Molding and Casting

Group assignment:

• Review the safety data sheets for each of your molding and casting materials
• Make and compare test casts with each of them
• Compare printing vs milling molds

Individual assignment:

• Design a mold around the process you’ll be using, produce it with a smooth surface finish, and use it to cast parts.

Learning outcomes

• Design appropriate objects within the limitations of your process.
• Demonstrate workflows used in mold design, construction and casting

As usual, here is my schedule for the week:

Group Assignment

After experimenting with various molding materials and methods, it’s clear that both milling and 3D printing molds have their pros and cons. 3D printed molds, like those using OOMOO 25 Silicone Rubber Compound, often show filament marks, resulting in a textured finish. Meanwhile, milling-produced molds, such as those using Sorta Clear 37 Translucent Silicone Rubber, tend to have faint lines from the drilling bit but generally offer smoother results. When it comes to mold design, it’s important to consider the limitations of each technique. Milling struggles with intricate details smaller than the drill bit’s diameter, while 3D printing excels in capturing such details due to its layer-by-layer construction. Despite their differences, both methods are viable for mold creation. The choice between them depends on the project’s needs and the desired level of detail in the final product.

Click here to view the group assignment

Individual Assignment

Here is a short note that I took during class

So for this week, I decided to make a batman logo as batman is currently trending and I happen to find the logo quite fun.

Hero Shot

So I will be using Fusion 360 for designing. Now let’s begin!

3-d Printing

Designing

As usual open your Autodesk and create a sketch. After that, insert an image(I inserted my logo to trace it). And then use lines to trace the batman logo like this:

After insering the image, consider the offsets!

NOW start tracing the image like this:

To make things easier, trace 1/2 of the image and then excrude it. after that mirror the image and then you’ll have your full batman logo like this:

Now Excrude the outer box that you designed earlier:

After joining the 2 components, I decided to add some letters. (To add letters aka texts, go to sketch and then create navigation bar where you’ll find “texts”)

Initially, I wanted to mill these words but then after considering the mill sizes and all, I decided to edit the text and this is how my final mold design looks!!

NOW export the file in stl like this:

After exporting the stl file, open your prusa slicer. Here is a the setting I set for my design:

And this is how it looks!:

Now let’s save it and then print it using The Prusa i3 MK3. Click here to know more about the printer!

PRINTING!!

Here is how it turned out!

Now let’s start with the molding process!!

Molding

Firstly, let’s talk about the kind of material I will be using. So I will be be using the SORTA Clear™ 37 silicone rubber (Smooth-on Mols Star-37) mainly because it is FOOD SAFE!!! And I am planning on casting chocolate!!!

Here are the links for the datasheets:

https://www.smooth-on.com/tb/files/SORTA_CLEAR_SERIES_TB.pdf

https://www.smooth-on.com/products/sorta-clear-37/

Guidelines

Safety: Make sure the area is adequately ventilated (using “room size” ventilation). To reduce the chance of contamination, put on rubber gloves, long sleeves, and safety eyewear. Only use vinyl gloves. Rubber cure will be impeded by latex gloves.

Material should be used and stored at room temperature (73°F/23°C). Increased temperature will significantly shorten the time needed to work and cure. Storing material at warmer temperatures will also reduce the usable shelf life of unused material. These products have a limited shelf life and should be used as soon as possible.

Cure Inhibition: Because no two applications are quite the same, a small test application to determine suitability for your project is recommended if performance of this material is in question.

NOW before we start mixing them, here are some safety precautions that you NEED to keep in mind.

There are health risks associated with it, including as irritation of the skin, eyes, respiratory system, and even cancerous effects if breathed. It is crucial to adhere to safety protocols as a result.

First Aid Procedures:

Inhalation: Take the affected person outside and remove the source(s) of contamination. Give artificial respiration if breathing has stopped, and oxygen if necessary. Speak with a doctor right away.

Eye Contact: Make eye contact by regularly lifting your upper and lower eyelids and flushing your eyes with lots of water. When it’s safe to do so, check and take out any contact lenses. Rinse for a minimum of fifteen minutes more. If inflammation increases, get help from a doctor.

Skin Contact: Wash your skin well with soap and water if you come into contact with it. Rinse for a minimum of fifteen minutes more. Chemical burns need to be attended to by a doctor right away.

Ingestion: Unless directed by a doctor, avoid making yourself throw up. Never administer anything by mouth to someone who is unconscious. Give the person who was exposed to the substance some water to drink if they are conscious. Stop if the person who was exposed feels ill, as vomiting could be harmful. In order to prevent vomit from getting into the lungs, the head should be maintained low if vomiting happens.

NOW PUT ON YOUR GLOVES AND LET’S BEIGN!

So start off by stirring both the parts properly and then start pouring a 1:1 ratio of Part A and Part B.

