Die Casting Leak Testing and Tightness

Pressure tightness should be defined as a measurable requirement: test medium, pressure, duration, allowed leak rate and the surfaces that must remain sealed.

A vague requirement such as leak free creates disagreement later. The equipment, fixture and acceptance threshold should be agreed before production.

• Define medium, pressure and duration
• State the allowed leak rate
• Identify the sealed surfaces
• Agree the fixture and method

Common methods include air decay, pressure decay, water immersion and helium testing. Each has different sensitivity, cost and cycle time.

The choice depends on the leak rate that matters to the application. A coarse air test may be enough for a weather cover but not for a fluid housing.

• Air and pressure decay are common
• Water immersion shows bubbles
• Helium is used for fine leaks
• Match sensitivity to the application

Tightness is controlled by the same variables that control porosity: gate and runner design, venting, cooling, shot profile and metal quality.

Machining can also create leaks by opening porosity near a sealing surface. Sealing faces should be planned with enough stock and a stable datum.

• Gate, vent and cooling affect tightness
• Shot profile controls fill and gas
• Machining can open porosity
• Plan sealing faces carefully

The acceptance rule should say how many parts are tested, what happens to a failed part, and whether rework or re-test is allowed.

Test records should be traceable to the lot so a field issue can be investigated against the production data.

• Define sampling and disposition
• State rework and retest rules
• Keep records by lot
• Link records to production data