Bridgeport Manual to CNC conversion...

[JAZZCNC]

A decision must be made before the controller is purchased as i believe i must specify incremental or absolute type (whatever that means?).
I was looking at the GSK clones such as Newker http://newker-cnc.com/index.php?m=co...=166&l=3&id=91

Yes, it's a bit of a mind field with these controllers so be careful, I've been looking for Mill controllers. Make sure you read all the tech spec because some have limited memory amongst other differences like how many simultaneous axis can be used at one time.

Regards Absolute and Incremental then it relates to the Encoder type used on the Servo. The BST uses incremental encoders as do most other types of servos unless you state you want Absolute.

The difference being that with incremental when you shut down the machine, the controller has no idea where the position of the machine is when it starts back up so you have to home the machine at the start of each day. (or if the servos are powered down) Just like you do with the stepper system.

Absolute Encoders retain the position of the servo even after shutdown, they do this by having a battery attached to the cable to power the memory of the encoder. This means you don't need to home the machine on startup and the drives/encoders know at all times where the machine is located, even if after power down someone manually moves an axis. (provided the battery power doesn't fail or the encoder cable is unplugged from the motor)
There is some setup I believe to be done when first installing because the drives/motors/encoders need to be told where Zero is located etc and the controller needs to support Absolute type but after that they work just like Incremental but without the need to home on startup.