KC_703 wrote:What's your layer height? I find that a separation distance set to 1.5 to 2 times the layer height seems optimal for my machine. I'm guessing it may also have something to do with the extrusion temp... an extrusion temp which is too high may not set on top of the raft, and bond too well. I normally use a rectilinear external infill, this bonds the edges of the model to the raft... because more filament is deposited when the infill overlaps with the perimeter. A concentric external infill could help resolve this...
Regarding your original question, its probably best to print a test cube and measure the Z height for accuracy... it shouldn't printing the layers lower or shorter than set.
I'm usually using a .2 layer height, and I've gone as high as 2.5 times that for the separation and I really don't see any difference no matter what the separation setting is.
Thanks for the suggestions on the temperature. I'll try adjusting that a little, although with the MakerBot "Smart Extruders" I've read that lower temps can contribute to clogging. We're getting a LulzBot soon, so maybe we can just stick with the Makerbot software with the Makerbot printer. It makes rafts that separate perfectly, but doesn't print as accurately for parts that require good precision & accuracy. I'm printing for some medical and health care applications, so that can be important sometimes.
You may be right about manually adjusting the Z height. I use the automatic leveling software that comes with the Makerbot and I do have trouble printing a good first layer without a raft. If that's off, it wouldn't matter what settings I put in the the raft, would it?