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I like internal machining

Is internal machining possible?

Vibratory finishing is an excellent process for machining external contours. When using disc-type centrifugal systems, the workpieces are machined together with abrasive in the continuous torroidal flow on the outer wall of the work bowl on their surface. This flow cannot build up in the inner area of a workpiece, even when the smallest abrasive are used. This also means that no machining takes place on the inner surface. The same situation can also be observed with strongly concave outer geometries on workpieces. Here, the flow is limited by the concave shape and reduces the intensity with which the abrasives can act.

In conventional trough systems, workpieces and abrasives are moved relative to each other by means of vibration and the cavities quickly fill with abrasives on the inside. Due to the "caging" of the workpiece, however, the abrasive move internally almost "synchronously" with the workpiece and thus do not develop any appreciable material removal. The process of "internal machining" is illustrated using aluminium profile sections as an example:

Raw part Grinded part Polished part

Limiting cases as a challenge

Internal machining requires that the abrasive can move freely relative to the workpiece. For example, the machining of edges on disc-shaped or ring-shaped workpieces is also possible without any problems on the inner areas, as long as abrasives can flow against them. When selecting the abrasives, it is therefore important to ensure that there is a good flow to the relevant surfaces. Basically, the deeper and narrower the passage (e.g. bore), the less flow and machining. The following example shows that the machining of the large diameter is complete on the inner edge. On the inside edge of the small diameter it can be seen that machining is less intensive.

Vibratory finishing is therefore only a conditionally suitable process for internal machining.

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