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It is part of the preparation of the respective sequence of operations to lay out all necessary working tools, objects of work and auxiliaries in a suitable way and according to regulations.
In doing so, observe the following rules:
- Check the necessary tools for operational reliability and put them down in such a manner that they are clearly arranged and ready at hand. So they can immediately be used, thus making work efficient.
- Put down measuring and testing means on bases provided for this purpose.
- Tools must not lie on top of each other.
| The work can be done in an optimum way only if the tools are sharpened and the necessary angles are observed.
- Choose all necessary auxiliaries according to the work order and place it on a base provided for this purpose (clamping bolts, baseplates for mounting of the workpieces, angle-plates, work rest, clamping gib, step block, clamp dog, machine vice).
Figure 5. Clamping auxiliary
1 clamping bolt,
2 baseplate for mounting of the workpieces
Figure 6. Clamping auxiliary
1 angle-plate
Figure 7. Clamping auxiliary
1 work rest,
2 clamping gib
Figure 8. Clamping auxiliary
1 step block
Figure 9. Clamping auxiliary
1 clamp dog
Figure 10. Clamping auxiliary 1
machine vice
What are the criteria according to which tools are to be checked
for
serviceability?
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For machine setting basically the following working steps are necessary:
Clamping the workpiece for shaping of grooves
- The quality of the workpiece to be machined is considerably influenced already by setting up.
- When grooves are shaped on shaping machines the cutting force acts parallel to the workpiece supporting surface.
Figure 11. Cutting force acts
parallel to the work support
1 cutting force related to the workpiece,
2 passive force
related to the workpiece,
3 partial cutting force
- Each workpiece clamping must be firm, safe and definite in position.
- Each workpiece clamping must be done in such a way that no permanent deformations on the workpiece result.
- The clamping forces must be so great that a displacement of the workpiece is prevented.
- When using the machine vice (mainly for chucking small workpieces with parallel outer surfaces), screw it firmly on the machine table by means of clamping dies.
- Locate the machine vice by means of tongues.
- There must be no dirt particles or chips between machine table and machine vice.
- Place the workpiece directly on the guideway of the vice (use parallels when the workpieces are flat - see Fig. 18) and tighten the vice.
Figure 12. Clamping of the
workpiece in the machine vice
1 clamping force,
2 guideway of the machine vice,
3
workpiece
- Knock the workpiece in place with a hammer from above so that it firmly rests on the guideway of the vice. Ground supports made of cast iron take up vibrations better than steel supports when knocking the workpieces in place. When clamping is made on the machine table, clamping is effected from both sides, e.g. by means of clamps (clamping workpiece on the machine table under compression - vertical clamping forces).
Figure 13. Clamping of the
workpiece on the machine table under compression with clamp
1 workpiece,
2 clamp
- Another possibility consists in pressing against tongues or stop blocks (clamping workpiece on the machine table - horizontal clamping forces).
Figure 14. Clamping the workpiece
on the machine table against tongues or stops
1 tongues,
2 workpiece,
3 clamping element with clamping
nut
- Use only serviceable nuts for clamping bolts.
- Choose the clamping forces to be 1.5 to 2 times as big as the cutting forces.
- Holding-down of the workpiece must also be effected by the clamping force. For this purpose the clamping forces shall be applied near the contact surface of the tool.
What has to be considered when clamping a workpiece for shaping
grooves?
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What purpose does chucking in the machine vice
serve?
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When is clamping on the machine table
applied?
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Clamping of tools for shaping grooves
Fix the shaper tool into the tool holder located on the lower part of the ram (tool post).
The following rules shall be observed:
- Clamp tool short and firmly to prevent bouncing.
Figure 15. Short and firm clamping
of the tool
(1) tool clamped short and firmly
(2) tool clamped too long,
chatter marks are produced on the workpiece
- Use only unobjectionable jaw wrenches.
- Clamping surfaces must be even and free from dirt and chips.
- Choose the length of the cutting part according to the depth of the groove to be machined.
- Clearance angle and rake angle depend on the material of the workpiece.
- Use tool, with largest possible shank section (prevention of vibrations).
- Tool must not bite during feeding.
- Chips must flow off well in the groves.
Why must the clamping surfaces be even and free from dirt when a
tool is
clamped?
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Explain how a tool is to be clamped and what rules are to be
observed in doing
so.
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Setting of stroke length and position of the ram stroke
The stroke length and position of the ram stroke must be set according to the length of the workpiece and position to the clamping table.
- The stroke length is composed of approach, length of the workpiece and overrun.
- The stroke length is adjusted by moving the crankpin. If the spacing is small, the stroke is also small. If the spacing becomes large, the stroke is large as well.
Figure 16. Adjustment of the stroke
length by moving the crankpin
1 crank gear (simplified),
2 crank arm,
3 fulcrum of crank
arm,
4 crankpin,
5 sliding block
- It must be ensured that stroke length and position of the ram stroke with short overrun path and accurately adjusted. The free run-out of the tool must be ensured also during cutting.
- The position of the ram stroke is correct, if there are run-out and overrun. The ram is displaced by operating the hand crank which turns the screw arranged in the ram. Displacement of the ram is forced according to the principle of screw and nut.
Setting of the number of strokes
The number of double strokes is derived directly from the cutting speed in connection with the stroke length. In case of fixed numbers of stroke on the machine that number of stroke shall be set which is closest to the calculated number of strokes. The calculated number of strokes should not be exceeded.
What is a stroke adjustment necessary
for?
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What are the criteria for choosing the stroke
length?
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What criteria are to be considered when setting the number of
strokes?
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