ASCU-128 Automatic Stylus Cleaning Unit for CMM Machines

ASCU-128 Automatic Stylus Cleaning Unit

The ASCU-128 Automatic Stylus Cleaning Unit is a compact cleaning system designed for CMM styli. It removes chips, dust, and coolant residue from the stylus using a targeted spray of IPA and compressed air, helping to maintain clean probing conditions and reduce manual cleaning effort.

The system has already been tested in real production environments and is currently in use on four measuring machines.

Why this system is useful

One of the main goals of this project is to reduce manual handling of the stylus. Manual cleaning or removing the stylus from the probe system can have a negative effect on repeatability, especially when contamination reaches the coupling surfaces.

This is also reflected in Renishaw’s TP200 documentation: for stylus changing, Renishaw specifies 1 µm max repeatability with the SCR200 and 2 µm typical for manual change. Renishaw also states in its cleaning instructions for TP20 and TP200 that insufficient cleaning of the kinematic coupling faces can lead to an accumulation of contamination and a loss of measuring performance.

For that reason, an automatic cleaning solution can help reduce unnecessary manual intervention and support more stable measuring conditions in daily operation.

How it works

During the cleaning cycle, a mixture of isopropyl alcohol (IPA) and compressed air is directed onto the stylus. This combination helps remove typical contamination from daily use, including fine chips, dust, and residues from metalworking fluids.

This makes the ASCU-128 a practical solution for improving probe cleanliness in automated or repeated measuring processes.

Printing

For reliable performance, the print quality of the nozzle is especially important.

Nozzle adjustment

To adjust the nozzle, simply screw the set screws into the holes, but do not tighten them all the way in. All of them should remain opened by approximately five turns.

The Venturi nozzle is adjusted using the air pressure so that a fine mist is produced. The easiest way to do this is by pressing “Test Valve” on the website. This activates the airflow for 5 minutes, allowing you to reduce or increase the air pressure until the desired spray mist is achieved.

SLA printed part

The nozzle file ("Düse") must be printed with SLA due to the required precision.

Recommended settings:

• Layer height: 0.04 mm

• Hollowing thickness: 2.2 mm

• Print directly on the resin printer build plate, with the narrow flat side facing the build plate and the larger flat side facing the vat

• Add internal supports (I added them manually)

• Re-cut all blind-hole threads after printing: 1/8", M4, and M3

• After printing, all holes and internal channels should be carefully cleaned with compressed air to ensure that they are fully open and unobstructed

FDM printed parts

All remaining parts are designed for FDM printing. No additional supports are needed, as they are already built into the model.

Important

The functionality of the unit depends heavily on a precisely printed and properly cleaned nozzle. If the internal channels are partially blocked, spray performance may be reduced significantly.

Additional Parts Required

• 1x Pneumatic air connector 1/8" to 4 mm, 90° ----(solenoid valve)

• 1x Pneumatic air connector 1/8" to 4 mm ----(Düse V2 SLA)

• 1x Pneumatic air connector 1/8" to 6 mm ----(solenoid valve pressure)

• 1x Normally closed solenoid valve 1/8", 12 V DC

• 1x Pressure Regulator

• 1x Pneumatic tube 4 mm ----(Düse V2 to solenoid valve)

• 1x Pneumatic tube 6 mm

• 1x Centrifuge tube 25 ml, Ø29,8 mm

• 4x Screws ISO 14581 M4x12 ----(Boden mit Befestigung FDM)

• 2x Screws ISO 14581 M4x10 ----(solenoid valve)

• 4x Screws ISO 4762 M4x20 ----(Düse V2 SLA)

• 2x Screws ISO 14579 M2.5x4 ----(VL53L0X)

• 1x Set screw ISO 4027 M4x10 ----(Düse V2 SLA)

• 2x Set screw ISO 4027 M3x10 ----(Düse V2 SLA)

