7. Computer Controlled Machining

Welcome to this week’s documentation, where we explore Computer-Controlled Machining, diving into the intricacies of CNC router operations, safety protocols, material testing, and toolpath generation to achieve precise machining results with our Shopbot CNC router machine.

Learning Outcomes:

• Demonstrate 2D design development for CNC milling production
• Describe workflows for CNC milling production

CNC Machining Crash Course

To start the Computer-Controlled Machining week, we had the privilege of attending a two-day crash course led by our CNC machining experts in the lab. This intensive session provided invaluable insights into various aspects of CNC machining, enhancing our understanding of tooling, techniques, safety protocols, and more. Below are the key points we learned from the course:

1. Tool Material Diversity:
2. High-Speed Steel (HSS), Tungsten Carbide (TC), Poly Crystalline Diamond (PCD), Ceramic, Cubic Boron Nitride (CBN), and Tungsten Carbide Tipped (TCT) are common materials for CNC tools.

3. Understanding the differences and advantages/disadvantages of each material aids in selecting the most suitable tool for specific machining tasks.

4. Drills vs. Endmills:

5. Differentiate between drills and endmills, understanding their distinct purposes and applications in CNC machining operations.

6. Cutting Diameter vs. Shank Diameter:

7. Grasp the significance of cutting diameter and shank diameter in tool selection and machining processes.

8. Types of Endmills:

9. Knowing the various types of endmills including flat, ball, square, tapered, V, bullnose, and form tools, and comprehend their unique functionalities.

10. Cutting Tool Variations:

11. Learn about different cutting tool types such as up cutting, down cutting, straight cutting, and compression cutting tools, and determine the appropriate usage scenarios for each.

12. Number of Flutes:

13. Understand the role of the number of flutes in endmills and its effect on machining performance and surface finish.

14. Up Milling vs. Down Milling:

15. Differentiate between up milling and down milling techniques, comprehending their operational variances and implications on workpiece quality.

16. Routing vs. Milling:

17. Explore the distinctions between routing and milling processes and their respective applications in CNC machining.

18. Spindle Speed and Feed Speed Calculations:

19. Gain proficiency in the equations and calculations used to determine spindle speed and feed speed for optimal machining results.

20. Tabs Implementation:

21. Learn about the purpose of tabs in CNC machining, when to use them, and how to effectively incorporate them into machining strategies to prevent workpiece movement.

22. Basic Safety Rules and Procedures:

23. Emphasize adherence to fundamental safety rules and procedures to mitigate risks and ensure a safe working environment in CNC machining facilities.

24. Collets:

25. Understand the function and importance of collets in securing tooling within CNC machines, ensuring precision and stability during machining operations.

This crash course equipped us with essential knowledge and skills, empowering us to tackle CNC machining tasks with confidence and proficiency. It served as a solid foundation for our endeavors during the Computer-Controlled Machining week, enabling us to navigate machining challenges effectively and achieve precise and accurate results.

Summary of Group Assignment:

Our group assignment for the Computer-Controlled Machining week encompassed various tasks and considerations, which are summarized as follows:

Machine Specifications and Safety Measures:

• We operate a Shopbot CNC router machine with a maximum spindle speed of 16,500 RPM and a bed size of 1220mm x 2400mm.
• Safety protocols include wearing eye and ear protection, avoiding accessories like watches or bracelets, wearing closed footwear, and ensuring proper dust collection. Safety posters and emergency stop buttons are also placed around the workshop.

Materials and Fixturing:

• We mcan machine various materials, including MDF, plywood, blockboard, acrylic, and foam, focusing on 18mm plywood and blockboard for this assignment.
• Fixturing involves using screws along the borders of the material for secure attachment to the machine bed. For smaller pieces, a vice attached to the machine bed is utilized.

Machine Setup and Toolpath Generation:

• Machine setup entails careful replacement of the bit and zeroing the axis using the ShopBot control software.
• Toolpath generation is achieved through VCarve, where we create profiles for cutting squares of varying dimensions, adjusting settings such as feeds, speeds, and toolpaths accordingly.

