1. Why wearable casings are difficult to manufacture
Focus on real problems:
Thin walls combined with high structural strength
Complex curved external surfaces
Small holes and button openings
Internal ribs and mounting features
Tight dimensional relationships with screens and internal electronics
Cosmetic requirements
Corrosion and sweat resistance
High-volume production requirements
2. When MIM makes sense for smartwatch and wearable casings
Explain that MIM is especially suitable when:
The casing has complex 3D geometry
Production volume is sufficiently high to justify tooling
Multiple machining operations would otherwise be required
Small integrated features can be moulded rather than machined
Consistent part-to-part production is required
Important point for the article:
MIM does not automatically replace CNC machining. Some critical cosmetic or precision surfaces may still require secondary machining, polishing, blasting, coating, or other finishing operations.
3. Material selection for wearable casings
Potential materials to discuss:
316L stainless steel — corrosion resistance and premium appearance
17-4PH stainless steel — higher strength where required
Other MIM-compatible alloys depending on mechanical and cosmetic requirements
For a wearable, discuss the actual decision factors:
Sweat and corrosion resistance
Skin-contact considerations
Strength-to-wall-thickness requirements
Surface finishing
Polishing behaviour
Cost
4. The biggest engineering problem: shrinkage and dimensional control
This should be a major technical section.
Unlike conventional plastic injection moulding, MIM parts undergo significant shrinkage during debinding and sintering. Therefore:
Critical dimensions must be planned around the complete process
Sintering deformation must be controlled
Wall thickness should be as uniform as possible
Thick-to-thin transitions should be avoided where possible
Critical sealing and assembly dimensions may require secondary machining
This is where HongYing can demonstrate real manufacturing knowledge.
5. Designing the casing for MIM
Discuss:
Uniform wall thickness
Avoiding unnecessarily massive sections
Managing corners and transitions
Positioning parting lines away from highly cosmetic surfaces where possible
Planning gates and ejection
Designing for sintering support
Identifying which features should remain for secondary machining
6. Surface finishing after MIM
For premium wearables, the surface is often as important as the mechanical performance.
Discuss possible operations:
Polishing
Sandblasting
Brushing
CNC finishing of critical surfaces
PVD or other surface coatings where appropriate
A useful engineering point:
The moulded MIM part should not be considered the final product. For premium wearable housings, the manufacturing route must be designed as a complete system from feedstock to final cosmetic finish.
Developing a wearable metal casing requires more than selecting MIM as a process. The part must be evaluated for geometry, material, tooling, sintering behaviour, secondary machining and cosmetic finishing. HongYing helps customers coordinate these manufacturing decisions and find the right production route for complex hardware components.
