Quote Originally Posted by george uk View Post
Hi



.

I have seen this happen, Nema23 on z, Z bocx mounted forward like you pictured. Z down gave it enough leaver, that when his limit switch failed, put a slight bend in a very well constructed Y gantry, both the mounting rails and ballscrew had a noticable movment when passing the point were it had bent.

He was very ham fisted with his limit switches, hence it failed, but it did bend it, i will have a go at doing the math tonight again,
Thats why i insist that only 2 possible models of homing and limit switches should exist, no other variation trade-offs, like the ones popularized by Mach3 in fact:

1. Small hobby machines with weak motors and more or less rigid / like mine current one/ - no limit switches, instead software limits . Mistake, axis go to end , motor stalls and nothing happens. Probably limits only on Z, as there could be a problem with flimsier ones/ like mine :-)/ Its typical situation where the BOB has limited I/O.

2.BOB with a lot of I/O and homing and limit on for each axis on SEPARATE I/O, so a limit switch is a limit switch, nothing else. Thats what i intend to do and advice you for your build, this with my limited knowledge. And if servos, the limit switches directly to the servos, not the BOB, i don't see a reason why the servo should wait for the BOB to tell him to stop. Cause with servo, a lot could happen in a very short time if geared and running fast. It seems most of the servos i looked at support it, so they stop and later they tell the BOB that they are not moving .