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12. Mechanical design & Machine design

Overview of week 12 assignment

  1. Group assignment
    1. Mechanical design
      1. design a machine that includes mechanism+actuation+automatio +application
      2. build the mechanical parts and operate it manually
    2. Machine design
      1. actuate and automate your machine
  2. Individual assignment
    1. document the group project and your individual contribution

1. Group assignment

For more information, see the Machine Building Project page.

2. Individual assignment

A. RYOAN-JI XY 2025

We, FabLab Kannai members decided to create the machine “RYOAN-JI XY 2025,” based on a CoreXY module, using an LLM to generate a desktop karesansui and haiku inspired by input images.

whiteboard

I was responsible for the hardware design of the machine, based on Quentin Bolsee’s UrumbotXY 2.0, adopting the CoreXY mechanism and adding features for Karesansui art. You can find CAD files and BOM at the bottom of this page.

overview

B. Modifications on UrumbotXY 2.0

First, we considered incorporating improvements in last year's Kannai project THE LONE ANGLER while using Urumbot as the base mechanism.

image

a. Aluminium frame:

Unlike the UrumbotXY 2.0, we chose to use a non-grooved aluminum frame (MiSUMi KHFS5-2020-1000) for easier availability, which resulted in instability of the V-wheels on the frame. So, we decided to use eccentric nuts and a four-wheeled carriage instead of a three-wheeled one to make it more stable.

b. Installation of eccentric nuts for fine adjustment:

We added eccentric nuts to one side of each moving part; the X-axis bracket and the carriage.

Eccentric nuts: An eccentric nut has an off-center hole; rotating it moves the attached part closer or farther, allowing precise adjustment of tension or alignment. eccentric_nuts

c. Design of a four-wheeled / double-sided X-axis bracket and carriage for stability:

Three-wheeled brackets were unstable on the non-grooved frame, so we added a fourth wheel to each moving part. We also used double-sided brackets to enhance durability, as our design relied on acrylic boards and 3D-printed parts, unlike Urumbot, which uses metal components. 4-wheeled

d. Wire fixture:

Based on the Urumbot, I modified the carriage bracket to fit M5 bolts, allowing the wires to be secured by tightening the bolts.
wire_fixture

Insert nuts are embedded in 3D-printed parts to create durable threads for screws. The carriage model includes recesses for insert nuts, designed to avoid overhangs during printing.

e. Slots and set screw (Observation of the Urumbot):

  • Slot holes are used to adjust wire tension
  • Insert nuts and set screws secure pulleys to motor shafts with notches

baka_ana_imoneji

f. Core XY motion system test:

Before building all functions, we quickly assembled the main frame and motors to manually test the CoreXY mechanism.

C. Custom components and design adaptations

a. Rake and rake bracket systems:

We adopted a simple solution to move and switch between two types of rakes by rotating them with a stepper motor. Since the rakes should passively follow XY movement, I designed a ball joint mechanism, which also allows easy swapping of different rake types.

Based on the 3D model of Nema 17, I studied the design of the bracket (3D model: GRABCAD | 17HS4401S NEMA 17 stepper motor | FreeCAD model).

  • Width: 42.3 mm
  • Length: 40 mm
  • Mounting pitch: 31 mm

rake

b. Karesansui field and LED lighting installation:

I designed an MDF box for the Karesansui sand field, sealing the corners with masking tape.

field

The bottom is made of acrylic to allow LED backlighting from underneath, illuminating the sand.

backlight

c. ESP32S3 camera module bracket:

I designed a bracket for the ESP32-S3 camera module with an adjustable angle, using a slotted hole. camera_bkt

d. Endstop bracket:

I reused two Y-axis endstop brackets designed by Yamada-san last year, one for the Y-axis limit and the other for triggering the ESP32 camera. I also designed a new X-axis endstop bracket to match the carriage height. endstop

D. Assembly process

  1. Assemble the carriage

    • Because of the height of the eccentric nuts and V-wheel, we added some spacers made of acrylic board to adjust the height of the other wheels.

    carriage

  2. Assemble the X-frame

  3. Install the X-frame into the Y-frame assembly_1

    Don't forget to install T-nuts

    Be sure to install the correct number of T-nuts before assembling the frames!

