3D printing, CNC injection molding, and vacuum forming are some of the different types of applications to which the design methodology can be applied.
- [Instructor] So I've talked about core definitions for prototyping. And now I'm going to talk about some of the types of mass manufacturers that design methodology is applied to. I'll come back to these types of production after you've got a solid understanding of procedural breakdowns and design considerations for prototyping. The applications discussed in this chapter are CNC carving, vacuum forming, compression molding, injection molding, 3D printing, rotational molding, and blow molding.
CNC is short for computer numeric control. Specifically, a CNC router, which is a subtractive manufacturing method, where a carving head follows computer code, carving incremental layers out of your material. This is extremely useful in creating mold cavities or forms for other production methods and standalone pieces. The most common configuration of a CNC is three axis. Three axis means that the carving head can move in both X and Y to carve flat patterns, but, also, up and down, in the Z axis, allowing for the creation of undulating forms and multi-depth cavities.
With the power of CNC, you can also carve rotational forms on a lathe for accurate revolve surfaces. Even cooler is a five axis CNC, which allows for movement beyond three axis by having the workpiece able to move and rotate in sync with the cutting head. Which can even cut at an angle. This articulation of movement allows for the workpiece to be manipulated at angles closer to what a human hand could sculpt, except with the powerful precision of computer calculations. 5 axis allows for more complex cutting operations.
Another form of production is vacuum forming. Vacuum forming is a one-sided type of thermoforming that is often combined with the CNC master which the plastic is formed over. Vacuum forming works by heating thin sheets of plastic with open faced oven coils, until it reaches the correct pliability. Once the plastic has reached the right temperature, it's stretched over a master form with vacuum and downward pressure. There's a short period of cooling so the plastic will hold the form it's taking. And then it's removed to repeat the cycle.
The plastic creates an eggshell-like layer over the geometry it's copying. This production method is commonly used in blister packaging. A way to position and display products for sale by sealing them in. Press forming, also called press molding or compression molding, is just what it sounds like. A heated two-part mold squishes material into its final form with high pressure until it's cured. Material to be press formed comes in raw, granulated material, pre-made sheets, or pliable putty blobs called charges.
Once a material has solidified, it's removed with injector pins. A common-used example of this process would be rubber shoe outsoles. Injection molding is a major form of plastic casting manufacture that requires a minimum of two mold halves. The B side remains in place, while the A side is clamped shut during the curing cycle and opened for part removal. During the process cycle, pellets are fed into the top of the machine, where they melt in the heated cylinder. The cylinder contains a long, rotating screw that stirs the pellets as they melt into liquid form.
Once a plastic is the right temperature, it's injected with forceful pressure into the mold. Ideally, filling it exactly where it cools in the mold until it's ready to inject. Injection molding machines often use temperature control built into the dye, to make sure the entire mold is the right temperature for each part of the process. The machine uses injector pins to pop the parts out of the mold, into a bin, where they wait for the next part of production. Injection molding has a fairly quick cycle time, depending on the part being made. Enabling it to make hundreds or more parts a day.
Because you can make so many parts quickly, unit price is lower. The savings per unit contrast the high upfront tooling cost of making the initial dye, starting at around 10,000 US dollars. 3D printing is an additive manufacturing method wherein plastic, guided by computer code, is formed layer slice by layer slice to create a final model. I'll go over a couple of different ways this can happen. The first of which is FDM, short for Fused Deposition Modeling. In FDM, plastic filament is pulled through a heated extruder head, following a pattern generated by the computer, depositing incremental layers.
These layers are created by depositing the heated plastic filament. Each layer very slightly overlapping the last. This overlap helps create lamination or bonding between the layers, so that your final print is relatively solid. 3D printing can sometimes require support geometry, due to gravity, utilizing generated support structures that need to be broken off after printing. Sometimes a separate filament support material is extruded at the same time. That could be dissolved away after the print is complete. Another method of 3D printing, creating similarly sliced additive layers, are resin cured printers.
Which cure liquid plastic with highly concentrated laser light. After each layer is deposited, the platform syncs a specified increment so the process can be repeated. With their layers combining to a complete geometric volume. These prints could also require support structures. Both kinds of printers can create high resolution prints with very small incremental layers, measured in microns, tiny fractions of a millimeter. I'm particularly excited about development in LED cured resin plastics. Which would bring this technology even closer to home.
More specific information on 3D printing can be found in the LinkedIn Learning Library.
- What are mold making and casting?
- Type of molds
- Designing a mold
- Types of casting
- Mold and box setup
- Complex molds
- 3D printing and CNC manufacturing for molding and casting
- Other molding processes