• 1x 1.3" OLED display, I2C, SH1106, 128×64

• 1x ESP32-C3 Super Mini

• 1x 12 V / 2 A power supply

• 1x XT30 male and female connector pair

• 1x VL53L0X ToF laser distance sensor

• 1x 4 × 6 cm perfboard

• 2x JST XH 2.5 mm 2P wafer

• 2x JST XH 2.5 mm 2P plug housing

• 2x JST XH 2.5 mm 4P wafer

• 2x JST XH 2.5 mm 4P plug housing

• 1x 12 V to 5 V DC-DC buck converter

• 1x Electrolytic capacitor 330 µF / 25 V

• 1x Electrolytic capacitor 100 µF / 16 V

• 2x Ceramic capacitors 100 nF

• 1x IRLZ34N MOSFET

• 1x 1N4007 flyback diode

• 1x Resistor 100 Ω

• 1x Resistor 100 kΩ

• 1x 2-pin rocker switch, dimensions: 15 × 21 mm

• 1x 20 AWG wire

• 1x 28 AWG wire

Wiring

The controller board is built on a 4 × 6 cm perfboard and uses an ESP32-C3 Super Mini, a 12 V to 5 V DC-DC buck converter, an IRLZ34N MOSFET for valve switching, a 1N4007 flyback diode, two electrolytic capacitors, two ceramic capacitors, and JST-XH connectors for the external devices.

Recommended wire sizes

• Use 20 AWG wire for the 12 V power input and the solenoid valve wiring

• Use 28 AWG wire for the OLED display and VL53L0X ToF sensor wiring

Connector layout

The board has four external connectors:

• 1 × 2-pin JST-XH for the 12 V power input

• 1 × 2-pin JST-XH for the solenoid valve

• 1 × 4-pin JST-XH for the OLED display

• 1 × 4-pin JST-XH for the VL53L0X ToF sensor

12 V input connector

The 2-pin JST-XH power connector is used for the main supply:

• Red = +12 V

• Black = GND

Solenoid valve connector

The 2-pin JST-XH valve connector is used for the solenoid valve:

• Orange = Valve +

• Black = Valve -

The valve is switched on the negative side by the IRLZ34N MOSFET.

OLED display connector

The 4-pin JST-XH display connector is wired as follows:

• Red = VCC

• Black = GND

• Yellow = SCL

• White = SDA

VL53L0X ToF sensor connector

The 4-pin JST-XH ToF connector is wired as follows:

• Green/Turquoise = VCC

• Black = GND

• Yellow = SCL

• White = SDA

The display and the ToF sensor share the same I2C bus.

Firmware pin mapping

The firmware uses the following ESP32-C3 pins:

• GPIO4 = solenoid valve control

• GPIO8 = I2C SDA

• GPIO9 = I2C SCL

Electrical function

The board is powered from 12 V DC. The 12 V input feeds both the buck converter and the positive side of the solenoid valve. The buck converter generates 5 V for the ESP32-C3 and the connected logic devices.

The solenoid valve is controlled by the IRLZ34N MOSFET:

• Gate = connected to GPIO4 through a 100 Ω resistor

• Gate to GND = 100 kΩ resistor as pull-down

• Source = GND

• Drain = valve negative output

A 1N4007 flyback diode is connected across the solenoid valve:

• Cathode (striped side) → Valve + / +12 V

• Anode → Valve - / MOSFET drain

This protects the MOSFET from voltage spikes when the valve is switched off.

For power supply stabilization, the board uses:

• 330 µF / 25 V across 12 V and GND

• 100 µF / 16 V across 5 V and GND

• 2 × 100 nF ceramic capacitors for additional decoupling

Assembly notes

Before connecting the ESP32-C3, adjust the buck converter output to exactly 5.0 V using a multimeter.

When assembling the board:

1. mount the buck converter, MOSFET, diode, resistors, capacitors, ESP32-C3, and JST connectors on the perfboard

2. connect the 12 V input to the buck converter input and valve positive line

3. connect the buck converter 5 V output to the ESP32-C3 power input

4. connect GPIO4 through the 100 Ω resistor to the MOSFET gate

5. connect the 100 kΩ resistor from gate to GND

6. connect the MOSFET source to GND and drain to valve negative

7. connect the diode across the valve output with the striped side on Valve +

8. connect the OLED display and VL53L0X sensor to their 4-pin JST-XH connectors

Firmware:

The unit can be fully configured through a built-in web server. When powered on, it creates a password-protected Wi-Fi hotspot that remains active for 5 minutes and leads directly to the configuration page.

The password can be changed in the .ino file:

static const char* AP_PASSWORD = "your_password";

Flash the firmware using the Arduino IDE.

Required libraries:
Adafruit GFX Library
Adafruit SH110X
Adafruit VL53L0X
Adafruit VL53L1X
PubSubClient