Why is it necessary to grind a surface?

Mass finishing (wet finishing) is a special form of grinding primarily used for the industrial conditioning of metal surfaces. Workpieces are usually processed in batches together with application-specific grinding media, water (99% of all mass finishing jobs are wet processes), and compounds (active cleaning additives) inside a mass finishing system. Contact pressure from the media and the relative movement of the finishing machines work together to create a consistent surface pattern across the complete batch of parts.

If you want to grind larger workpiece batches of mass-produced parts that are relatively robust, then mass finishing machines are the most cost-effective solution. With the right grinding media and compounds, such systems enable the most efficient and economical results. In addition, mass finishing offers the unique advantage that multiple processes can run batch jobs within the same system—like degreasing, grinding, cleaning, deburring, rounding, corrosion protection, or rust removal.

Such systems can easily be integrated into complex production lines. In highly automated workflows, parts only need to be loaded once at the beginning of the batch window. They then pass through the entire batch job cycle without further human intervention. This approach exemplifies modern batch processing applications for repetitive tasks and high volume processing, providing significant cost saving.

To achieve optimal coating results, many surfaces must first be ground. Grinding creates a homogeneous, grippy surface that improves adhesion of coatings. Specially equipped mass finishing systems can reliably and cost-effectively process large batches of small or micro parts for this purpose.

Depending on the method, abrasive grain, and processing stage, industrial grinding can yield a wide variety of surface results. Generally, grinding produces a uniform surface, though roughness may vary considerably—from coarse and visible to extremely smooth.

• Rough grinding results in distinctly rough surfaces with visible grinding structures and medium roughness values (Ra) between about 6 and 1 µm. Such surfaces are ideal for subsequent processing steps.
• Fine grinding produces much smoother surface results, often with roughness values between Ra 1 and Ra 0.2 µm. The surface appears uniformly matte to slightly shiny, with barely visible grinding marks.
• Ultra-fine or polishing grind achieves surfaces with very low roughness below Ra 0.2 µm. These areas appear smooth or even glossy and are ideally suited for high-gloss polishing.

In total, grinding—particularly metal grinding—offers a wide spectrum of possible outcomes, ranging from functional roughness to decorative smoothness. Even finely ground surfaces remain microscopically rough but, free of abrasive particles, can already be considered “finished” for many applications.

Water is not always required for mass finishing. If the material demands it (e.g., wood, certain plastics) or if disposal reasons favor it, dry finishing is used. Dry processes are usually less aggressive and remove less material than wet processes, but this lower performance can be compensated for with more intensive systems such as drag finishing, surf-finishing, or centrifugal systems.

Dry processing methods are also employed for high-value workpieces in aerospace and medical technology. These hybrid systems process large amounts of data-like tasks without user interaction, providing flexibility on an as-needed basis.