Speeds, Feeds, and Testing:

• Optimal speeds and feeds are determined using online tools like fswizard.com, with recommendations of 15500 RPM spindle speed and 2800 mm/min feed rate for engraving blockboard.
• Practical tests involved exceeding and reducing the recommended spindle speed, as well as adjusting feed rates, to assess their impact on machining quality and efficiency.

Runout & Alignment:

• We conducted tests to evaluate runout and alignment by cutting a square with dimensions of 35cm by 35cm, which demonstrated excellent alignment and minimal runout.

In summary, our group successfully completed the assignment tasks, ensuring safety measures, testing various machining parameters, and achieving precise and accurate machining results.

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This summary encapsulates the key aspects of our group assignment documentation, providing insights into our activities and findings during the Computer-Controlled Machining week.

Individual Assignment:

Introduction

This week, I chose to dedicate my efforts to advancing my final project, focusing on the development of a specialized 3D scanner tailored for capturing intricate details of hands and arms. This project holds significant potential in revolutionizing the process of 3D print design and production, particularly for applications in prosthetics, custom-fit accessories, and anatomical studies. I docemnted the journey, providing insights into the design, machining, and assembly phases, aiming to showcase the innovation and dedication driving this project forward.

Design Phase

1. Initial Concept in Google SketchUp

In Google SketchUp, I began by sketching out the rough concept of the 3D scanner design. Using the intuitive tools available, I created basic shapes and forms to represent the overall structure of the scanner. This initial stage allowed me to explore various design ideas and iterate on different concepts before committing to a final design direction.

• Sketching Ideas: I brainstormed and sketched different ideas for the scanner’s layout and features, considering factors such as size, shape, and functionality.

• Exploring Functionality: Through experimentation with SketchUp’s tools, I visualized how different components of the scanner could interact and function together to achieve the desired outcome.

• Feedback and Iteration: I sought feedback from peers and mentors, incorporating their insights to refine and improve the initial concept further. This iterative process helped me identify strengths and weaknesses in the design, guiding me towards a more robust and functional solution.

• Refinement in Fusion 360

Transitioning to Fusion 360, I started refining the initial concept into a detailed and functional 3D model. Leveraging Fusion 360’s advanced features, I focused on creating a parametric design which can be altered and changed based on specific parameters like material thickness for example.

Importing DXF Files:

• Utilized Fusion 360’s “Insert DXF” feature to import the DXF files of the parts into the Fusion 360 environment.

Creating Parameters:

• Opened the parameters dialog from the “Modify” menu and selected “Change Parameters”.
• Defined key parameters such as material thickness to establish the foundation for creating a parametric design.

Adding Dimensions and Constraints:

• Used the defined parameters to add dimensions and constraints to the sketches.
• This step facilitated the creation of a parametric design that could be easily altered and modified as needed.

Extrusion to Material Thickness:

• Extruded all sketches to the specified material thickness parameter to ensure consistency and accuracy throughout the design.

Conversion to Components:

• Converted all bodies into components to organize the model for assembly.

Assembly Using Joints:

• Utilized Fusion 360’s joints feature to assemble all parts and create joints between them, ensuring proper alignment and functionality.

Verification and Export:

• Verified the correctness of the assembled model.
• Exported the sketch as a DXF file to ensure compatibility with VCarve for toolpath generation.

By following these sequential steps and leveraging Fusion 360’s versatile capabilities, I was able to refine the initial concept into a detailed and functional 3D model, laying the groundwork for the machining and assembly phases of the project.

Toolpath Generation and Setup

1. Path Creation in VCarve

In VCarve, I mcarefulky created toolpaths for machining the components of the 3D scanner, ensuring precision and accuracy in the manufacturing process. The following steps outline the path creation process:

• Importing DXF Files: I imported the DXF files exported from Fusion 360 into VCarve, providing the foundation for generating toolpaths.

• Selection of Tools: I carefully selected the appropriate tools for machining plywood, considering factors such as bit diameter and cutting depth. For this project, I opted for a 6mm 3-flute endmill to achieve clean and accurate cuts.

