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Shaping of horizontal and plane surfaces can be classified into:
- shaping of plane surfaces
Figure 25 Shaping of plane surfaces
1 cutting movement,
2 feed movement
- shaping of end faces
Figure 26 Shaping of end faces
1 cutting movement,
2 feed movement
- shaping of parallel surfaces
Figure 27 Shaping of parallel
surfaces
1 cutting movement,
2 feed movement,
3 parallel surfaces
Plane surfaces are flat surfaces laying in parallel to the cutting and feed movement. They are mainly machined as reference or locating surface for subsequent operations. The clamping, locating and machining surface of the workpieces often is still unmachined.
When shaping plane surfaces, make sure that
- forged workpieces (steel) are machined with SHSS tools and workpieces made of cast iron are machined with cemented carbide tools- workpieces sensitive to distortion are unclamped (i.e. released and clamped again) before finishing in order to avoid elastic deformations (dimensional changes after unclamping due to distortion)
- the tool point acts below the hard cast-iron or forged edges,
End faces are flat rectangular limiting surfaces on workpieces. They are created when shaping is made vertically to the plane surface.
When shaping end faces, make sure that
- the position of the horizontal reference surface is checked (adjust the workpiece, check by following the outline with the dial gauge before cutting and with the vernier caliper after the first cut).- the lower end faces are lying free to avoid damage to the table.
- the tool slide is set vertically.
- the cutting edges of the tool are always sharp.
- the tool is clamped sufficiently long according to the cutting height.
- the clapper-type tool block is adjusted so that an inclined position from bottom left to top right results. The tool must lift itself from the surface to be machined during the return stroke.
- the recommended values for machining are reduced by approximately 50 % compared with face-shaping, as the force and movement directions are less favourable.
Parallel surfaces are surfaces of equal shape which are equally spaced to each other. They occur most frequently as plane and end faces on workpieces. Shaping of parallel surfaces is characterized by machining several surfaces lying parallel to each other, with the position of the workpiece remaining the same. This is possible, because the direction of the primary motion is not changed by the ram guide.
Parallel surfaces should be machined in such a way that re-clamping of the workpieces does not become necessary, if possible. If nevertheless reclamping of the workpieces is necessary, the parallelism to be reached is determined by the exact position of the surface machined first.
The proper use of the clamping equipment and, in connection with this, the choice and application of the elements for securing of position (stops, tongues, parallel strips, etc.) are of decisive importance for a manufacture meeting the quality standards.
When shaping parallel surfaces, always make sure that
- the surfaces machined first are used as bearing or supporting surfaces- in each case one and the same parallel strips (base by several parallel strips) are used
- adjustment of a surface already machined is made by checking with appropriate means (e.g. dial gauge)
- checking of parallelism is made in the clamped state, if possible.
Shaping of parallel workpiece surfaces can also be made in connection with shaping of shouldered workpiece surfaces.
Sequence of operations 'during shaping
- Preparation of table and tool carrier for the clamping process (suitable positioning, freedom of motion)- Clamping the workpieces and alignment to the tool
- Clamping of tool
- Scratching of workpiece
- Feeding, setting of cutting values
- Sample cutting (approx. 2 to 3 double strokes)
- Preliminary check
- Finish shaping (roughing or finishing)
- Final check
Feeding should be made when machine is at rest. For determining the length of stroke and cutting speed (number of double strokes) the following shall be applied:
length of stroke L = l + la +lo (mm)
where
(l = workpiece length,
la = approach,
l = overrun)
number of double strokes
Note that the machining recommendations must be halved when determining vm.
What surfaces are machined by the technique of shaping
horizontal and plane
surfaces?
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What are the fundamental working steps of machining by means of
shaping?
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