Choosing the right injection molding machine is one of the first questions in any mould project. Pick a machine that is too small and the mould will flash. Pick one that is far too large and you pay for capacity you do not use. This article explains how clamping force is usually estimated, what else limits the choice, and how Hailong’s machine range from 80T to 1400T is used for trial shots and production.
What clamping force does
When molten plastic is injected, it pushes the two halves of the mould apart. The machine’s clamping force, rated in tons, holds the mould closed against that pressure. If the clamping force is too low, the mould opens slightly and plastic escapes at the parting line, which shows up as flash on the part. If it is much higher than needed, the extra force adds energy use and wear on the mould without improving the part.
A common way to estimate tonnage
A widely used rule of thumb multiplies the projected area of the part by a clamp factor:
- Find the projected area. This is the area of the part (and runners) seen from the direction the mould opens, multiplied by the number of cavities.
- Apply a clamp factor. Factors of roughly 2 to 8 tons per square inch are often quoted. Easy-flowing materials and thick walls sit at the low end, while stiff engineering plastics and thin walls need more.
- Add a margin. Choose a machine with some capacity above the estimate rather than running at its limit.
For example, a single-cavity part with a projected area of 80 square inches and a clamp factor of 3 tons per square inch needs about 240 tons. A 320T machine would be a sensible choice. These figures are only a starting point. The material supplier’s data and a mould flow review give a better answer for a specific part, and our engineers confirm the machine size during quotation.
Tonnage is not the only limit
- Mould size: the mould must fit between the tie bars and on the platens.
- Opening stroke: deep parts need enough daylight to eject the part.
- Shot size: the machine must inject enough material for all cavities and runners in one shot.
- Your own plant: if the mould will run at your factory, it has to match the machines you already have.
Our injection molding machines
Hailong Group runs nine injection molding machines, from 80T to 1400T:
| Clamping force | Quantity | Brand |
|---|---|---|
| 1400T | 1 | Chen Hsong |
| 1200T | 1 | Hilectro |
| 1000T | 2 | Chen Hsong |
| 800T | 1 | Yizumi |
| 500T | 1 | Chen Hsong |
| 320T | 1 | Haida |
| 160T | 1 | Haida |
| 80T | 2 | Haida |
This range lets us run trial shots on our own machines for small precision parts up to large molded parts, and supply molded parts in production as well as the mould itself.
From mould design to trial shots
Mould components are machined on the same equipment as our stamping dies, including a 1614 high-speed machining center at 20,000 rpm for high-gloss mould inserts, vertical machining centers, EDM and wire EDM. After assembly, the mould is tried on a suitable machine and the parts can be scanned in 3D and compared with the CAD model. Each project follows a quality management plan covering design, programming, machining and assembly, and testing. More on our plastic injection moulds page.
What to send for a quotation
- 3D data of the part
- Plastic material grade
- Annual volume and number of cavities you prefer
- The clamping force, tie-bar spacing and platen size of your machine, if the mould will run at your plant
See the RFQ guide for the full checklist.
Talk to our engineers
Send your part drawings or 3D data using our RFQ guide or the contact page. You can also email nora@qdhailong.com or call +86-532-66090318.