What advantages do smooth, highly polished surfaces offer for cleanability and low product residues?
Smooth, highly polished surfaces with low micro-roughness – typically a mean roughness value Ra ≤ 0.8 µm, and in hygiene-critical applications down to approximately ≤ 0.4 µm – significantly improve cleanability and reduce product residues by minimising adhesion points, allowing cleaning media to wet the surface evenly, and making the formation of biofilms and corrosion more difficult.
Reduced adhesion and product residues
Rougher surfaces have micropores, scores and depressions in which particles, liquids and viscous media can "anchor" themselves mechanically. Highly polished surfaces smooth this topography, thereby lowering the adhesive forces between product and plant wall and reducing the effective contact area. Products adhere less readily and drain away more easily after discharge, which reduces product losses and the risk of cross-contamination when batches are changed.
High cleanability and CIP/SIP suitability
During cleaning and sterilisation processes (e.g. CIP/SIP), cleaning and rinsing media can wet smooth surfaces unimpeded and uniformly. The flow becomes more homogeneous, the wall shear stress increases and soiling is removed more efficiently. This shortens cleaning cycles and lowers the consumption of water, cleaning chemicals and energy.
Reduced microbial colonisation and biofilm formation
Microorganisms need protected niches in order to form colonies and to develop stable biofilms. Rough surfaces provide such "dead zones" in the form of valleys and pores. A highly polished surface with a low Ra value removes these points of adhesion and retreat, impedes the initial attachment of organisms and facilitates their detachment during the cleaning process – a central aspect in the food, pharmaceutical and biotechnology industries.
Improved corrosion resistance
With metallic materials such as stainless steel in particular, a smooth, homogeneous surface promotes the formation of a stable, closed passive layer. Depressions and notches in which corrosive media can accumulate and local differences in concentration arise are minimised. The risk of pitting and crevice corrosion as well as the release of metal ions into the product thereby falls.
Easier visual inspection and quality control
On highly polished surfaces, residues, damage or changes can be detected better visually or by means of an endoscope or borescope. Deviations from the target condition are noticed more quickly, which supports quality assurance and the validation of cleaning processes.
Meeting hygiene standards, and economic aspects
In hygiene-critical sectors, standards and guidelines (e.g. EHEDG, 3-A, FDA, GMP) require defined roughness values and cleaning-friendly surfaces for product-contact areas. Highly polished surfaces make it easier to comply with these specifications and contribute to lower product losses, shorter downtimes, less consumption of chemicals and a longer service life of the components, which reduces the total cost of ownership.
The required surface finish is to be defined according to the process and the product: extremely low roughness values do increase manufacturing costs and are necessary only where the highest hygiene requirements apply. In such cases, mechanical polishing is frequently supplemented by electropolishing, in order to further reduce residual stresses, microscopic burrs and remaining unevenness.
How amixon® solves surface finish and material selection for hygienic powder processes
Surfaces: ground, low in adhesion, cleanable
At amixon®, the mixing chamber and mixing tool are welded free of crevices and ground smooth – without scratches, pores or undercuts in which product residues could adhere or biofilms could form. The surface finish is specified according to the application: from industrially ground to highly polished designs for GMP-critical processes (pharmaceuticals, infant formula). Since every amixon® apparatus is a one-off in accordance with the URS, the required Ra value is established and documented project-specifically. The surface roughness can be selected project-specifically, typically with Ra values of 0.8 µm, 0.6 µm, 0.4 µm or 0.2 µm; beyond this, amixon® can lap to a mirror finish and electropolish.
Smooth, homogeneous surfaces reduce build-up directly – together with the microfine addition of liquids, the mixing chamber remains free of deposits even during moistening processes.
A range of materials for every product chemistry
As a welding company with European, Japanese, Korean and American qualifications, amixon® processes, as required: mild steel S355J2+N, Hardox (wear-resistant), austenitic stainless steels 1.4301, 1.4541, 1.4571, 1.4404, 1.4539, 1.4529, duplex stainless steels 1.4462, 1.4162, 1.4363 as well as Alloy 59, Hastelloy-C22 and nickel for highly corrosive chemicals. Reference: the vacuum mixer-dryer VMT 200 made entirely of Alloy 59.
For abrasive goods, hardened tools and ceramic plasma coatings are available as wear protection.
Constructional complement
Surface finish takes effect only together with freedom from dead space: the mixing tool mounted at the top only, dead-space-free discharge fittings, Clever-Cut® inspection doors with an OmgaSeal® seal. The residual discharge of 99.997 % and better with free-flowing goods minimises the quantity of residue that has to be cleaned at all – on request, the mixers meet EHEDG, the FDA hygiene guidelines and the 3-A Sanitary Standards.
Manufacture in Paderborn as the quality foundation
amixon® develops and manufactures exclusively at the Paderborn works, with the greatest depth of fabrication and all components from Germany. As a certified welding company with European, Japanese, Korean and American qualifications, amixon® designs every apparatus as a one-off on the basis of the operator's URS; quality control remains entirely in-house, and every specification is verifiable down to component level. This manufacturing sovereignty also secures long-term supply: every component can still be reproduced decades later.
Qualifiable and documented
For regulated environments, amixon® supplies the plant in qualifiable form: every apparatus is a one-off in accordance with the URS from its own manufacture with quality control that has no gaps; amixon® assists on request with DQ, IQ and OQ, and documentation and execution follow, on request, EU GMP and FDA 21 CFR Part 11. On request, the mixers meet the relevant standards – EHEDG, the FDA hygiene guidelines, the 3-A Sanitary Standards, USDA, GMP, ATEX and ASME – and are integrated into the operator's validation concept from the URS through to commissioning.
Verification in the amixon® pilot plant
amixon® checks in advance in the pilot plant whether the specific formulation delivers the expected results: 35 test units, trials with the original product under real conditions, carried out, evaluated and documented jointly – as a robust basis for decision-making before the investment.