Controlled machining by computer

• Group assignment:

Complete your laboratory safety training

Testing for runout, alignment, clamping, speeds, feeds, materials, and toolpaths for your machine

Document your work on the group work page and reflect on what you learned on your individual page.

• Individual project

Make (design+mill+assembly) something big

Group objective

Analyze and understand the operation of computer-controlled machining (CNC) through safety testing, calibration and machine operation, evaluating parameters such as material clamping, speeds, feeds, runout and toolpaths, to identify how they influence the accuracy, quality and stability of the digital manufacturing process.

GROUP ASSIGNMENT

Computer Controlled Machining

Group Assignment Page:

https://fabacademy.org/2026/labs/lima/Weeks/Week7/Week7.html

Laboratory Safety Training

As part of the group work, safety training was carried out at the Fab Lab Huando, understanding that CNC machining involves mechanical, electrical and high- speed particle projection risks.

During this stage it was internalized that security is not an add-on, but a mandatory requirement within the digital manufacturing flow.

The following personal protective equipment (PPE) was used:

• Safety glasses
• Ear protection
• Safety gloves
• Lab coat

Also, before starting any machining operation, the following was verified:

• Proper securing of the material on the work surface
• Condition and adjustment of the cutting tool (milling cutter)
• Axis calibration and home reference
• Location and operation of the emergency stop button

These checks ensured a safe working environment, minimizing risks for both the operator and the machine.

CNC machine testing

Experimental tests were carried out with the CNC milling machine of Fab Lab Huando with the aim of analyzing the behavior of the machine in the face of different critical variables of the machining process.

The following parameters were evaluated during the experiment:

• Tool runout
• Alignment of the axes (X, Y, Z)
• Securing the material to the work surface
• Spindle speed (RPM)
• Feed rate
• Toolpaths

Materials used:9mm MDF

Tool: 6 mm straight milling cutter

Results analysis

The tests made it possible to identify how small variations in configuration directly affect the quality of machining:

• Material fixation:

It was observed that inadequate clamping generates vibrations during cutting, which causes dimensional inaccuracies, irregular edges, and a risk of material displacement.

• RPM – advance relationship:

An imbalance between spindle speed and feed produces negative effects such as MDF burning, material buildup on the milling cutter, and premature tool wear.

When this relationship is adjusted correctly, the cut is clean, continuous, and without overheating.

• Runout:

It was shown that small deviations in the tool rotation generate inconsistent cuts, mainly affecting fine details and tight tolerances.

• Toolpaths:

Proper toolpath planning allowed for optimized machining time and avoided unnecessary stress on the tool, improving process efficiency.

Technical conclusion

CNC machining depends not only on digital design, but also on the precise balance between mechanical and operational parameters.

The final quality of the part is directly related to the correct calibration of the machine, the fixing of the material and the appropriate selection of speeds and paths.

These tests demonstrated that experimentation is fundamental to understanding the actual behavior of the machine and achieving consistent, professional results.

Image: CNC cutting test

Learning achieved

During the group work, I learned that the success of CNC machining depends not only on the digital design but also on the correct machine setup and operation. I understood the importance of safety training, the proper use of personal protective equipment (PPE), and pre-checking the machine before starting any cutting process.

I also learned to identify how factors such as material fixturing, axis alignment, tool runout, spindle speed (RPM), feed rate, and cutting paths directly influence machining accuracy and quality.

The tests I performed allowed me to observe that poor material clamping generates vibrations and dimensional errors, while a correct relationship between speed and feed produces cleaner and more efficient cuts. I also understood the

The importance of properly planning toolpaths to optimize manufacturing times and reduce milling cutter wear.

Finally, I learned that CNC machining is a holistic process where design, machine, tooling, and operator work together to achieve precise, safe, and professional- quality results. This experience strengthened my understanding of large-scale digital manufacturing processes and the importance of experimentation to learn the true limits and capabilities of the CNC machine.

INDIVIDUAL ASSIGNMENT

Individual objective

Design, machine and assemble a large format modular shelf using CNC technology, applying parametric design principles, press-fit systems and digital manufacturing, in order to develop a functional object at real scale considering tolerances, cutting paths and material behavior during the machining process.

My process:

For the individual project, alarge format modular shelf, meeting the requirements established by Fab Academy for CNC machining.