• Adjustment of Settings: In VCarve, I adjusted various settings to optimize toolpaths for plywood machining. This included specifying feed rates, spindle speeds, and plunge rates to ensure efficient material removal while minimizing the risk of tool breakage or damage.

• Dogbone Fillet Tool: To enhance the assembly process and ensure precise fitting of joints, I utilized the dogbone fillet tool for all inside corners of the slots. This feature helped alleviate the need for additional adjustments during assembly, ensuring a seamless fit between components.

1. Material Preparation and Fixturing

2. To prepare the 18mm plywood sheet for machining, I secured it onto the CNC machine bed using screws. This fixation process ensures stability and accuracy during machining operations by preventing material movement.

3. Proper material fixation is crucial for achieving precise machining results, as it minimizes the risk of inaccuracies or errors caused by material shifting during cutting.

1. Machine Setup

2. I began by setting up the CNC machine, which involved installing the appropriate tool, a 6mm 3-flute endmill, and zeroing all axes to establish the starting position for machining.

Machining and Assembly

1. Test Path for Joint Fitting

Prior to machining the entire set of components, I generated a test toolpath for two small pieces to evaluate joint fitting and tolerances. This test served as a crucial step in verifying the accuracy of the design and assessing the suitability of the selected toolpaths.

• Evaluation of Joint Fitting: By machining two small pieces and assembling them, I assessed the fit and tolerances of the joints, ensuring that they aligned seamlessly without any gaps or misalignments.

• Significance of Testing: Testing the toolpath on a small scale allowed me to identify any potential issues or discrepancies in the machining process early on, mitigating the risk of errors in the final production. It also provided valuable insights into the performance of the chosen toolpaths and settings, enabling necessary adjustments to be made before machining the entire set of components.

• Tab Cutting and Assembly

• After machining the components, I proceeded to cut tabs on the pieces using a multitool. Tabs provide additional support to prevent workpieces from moving during machining and facilitate easy removal after cutting.

• During the assembly process, I utilized a rubber mallet to seat joints and ensure tight tolerances between components. This technique helped achieve a sturdy and precisely assembled frame without the need for additional fasteners.

Connecting Components Together

In addition to machining the individual components of the 3D scanner, it’s crucial to consider how these pieces will be interconnected to form a functional assembly.

The piece shaped like an arc, which serves as a pivotal element in the scanner’s design, will be connected to the base using a combination of bearings and a shaft. While the exact specifications of the shaft are yet to be determined, the bearings and shaft will allow the arc piece to rotate freely, enabling pivotal movement essential for the scanner’s operation.

Furthermore, to control the rotation of the arc piece, a motor and a controller will be incorporated into the design. However, at this stage, the specific type of motor and controller have not been chosen or designed. These components will be selected based on factors such as torque requirements, precision, and compatibility with the overall system.

By integrating bearings, a shaft, a motor, and a controller into the design, the 3D scanner will achieve the necessary functionality to capture intricate details with precision and accuracy. As the project progresses, further refinement and integration of these components will be undertaken to ensure seamless operation and optimal performance.

Conclusion

In conclusion, the individual project focused on designing, machining, and assembling a robust frame for a 3D scanner has been successfully completed. The process involved meticulous design work, precise machining, and careful assembly, resulting in a solid and interconnected frame capable of supporting the scanner’s components effectively.

Through this project, I gained valuable insights into the intricacies of CNC machining and assembly processes. I learned the importance of attention to detail during design and the significance of proper fixturing and toolpath generation in achieving accurate machining results. Additionally, the assembly phase highlighted the importance of patience and precision in ensuring tight tolerances and secure joints.

Overall, this project has been a rewarding learning experience, providing practical hands-on knowledge in CAD design, CNC machining, and assembly techniques. The successful completion of the 3D scanner frame underscores the effectiveness of iterative refinement and quality assurance processes in achieving desired outcomes in maker projects.

Files

Sketchup File

Fusion 360 File

DXF File

My Notes from CNC Crash Course