11. Molding and Casting¶
Learning outcomes¶
- Design appropriate objects within the limitations of at least 3-axis machining
- Demonstrate workflows used in mold design, construction and casting
Objectives¶
- Link to the group assignment page and reflect on your individual page what you have learned
- Review the safety data sheets for each of your molding and casting materials,then made and compared test casts with each of them
- Document how you designed your 3D mold and created your rough and finish toolpaths for machining, including machine settings
- Shown how you made your mold and cast the parts
- Described problems and how you fixed them
- Included your design files and ‘hero shot’ of the mold and the final object
Link to the group assignment page¶
https://fabacademy.org/2021/labs/vancouver/students/christopher-proute/group/week10/
Creating the desion using Fusion360¶
I decided to create a 2 part mold for the casting of a pawm piece.
For this weeks assignment i decided to draw a pawn piece using fusion360.
I reviewed the dimensions of a pawn piece and decided to use a canvas for measurements from the following website.
https://grabcad.com/library/pawn-chess-coin-1
The first thing i did was created a sketch outline of the object.
I then used the revolve command which created a 3D solid by sweeping the object around an axis.
A 3D representation of the pawn piece was created as shown in the image below.
I then created another sketch of a rectangle approximately 2in x 3in.
I then used the extrude command to create a height of 1.5in.
I used the offset command to create another sketch of a rectangle on top of the solid created.I then used the extrude command again to create an inner cut out of the block created.
I then aligned the pawn piece and using the move/copy command i placed the pawn piece in the center of the rectangle
I then grouped the two objects together as one solid object.
I then created some studs and holes o.5cm in height and depth on the inner surface of the material so that when the two parts are put in place the would lock together.
I then set the stock dimensions:
- stock width (X) > 75mm
- stock depth (Y) > 50mm
- stock height (Z) > 38mm
Generating the toolpath for milling¶
I went to the 3D banner and selected 3D pocket clearing.
Next I selected the tool for milling 1/8” inch flat end mill.
Then I disabled the coolant because the machine i will be using doesnt have any.
Changing the cutting feedrate to determine how fast you want the tool to go on the surface while cutting(leave as default)
Adjusting the lead in and lead out feedrate to determine how fast the tool enters and leaves the material(adjusted both to 700mm/min)
Next I selected the proper geometry of the model I want to carve.
Then I double checked clearence height for the model(leave as default)
Next i went to the passes tab and unchecked the stock to leave box and checked the multiple depths box and changed the maximun roughing stepdown to 0.5mm
I then navigated to the linking(how the tool operates between different g-codes) tab and reviewed the ramp type to determine how the tool will go down into the stock material.
I clicked OK when I was finished and fusion360 calculateed the toolpath.
I the proceeded to create a simulation of the milling toolpath to see if the material was being removed correctly and what changes need to be made for correct operation.
The tools used for milling was the 1/8 flat end mill for the roughing operation and the 1/8 ball end mill for the smoothing operation.
The following shows a simulation of the holes being drilled.
Generating the GCODE¶
Right Click on the 3D Pocket and Click post process
The milling process¶
Materials used Machinable wax - 2 pieces of size 2”x3”x1.5”
From Youtube¶
The above image shows the two pieces of wax that was used in the creation of the molds for the porn piece.
Preparation for moulding and casting¶
For making of the mold i used - Smooth-Sil 940 both partA and PartB 100 parts Part A to 12 parts Part B.
For making of the casting i used - Smooth-on 101 fast PartB Smooth-on EpoxAcast 650 100 parts Part A to 12 parts Part B.
Color Pigment i used - So-Strong Colorant red and blue
Smooth-On universal mold release for spraying 0n the wax surface before applying the mold mixture.
Comparison between the Printing and Machining Molds¶
Printing molds and milling molds are two different manufacturing processes used to create molds for various purposes.
The following mold was done from wax and also 3d printed. This was the pawn mold which was fairly small and had some fine details.
It can be noted that from the 3d printed mold there are clearly visible lines on the surface as compared to the milling mold from the wax which is very smooth. Some very fine line may be also visible on the was mold but it is very subtle when noticed.
Printing molds involves using 3D printing technology to create molds layer by layer from a digital model. This method is beneficial for creating complex geometries and intricate designs that may be difficult or time-consuming to achieve through traditional manufacturing methods. It also offers the flexibility to produce customized molds with relatively quick turnaround times.
On the other hand, milling molds involves using CNC (computer numerical control) machines to carve out the desired mold shape from a solid block of material, such as metal or plastic. This process is known for its precision and the ability to work with a wide range of materials, making it suitable for producing high-precision molds with excellent surface finishes.
The choice between printing molds and milling molds depends on various factors such as the complexity of the mold design, the required material properties, production volume, and time constraints. Both methods have their advantages and limitations, so it’s essential to evaluate the specific requirements of the project before selecting the most suitable manufacturing process.