Start by defining the result you need. Most mass-finishing processes are intended to remove material, pre-polish, polish, burnish, or perform a combination of these actions.
Some parts can be completed in one operation. Others require multiple stages—for example, an aggressive deburring step followed by pre-polishing, polishing, or burnishing. Media should be selected separately for each stage while considering the surface condition produced by the preceding operation.
Important selection factors include:
- Starting surface condition: Determine the amount of burr, scale, roughness, machining marks, or other material that must be removed.
- Required finish: Define the acceptable edge condition, surface roughness, brightness, and overall appearance.
- Part material: Steel, stainless steel, aluminum, brass, plastics, ceramics, and delicate components may require different media compositions.
- Media function: Determine whether the media must cut, pre-polish, polish, burnish, or perform more than one action.
- Part geometry: Media must contact the required surfaces without becoming lodged in holes, slots, threads, recesses, or other features.
- Equipment: Vibratory, rotary barrel, centrifugal, magnetic-pin, and drag-finishing machines apply different levels and types of energy.
- Separation: Media and parts should be easy to separate after processing.
Production requirements matter as well. The technically finest finish may not always provide the best manufacturing process. Production volume, processing time, labor, maintenance, material loss, wastewater requirements, and cost per finished part should also be considered.
Two visually similar components may require different processes when their materials, manufacturing methods, initial surface quality, production volumes, or final requirements differ. Sample processing is often the most reliable way to confirm the complete combination of media, compound, equipment, and operating parameters.
For more guidance, see FAQ: What Media Should I Use.