NOW make sure to measure both the parts to have an equal ratio:

After measuring both the parts, mix them together properly for few minutes:

So we can use the baby powder in your lab on the mold you printed earlier as applying baby powder before pouring silicone rubber serves to prevent sticking, enhance detail, reduce air traps, facilitate release, and improve workability.

After applying the baby powder (Aka our releasing agent) let’s pour our mixture to it:

After pouring the mixture, we used the tapping / vibrating technique to reduce the air bubbles as . it helps dislodge air bubbles and allows them to rise to the surface.

Here is a picture of me vibrating my mold:

Finally let it set and to speed up the curing process, it is recommended to raise the room temperature. I intentionally left some leftovers of the mixture next to my mold so that I can check the other mixture instead of the mold to verify if the mold has cured or not. Like this:

After letting the silicon sit overnight, I checked the test mixture to verify if the mold is done with the curing process. The test silicon rubber was cured but then after I checked the bottom part, it was not fully cured so then I let the mold sit for few more hours.

And after few hours, this is how it looks:

Now let’s take it out :

And this is how it looks:

Now let’s begin with the casting process.

Casting

For casting, I will be using Smooth Cast 305. Click here to view the datasheet!

NOW start with pouring and then weighing the parts equally:

Then Mix part A and Part B:

After Stirring for a while, pour it on the silicon rubber mold:

Then let it sit for few hours as casting taks less time compared to molding!

And then boom!! it’s done:

Output

Here is how it turned out!

Milling

For miling, I am going to use Roland SRM 20 miling machine.

Here are the drills that we will be using:

Now let’s design!

As usual create a sketch and for milling, I will be making a angry face emoji so this is how the sketch should look like:

The 2 rectangles are for references for the wax mold

So I used slots and circles to create this sketch and to reduce extra work, I mirrored most of the designs like this:

After finishing the sketch, excude the emoji:

After that, excrude the base. This is how the design should look like:

NOW as before export the file. (where by you can go to files -> export -> select stl -> then choose the relative path where you want to save it) like this:

Now let’s create the roughing and finishing files using Modela Player 4

Similar to the mit mods, we can use the modela player software to generate g-code for the SRM-20 machine. So let’s begin!

Modela Player 4

Modela Player 4 is an advanced software tailored for milling operations. It provides comprehensive control over machining parameters, precise toolpath generation, real-time monitoring, and efficient simulation, empowering operators to optimize milling processes with accuracy and efficiency.

SO now, let’s begin editing!! Firstly, open modela player and then go to file -> open -> select your stl file. Then select the material as modelling wax. Then create a new process:

Since we need to create the roughing file first, select it:

Then select 1/8 inch square drill for roughing:

After that, set the start height according to your design. So I will be setting 5mm for now(This is the origin I am setting!):

You don’t need to change anything regarding the type of tool path so click ‘next’:

Similarly, you dont have to edit the cutting parameters:

Then finally finish the process like this:

That’s it for the roughing file. Now create another process and select finishing:

And then select the 1/8 inch ball drill:

Remember to set the starting height same as the one you set while making the roughing file:

Now do the same thing you did while making the roughing file. And then finally save the finishing file.

After creating both the files, click here to save thses files to your desktop and you can click here to view yout design like this:

And here is how it looks:

Now Open your Vpanel and set the settings like this:

I used the above settings to set the orgin to mill the stl file. So one thing that we need to keep in mind is to make sure that we set the “z” axis prperly(zeroing of the z axis due to gravuty) after putting the mold in!

Then let’s start milling :

After roughing, remember to clean and then change the end mill:

Now let’s do the finishing :

After it’s done, clean the machine!

Here is how it turned out!!

Now let’s start molding!!

Molding

As mentioned earlier, follow the safety precautions and as I will be using the same materials, follow the steps correctly! Do not forget to mix a 1A : 1B ratio. SO let’s start mixing:

Remember that using baby powder can be useful:

And then pour:

Then vibrate the mold!

Then let it cure overnight!!

Fewww hours later:

Here is how the silicon rubber turned out :

Now let’s move on to Casting!!

Casting

For casting also, I will be using the same materials so do follow the steps and precautions mentioned earlier. SO now let’s begin by mixing a 1A : 1B ratio. Then after stirring for a while, pour it on the silicon mold from earlier and then let it cure for few hours.

Ps: I forgot to take pictures of me mixing the parts :((( but you can scroll above to see some pictures of me mixing it:)

Here is how it should look after few hours.

AND now let the magic happen!!

Output

Here is how it turned out!!!

Files

• Stl File for 3-d printing
• Stl file for milling

THAT’S IT FOR THIS WEEK!!

HAVE A GOOD DAY!

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Last update: June 23, 2024