|Operations with Shaping Machines - Course: Mechanical woodworking techniques. Trainees' handbook of lessons (Institut für Berufliche Entwicklung, 18 p.)|
Shaping machine operate at high rotational speeds. This denotes, apart from a greater strain on tools and the rotating machine parts, also a greater risk of accidents.
If the machine is not properly handled and the accident-prevention stipulations remain unheeded, two serious of accidents can ensue:
- injuries through loosening tool parts, tools or parts of the tool chucking facilities,
- cuts of the hands by touching rotating tools.
The machine must not be operated without sufficient knowledge of commensurate labour safety measures!
In order to avoid industrial accidents the following labour safety hints must be strictly observed.
- cutter arbors with top bearing tenons can only be utilised along with top bearings,
- the tool should be positioned as close as possible to the spacer nut on cutter arbors without top bearing tenons,
- the maximum rotational speed cited on multi-part and heavy tools must not be exceeded, otherwise the centrifugal forces within the tool could lead to its destruction,
- the tools must be exactly set and all cutters shall only operate within their commensurate knife cutting circles,
- tools with broken off cutters or with removed tool parts are no longer dynamically balanced. Vibrations can ensue given high rotational speeds. These in turn result in irregular blows on the workpiece and damage to the machine. Considerable accident risk.
- the tool bore must conform to the shaft diameter. Turned gauge rings may be used on small cylindrical cutters to compensate for a bigger tool bore on the cutter arbor shaft.,
- the machine has a braking device to attain spindle standstil within 10 s of switching off the motor,
- the guide rule must not feature any defects
- no screw or impact clamps should be used to attach additional devices to the machine table or guide rule as the cited clamps can easily loosen through vibrations and cause accidents,
- given hand feed, only counter-rotational cutting is possible!
- do not use any blunt tools for they exert a considerable cutting force and, then, the workpiece can only be held and guided manually with great difficulty,
- stop blocks must be placed alongside the stop faces of the guide rule if surface milling takes place. This prevents back movement of the workpiece.
Figure 15 - Guide rule stop for surface million operations
1 stop block, 2 workpiece, 3 sequence of movement
Additional guides and blocks can, if required, be attached to the machine table. This is ensured by the throughgoing bores with internal thread in the table surface. Steel strip deflectors, protective caps and guard spacers are frequently employed to ensure that the hands do not come into contact with tools. The guard spacer should always be greater than the tool diameter. It is envisaged for milling operations on starting-up spacers, that is to say where no guide rule can be employed. The guard spacer is of light alloy and has rounded edges. Hand contact with the guard spacer can ensue and may even be painful, however cut injuries through the tool are prevented. Where possible the guard spacer should be set up a little distance away from the tool. If the distance between machine table and tool top edge is more than 30 mm the guard spacer no longer serves its envisaged purpose. In such a case a different protective device should be employed.
The guard cap is attached to the radial arm. As applies to the guard spacer, the guard cap too is envisaged for cutting operations without a guide rule. The guard cap cannot be used in conjunction with a cutter arbor with top bearing. Generally speaking, because of the partial view hindrance, the utilisation of a guard cap makes necessary additional stops or guide facilities. A guard cap is also handy in preventing cut injuries. The guard cap should also be greater than the tool diameter.
Figure 16 - Utilising the guard cap
1 guard cap, 2 workpiece
The steel strip deflector is an elastic steel belt with two holders which are used to place the steel strip deflector into two bores of the top narrow faces of the guide rule. The height is set so that its lower edge is not more than 8 mm away from the workpiece top edge. The elastic steel belt, given a favourable selection of bores in the stop rule, permits an arc-like shielding of the tool working area.
Pressure acombs can be attached to the machine table and guide rule for improving tool handling capacity and preventing a backwards movement of the workpiece. A pressure comb ensures a partial covering of the tool.
Pressure combs are not standard machine equipment and must be made in the workshop.
What is the function of the pressure comb as an aid
and labour safety
Why is only counter-rotational milling permissible for manual
Cleanliness and proper order are essential preconditions for accident-free operations!