SK-Go Belted-Z
Assembly Manual
v0.96 (20201231)
0. Overview
Overall steps
Decide gearbox position and print a stepper mount
Assemble parts
Install & align belts
Tense belts
Compile and flash a new firmware tuned for Belted-Z
1. Decide Stepper Position
Preparation
Download and print a stepper mount from SecKit GitHub repository.
Action
The stepper mount position in this manual is placed at the left rear side, with frame setup B which Y rails are at the front.
If you chose frame setup A which Y rails are at the back side, there won't be enough room for the Belted-Z stepper because the power switch is there. Please print a mirrored stepper mount and assemble the stepper & the 60T pulley to the right side of frame.
2. Top Pulley Housing
Preparation
1 set of top pulley housing assembly:
1 top pulley housing
1 30T idler
2 bolt M4x8
1 bolt M5x30
1 thin nut M5
2 T-nut M4
Make 2 sets.
Action
Assemble 2 top pulley housing assemblies as shown in the picture, fasten the thin M5 nut, and attach them onto Y aluminum extrusions. One bolt holding the Y rail onto Y plate needs to be removed.
The top pulley housing also acts as a belt tensioner so don't fasten those M4x8 bolts yet.
3. Belt clamp
Preparation
1 set of belt clamp:
1 aluminum belt clamp plate
1 self-printed belt clamp base
4 bolt M3x10
2 bolts M3x16
6 nuts M3
Make 2 sets.
Download the STL for belt clamp base from SecKit GitHub repository.
Action
Assemble and attach belt clamps onto L-shape bed supports. Don't fasten those M3x10 bolts for later belt installation.
4. Sync Shaft
Preparation
1 sync shaft
2 bearing mounts
2 30T pulleys
1 60T pulley
1 closed loop belt
4 bolts M5 x 8
4 T-nuts M5
Action
Assemble the sync shaft as shown in the picture.Don't fasten the M5x8 bolts, nor those tiny screws in the pulleys for later alignment
5. Planetary gearbox
Preparation
1 planetary gearbox
1 self-print stepper mount
1 20T pulley
4 bolts M3x10
2 bolts M4x8
2 T-nut M4
Download the STL for stepper mount from SecKit GitHub repository.
Action
Attach the planetary gearbox as shown in the picture. Don't fasten the M4x8 bolts for later belt tensioning.
6. Install & align belts
Preparation
2 sections of 100cm belts
Action
Carefully cut and reduce the belt so both ends can be clamped with the most number of teeth and won't overlap. If necessary, cut the belt tooth-by-tooth.
Take the belt clamp as the reference position, adjust top and bottom pulley so the belt is straight.
Fasten the bottom bearing mount.
Lift the side of the top pulley housing near the belt clamp and fasten the M4x8 bolt first, and then fasten the other side, so the belt can be tensed.
Exam
Make sure the belt (green section) is straight in both directions viewed from front and side of the frame. Slide the bed supports up and down and the belt should not be scratched by pulleys.
7. Align closed loop belt
Action
Adjust and fasten the position of 20T pulley so the closed loop belt won't be scratched by pulleys.
Pull the gearbox to Y-Max direction and fasten bolts to tense the belt. Note that both sides of the belt should be equal tensed.
8. Compiling and flash a new firmware
Action
Define SK_BELTED_Z as true and compile, flash a new firmware for your SK-Go². Below are the major
Z_CURRENT: 600mA is more than enough
Z steps/mm: 3200
DEFAULT_MAX_FEEDRATE: at most 7.5 mm/s
HOMING_FEEDRATE_Z: at most 450 mm/min (7.5 mm/s x 60 s/min = 450 mm/min)
Download SecKit Marlin source code from SecKit GitHub repository.
Exam
To provide enough torque and static friction against free fall of the bed frame, a high reduction ratio 1:20 gearbox is used so the max feed rate is low. Make sure the max feed rate is at most 7.5 mm/s, or the stepper will start skipping steps with strange noise.
9. Gearbox noise reduction
Action
Open the cap from its front end. Loosen the bolts with WD40 if needed.
Fill plenty of grease until the chamber is almost full. Don't worry, the gearbox is simple inside. If the gears fall out just put them back as shown in the picture.
Exam
Don't over-torque and strip the threads of those 4 tiny bolts.
