Resin Casting vs. 3D Printing

Comparing Traditional and Contemporary Manufacturing Methods

By Mark Casilang

Look around you. How many products do you see that have been manufactured utilizing a method known as casting? How do you tell? If the object was poured into a mold, it utilized casting.

Casting is one of the first manufacturing methods known to humankind. Believe it or not, it actually dates back 5,000 years. The oldest known casting was a copper frog made in Mesopotamia in 3,200 B.C. but as far as we know, casting didn't gain popularity until 800 B.C. when it became commonly used in China.

Casting Process

The original casting process involved molten metal poured into a mold. Resin casting, a popular hobbyist method today, involves the use of liquid synthetic resin mixed with a hardening catalyst and poured into a mold. The casting process starts by making the product model with the correct dimensions in a casting material, which is often silicon. Next, a two-part resin is put together and poured into the mold. The chemicals in the resin cure. Once the resin hardens, the final model is created. There are several different types of resin materials and each takes a different length of time to cure.

Resin casting can be used to make products that require precise models like buildings, trains, or ships. The final product also has a stronger finish than most 3D printed counterparts of today, and casting will usually have more longevity as well. Collectible and customizable toys can also be made with both methods, but it's also used in more professional settings. Dentists, for example, prefer to use resin casting to create accurate molds of a patient's teeth.

Resin casting typically produces a very strong final product and is done in a quick production time; the final product is complete as soon as the resin hardens. Resin casting can be heavy and uses multiple materials to make both the mold and the resin. It also is limited to smaller scale production and the amount of resin you have available.

Artificial Silicone Human Ear on Plaster

3D printing is increasingly an alternative to casting. 3D printing, or additive manufacturing, is a process that produces a three-dimensional physical object from a digital model by laying down many successive thin layers of material.

In the early 1980's, Hideo Kodama of Japan published the first account of a working "rapid prototyping system." His system used photopolymer, a light-sensitive polymeric material, as a fast and cost-effective method for creating prototypes for product development. It's said that Kodama began the patent process. It's unclear if there was not enough interest in the machine or if there was another reason, but the patent was never completed.

Then in 1984, Chuck Hull developed the process known as stereolithography, or STL for short, where layers are added by curing photopolymers with ultraviolet light lasers. Hull created the design of the STL file format widely accepted by 3D printing software that includes the digital slicing of layer upon layer used in today's 3D printers.

The current technology used by filament or metal wire is unwound from a coil and supplies material to an extrusion nozzle. The nozzle is heated to melt the material to form the layers designated by the digital blueprint.

The applications for 3D printing are vast, ranging from toys to mechanical parts to food and clothing. There's even a completely 3D printed car. Gears, screws, and nuts are 3D printed to be used as spares to replace worn or broken parts. Fighter jet parts are being made with 3D printing technology in order to save maintenance and service costs. 3D printed prosthetic limbs for both human and animal amputees are helping many have a better quality of life. Research scientists are even using cells to 3D print organs.

3D Printed Human Ear

Besides endless applications, there are many benefits of 3D printing which include cheap manufacturing, quick production, less waste, accessibility, and sustainability. Manufacturing costs can be cut by almost 70% compared to using the more traditional manufacturing methods. This is accomplished through lower shipping and packaging costs from overseas suppliers, cheaper and sometimes more reliable raw materials, and less human resources involved.

Industrial 3D printers can make most objects in a matter of hours which can save substantial amounts of cash and lead to an on-demand manufacturing model. Most 3D printed designs are open-source, so with more and more people able to access 3D printing, we become more proficient and efficient in creation processes.

The finished product of a 3D printed object can be up to 60% lighter compared to a machined part that usually has a surplus of material cut off and thrown away that produces more waste. Making a similar object using additive manufacturing, like 3D printing, not only uses less energy, but reduces the waste. 3D printed fabric also reduces waste as compared to traditional clothing manufacturing. Clothing manufacturing typically involves a large amount of fabric being cut into a design. Sometimes the extra fabric is reused, but other times it is not. 3D printed materials can use the exact amount of material needed.

3D Printed Shoe
The possibilities can seem quite endless with 3D printing, but it does have its limitations. Limited materials, questionable accuracy, manufacturing confines, size and durability are just a few. There are not that many materials that provide high strength and can be subjected to high temperature, so what the product can be made out of is also restricted. All 3D printers have an accuracy range, meaning there is room for error, especially if the printer was hit or slightly moved while printing, it would most likely produce an inaccurate final product. The final product of a 3D printed object can break easily if there is too much force between the layers, since layers are not fully bonded together. Many 3D printed objects are not built for longevity, which comes at the cost of it being fast and easy to make.

What do you think about the differences between casting and 3D printing? Do you have a preferred method? Should we stick to updated traditional methods or do you think that 3D printing will overtake manufacturing of the future? Share your thoughts at [email protected].

Mark is a graduate from Cal Poly, San Luis Obispo in Electrical Engineering. He is originally from sunny San Diego, CA. His interests include travelling, movies, games, sports, music, playing tennis and going to the beach.