CNC will put a lot more wear and tear on the mill.
It really isn't appropriate to use for production. I suggest you keep your current Sherline for prototype work, then buy something a bit beefier for production.
I tried using a Sherline CNC mill for production, and here were my problems:
- backlash increased to unacceptable levels very quickly
- repeatability is not good enough, especially when you are using the extents of the travel to make a lot of parts. For instance, I used a spot drilling cycle, then two drilling cycles, and then two milling cycles for a single lot of twelve parts. The lead screws' relatively low quality/accuracy/repeatability was not good enough to use the entire table, and the finished parts were unacceptable. I can only effectively use 1/4 to 1/3 of the table for production type work.
- You will find yourself increasing spindle speed so you can increase feeds. The leadscrew pitch is very low, and steppers will run out of speed very quickly. My metric Sherline mill is maxed out at ~18 inches/minute, and I dare not go faster in fear of lost steps. I am using 3/16" 4 flute endmills in tempered aluminum, and it needs to feed faster (with 5500 rpm pulleys).