Hollow Resin or Concrete Castings: Even Wall Thickness and Core Stability

RUUIPON already has:

/silicone-mold-inner-core-design/

P38 also rewrote that intent around:

• core centering;
• buoyancy;
• top/bottom support;
• drainage;
• demolding.

P70 should add the measurement/validation sections below to the same canonical page.

Module A: define nominal wall and allowed variation

Do not write only:

target wall = 5 mm.

Also define:

• measurement locations;
• allowed variation;
• base thickness;
• rim thickness;
• whether variation is cosmetic or structural.

A flexible mold requires a defined measurement condition.

Module B: core buoyancy and lateral load are different

A core can:

• float upward;
• tilt sideways;
• rotate.

Top restraint may stop float but still allow lateral shift.

Use locating features that control all necessary degrees of freedom.

Module C: top/bottom locators and spacers

Possible strategies:

• top bridge;
• bottom pin;
• keyed shell;
• removable spacers;
• through-rod.

Select according to:

• casting material;
• load;
• demolding access;
• witness marks.

Module D: locator witness marks should be intentional

A core locator can create a visible feature on the casting.

Place it where:

• hidden;
• easy to fill/patch;
• functionally acceptable.

If the surface is cosmetic, use another support route.

Module E: pour sequence around the core

Map how material flows through the annular space.

Check:

• narrow gaps;
• flow split around core;
• air at rim;
• core support blocking flow;
• high-point vents.

A well-centered core can still produce a bad casting if the material cannot fill around it.

Module F: section the first test casting

For high-risk hollow parts, the first casting should be measured.

Options can include:

• physical section cut on a sacrificial test casting;
• ultrasonic measurement where suitable;
• caliper access from open rim;
• go/no-go fixture.

Record wall thickness around multiple positions.