Am 12.01.2014 01:48, schrieb DaveC: 1.) Safety issues. It is a lot safer to have the machine shut off, when the power is cut. Otherwise the saw might start up again, while you have your fingers on the blade or so. Or the blade is stuck and starting the saw can ruin the blade/motor/mechanics. 2.) When using a simple on-off-switch, there is really no good way to have it stop, other than turning the switch. When you use a contactor, you can start and stop the saw with multiple switches, for example a two-button-start, to ensure both hands are away from the blade, or one stop-button and a sensor/switch, that stops the saw, when it hits a certain point or so. In our company we have special motor-switches, that have an under voltage-switch attached. The switch has two buttons (on and off; who would have thought :-) and the under voltage-switch is attached on the side and turns the switch off, when the voltage drops below a certain value, via a mechanical rod assembly. And that on machines, that, theoretically will just give you a good whack if it starts up and you have a body part in there. Might also be a good reason to install something like that in a band saw.
- posted 8 years ago