The surface finish of JACAN pharmaceutical-grade ACM air classifying mill follows cGMP, FDA 21 CFR and EHEDG hygienic design rules, split into product-contact surfaces and non-contact external surfaces. All product-wetted components are built from 316L stainless steel as standard.
1. Standard Roughness Specification
- Product-contact surfaces (grinding chamber, rotor hammers, classifier cage, scroll liner, feed inlet, powder outlet): Ra ≤0.8 μm mechanical polish as baseline GMP standard for oral solid dosage APIs and excipients. Weld seams are ground flush and blended to match base metal roughness, eliminating crevices, pits or trapped powder residues.
- High-critical upgrade option for sterile, injectable or high-purity APIs: Electropolished finish to Ra ≤0.4 μm, sometimes Ra ≤0.25 μm, conforming to ASME BPE SF4. Electropolishing removes surface free iron, enhances corrosion resistance and reduces biofilm adhesion for CIP/SIP processes.
- External non-product-contact surfaces: Standard mill finish or brushed polish Ra ≤1.6 μm, cosmetic requirement only, not for cleaning validation.
2. Fabrication & Post-Treatment Features
- Weld treatment: All internal welds use orbital TIG welding, fully ground and blended, no undercut or sharp corners. Internal transitions adopt rounded radii (R≥3–10 mm) to prevent material dead zones.
- Passivation: All product-contact stainless steel parts undergo full chemical passivation after polishing to build a stable chromium oxide protective layer, with passivation test documentation supplied.
- Surface inspection: Roughness test reports, borescope inspection records and material certificates are provided for IQ/OQ validation. No scratches, pinholes or embedded abrasive particles are permitted on wetted surfaces.
- Wear components: Replaceable grinding liners, hammer tips and classifier wheel segments also follow the same Ra finish standard. Ceramic wear parts for abrasive pharma materials are polished to smooth non-sticking surfaces.
3. Compliance Notes
FDA and EMA do not enforce a single fixed Ra value, but require surfaces to support validated cleaning. Ra ≤0.8 μm mechanical polish is the most widely adopted standard pharma ACM mill finish for oral solid production. Electropolished Ra ≤0.4 μm is selected when handling high-potency APIs, sterile materials or when online CIP/SIP sterilisation is required.
The standard surface finish for pharmaceutical-grade ACM mill product-contact surfaces is mechanical polish Ra ≤0.8 μm on 316L stainless steel, with flush blended welds and post-fabrication passivation. Electropolished Ra ≤0.4 μm is available as an upgraded specification for high-purity and sterile pharmaceutical manufacturing. External casing surfaces use a simpler brushed finish at Ra ≤1.6 μm.
