As previously noted in this thread, My N2+ arrived with a warped heated bed, which was badly out of adjustment. In working out this problem, I have developed what I feel is a significantly improved technique to adjust the level of the heated bed.
I know Raise3D advertises “factory adjusted” level beds, but the factory adjustment on mine was quite bad. They do suggest a procedure for user leveling of the bed, which does not work for me at all.
Because this bed is mounted at 13 points (actually 39 points, with 3 adjustments for each of 13 bolts) the adjustment process is much more complex and difficult than the 3-point compression spring mounting used on most smaller 3D printer beds. There are 13 bolts whose function is to pull the bed down against 13 pairs of vertically adjustable support pins whose function is to establish the flat plane parallel to the plane of travel of the extruder nozzle and support the bed upward on this plane. To move any one of the 13 points up you must loosen the nut on the bolt, adjust both associated level pins upward (tighter) maintaining the correct flat plane between the 2 pins, then retightening the nut on the pulldown bolt, all this while measuring the vertical position of the bed at that point.
There are 4 potential critical errors in this adjustment. The pair of locating pins could be too high or too low relative to the flat plane, or one of the pins could be higher or lower than the other, warping the bed at that point, or the nut on the bolt could be too loose allowing the bed to float above the 2 pins, or too tight warping the bed downward between the 2 pins.
The ability to accurately measure the position of any point on the bed relative to the plane of the extruder nozzle is critical. With the 3-point compression spring mount this was fairly easy using a feeler gauge. With repeated measurement necessary at least at 26 points on the N2+ I find mounting a dial indicator securely to the extruder mount greatly simplifies and speeds up the measurement process and improves accuracy as well. Accuracy is not critical here at all, only repeatability is required to identify relative differences at various points on the bed, so inexpensive units starting around $15 on amazon will do fine. I have 3D printed a secure mount to attach my dial indicator in place of the fans on the extruder mount. https://www.amazon.com/Indicator-Resolu ... +indicator
Having been very frustrated by the difficult triple adjustment at each of the 13 bolts, I decided to eliminate the most difficult one with a simple modification. I removed the bed from the machine by lowering the bed, detaching the electrical connections to the heater, and removing the 13 nylon insert nuts from the bed attachment bolts. With the bed out of the machine, I removed the 13 attachment bolts, saving the 13 nuts and lock washers for reuse. I purchased the following parts on Amazon:
M3x45mm 304 Stainless Steel Flat Head Hex Socket Screws https://www.amazon.com/gp/product/B01N5 ... UTF8&psc=1
M-jump Heated Bed Compression Spring 7.5mm For 3D Printer Extruder DIY Accessories (20 pack) https://www.amazon.com/gp/product/B0744 ... UTF8&psc=1
M3 Carbon steel Knurled Thumb Nuts https://www.amazon.com/gp/product/B01HS ... UTF8&psc=1
And a package of #6 flat steel washers.
I replaced the 13 20mm long flat head screws with 13 45mm long flat head screws, reusing the 13 lock washers and nuts. I noted that the lock washer on the center screw had cut into the small fiber washer under it, so I added one of the #6 flat washers on the fiber washer and the lock washer on that. I used a 7/32” deep socket or nut driver to tighten all the nuts securely, since we don’t want these screws to turn after reassembly.
Before reinstalling the bed plate on its support, I used my dial indicator attached the extruder mount to check and adjust the level of each of the 26 adjustable support pins to a flat plane parallel to the travel plane of the extruder mount. I then adjusted the 4 pairs of pins at the mid point of the 4 sides (left, right, front and rear) about .002” higher, to start with the bed slightly higher than all the other pins. We will then start our leveling at these 4 locations, then easily bring all the other locations up to match these 4 locations.
I then set the bed plate back on its support, with the 13 longer screws extending through and below the support frame. Now I installed one of the springs, followed by a #6 flat washer, followed by a knurled thumb nut on each screw. Note that these springs will now function to pull the bed DOWN against the adjustable supports, and will provide a relatively constant pressure downward regardless of the level of the support pins. More importantly, it will no longer be required to loosen this thumb nut in order to adjust the level of the support pins, as it will be effectively “self adjusting”. At this point, leave ALL of the thumbscrews close but NOT compressing the springs, because you don’t want to pull the bed down to an adjustment pin that is set too low (nearly all of them at this point).
Now comes the actual adjustment. Start with the 4 outside mid point thumbscrews and tighten them to compress the springs about 3 or 4 mm, seating the bed firmly on the pre adjusted pins there. Move the dial indicator directly over each of the 8 pins (2 beside each screw) and adjust each pin as required to exactly match the measured level of the other 7. Set the dial indicator dial to exactly 0 at this level.
Now follow a pattern to adjust each of the other attachments. I started with the center, followed by the square outside the center, followed by the outside corners. At each point set the dial indicator over one of the adjustable support pins, tighten the knurled nob to pull the bed down, while observing the dial indicator and moving the adjustable pin up to locate the bed at the proper level so the bed is not pulled too low. Check both pins next to this screw, and adjust each as required. Do this for each screw in the bed.
After the first pass, check all points again. It is expected that changing the level at any point may affect the level at other previously adjusted points. Repeat until satisfied that all points on the bed are properly in level. Optimally, variations should be less than .001”.
I have done this for my already warped and partially straightened bed, and found the process much easier, faster, and more effective than without the compression springs. I have not quite reached what I consider optimum level, but I’m way closer than before.