How heavy is a case mould?

Answer: A four-cavity case mould for a 280 mm body runs about 3.8 t, base included. Plan a 650 t press.

Can the draft angle be smaller?

Answer: 1.5° is comfortable at 200 mm of depth, 1° is the limit, and below that scuff risk outweighs the gain.

Does cooling have to be conformal?

Answer: Only at volume. Under 50,000 parts a year, drilled channels at 55 s are enough; past 200,000, a conformal insert at 42 s pays.

How many trial parts count as a pass?

Answer: 300, with drift inside 0.15 mm. Fewer than that and cavity temperature has not settled.

How long does a case mould last?

Answer: It is designed for 300,000 cycles. Polish yearly and grease the pillars quarterly, or flash shows near 150,000.

Case Mould: Structure and Process in Five Points

Quick answer: A case mould decides how even the box wall runs, how the lid meets the body, and how long one part takes. Five points carry that: plate stack, gate position, cooling, ejection with draft, and the trial run.

How a Case Mould Is Stacked
Gate Position and Runner Balance
Cooling Channels and Cycle Time
Ejection and Draft Angle
Trial Runs and First Article
FAQ

1. How a Case Mould Is Stacked

A case mould stacks seven to nine plates between the clamp plates. The top plate carries the sprue bush, the cavity plate cuts the lid, the core plate cuts the body, the support plate backs the core, and two spacer blocks open the ejection space.

Plate	Material	Thickness	Job
Top clamp plate	45 steel	40 mm	Holds sprue bush
Cavity plate	718H, 33 HRC	90 mm	Lid cavity
Core plate	718H, 33 HRC	90 mm	Body core
Support plate	45 steel, hardened	60 mm	Backs the core
Spacer block	45 steel	120 mm	Ejection travel

Plate thickness is not free. At a 280 mm body the support plate goes from 50 to 60 mm; leave it thin and the core sags 0.1 mm, giving one thick wall and one thin wall. Stacked this way a four-cavity mould weighs about 3.8 t and needs a 650 t press. An 800 mm plate also grows 0.28 mm from 25 °C to 60 °C, so guide clearance is set cold.

2. Gate Position and Runner Balance

The body is 3 mm thin-wall and deep, so a centre gate lets melt climb all four walls at once, while a side gate leaves a weld line where cracks start.

Case Mould: moulds lined up by number, a steel cavity block face up in front, two workers checking on the right, blue racking above

Runners run as an 8 mm trapezoid off a 6 mm sprue. Keep the four branches within 5 mm in length and 0.5 mm in section, or far cavities starve and the box warps. A 0.03 mm vent at the parting line, where the melt arrives last, keeps corners from scorching.

3. Cooling Channels and Cycle Time

Cooling sets about seventy percent of the cycle. Cavity and core each run a circuit of 12 mm holes on a 60 mm pitch, 15 mm from the moulding surface, water at 45 °C and 8 litres per minute.

Cooling layout	Pitch	Cycle	Warpage
Straight drilled	60 mm	55 s	0.6 mm
Baffle plus insert	45 mm	48 s	0.4 mm
Conformal insert	Follows surface	42 s	0.2 mm

Cost differs by an order of magnitude: a laser melted conformal insert can cost as much as half a mould base, so it pays only at high volume. Cooling also gates ejection: the timer must follow the thick section, or each pin leaves a white mark.

4. Ejection and Draft Angle

A deep body grips the core hard, so ejection is where white marks appear. Eight pins of 6 mm sit at the corners and long-side midpoints, on a 60 mm stroke, sized for 12 kN.

Case Mould: an orange hoist above the workshop aisle, a worker in red between the moulds, black plastic cases stacked on pallets at right

A deep body runs 1.5° of draft, which at 200 mm of depth opens 5.2 mm per side. Below 1° the wall scuffs at release. Hold all eight pins within 0.05 mm, or the first few take the whole load and bump the base.

5. Trial Runs and First Article

A case mould is tried three times: dry cycling for motion, short shots for fill order, and a full shot for size. At sixty percent fill the melt should reach the same point in all four cavities; if one fills first, the runner goes back for rework.

Check	Method	Accept
Wall thickness	Ultrasonic, five points	3 mm ±0.1 mm
Parting gap	Feeler gauge	0.02 mm blocked
Lid fit	Hinged and cycled	No interference
Seal flatness	Plate and dial gauge	Within 0.05 mm
Latch alignment	Visual at closure	Tongue seated

A passed first article is not the end. Run 300 parts: cavity temperature climbs over the first 50 shots, so dimensions drift, and the mould is signed off only if drift stays inside 0.15 mm.

Conclusion

The plate stack sets stiffness, gate and runner set fill, cooling sets cycle, ejection and draft set appearance, and the trial run decides whether it repeats. Skip one and the fault surfaces three months into production. Fix them in order and the sealing face and latch seats hold, which is how a case mould is judged.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.