9. Moulding and casting¶
In this week, I work at the beginning on a design to be utilized for the molding and casting purpose. This design was used in the CNC milling machine in order to make the shape on a wax material which was later on used to make the mold using silicon. After the preparation of the mold, it was casted using different materials to test the differences.
Fusion 360 design¶
To begin with, a simple design was constructed for the preparation of the mold. The design was a traditional shape like those seen in holy arabian occasions like eid. The design was made to meet the CNC milling and design restrictions of 80mm length, 40mm width and 10 mm height. Firstly, an elipse shape is made in Fusion 360 with a 40 mm length and 5 in width as shown in the follwoing pictures:
Then, the circular pattern command is used to have a circular pattern consisitng of 20 of the pre-made elipse:
After that, a circle is made in the middle of the shape (where the elipses are meeting) to cover the very small details in the design with a circle as ot would be very difficult for the drill bit in the CNC milling machine to make these very small details.
Three main parts were found to be within the constructed design: The circle, the outer elipses and the triangle like shapes between the two prior stated parts. The parts are demonstrated below:
The circle:
The triangle like shape:
The outer shape:
Firstly, the circle was extruded 5 mm:
Then, the triangle like shape was extruded 7 mm:
Finally, the outer shape was extruded 10 mm:
The three different parts were extruded with different altitudes in order to have various textures within the design. At last, the final design looks as follows:
After the design was done, it was converted into an stl file to be transferred to the CNC milling machine.
CNC milling machine preparation and utilization¶
The design made by Fusion 360 was transferred in an stl format to the CNC milling machine to be engraved in a wax block which would be later on used to prepare the mold and the cast.
For better utilization of the wax material and conserving the materials available, two designs were made on the same wax block. At the beginning, the stl file containing the designs was imported in the program utilized for the CNC milling machine which is called SRP player, which is used to adjust and modify the settings of the designs for the CNC milling machine.
When the design is imported, the following page will show up indicating the first sector of completing the set up which is the (Model Size and Orientation), where you need to put the dimensions of the design (length,width and height) in the specified sections:
Then, we move to the (Type of milling) sector, where the type of milling is decided on:
As seen in the picture, the first choice is chosen to be (Better surface finish) to get the most accurate and precise results, as if the faster time cutting choice is taken, this might lead to some inaccuracies and missing some crucial details in the design. Therefore, the first choice is taken as it guarantees better results with regards to the outcome of the milling process. The second choice is (Model with many curved surfaces). This is done in order to account for the many curves present in the designs and make the milling machine eligible to doing the needed curved in the deigns with the best accuracy possible. Finally for the final choice, It was chosen as a block workspace with cutting the top only as the wax block is in a rectangular shape, and the top is only cut because we want to prepare the wax to be able to hold the molding material inside to make the mold and not cut the designs separatly from the block, resulting in being unable to contain the molding material as the design is not confined.
Later on, in the (Create ToolPath) sector, the size of the wax board will be set. Make sure that the size of the wax board used is greater than or equal to the design dimensions, preferibally the length and width are higher so that the wax piece is confined from the edges and the mold can stay inside for the upcoming step. Then, you can either create the toolpath or edit it. This is illustrated in the following picture:
For the editing, both the roughing and the finishing were adjusted with the same specifications (which were mainly default settings), except for the drill bit, a larger drill bit was set for the roughing part as this part is associated with preparing the surface which would take longer time in general. As a result, the following two drill bits were chosen, the bigger one being for the roughing part:
The only main change to the default settings were that the boarder of the design was put closer to the wax board than the default settings to ensure that the mold has outer area which would be useful as the mold would be easier to be removed from the wax board. This is shown below:
After that, the path is created:
With regards to the wax board, it was surfaced before usage in order to reduce the time needed for roughing and to make the surface uniform as it will affect the quality of the milling as there would be different depths at each point of the wax point. The following show the wax board before and after surfacing:
Also, the mid point on the wax board was defined as it will be needed fot setting the origin of the drilling bit. the mid point can be seen as a small hole in the latest image. This mid point will be used as the origin point of the drill bit. The origin of the of the drill bit is adjusted using Vpanel for SRM-20, where the x,y and z directions are adjusted. The x and y are adjusted in order to be exactly on the mid plane. The z is adjusted to be exactly on the wax board so that the design depth is achieved successfully. The origin program is shown below:
After creaing the path and going to the (Preview Results), the required duration to complete the milling will show up as shown:
When you press on review cutting, a simulation of the milling output will be shown. It can been that some details out of the design were lost. This is mainly due to the significantly small spaces that cannot be milled with the specified settings and drill bits. As a result, these spaces were not milled. This picture demonstrates this defect:
Finally, when you start cutting, after complying with the default settings, the time estimated and the drill bit used for the roughing will show. Same thing for the finshing where if the roughing is done, you will change the drill bit and later start the finishing:
After the milling is done, this is how the wax board will look like:
Material Safety Datasheet¶
Link to group assignment:Group assignment
Molding¶
For the molding, the prepared wax board was utilized in order to make the mold which would be used later for casting the design. Firstly, a solution that is mainly silicon was prepared by mixing equal proportions of both the white and blue materials shown below:
These materials were mixed gradually and slow in order to avoid the formation of bubbles inside the solution mixture. It was mixed for roughly 10 minutes and then it was poured slowly inside the wax board until it filled the whole compartment. Extra silicon was added on the edges for easier removal of the mold from the wax material. A demonstration of the wax board before and after adding the silicon is shown below:
For the mixing of the solution, the required quantity was determined by the volume of water needed to occupy the space designated for molding. Then the same volume (i.e. the volume inside the cup) was utilized but instead the silicon solution was used and not water. After finding the required volume, the cup was used again but with both the white and blue materials added equally and a scale is used to ease this process.
The mold is left in the wax board for around 4-5 hours until it strengths. The final result of the mold will look as follows:
Casting¶
For the casting, different material were utilized to make the casting. Firstly, soap was utilized to make the design. It was microwaved for several seconds to melt the soap. A picture of the soap before and after melting is shown below:
After melting, it was quickly taken to be poured in the mold as it solifies very quickly. The melted soap is poured inside the mold and after that we have to wait for around 10 minutes for it to become rigid.
The final outcome will look as follows:
In addition to the soap, several dyes were used to make the soap which were added after melting as shown:
The final outcome will look as follows:
