Choosing between a 120 ton vs 125 ton machine for houseware rarely comes down to clamp. Five tonnes is about 4% more force, worth roughly 10 cm² of extra PP part area. The machine that suits houseware is the one whose tie-bar space, opening stroke, daylight and injection unit fit your deepest and widest moulds.
Two machines this close in clamp can still differ widely in those dimensions, because they may be built for different jobs. So compare the mould-fit figures on both datasheets first, then the drive and running cost, and only then the clamp.
Key Takeaways
- With a 10% reserve, only parts needing between about 109 t and 114 t of clamp fit 125 t but not 120 t.
- Tie-bar space, shut height, stroke and daylight decide houseware mould fit more often than clamp does.
- A mould should cover at least about 70% of the tie-bar distance; a much smaller mould lets the platens bow.
- Base load and power factor can move the power bill more than 5 t of clamp, especially under kVAh billing.
What Does the 120 Ton vs 125 Ton Machine Difference Mean for Clamp?
Very little. Five tonnes is about 4% more clamp, so about 4% more projected area at any tonnage factor: roughly 10 cm² more at a PP factor of 3. With a 10% reserve, only parts needing between about 109 t and 114 t fall in that gap.
Largest total projected area at 120 t and 125 t, with a 10% reserve (a starting margin, not a rule)
| Tonnage factor (US t/in²) | Largest area at 120 t | Largest area at 125 t | Extra area at 125 t |
|---|---|---|---|
| 2 | 388 cm² | 404 cm² | 16 cm² |
| 3 | 259 cm² | 269 cm² | 10 cm² |
| 4 | 194 cm² | 202 cm² | 8 cm² |
| 5 | 155 cm² | 162 cm² | 7 cm² |
| 8 | 97 cm² | 101 cm² | 4 cm² |
The figures follow the projected area method explained in the applications article in this series, converted at 1 US t/in² to about 0.141 t/cm². At the PP factors of 2 to 3, the extra 5 t buys 10 to 16 cm², which is less than the area of one small knob.
So if your largest houseware mould needs 118 t with its reserve, both machines can hold it. If it needs 130 t, neither can. The narrow band between is the only place where the extra 5 t helps.
Our view: if a mould only fits because of the last 5 t, reduce a cavity or pick a clearly larger machine. Running at the clamp limit leaves no room for a hotter melt or a worn parting line.
Which Machine Dimensions Matter More for Houseware Moulds?
Tie-bar space, shut height range, opening stroke, daylight and injection unit size matter more. Two machines of near-equal clamp can differ on each, and any one can rule a mould in or out. For deep houseware such as mugs and buckets, compare these before clamp.
Bruce Catoen's MoldMaking Technology article on machine sizing says the mould should ideally fit within the tie bars, and at minimum the parts' projected area must sit inside them, because platens can pull in near the tie bars and wear the parting line. Mould thickness must also fall inside the machine's shut height range.
Too small a mould is a problem as well. A Plastics Technology article on mounting moulds 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 under clamp and flash in the middle, and very small ones can damage the platens.
Stroke and shot size are the other two checks. Deep parts need an opening stroke of about 2.5 times their height, and the injection unit must suit the shot volume; the mugs and bowls article in this series works through both. The same Catoen article notes that most moulds use a 101.6 mm or 120 mm locating ring.
Weight is the last fit check. Catoen advises confirming the maximum mould weight for both platens, not just the moving one, and gives platen parallelism of 0.025 to 0.05 mm as generally acceptable on machines under 500 t. Houseware moulds with slides and stripper plates can be heavy for their size, so ask the toolmaker for an estimate early.
What to compare on the two datasheets for a houseware mould
| Item | Why it matters | What your mould needs |
|---|---|---|
| Tie-bar clear space | The mould must pass between the tie bars | Gap larger than the mould, and the mould at least about 70% of the gap |
| Shut height range | The mould must close and clamp | Mould thickness between minimum and maximum |
| Opening stroke and daylight | Deep parts must clear the core | Stroke at least 2.5 × part height; daylight at least mould thickness plus stroke |
| Injection unit | Shot quality and pressure | Shot about 20% to 65% of barrel capacity |
| Drive type | Base load and running cost | Compare measured or quoted kW at idle and on cycle |
How Do Running Costs Compare Between Two Close Sizes?
The drive and the match to the job matter more than 5 t of clamp. A standard hydraulic machine's base load can be 75% or more of its energy; all-electric and hybrid machines run at about 10% to 20%. A high base load can mean the machine is too large.
Those figures come from an energy guide by ExxonMobil, AMI and Tangram Technology. It adds that ten-year energy cost exceeds purchase cost in almost every case, so a small difference in price matters less than a difference in drive.
Base load is the energy the machine uses whether or not it is making parts: pumps, heaters and controls. On a hydraulic machine sized well above the job, that fixed share grows. Ask each supplier for idle and on-cycle power on a cycle close to yours, and compare those figures side by side.
In Maharashtra, MSEDCL charges demand on kVA and energy on kVAh for HT consumers and LT consumers above 20 kW, under a MERC decision from April 2020. At a power factor of 0.85, 15% of the power drawn does no useful work. Capacitors or an APFC panel correct that, whichever machine you buy.
How Should You Choose Between the Two?
Take your widest, thickest and deepest houseware moulds and check each against both datasheets for tie bars, shut height, stroke, daylight and shot size. Then compare drives and only then clamp. See the 120 ton horizontal injection moulding machine page.
Frequently Asked Questions About a 120 Ton vs 125 Ton Machine
Can a mould built for a 125 t machine run on a 120 t machine?
Often, if the clamp calculation with its reserve stays under 120 t and the mould fits the tie bars, shut height and stroke. Check the locating ring size, the mounting pattern and the ejector pattern too. A mismatch in the ejector layout may need an ejector box or a change to the mould.
Is a bigger platen always better?
No. A larger platen takes bigger moulds, but a small mould on it covers too little of the tie-bar distance. The platens can then bow under clamp, giving flash at the centre of the mould. Very small moulds can damage the platens, so match platen size to the moulds you will run.
Does a longer opening stroke slow the cycle?
Only if the machine opens further than it needs to. Set the opening to what the part needs to clear the core, not the maximum. Dry cycle figures of 3 to 5 seconds are typical for conventional machines, so the open and close travel is a small share of a houseware cycle.
Should I choose the machine with the bigger screw?
Not by default. A bigger screw on the same injection unit usually gives lower plastic pressure, and very small shots in a large barrel stay too long and can degrade. Choose the screw that puts your typical shots between about 20% and 65% of barrel capacity, as the mugs and bowls article explains.
Does a 125 t machine use more power than a 120 t machine?
Not necessarily. Energy use depends more on the drive, the heater load and how closely the machine matches the mould than on 5 t of clamp. Compare quoted or measured kW at idle and on a similar cycle, and check power factor, since kVAh billing charges for the wasted share.
Related Articles
- What Can You Make on a 120 Ton Household Moulding Machine?
- Moulding Mugs, Bowls and Lunch Boxes on a 120 Ton Machine
- Starting a Houseware Unit With a 120 Ton Machine
Sources & References
- MoldMaking Technology, B. Catoen: Machine Sizing and Specification for Optimal Mold Performance, Part 1
- Plastics Technology, P. Witaszek, J. Klees, J. Fattori, E. Di Siro, J. Bozzelli: How to Mount an Injection Mold
- ExxonMobil, AMI and Tangram Technology: An Energy Saving Guide for Injection Moulders
- Maharashtra State Electricity Distribution Co. Ltd (MSEDCL): kVAh Billing: Frequently Asked Questions
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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