Injection Molding Clampage

[Sunny]

What is formula to calculate machine clampage required?I need a very basic formula to get the answer.
I have following questions
Whether the hot runner and cold runner mold with same weight varies clampage of machine?

[CM8787]

Easiest way is to start at maximum tonnage suggested for the mold according to the manufacturer. (Most molds have general suggested setups. If you don't have that, call the manufacturer. They should have records of it.)

Then reduce in small increments watching for flash....adjusting hold pressure/ transition position and so forth watching for pressure spikes. The less pressure needed maximizes mold life.

Tonnage needed is affected by fill speed/pressure and hold pressure needed to hold the mold closed during injection and packing out the part which is affected by your cavitation, part weight, etc. Generally, slower fill speed, lower pressures equals lower tonnage needed and less cavity pressure being applied and vice versa. There is no easy way to calculate it.

If you're in to apps, Finn Tech has a scientific molding app with a tonnage calculator on it which may aid you.

Hope this helps!

[rickbatey]

Tonnage requirements are dictated by surface area, resin used, nominal wall stock (thickness), part dimensions or cosmetics, cavity pressure requirements, and tooling concept/design. Now larger surface area parts can be molded with lower peak injection/clamp pressure using sequential valve gating or even chemical foaming agents. But the rule of thumb is based on surface area and resin used. So for shop resins, PP to HIPS with no fillers; 2-3 tons per inch squared. ABS-PC or PA, 3-5 t/in2.
Rick.

[brosamer]

http://www.ptonline.com/columns/clamp-tonnage-more-is-betterright

great recent article about this topic

[MTUHusky]

Clamp Tonnage = ((The number of cavities x The projected area for each cavity) + Projected area of the runner) x Material Clamp Factor x 1.1

The Material Clamp Factor: Based off of the FlowLength/Nominal wall thickness (L/T)
IF:
- L/T < 100:1, then Material Clamp Factor = 2.5 tons/in^2

- L/T = 100 - 200:1, then Material Clamp Factor = 5.0 tons/in^2

- L/T = 200+:1, then Material Clamp Factor = 6.0 - 8.0 tons/in^2

[Joel JS]

What is formula to calculate machine clampage required?I need a very basic formula to get the answer.
I have following questions
Whether the hot runner and cold runner mold with same weight varies clampage of machine?

Lots of other good info here.... but to your question..... the clamp tonnage will be almost the same for cold vs hot runner, but a cold runner does require a little more tonnage, maybe 5% more.

Hope that helps,
Joel