You adjust the print head gap the same way you do now, then you adjust the probe height so that it triggers at that exact height.  You do the mechanical adjustments and get it as close as you can, then you use software settings (M212 command) to adjust the offset until you get it as close as it needs to be.

Once that's done, all you need to do is issue a bed probe command (G29) before each print, by putting the command in your beginning custom G-Code section. 

So when you click print, the head goes out and does a 3 point probe before each print.  At each point it measures the distance to the bed, relative to it's saved settings and uses the offset delta to continuously adjust the distance to the bed surface during the printing of the first layer.

So the idea is that you don't have to adjust or re-adjust the bed levelling screws, the printer adjusts the height of the head automatically instead.

Obviously that doesn't matter if your bed is perfectly level all the time and doesn't go out of adjustment, but we all know that doesn't happen very often, so an auto-levelling device sound like a great idea.  The problem comes in when that very device starts to do funny things like getting false readings that lead to bad adjustments, head crashing into the bed surface, or being too far. 

In my case, I was using a PCB heater (MK2A) with glass on top, so the probe had to be very close to the glass.  Not only that, but I found that it worked OK when the heater was turned off, but it lost its position when the heater was on.  It turned out it gets confused by the electrical field generated when the PCB heating element would get power.

how would people stack these printers against each other?

I initially had a order of 2x press and 1 wb apprentice with SD but have since adjust it to 1 press as i dont have a lot of faith in SD anymore but i want to give them one last chance ( i.e if the press really is a "exceptional product" and then get there act together with adding a fan / releasing design file for it)

i refer to the printrbot simple as including the heated bed add on and the imminent upgrade to dual direct drive extruder and full metal hot end.

I personally really like the implementation of the non contact bed level compensator and the design on the thing feels really solid

what do you guys think?

I don't have the metal version, but I do have  Pirntrbot Simple, and I do have a Solidoodle 3, and I can tell you they're 2 different beasts, you can really compare the two. 

If you like the simplistic design of the Printrbot simple, and are willing to make a few concessions (like the reduced print surface), then it might be a good solution.

I like it because of it's simplicity, because I can simply pick it up, put it in a bag and take it with me to work or whatever.  I added a heated bed to mine simply because I wanted to use ABS (can't stand working with PLA). And for what it is, it's pretty darn good.

On the other hand, if you want a large print volume (8x8x8 instead of 6x6x6), if you want a heated bed out of the box (not an upgrade for extra money), if you want and enclosure, and one of the best support groups around (US, right here, not Solidoodle), then perhaps you should stick with the Solidoodle.

As for the contactless bed leveling sensor, it's more work and frustration than it's worth.  Most of them stop working after only a few weeks.  The wires inside the cable were not designed for constant motion and the break, requiring a replacement or a complete rewiring.  It's not always accurate (or responsive) and sometimes it makes the head crash into the bed surface.  I ended up replacing the original sensor with a Fotek sensor which much more accurate.

My point is that the auto leveling feature, while it sounds really cool, is overrated and I wouldn't base my decision to buy a printer on this feature alone.  If you want to read up more on my ( and other users) frustration with it, here is a link at the PritrbotTalk forums (I'm the topic originator, Dudemeister)

http://www.printrbottalk.com/forum/view … amp;t=7696

Then again, considering how low the prices are, maybe should get both.

I initially had a order of 2x press and 1 wb apprentice with SD but have since adjust it to 1 press as i dont have a lot of faith in SD anymore but i want to give them one last chance ( i.e if the press really is a "exceptional product" and then get there act together with adding a fan / releasing design file for it)

i refer to the printrbot simple as including the heated bed add on and the imminent upgrade to dual direct drive extruder and full metal hot end.

I personally really like the implementation of the non contact bed level compensator and the design on the thing feels really solid

what do you guys think?