Over the past 3 months I have received a number of emails about Impact Engraving and how it has been made to work with Mach3. I certainly had many difficulties to start with so thought I should try to explain the principal for the benefit of others that follow.
The credit must all to go to Andrea for discovering ? that an electro-magnet can be driven directly from one phase of a bipolar stepper motor driver and the, perhaps obscure, principal that advantage can be taken from the fact that electromagnets, just like stepper motors will stall when pulsed too fast.
In operation and when at rest, a stepper motor shaft is locked but when that same stepper motor is pulsed too fast it will stall and then the shaft is free to rotate, in either direction, quite easily by hand – the energy within the coils is not transmitted to the iron core of the rotor or at least if it is transmitted then it is in complete balance and cancels itself out.
It is the same with an electromagnet – in operation and when at rest, it is energised but when it is pulsed too fast it will effectively ‘stall’ and drop out. As the pulse rate is reduced, a threshold is reached and at that point the electromagnet will again be energised and this is the way in which the impact engraver can be used.
The actual needle impacts with the work are made only on the ‘overshoot’ of the return or spring stroke and the Z height has to be precisely adjusted to take advantage of this. Setting up is perhaps easier the second time around but once mastered is extremely easy to reproduce.
There is still some work to be done here and I am perhaps lagging behind on updating the pdf document (Engraving.pdf http://www.cooperman.talktalk.net/Engraving.pdf
) which so far attempts to cover Laser but not yet Impact – it is on my ‘to do’ list and will be completed as and when.
In the meantime if anyone else has any experiences with Impact Engraving I would be extremely please to hear them.