CNC Metal Spinning
The figure illustrates the typical setup and the processes involved in multi-pass spinning.
The
blank, in this case a plain, sheet-metal disc, is concentrically
clamped against the mandrel by the tailstock and driven via the
main spindle. Rotating at high speed, the workpiece is then formed
by the spinning roller following a pre-set path to produce a series
of strokes or passes. In so-called 'continuous' spinning, the
roller remains in permanent contact with the workpiece and is
driven by frictional contact, the translated motion being generated
by the cross-slide. A number of passes are normally needed to
form the part onto the mandrel which also prevents premature failure
through splitting or buckling.
| 1. Disc Blank | 2. Spinning Roller | 3. Mandrel | 4. Clamping Plate | 5. Blank Support Unit |
| 6. Trimming Plate | 7. Spindle | 8. Cross Slide | 9. Tailstock |
View a CNC Metal Spinning Video demonstration.
The
blank support attachment in the forward position, is used in
the early stages of the spinning operation. Its purpose is,
by means of a pre-set pressure, to apply an axial, compensating
load to the workpiece in the zone being worked. Sandwiched between
the blank support and the work roller, the metal is thus less
prone to failure through buckling. For lighter gauges, the blank
is supported by a disc, as illustrated, whilst a cone-shaped
roller is used for thicker materials. The roller or disc is
usually driven by contact with the blank.
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To improve finish and accuracy, intermediate and finishing passes, generally called planishing passes, are made. The planishing passes are designed to remove any waviness resulting from different stages in the spinning process. High feed rates are usually applied to minimize tangential flow and improve accuracy.
The final roller pass serves to enhance surface finish. Feed and speed are reduced and a relatively high radial force applied.