Material dimensions:

• MDF board:1200 mm x 1200 mm (4' x 4')
• Thickness:9 mm

The design was developed inInkscape (2D vector), considering digital manufacturing principles and the inherent restrictions of CNC machining.

Design features:

• Systempress-fit (assembly without screws or adhesives)
• Designadaptable parametric
• Space optimization throughnesting of pieces
• Consideration of tool diameter (6 mm)
• Tolerance adjustment:+0.1 mm for precise fit

Strategic grooves were designed to allow the pieces to fit together firmly, creating a stable and functional structure.

The design was distributed across the entire board of1200 x 1200 mm ensuring that all parts can be machined on a single plate.

Vector design in Inkscape with layout of parts (nesting + measurements)

Trajectory generation (CAM)

For the manufacture of thelarge format modular shelf (1200 mm x 1200 mm) machining path generation was performed (toolpaths) from the previously designed DXF file.

The file was imported into the CAM software, where the cutting strategies were configured considering the actual dimensions of the complete board and the distribution (nesting) of all the pieces within the work area.

Configured parameters:

• Work area:1200 mm x 1200 mm (4' x 4')
• Material:9mm MDF
• Tool:6 mm milling cutter
• Cutting strategy:interior (slots) and exterior (contours)
• Compensation per tool:3 mm offset (milling cutter radius)
• Cutting depth:3 passes of 3 mm (step-down)
• Safety height:5 mm
• Machining order:First internal cuts, then external ones
• Inclusion oftabsto prevent movement of parts during cutting
• Spindle speed:configured for MDF
• Forward speed:adjusted to prevent burning and vibration

Amachining pre-simulationallowing verification:

• Correct distribution of trajectories across the entire board
• Logical sequence of cut without interference
• Stability of the pieces using tabs
• Absence of collisions or trajectory errors

Due to the size of the design, it was essential to correctly organize the cutting order to avoid material displacement and ensure accuracy in all pieces.

Finally, the file was generated.G-code, which contains the instructions that control the movement of the CNC machine for the complete machining of the shelf.

CAM software view showing the full board (1200x1200 mm), cutting paths, tabs and machining simulation

CNC machining process

The machining of thelarge format modular shelf (1200 mm x 1200 mm)It was carried out in the Fab Lab using a CNC milling machine, working on a full board to validate the process at real scale.

Configuration:

• Material:9mm MDF
• Board dimensions:1200 x 1200 mm (4' x 4')
• Tool:6 mm end mill
• Machine:large format CNC laboratory
• Software:Corel + CAM (G-code generation)

Machining parameters:

• Spindle speed:12,000 – 16,000 RPM
• Forward speed:1800 – 2500 mm/min
• Cutting depth:3 mm per pass (3 passes)
• Safety height:5 mm

These parameters were selected considering the size of the board and the need to maintain stability throughout the cutting process.

Process:

1. Fixing the complete board

The board of1200 x 1200 mmIt was secured to the CNC bed using screws, preventing displacement or vibration during machining.

2. Axis calibration (X, Y, Z)

The tool positioning and axis calibration were performed, defining the origin point (0,0,0) in a corner of the board.

3. Pre-test (dry run)

A no-cut simulation was run to validate the trajectories across the entire board and avoid errors.

4. Execution of the cut

Machining began following the generated G-code, respecting the order:

• Internal cuts (assembly slots)
• External cuts (part contours)

5. Constant monitoring of machining During the process, the following was monitored:
   • Material stability
   • Vibrations in distant areas
   • Chip generation
   • Correct functioning of the tool

Post-processing:

• Removal of board parts
• Tab removal
• Hand sanding to improve finish
• Verification of the press-fit type

CNC milling process in progress

Product assembly

Once the machining was completed, the assembly of thelarge format modular shelfusing a type of systempress-fit, designed to allow the joining of parts without the use of additional elements such as screws or adhesives.

The assembly was done manually, inserting the parts using controlled pressure into the previously designed slots.

Assembly results:

• Firm and precise connection between parts
• Assemblywithout the use of screws or glue
• Goodstructural stabilityon the entire shelf
• Proper fit thanks to thetolerance of +0.1 mm
• Correct alignment of the parts in the modular system

During the process, it was verified that the slots allowed the pieces to be inserted without causing deformations in the material, maintaining a balance between a firm fit and ease of assembly.

