Maybe this should go in the controllers section of the board but it does relate directly to Chinese machines running NC-studio...
I just got hold of a used JX-1212 http://www.jxsycnc.com/En controlled with NC studio. It may be a few years old and, seems like it was constructed fairly well.
To test out the machine I ran a small job on it to compare with the results I was getting from a Liyu 500x300 machine - retrofitted with mach 3 and a smoothstepper. The Liyu is actually a really solid and accurate machine and I use it to make scale model parts ranging in size from a few mm to bigger than the machine.
I wasn't expecting the 1212 to have the same accuracy as the smaller machine but I was concerned about some tool marks and odd lines on the surface of the machined part controlled from NC-studio.
So I took a mach 3 compatible breakout board and wired it to a 15 pin D connector via a piece of ribbon cable so I could plug it straight into the 15 pin connector on the machine without disturbing the original NC studio setup. After tuning the motors and rigging a touchprobe I ran the same toolpath.
Here's a picture of the results - they're machined from 20mm thick acrylic with a 3mm ballnose then painted in primer grey.
Original part from the 500x300 machine on the left, mach3 controlled 1212 in the middle, NC-studio on the right. So, even though the they were all made with the same toolpath, NC-studio seems to have a bit of trouble with the interpolation. I believe the spurious tool marks on the part on the right are caused by rounding errors in the algorithm which interpolates the X Y Z position of the machine from the g-code.
As I said, the machine is a few years old so maybe the NC-studio firmware has improved but I think I'll be making my mach3 mod to the machine permanent.