DAB
A Precise Nozzle-As-Probe
Extruder Carriage
v1.07 (11/04/2023)
Add notations in the pictures
Components
Z endstop
Printed Z endstop mount (STL here)
Microswitch endstop module
Bolt m3 x 06 (2)
Square nut m3 (2)
Stator
Rail ↔ CF stator
Carbon fiber stator plate
Rail (1)
Countersunk bolt m3 x 07 (3)
Latch ↔ CF stator
Aluminum latch
Printed latch housing (STL here)
Bolt m3 x 18 (2)
Nyloc nut m3 (2)
Washer m3 x 8 x 0.8 (2)
Z endstop ↔ CF stator
Bolt m3 x 10 (1)
Square nut m3 (1)
Slider
Steel stopper ↔ CF slider
L-shape steel stopper
Countersunk bolt m3 x 10 (2)
Nyloc nut m3 (2)
Rail ↔ CF slider
Carbon fiber slider plate
Rail (2)
Countersunk bolt m3 x 07 (6)
Printed endstop finger (STL here) ↔ CF slider
Printed endstop finger
Countersunk bolt m3 x 07 (2)
Square nut m3 (2)
Temporary for extruder mount ↔ CF slider
Countersunk bolt m3 x 10, or longer for your customization mount (4)
Nut m3 (4)
Actions
When installing the L-shape steel stopper, keep it as horizontal as possible, so later when the latch is installed and being moved left and right, the ball plunger in the latch can enter and leave the stopper smoothly.
Assemble stator & slider
Exam
The latch can be shifted by the force of extruder movements.
The slider can ONLY move in Z direction. No wobbles in XY are allowed. (Check step 5 in the Actions)
Actions
Shift the latch rightward to the unlock position.
2. Stack the rails and cross roller bars as the order in the picture.
3. Insert the belt clamps to both side of DAB.
4. Loosen the bolts of rail (component E) in the above picture.
5. Press the rails with the belt clamps, so all the 4 rails lean against its paired one firmly. No wobble in XY directions are allowed.
6. Fasten the bolts of both rails.
7. Might need to loosen and tighten the bolts of the printed latch housing for the latch to move smoothly.
Belt clamp
Bolt m3 x 10 (4)
Square nut m3 (4)
Action
Insert the belt clamps in between the stator and the slider, and fasten the bolts after the belts are installed.
Install a new extruder mount
AFTER
the XY belts have been installed
The condition
After the XY belts are fastened to the DAB stator, installing a new extruder mount will be cumbersome which involves to remove and fasten the belts again.
Here is another approach of disassembling the DAB when it is still on the gantry.
Action
Remove the bed from bed brackets so it can lay down to the floor.
Tilt the whole frame down to the right side and carefully put the bed assembly on the floor.
3. Disassemble the DAB slider by loosening the front countersunk bolts to the rails.
4. Temporarily fasten countersunk bolts and nuts to the mounting holes for the extruder mount on the DAB slider.
5. Unlock the latch.
6. Attach one rail to the slider and put its cross roller bar on.
7. Put the other cross roller bar on the other rail at the stator, and stack the pair
8. Carefully combine the slider and fasten the countersunk bolts to the rails.
9. Stand the frame up.
10. Adjust the parallelism of the rails by loosening the 2 rear bolts of the right rail. Push the rail using a stick and tighten the two bolts.
11. Put washers, M3 nuts, and the new extruder mount to the countersunk bolts. The friction between the CF plate and countersunk bolt is enough to prevent bolt rotation when tightening the nuts.
DAB fork
Printed DAB fork (STL here. Prepare multiple copies as spares.)
Printed DAB fork for tuning (STL here)
Actions
For the DAB to work properly, some coordinate points are necessary to be fine-tuned in the Klipper DAB.cfg file.
Please slice the fork in the orientation as shown, so that when the motion system is occasionally in chaos, the fork can break easily and avoid damaging the DAB assembly.
Use the tuning fork temporarily while you're tuning the coordinate parameters. It doesn't actually touch the DAB latch thus won't crash if you haven't find the proper coordinate points.
Refer to the next page for DAB tuning.
DAB coordinate points
The parameters you need to adjust in DAB.cfg are illustrated in the pictures below.
Note that in the DAB.cfg, the [homing_override] section was commented out by default, so before your position_endstop, position_min, position_max in the printer.cfg are tuned, the [homing_override] section which rely on the 3 parameters will not be used.
P.S. In Klipper, user-defined parameters are declared as variable_xxxx and are used as xxxx.
DAB tuning procedure
Klipper firmware and config files are used here.
Note again that in the DAB.cfg, the [homing_override] section was commented out by default, so before your position_endstop, position_min, position_max in the printer.cfg are tuned, the [homing_override] section which rely on the 3 parameters will not be used.
Actions
During the initial tuning, it's highly possible to crash and hurt your nozzle, so instead of testing and tuning with the real nozzle, use a thin hex key or a toothpick as a fake nozzle.
2. Attach the tuning fork to the frame.
2. To avoid nozzle crash, manually UNLOCK but imagine the latch is in its locked position. Also prepare your hand for the emergency stop button.
3. In the klipper.cfg as shown below, find proper values for position_endstop, position_min, position_max parameters:
At this moment, the [homing_override] section in DAB.cfg is commented out (disabled) so the Klipper default homing procedure is used.
4. Once the above position relative parameters are tuned, uncomment (enable) the [homing_override] section in the DAB.cfg as shown below:
5. Find proper coordinate points for the fork.
6. Switch to the formal fork and test. Again, prepare your hand for the emergency stop button.
Z offset in Klipper.cfg
Z offset is the Z coordinate where the endstop triggers.
Unlike the positive Z offset value with an inductive sensor, the Z offset is a negative value with the DAB. For example, -1.45.
Z offset adjustment
Klipper command PROBE_CALIBRATE brings up an UI for you to find a proper z_offset value with the paper method, and then saves it into Klipper.cfg.
Later, if you're not happy with the offset, fine-tune it by observing the 1st layer as shown below.
For example, if your current Z offset is -1.5 in Klipper.cfg ...
