7. Computer controlled machining¶
Gyumri lab¶
The group assignment was conducted by instructors Rudolf Igityan and Mkhitar Evoyan together with students Ani Petrosyan and Gevorg Malkhasyan at Fab Lab Gyumri
Machine Overview¶
We worked with the OLSK Large CNC V1 at Fab Lab Gyumri — an open source large format CNC milling machine designed by Daniele Ingrassia / InMachines Ingrassia GmbH. The machine is part of the Open Lab Starter Kit (OLSK) family of open source digital fabrication machines.
Key specifications:
- Milling volume: 2500 × 1250 × 300 mm
- Frame: steel pipes, CNC milled solid aluminum and profiles
- Motion: ball screws 25 mm, rack and pinion
- Guides: 25 mm linear rails
- Motors: stepper NEMA 34
- Spindle cooling: air
- Homing: inductive sensors
- Power: 220V
It operates along three main axes:
- X — left/right
- Y — front/back
- Z — up/down
The machine is controlled via Universal G-code Sender (UGS) — open-source software that sends G-code to the machine, allows manual axis control, and monitors the job in real time.
Safety Training¶
Before operating the machine, we reviewed the safety rules together with the instructor.
Personal Protective Equipment (PPE):
- Safety glasses must be worn at all times
- Long hair must be tied back
- Loose clothing and jewelry must be removed
Before starting:
- The workpiece must be firmly fixed to the bed using clamps or screws
- The cutting tool must be properly installed and tightened in the collet
- Never leave the machine unattended during operation
During operation:
- Keep hands away from the cutting area
- In case of unusual sound or vibration — stop immediately using the Emergency Stop button
After finishing:
- Turn off the machine
- Clean chips and dust from the work area
- A fire extinguisher and fire blanket must be accessible in the workspace
Machine Components¶
Power Switches¶
The machine has two main switches:
- MASTER ON/OFF — controls the overall power supply
- SPINDLE — turns the spindle motor on and off
Collet Set¶
The spindle uses ER collets to hold cutting tools. Each collet is designed for a specific tool diameter, ensuring precise and stable clamping.
Cutting Tools¶
We examined the following types of milling bits:
| Type | Description |
|---|---|
| Upcut | Pulls chips upward — good chip removal, but top surface may be rougher |
| Downcut | Pushes chips downward — cleaner top surface, but chips can accumulate in the cut |
| Compression | Combines upcut and downcut geometry — clean edges on both surfaces; the bit in our lab |
| Flat End Mill | General cutting, flat surfaces |
| Ball Nose | Curved surfaces and 3D machining |
| V-Bit | Engraving |
Machine Setup in UGS¶
If the computer does not recognize the machine after power-on:
- Go to Machine → Setup Wizard
- Click through steps, enable Enable Homing
- Enable Enable Soft Limits, then click Finish
- Press Home Machine to return to zero position
Setting Z-zero:
- Lower Z axis (step size: 1 mm)
- Switch step size to 0.1 mm for fine control
- Lower until the tool touches the material surface
- Press Zero Z
In our machine setup, the X/Y zero point (0,0) is located at the bottom-right corner of the table.
Software: Aspire 9.5¶
For CAM toolpath preparation we used Aspire 9.5.
Setup steps:
- Create a new project, set material dimensions (length, width, thickness)
- Set Z origin — on the material surface or on the machine table
- Set X/Y origin at the bottom-left corner
- Import the design file
- Open Toolpath → Material Setup and define:
- Clearance (Z1): 100 mm — safe travel height
- Z Gap Above Material: 100 mm
- Define toolpaths, select tool, set feeds and speeds
- Export G-code
