Nice!  How consistent are the height dimensions across the 4 corners?

29.5mm tall on all four corners (it was designed at 30mm, but *shrug* I may have nicked some off removing the brim.) I printed it the tall way. It is the base for a ruler guide (1mm slot in the center.) Part of a tool I am designing. The ruler slid in perfectly first try.

So, consistent, but we are talking about 30x30x5.5mm for that model. Larger builds is where I start having issues with layer separation in the front, mostly on the right corners.

Any, still impressive with all the issues I am having.

BTW it took 2 hours to print that little piece at .05mm. lol. At least I know it is possible when I am printing small things and need the precision.

It's not that the build surface needs to be "level".  It needs to be parallel to the plane of the carriage movement.

Agreed. While discussing this with a coworker today, I came to the same conclusion. It only needs to be parallel, so I will plan to take angle measurements and adjust the bed to match the extruder at the four corners (assuming it is linear, which I have not verified yet.)

So far, it seems to be only the front to back that is off.

Here is what I did: First, set the angle gauge on the bottom of the SD4 and zeroed it. Then I used the angle gauge at the three adjusment screws on the glass bed and dialed each one in until they read zero (and then went around and did it again until the readings were stable. Then I adjusted the Z-Stop at the center of the bed. When I moved the extruder around the bed, I noticed that it was still changing the gap between the hot end and the bed, so I placed the gauge on top of the extruder and moved the extruder, letting readings settle. I did mention that I found the Y carriages seemed off a bit, so this could be one reason that the extruder carriage is slightly off too.

I will pursue a permanently solution rather than just "dealing with it." The bed leveling gets knocked off quite often and I am not going to go through a huge process every time I need to level it again.

In context, I didn't buy a $6000 printer, so I did not expect it to perform like one out of the box. I would still recommend the Solidoodle to any of my friends that are tech-savy or at least mechanically inclined. Especially when I can get the results in the attached picture without any mods performed yet other than the glass bed and my stiffer springs I added (printed at .05mm with specialized flow rates and temperature settings.)

You are measuring on the glass, correct?

- What is the greatest variance of the indicator readings from side to side and front to back?
- Are the variances linear?  If not, this would indicate a bent rod.

If your variances are linear, then your carriage is still traveling about a defined plane.  You should then be able to adjust the build surface to compensate. 

It's not that the build surface needs to be "level".  It needs to be parallel to the plane of the carriage movement.

But.. But... What if I have a strong desire to optimise everything?

Isn't that the point?

Of course I want things to be as optimized and precise as possible in a 3D printer. Well, as optimized and precise as possible without going insane (or broke.)

For example, I just took a digital angle gauge and ran it all over the place and was dismayed that one Y-axis rod appears to be bent or slightly tweaked (just a smidgen lower in the front.) I also turned red when I realized that the extruder carriage is not absolutely perpendicular to the platform. That means no matter how perfectly level I get the platform, the carriage will bring it closer or farther away from the bed from front to back. Grr!!

When I go insane, I don't suggest anyone follows me. Haha

Thermal transfer doesn't have to be amazing. Just even-enough. If it's not perfect transfer, increase the aluminum plate temp .  Benefits of having a more-than-sufficient heater.

But.. But... What if I have a strong desire to optimise everything?

(I suppose leaky bed heater just means more heat into the enclosure = good too)

On a very very stuck print, I can pop my glass in the freezer and the part will pop off . 

Thermal transfer doesn't have to be amazing. Just even-enough. If it's not perfect transfer, increase the aluminum plate temp .  Benefits of having a more-than-sufficient heater.

Good luck...show us some pics!

I'd be wary bonding the glass in permanently - Murphy's law and all that. Otherwise consider the heater+glass to be disposable...

This is why I had considered mounting it to the aluminum plate instead. But, right now it is just laying on the kapton tape with hairspray between them and does not move. The bonding was more to ensure complete thermal transfer. But maybe I am thinking overkill there.

Good Luck Retroplayer , Don't forget to mount the SSRs to the metal of the case and put a little heat sink compound on the backs at least on the bed heater SSR. I can't wait to see photos .  Bill D.

Apparently my SSRs are coming across the ocean on a boat. It is going to be a little bit before I get all the parts.

I'd mount the glass and heater together (don't worry about alu - the heater board and glass will be strong enough to be the bed surface) and use a bit of high temp + fire retardant insulation (e.g. fiberglass, automotive muffler insulation, etc.) underneath. This will likely be much more effective than just plain air.

I'd be wary bonding the glass in permanently - Murphy's law and all that. Otherwise consider the heater+glass to be disposable... I've had no trouble with wardjr's favourite hairspray-under-glass trick to stick the glass down on kapton, I presume it would be just as good on the mk2b - just make sure you really lather it in there to take up all the air gaps... Minimum bubbles left over is the aim. I've also considered trying silicone heat transfer goo... feel free to experiment but it's just an idea at present!

Stick the insulation underneath either with the adhesive it came with if you get that kind (auto store stuff for doing engine bays / exhaust lining) or find a high-temp spray glue of some kind. Should be able to find something at an auto or hardware store, go for whatever's got the best temp rating (minimum rating maybe around 120C?).

tl;dr: aim for good conductivity between heater and glass, and good insulation underneath. enjoy!

I am not, however, impressed with the heater in the SD4. It doesn't seem to be able to keep up the heat very well,  is not very uniform, and takes forever to heat.

I had previously also ordered an MK2B PCB heater and an aluminum plate. The plan is to convert to a 4 point mount system.

So here is the plan and I am hoping some others will chime in and help with any suggestions:

Modify Z platform with bar stock to bring it out to 4 points for mounting the bed. The sandwich I am picturing is aluminum plate, MK2B heater, then glass. The MK2B has a spot for an LED which indicates when the bed is on. I was thinking about a high output side-looking blue LED which would transmit through the glass and light the whole bed up (just for the cool factor.)

The bed will be mounted with stiff springs to dampen any movement and the MK2B and aluminum would be screwed down just as now. Considering whether it might make sense to put some washers to space the aluminum from the heater and seal around the edges with aluminum tape (to create a heat chamber to store the heat and also keep any warping of the aluminum from the glass.) 4 stiff springs on the Z platform creating a square in the center of the plate adds additional stability.

To power the new heater (and my E3D hot end) I also picked up a 12V 30A supply and 2 SSRs.

I am wondering about attaching the glass directly to the MK2B using thermal adhesive and the adhesive that is used to fix your rear-view mirror. I really don't need to remove it, I don't think. But this might make more sense to switch the sandwich around and bond the glass to the aluminum instead (all else the same) in case the heater were to blow out and need to be replaced. Also the "chamber" might be more effective with the aluminum on the top so it doesn't rob heat away from the MK2B.

Missing anything? Suggestions? If successful, I will be posting the complete details of the mod. Actually, I would like to document every mod I do with full parts lists and links to make things easier for others. So many of these mods are scattered all over the place and complete parts lists are very rare.