2. Project Overview CNC Introduction Applying CNC Designing for CNC
CNC Manufacture
Open Design for CNC Challenge
Total VEX Robotics manufacture

3. LESSON 04

4. Lesson 04
Learning objective: Quality check and send manufacturing files to a CNC machine, fabricate parts that can be post processed, and carry out post processing on parts using hand or equipment applied techniques.
In this lesson… You are going to fabricate the parts you have designed in CAD. Before you commit materials you are going to conduct two virtual quality checks: 1. use the dimension tool to assess your part and an existing VEX part to confirm holes, material thickness and hole location match. 2. Assembly your part to a VEX part in an assembly file
Key words: CAD, Library, heat processes, acrylic, MDF, profile, forming.

5. CNC Manufacture Quality checking CAD files
Watch the following two videos and use these techniques to quality check your VEX virtual parts before fabrication.

6. Fabrication Time…

7. CNC Manufacture Post processing techniques
Use a sheet metal bender to form your parts. To do this, you will need to pay careful attention to the specific position of the bends, the angles you need to achieve, and you will need to constantly check your parts are not out of tolerance with a range of tools.
Warning Once you form a sheet steel part, the properties of the metal change in the bend zone, making it harder to undo any of the forming. This is called work hardening, and is a physical change to the metals structure, and thus its hardness.

8. CNC Manufacture Post processing techniques
With your parts cut, they are now ready to bend and form. Many of the bends will allow for a sheet metal bender to be used. However once one bend has been made, it can prevent another being made easily. This is where you will need to problem solve, and plan how you will form the metal parts from their 2D cut out form into their 3D structure for your robot.
In this example, the corner of a metal vice has been used to bend the ends of the part once the main length had been bent using a sheet bender.

9. CNC Manufacture Post processing techniques
(From left to right) - different thicknesses of steel - a surface comparison of thick steel to thin post cutting - the hole shape cut into thin steel - the curve created in thin steel from plasma cutting
The quality of your plasma cut parts will be dependent on the settings of the machine, the gauge (thickness) of steel used, and the design of the part file. For example thin material will be susceptible to reaction to the high focus of heat, causing the part metal to melt, deform or lead to inaccurate cutting. Thicker material will cut better but be tougher to bend and form after the plasma cutting, and be difficult to form into a high tolerance part.

10. CNC Manufacture Post processing techniques
Before and after the use of fine emery cloth and a thin oil.
Post processing techniques
Surfaces of sheet metal are cleaned up following plasma cutting in the same way other sheet steel is. Task: Use the hand out to describe and draw the stages outlined. Alternatively take photos of each of these approaches and create a digital guide to follow for metal finishing.

11. CNC Manufacture Forming Poor forming
Forming parts consistently is important for a typical VEX build. Why do you think this is so? Here you can see consistently formed parts for the Clawbot build. What is important to get right with each?
Look at the photo below of two parts that should be identical in dimension and shape. What is the issue in differences in forming? Why might this cause problems? How could it be overcome?

12. CNC Manufacture Assembly
With all the parts formed using a range of tools, now you can start to build … Remember to fit parts together using the same techniques you have used when working with VEX EDR previously. If you find holes do not match up, use a metal vice, hammer and other hand tools to adjust the shape and form of your plasma cut parts so that they meet. Remember lastly to also flex and adjust your metal as you assemble parts together.

13. Lesson 04 Plenary
As a class, let us consider the following questions? A. What are necessary quality checks for a CAD file? B. What file types can be produced in CAD software for manufacturing in 2D? C. What did you note about the manufacture of your parts? D. Which finishing techniques did you plan for, and which did you not?

14. Lesson 04 Summary Today you have:
Learning objective: Quality check and send manufacturing files to a CNC machine, fabricate parts that can be post processed, and carry out post processing on parts using hand or equipment applied techniques.
Today you have:
Applied a series of quality checks on a manufacturing file before fabrication
Sent files to a machine and conducted the processing of materials
Carried out post processing on the fabricated parts suitable for assembly into the VEX system