The modular system allowed for quick assembly, as well as facilitating disassembly if necessary, which is an advantage in products designed for digital manufacturing.

Design validation:

The assembly confirmed that:

• The tool diameter compensation was correct
• The tolerances applied were adequate
• The design is functional at full scale (1200 x 1200 mm)

The assembly allowed the design to be validated not only digitally, but also under real- world conditions, highlighting the importance of considering tolerances and material behavior in press-fit systems.

6. Final Result – HERO SHOT

The end result is alarge format modular shelf (1200 mm x 1200 mm / 4' x 4'), designed, machined and assembled entirely using digital manufacturing processes with CNC technology.

This project allowed for the validation of full-scale manufacturing, demonstrating the correct application of parametric design principles and assembly typepress-fitin a functional object.

Results obtained:

• Fully functional assemblywithout the use of adhesives or screws
• Structurestable and resistantin large format
• Precision machining along the entire board (1200 x 1200 mm)
• Design optimized for large format CNC manufacturing
• Compliance with required dimensions (4' x 4')
• Modular system that allowsdismantling, transport and reconfiguration

The shelf demonstrates that it is possible to manufacture large-scale structures while maintaining precision in the joints, provided that the tolerances, the tool and the cutting parameters are properly considered.

Fully assembled shelf (1200 x 1200 mm), showing structural stability and final finish

Additional designs in Huando:

Shelves for the projects student

Problems and Solutions

Problem 1: The material moved during machining

Solution:

The material was properly secured to prevent movement and errors in cutting.

Problem 2: The cutting depth was incorrect

Solution:

The Z-axis was recalibrated before starting machining.

Problem 3: The finish was uneven

Solution:

The speed and depth of cut were adjusted according to the material used.

Learning achieved

During this week, knowledge of theComplete flow of large format CNC machining (1200 x 1200 mm)integrating the design, preparation and manufacturing stages.

Learning outcomes:

• Understanding the flowCAD→CAM→CNC machiningapplied to a real project
• Manufacturing-oriented design, consideringTool limitations (6 mm milling cutter)
• Application oftolerances (+0.1 mm)to achieve functional press-fit assemblies
• Configuration and operation of alarge format CNC machine
• Control of key parameters:RPM, feed rate, and depth of cut
• Importance of thematerial fixationto avoid vibrations and errors
• Generation and validation of trajectories (G-code) before machining
• Solving real-world problems during the manufacturing process

📋 Check-off List

1. Linked to the group assignment page ?

Yes, the link to the group work was included and the security analysis, CNC testing and machine behavior were documented.

2. Did you reflect on your individual page what you learned from your lab's security training?

Yes, the use of PPE, the importance of material securing, axis calibration, tool inspection, and CNC safety protocols were documented.

3. Did you document how you designed your object and created its CAM toolpath?

Yes, the design of the modular shelf in Inkscape was explained, as well as the press-fit system, nesting, tolerances, and the generation of CAM and G-code paths.

4. Did you document how you milled and assembled your final product (including machine setup, clamping, feeds, speeds, etc.)?

Yes, machining parameters such as RPM, feedrate, depth of cut, MDF fixing, axis calibration, CNC machining and final assembly were detailed.

5. Did you describe the problems and how you solved them?

Yes, problems such as material movement, incorrect depth, and uneven finish were documented, along with their respective solutions.

6. Does it include your design files and the 'hero shot' of your final product?

Yes, it includes the Hero Shot of the assembled shelf, but it is recommended to check that the downloadable files (SVG, DXF, G-code or CAD files) are also uploaded.

❓ Frequently Asked Questions

1. How big is big?

Answer:

In this project, “large” means working with a full-scale board, in our case an MDF board of1200 mm x 1200 mm (4' x 4')The modular shelf design was distributed throughout the material, applying techniques ofnestingto utilize the entire area. This allowed for demonstrating the practical application of large-format CNC machining, including material clamping, toolpath control, and press-fit assembly.

2. Does it have to be wood or wood products?

Answer:

Not necessarily. In this week's case, it was mainly used9mm MDFSince it's a standard material for CNC machining tests due to its stability and ease of cutting, it's not recommended. However, it's also possible to work with other materials such as acrylic or MDF, depending on the laboratory's capabilities. The important thing is not the material itself, but demonstrating the complete design, manufacturing, and assembly process using CNC in a safe and controlled manner.