Would rather go in a different direction than making an industrial torture machine.

My version would be simpler and self-powered :)
1. Put prisoners' feet into "high heel shoes" that have long nails in place of heels and as the prisoner walks they gradually grind into her heels deeper and deeper

2. to prevent the prisoner from escaping I would tie her with a cable which is simply skewered through her body so as she moves the cable will be sliding inside.

for more fun, I do not lock prisoner and do not even guard her that obviously but give her an illusion that nobody is washing and she can escape.