George,
Lets look at this logically. Anyone building a stepper driven MDF machine isn't looking to hold 0.001" on it.
By virtue of using MDF and threaded rod for lead screws the build will limit then to far more than this.

Your 0.18mm with a heat gun is far more than a stepper will get and if you are using decent drivers the motors drop back to half current when parked so working hard they will only get reasonably warm.

Where MDF scores is it's cheap and easily worked which means a beginner can quickly cut their teeth on the MKI router which often leads to the MKII and so on.

.