  4. Assemble the remaining main frame and Z-frames while securing 90 degree angle assembly_2

  5. Fix and wrap the 2 wires wire
  6. Assemble the Karesansui sand field
  7. Mount the camera modules and endstops
  8. Wiring and covering in the aluminium frames

E. Testing and calibration

a. Wire Tension Adjustment:

Initially, the wires were too tight, causing jerky movement. We resolved this by loosening the wires using the pulley slot holes.

Tuning to equalize the tension of two wires.

b. Calibration of movements:

We tested how much the carriage actually moves when controlling a parameter in the PC program. By drawing a '50 x 50' square using a pen attached to the carriage, we measured an actual size: 80 x 80 mm. This means the system moves at 8/5 = 1.6 of the programmed scale. Therefore, by multiplying the parameter by 5/8 = 0.625, the units within the program were adjusted to match mm.

c. Rake calibration based on sand behavior:

The rake was initially too high and didn’t press into the sand enough, so I added nuts between the ball joint and the rake to lower it.

F. Future improvements for the next spiral

  • The current rake lift mechanism doesn't support software-based Z-axis calibration. Replacing it with a pantograph or similar system would allow programmatic calibration and better adaptability to sand height changes.
  • The rake’s passive rotation is limited by the short distance between its pivot and tip, causing it to lag behind movements. Extending the rake from the axis would improve responsiveness.
  • The LED backlight isn't program-controlled. Integrating it would enhance interactivity.

3. Files & BOM

  • 3D print / lasercut parts: Ryoan-Ji_XY_2025_v1_BOM.stp.zip

  • Assembled (*Includes imported models from Urumbot 2.0. Some purchased parts such as bolts are not included.)

BOM

Electronic components

Item Details Qty Remarks
Stepper Motor NEMA17 1.5A 3 Motor for Y-axis
Limit Switch Normally Open 3 XY axis and trigger
USB 3.0 Hub Amazon 1
USB Type C cable Amazon 4 For 3 motors and a ESP32S3
XIAO ESP32S3 Sense Seeed 1
XIAO RP2040 Seeed 3 For 3 motors
Modular-Things CoreXY 2024 Bootcamp 3

Mechanical components

Item Details Qty Remarks
V-Slot Wheel 16 For all axis motion
Bearing D16xd5xH5 4 Motor pulley
M5 eccentric nut 6 Carriage
Non-stretch Fishing Line Amazon: 9KM DWLIFE Kevlar Cord, Load Capacity 22kg~680kg 1

Structural components

Item Details Qty Remarks
20*20 Aluminum frame (HFS5-2020-390) 390mm 2 Frame base Y
20*20 Aluminum frame (HFS5-2020-350) 350mm 2 Frame base X
20*20 Aluminum frame (HFS5-2020-346) 346mm 1 X-axis carriage
20*20 Aluminum frame (HFS5-2020-175) 175mm 5 Foot and camera

Fasteners

Type Details Quantity Remarks
M5 Socket Head Screw 8mm 61 General frame & assemblies
30mm 6 Pulley, captain
40mm 4 X-axis carriage
50mm 16 XY-axis carriage
M5 Nut 16 Carriage, pulley
M5 washer 6
M5 spring washer 16 For pulleys and wheels
M5 T-Slot 70 Frame and all axis assemblies
M5 Acrylic Spacer 5mm 36 Pulley and eccentric nuts
3mm 8 Carriage
M3 Socket Head Screw 8mm 16 Stepper motor, ESP32S3
15mm 2 Rakes
M3 nut 8 Fishing line holder
M3 washer 8 Fishing line holder
M2 Socket Head Screw 12mm 6 Limit switch
M2 nut 6 Limit switch
M3 Set screw 8 Pulleys

Zen components

Type Details Quantity Remarks
Sand Amazon: アマゾン川源流の白砂 3kg (約1.8L) 1

Afterthoughts

  • Calibrating the rake to achieve good sand behavior was the most challenging part, I should have worked on it earlier.
  • Rhino is more Zen than Fusion360, allowing me to focus on the present instead of worrying about the future or being haunted by the past.
  • What I did was the "Kan-gineering" (勘ジニアリング) approach; a Japanese term used in manufacturing industry, combining kan (intuition) and engineering, meaning to rely on intuition and experience over exact calculations. It has its pros and cons, but I believe it's still essential, especially when making (almost) anything.
  • For the other aspects of this project, such as project management, electronics design, programming, and application development, please refer to the documentation by Ito-san and Tokuyama-san. Big thanks to both of them for their great work!