because it fixes the drying, melt and blowing settings that follow.
What Does 125 t Add Over a 100 t Machine?
About 25% more projected area at the same factor and reserve: roughly 162 cm² against 129 cm². In practice that turns a three-cavity 70 mm jar mould into a four-cavity one, a third more jars per shot, while narrow-neck preform moulds gain little because clamp was never their limit.
More cavities also mean a wider mould and a bigger shot. Bruce Catoen's sizing guide in MoldMaking Technology says the parts' projected area must sit fully inside the tie bars, and ideally the whole mould should, because platens can pull in near the bars and wear the parting line.
So the jump from 100 t to 125 t is worth it only if the barrel and the tie-bar gap grow with the clamp. Those two checks, and how they compare with a 150 t machine, are worked through in the 125 ton vs 150 ton sizing article in this series.
Our view: step up to 125 t when your plan includes wide-mouth jars or heavier oil preforms. For light water preforms alone, clamp is not a reason to buy the larger machine; a better barrel match is.
What Changes When the Product Changes?
The resin grade, the neck, the wall and the quality tests change with the product. A still-water preform is judged on taste and clarity, an oil preform on wall and neck fit, and a jar preform on its wide neck. Each one shifts what you check first on the machine.
Still-water preforms bring acetaldehyde into play, and clear preforms of any kind can show haze from the process. Both are covered in the haze and acetaldehyde article in this series. Heavier oil preforms and five-litre jar preforms are covered in the edible oil article.
What Should You Send Before Choosing a 125 t PET Machine?
Send the preform drawings with weight, neck finish and widest diameter, the resin grade, the cavity count and the hourly output you need. The clamp check is quick; shot volume and mould width usually decide the machine. See the 125 ton PET injection moulding machine page.
Frequently Asked Questions About PET Products on a 125 Ton Machine
Can a 125 t machine mould five-litre oil jar preforms?
The clamp usually allows it, because even a large neck projects well under 162 cm² in one or two cavities. The real checks are the shot weight against the barrel and the cooling time of a thick wall. Run those before committing, as the edible oil article in this series shows.
Why use a factor of 5 when 3 is the usual starting point?
PET preforms are filled fast through a small gate, and a higher assumed factor leaves room for that. A factor of 5 is the top of the conventional range, so it is a cautious assumption, not a measured value. Trial data on your mould should replace it.
Does a hot runner change the clamp check for preforms?
Yes. With a hot runner the manifold melt does not press on the parting line, so only the cavities count. A cold runner adds its own area and weight, which can cost a cavity at 125 t on large jars and adds runner scrap to every shot.
Can I run preforms and PET jars on the same 125 t machine?
Yes, with mould changes. Narrow-neck and wide-mouth moulds differ in width, shot and cooling, so check each against the barrel and tie-bar gap. Plan grade and colour changes together, and keep the dryer settings matched to whichever resin goes in next.
Is more clamp always safer for preform moulds?
No. Clamp only needs to hold the mould shut with a margin. Excess clamp adds stress to platens, tie bars and the mould's parting line, and can crush vents. Running a small mould on a large machine also wastes energy. Size by the mould and its reserve, not by headroom.
Related Articles
- Edible Oil Bottle Preforms on a 125 Ton Machine
- PET 125 Ton vs 150 Ton: Sizing by Shot Weight and Mould Size
- Controlling Haze and Acetaldehyde in PET Preforms
Sources & References
- Plastics Technology, J. Williams (RJG): Clamp Tonnage: More Is Better...Right?
- PlasticsToday, G. Tremblay (Sabic Innovative Plastics): Never too thin
- MoldMaking Technology, B. Catoen: Machine Sizing and Specification for Optimal Mold Performance, Part 1
- UL Prospector: Polyester: Relpet grade listing (Reliance Industries)
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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