It did not take 'shocking' statement (OK, really the title was a flat out blatant, slanderous lie.). He asked about it on the Warp9 forum and Greg responded promptly, located the problem and took steps to correct it. While I agree the advice given to the OP was valuable, the title and other misinformation given is at the very least misleading.

All that being said, one should never rely on ANY piece of HW, like the SS or a Gecko stepper driver, or Mach III, or etc. to keep them safe. What do you think happens when you loose an encoder on a servo drive? It runs away! A proper, operation E-Stop circuit is a must.

I just can't resist putting my spoke in again on this thread.

No matter how unlikely, sudden and unexpected, power outages will and do occur at the most inappropriate moments. The design of all machines must be able to handle a sudden power disconnection in a controlled and safe manner. The ultimate and effective emergency stop will disconnect all power to the machine instantly. In other words - if for some unlikely reason the software polled e-stop has no effect on a runaway machine then pull the power.

Tweakie.

Hi All,
In design of industrial facilities most sites go through what we call Hazards Review and What If ( just a few of the buzz words ) thinking around what will be built, operated and maintained. The discussions are intense in review of each and every component that can cause personal or physical injury or damage. These reviews are well led, documented and provide basis for control by responsible individuals. As the complexity of machine systems increase, even at the amateur
level, it behoves us to stop and pull back and go through a thought process and address any and all hazards which are
identified. An e-stop is just one component of the system. In the big picture the dollars spent are appropriate for pre-defined base guidelines as they relate to investment. Safety on the other hand is defiined as goal of "0" ZERO incident and appropriate safeguards, procedures, training, supervisory controls etc are implemented to achieve the goal.
 
RICH