Several months ago, I started gathering information with the intent to build a rotary attachment for my Epilog laser engraver and found a lot of good information on SMC. But, in February, I took a detour and bought a laser rotary attachment through ebay from a guy in North Carolina because the price I paid was about what parts and shipping were going to cost me for making my own.
Although I never received anything but excuses, another SMC member recently informed me that he has finally received a rotary attachment after months of delay. However, he says it is non-functional. He gave me the model number of the stepper motor used in the unit he finally received.
According to the motor manufacturer, it is a discontinued NEMA 17 motor that is only rated for 6V. Epilog uses a larger NEMA 23 motor rated at 24V and drives it with 48V. One of the motor manufacturers told me they don't warrant the motors when over driven with constant current sources. Although it is common to overdrive steppers when you have current limiting circuitry, Epilog apparently doesn't use active current limiting so the 6V motor would be over-driven by a factor of 8 with Epilog's 48V driver, seriously exceeding the motor's I^2R rating. I'm not sure what max current Epilog's circuit can provide, but these 6V motors will try to pull four times as much as the OEM motors and eight times their own rating. Power dissipation goes up by the square of current. Anybody know how much a new Epilog driver board costs?
So I'm back to rolling my own chuck-based rotary attachment around a custom-wound NEMA 17 motor that is designed from the get-go for 48V operation. It draws less current than Epilog supplies to their 24V motors without overdriving (or overheating) either the motor or the driver. My thanks to Kim, Peter, and Dave for their kind help.
-Glen