Moldingand Casting

Then the mold was then used to cast remaining casting material and produce very cool looking brain models. The first was cast with the remainder of the liquid plastic used for the letters, the second with the liquid plastic used for the back panel and the third using the resin from the capsule with two drops of red pigment placed in the mold before casting to produce a blood effect.

Then I created a box around the model equal to two blocks of wax and subtracted the model from the box. I also created an extrusion which extends to the aluminum extrusion in the middle. The aluminum extrusion is represented by a 3D printed piece of plastic that has two extrusions at the bottom and a thin pole extruded from the top to ensure correct placement within the molds once the silicone is cast.

I milled each side using a different CAM program for the sake of learning and comparing between both workflows. For the first mold I used Modela and for the second I used Roland's SRP player. In both workflows, I used a 1/8 inch flat endmill for the roughing process and a 1/16 ballnose endmill for the finishing process. In both cases I zeroed the Z-axis by placing 1mm paper under the mill and slowly wend down. Once there was resistance when moving the paper, I took the Z-axis 1mm downwards and set the home. As for the X and Y axis, I drew an X from the corners of the wax block and centered the endmill at the cross-section of both lines.

Before setting up the toolpaths, I must first import the model by locating it from the open button. Afterwards setting the dimensions of the wax block, orientation of the model and XY home position. Then the next step is to specify the type of milling and edges in the model. As is obvious, this program is quite automated and doesn't allow much personalization at first. The next step before simulation would be creating the toolpath.

For Modela, I imported the model and input the correct size and orientation in the pop-up window that appears. Then I had to introduce the tools I will be using as they weren't available available in the tool library. Luckily, this was easy as after inputing the flute diameter, Modela can automatically generate suitable cutting parameters.

As opposed to SRP player's user-friendly path creation, modela requires the creation of each path seperately. This means increased control over the job and how the model is milled. The first toolpath would be the surfacing toolpath, so after creating a new toolpath, I was guided through a wizard. I selected surfacing, then selected the tool I will be using, then specified the paramaters and depth of the surface leveling, 1mm in this case.

For the roughing and finishing jobs, the wizard is pretty much the same, however the settings differ. I left in 0.44mm when roughing, to be removed in the finishing jobe. Also to achieve a better finish for the curved surfaces in 3D, I chose the spiral upcut toolpath.

To output the file, choose the SRM-20. The progress window will indicate the progress of the job and instruct you to change the tool once a tool change is required.

Below is a picture of the resulting wax molds.

The first step in manufacturing the logo was designing the logo itself in 3d including the negative molds that will be fabricated in order to cast into them. For the logo itself, I simply extruded the letters out and made the O's and bubbles into half spheres.

This was my first time using fusion360 CAM for practical application. Therefore, it took sometime for me to understand each setting and choose the correct technique/tool to simulate a CAM job and produce a part of the correct specifications. The first step was to measure the aluminium block available and input the dimensions of the block. Then I had to specify the origin point in reference to the job.

One the job setup was complete, I proceeded to add the holder and tools I will be using for this job. I chose to use a 3/8 inch flat 2-flute endmill to do the initial adaptive cut and material removal, leaving behind some extra stock for removal during the finishing jobs. Then I used 1/8 inch ballnose 4-flute endmill using a morphed spiral technique for the finishing of the larger spheres. Then, I used a 2-flute 1/16 flat nose to finish the horizontal surfaces and perform morphed spiral roughing, leaving behind some stock for the two smallest spheres. Finally, I finished the the smaller spheres with a 2-flute ballnose endmill. All the tools were done by measurement using digital calipers.

For each job , the technique is first picked, afterwhich, the speeds and parameters are set. The area in which the machine is allowed to work, as well as areas that this job will be performing can be specified. For roughing jobs, the stock to leave can be specified. For finishing jobs, the stepover and stepdowns can also be specified to achieve the desired precision and quality.

Before starting the milling job on the Tormach 1100 CNC, I placed parallel bars, onto which I placed the aluminum block. This ensured the block had all its sides at equal points on the same plane. Then after installing the tool to be used, I checked if there was any stability problem. To do this I fixed an angular dial and set it against the tool. Once the tool started turning, minimal changes in the reading ensure stability. Finally I used the edge finder to find the 0. It is basically a shank attached to a spring, which achieves flushness once the edge is sensed.

As mentioned previously, I 3D printed a model of the logo including the back panel. I then used some polysterene and a nylon bag to make a mold of this anti-mold using of Sorta-Clear 37. Sortaclear is mixed with a equal A to B volume mixing ratio, I chose this because it is the most advisable material available for use with resin according to the datasheet. Once the mold set. I mixed some Smooth-cast-305 liquid plastic, which is medium setting liquid plastic and is mixed using an equal A to B mixing ratio, as specified in the datasheet. I added some blue and yellow dye until I achieved the teal/turqoise colour I was aiming for, not mixing to much to create an inconsistent color effect. I used droppers for this process, as it was a small ammount and I needed to ensure the resin is poured directly into each letter and does not overflow. Once the letters were set, I placed the cast lead bubbles and poured non-pigmented white liquid plastic over it to form the back panel. Below is the resulting part. It is important to keep in mind the short 7 minute pot life of the Smooth-cast 305 liquid plastic and make sure all required tools and components are in front of you before starting the mixing process. NOTE: In the next section is a full video presenting the complete process.

I repeated the process by making an acrylic mold instead of a plaster mold for a smoother surface and better finish. After it was ready, I sanded the clear resin to give it a mirror finish using wet sand paper, starting from 320 to 800, 1000, 1500, 2000 grit in order. Below is the second version which looks much clearer and better in terms of finish. It is important to note that the yellowish colour is due to a heatwave that affected the resin as I had it stored at home, withouth which the clear resin would be completely colourless.

I took advantage of the materials available this week to make a mold for the forarm rest. The process entailed placing my arm on a piece of mixed dental algenate to form the surface topograph, and then pouring plaster on the surface to form a cast of the bottom of my forearm.