Describes the rotation of a rotatable, cylindrical machine part (e.g. cutter block, feed roller, glue roller, metering roller, application roller) with regard to the workpiece or another machine part. Here, 'down-cut' means that the movements of the parts lead to a common feed direction. When the cylindrical parts are rubbing against each other, it means opposing rotational motion (see sketch)!

Milling tools, planer heads

The cutting movement of the tool runs in the same direction as the feed of the workpiece. The first cut starts immediately with the impact of the main cutter on the wood and runs, with decreasing intensity, to the maximum immersion depth. This results in a short chip, tapered towards its end.

Advantages

• clean cut edges even with bad grain
• lower feed force than for milling in up- cut, since the tool movement does not counteract to the workpiece feed.
• higher feed rates possible

Disadvantages

• shorter tool life
• because the cutting force builds up quickly at the blade during immersion
• because of longer working ways due to the lack of pre-splitting
• higher cutting load
• higher tool-driving force necessary because of the lack of pre-splitting
• only suitable for mechanical feed

Application

Due to its economic advantages in terms of tool life, the majority of cutting operations on woodworking machines are carried out in up-cutting. In order to nevertheless achieve a good cutting quality and to exclude tear-outs, down-cut spindles are used.

• Cutting of plastic materials or wood-based panels with hard, brittle surface coatings.

Sanding aggregates

Sanding units also usually work in counter-rotation, as this ensures a high chip removal and a short dwell time of the abrasive on a certain workpiece surface (keyword heating). For the production of very smooth wood surfaces with minimum fibre length, however, longitudinal sanding units are equipped with reversion of rotation in order to let them work in synchronisation if required and in combination with an upstream counter-rotating sanding unit.

Protective equipment for synchronous machines

Multi-blade saws

• Multi-rip saws require a protective device in the workpiece outlet to ensure that any ejected workpieces do not pose a danger and do not injure anyone. The German manufacturer PAUL solves this problem e.g. with its model K34/ ... GL by means of protective tunnels with deflectors or so-called discharge tongs.

Immediately after being cut open, the workpieces are conveyed into a tunnel that is closed on the outside and, after being completely cut open, are released downwards onto a roller conveyor. Machines with this protective device have a limited workpiece processing length (limited by the max. length of the protective tunnel).

• Saw blades with chip thickness limitation are also recommended.