Assignments

Week 7 – Computer Controlled Machining

Assignment

Group assignment

Do your lab's safety training.
Test runout, alignment, fixturing, speeds, feeds, materials, and toolpaths for your machine.

Individual assignment

Make (design + mill + assemble) something big (~meter-scale).
Extra credit: Don't use fasteners or glue.
Extra credit: Include curved surfaces.
Extra credit: Use three-axis toolpaths.

Group Assignment-Summary

In the group assignment, I explored how to operate the MultiCam 3000 CNC machine. We tested several parameters including runout, alignment, fixturing methods, speeds, feeds, materials, and toolpaths. Through these tests, I was able to observe how each parameter affects the machining process and compare different configurations to determine which settings worked best for the material and cutting conditions.

Lab Safety Training

Lab safety training is important because it teaches how to operate machines safely, understand potential risks, and prevent accidents in the lab, especially when working with high-speed CNC machines.

Learnings from the Group Assignment – Safety

Safety Training – User

Wear protective glasses to avoid chips or debris during machining.

Use hearing protection to reduce noise from the CNC machine.

Avoid loose clothing, jewelry, or accessories that may get caught in the machine.

Use gloves only when handling material or cleaning the area.

Do not touch the spindle, tool, or cutting area while the machine is operating.

Use a mask when machining materials that produce dust .

Machine Specifications

The CNC machine used for this assignment was the MultiCam 3000 Series CNC Router. This machine allows large-scale machining of materials such as plywood, MDF, plastics and composite materials using computer-controlled toolpaths.

Machine Model: MultiCam 3000
Number of Axes: 3-axis (X, Y, Z)
Working Area: approximately 1270 mm × 2540 mm
Drive System: Rack and pinion (X,Y) and ball screw (Z)
Spindle Speed: up to 24,000 RPM
Tool Type: End mill router bit
Dust Collection: External dust extraction system
Work Surface: Sacrificial bed

Machine Testing

Cutting Parameters

For machining the plywood sheet (18 mm thickness), the following cutting parameters were used during the CNC process. These values were selected to achieve stable cutting and avoid burning the material.

Material: Plywood (Triplay)
Material Thickness: 18 mm
Tool: End mill
Spindle Speed: 18,000 RPM
Feed Rate: 60 mm/s
Cut Depth per Pass: 6 mm
Number of Passes: 3 passes
Total Cut Depth: 18 mm

Tabs / Bridges Test

One of the important tests performed was the use of tabs (bridges). Tabs are small connections that keep the piece attached to the material sheet during the machining process. Their purpose is to prevent the pieces from moving or being displaced when the final contour is cut.

This technique helps maintain stability during cutting and avoids potential damage to the tool or the machined part. After machining, the tabs are manually removed during the finishing stage.

Example of bridges (tabs) used to hold the pieces during machining.

The tabs prevent the pieces from moving while the CNC is cutting the contour.

Press-fit Tolerance Test

To determine the correct press-fit tolerance, several test slots were designed before machining the final model. The tests started from 18.0 mm and increased gradually up to 18.5 mm, increasing by 0.1 mm each time.

This process allowed us to observe how tight or loose the joint would be when assembling the parts. The objective was to find a dimension that allowed assembly by pressure without damaging the material.

18.1 mm
18.2 mm
18.3 mm
18.4 mm
18.5 mm

After testing these values, the tolerance that provided the best press-fit result was selected and applied to the final design.

Press-fit tolerance tests used to determine the best slot dimension for the 18 mm plywood.

Individual Assignment

Introduction

For the individual assignment, the objective was to design, machine, and assemble a large-scale object using a CNC machine. The goal was to create a functional piece of furniture that could fit a real space requirement. In this case, the project focused on designing a desk for my sister, since she had limited space available for her study area. Based on her needs, I designed a custom desk structure that could fit her workspace while remaining stable using press-fit joints without screws or glue.

Design Concept

The project started by analyzing the available space where the desk would be placed. Since the area was limited, the design needed to adapt to the environment while still providing enough surface for studying and organizing objects.

The available workspace was analyzed to understand the dimensions and limitations of the area.

Based on these requirements, the desk structure was designed in CAD considering assembly and stability.

Material Measurement

Before defining the slot dimensions, the thickness of the plywood available in the lab was measured. The material used for the project had an approximate thickness of 18 mm.

The plywood thickness was measured to determine the correct slot size.

A tolerance value was added to the design to ensure the parts could fit correctly.

Tolerance Test

A press-fit tolerance test was performed before machining the final design. A tolerance of 0.5 mm was applied to the slots and tested using the CNC machine.

A small press-fit test was machined to verify the tolerance.

After confirming the tolerance, it was applied to the full design before generating toolpaths.

CAM and CNC Preparation

The CNC bed was cleaned with a vacuum before machining.

Material Preparation

Before starting the machining process, the selected material had to be prepared. In this case, 18 mm plywood (triplay) was used for the project. The board was placed on the CNC sacrificial bed to avoid damaging the machine table during cutting.