One of the reasons we are seeing so many innovations in the 21^st Century is due to the shortened product design cycle. With a wide variety of physical and virtual tools available, the time from idea conception to market launch has never been shorter. One of these tools is metal rapid prototyping.

Using metal prototyping, Engineers can now dream up new ideas, bring them to life, and test them at an accelerated pace. Because of this, product quality and functionality are now increasing exponentially.

In this article, we will explore various methods of prototyping for metal products. We will show you how we use prototyping processes to bring your creation to life in record time without sacrificing quality.

What Is Metal Prototyping?

Metal prototyping involves creating prototypes using metal as the base material. To understand metal prototyping fully, let’s first look at what prototyping is:

Prototyping involves building an early version of a product or model using rapid production methods. Product engineers use it to test out and validate the features and design of the product.

Now that we know what prototyping is, we can fully define “Metal Prototyping” in depth. Metal prototyping involves using metal as a base material to build or create a model or an early version of a product.

When Can You Use Metal Rapid Prototyping?

Metal rapid prototyping is an integral part of the testing and design stage, but metal prototyping processes have many more uses. These prototyping methods can fulfill so many manufacturing requirements.

Let’s look at some of these uses:

• They can be used in creating high-quality one-off parts or for low-volume production.
• They help designers in creating products for market testing and investor pitches
• Metal prototyping can be combined with conventional manufacturing methods like injection molding to reduce production costs and time (Rapid tooling).

Advantages of Metal Prototyping

Metal rapid prototyping has many advantages that make it the method of choice in the industry. Let’s look at some of them.

• We can create highly functional and capable products relatively cheaply in a short time.
• It gives the product designers a chance to test out their design before production
• It provides a wide range of metals for creating products.
• It reduces the time from idea conceptualization to product launch.

How Do you Create A Metal Prototype?

There are two main steps we take in creating a metal prototype.  The first step is the design stage while the second step is the manufacturing or prototyping stage.

Step 1 (Design Stage): Here, the product engineers and designers create a sketch or a 3D model of the product. They then compile a document called the Product Manufacturing Information (PMI). The PMI contains information such as the 3D model, material specifications, tolerances and precision required, etc.

The designers then submit this document to the vendor for manufacturing.

Step 2 (Manufacturing stage): In this phase, the virtual designs are brought to life using one or more manufacturing methods. There are several manufacturing methods that we can use for metal prototyping. Let’s go through some of them:

1. CNC Machining

CNC machining is one of the most popular metal prototyping methods. Computer Numerical Controlled (CNC) machining is a subtractive manufacturing method in which a computer-controlled cutting tool removes material from a blank to form the desired shape.

The CNC machining process starts from the 3D model or the CAD file. A technician feeds the CAD file into a program that converts it into a series of instructions for the machine called the “GCODE”.

The GCODE controls the machining operation. It tells the machine how fast to move, where to cut, and which path the cutting tool needs to follow. The GCODE is sent to the CNC machine to program it, and the machining can begin.

CNC machining covers a wide range of subtractive manufacturing processes. These processes include CNC Milling, CNC turning, CNC drilling, etc. The most popular methods in use are CNC milling and CNC turning.

With CNC machining, you can achieve a wide variety of shapes and geometries. You can create elaborate 3D geometries and patterns with CNC milling. You can also fabricate perfect cylindrical geometries, hollow parts, and even cut threads with CNC lathe machines.

√ Materials Selection Available

There are a wide variety of metals to select from when using CNC machining. They range from metals like Aluminum, Steel to precious metals like Gold and Silver. Almost any metal can be CNC machined.

√ Pros of CNC machining

• It is fast, accurate, and precise.
• There is a wide selection of materials available.
• It provides high-quality prototypes consistently.
• It is easy to modify the digital design.

√ Cons of CNC Machining

• It is more expensive than other methods.
• The process waste generated can be a bit much.
• There are some geometrical restrictions on CNC machines

√ Design Tips for CNC Machining

• Avoid designing overly thin walls and sections.
• Always add fillets to internal edges.
• Avoid overhangs and undercuts
• Maintain good depth to width ratios when designing holes

2. 3D Printing (SLM, DMLS)

3D printing or additive manufacturing is the construction of a three-dimensional object from a 3D model using material deposition processes. During 3D printing, the material is deposited and fused layer by layer until the final part is obtained.

Metal 3D printing also starts with a 3D model or a CAD file. A technician feeds the CAD file into a program called a Slicer. The program Slices the model into many thin slices called layers and sends them to the 3D printer.

The 3D printer forms the object by printing and fusing successive layers from the ground up. Depending on the material, we can use various 3D printing processes. For 3D printing metals, we use Direct Metal Laser Sintering (DMLS) and Selective Laser Melting (SLM).

Both DMLS and SLM share similar printing mechanisms. In both methods, a laser fuses metal powder in a controlled environment, to create a 2D layer. Another layer is then created and fused on the previous layer. The process continues until the final 3D part is created.

The main difference between DMLS and SLM is that, while DMLS sinters alloy powder SLM melts the pure metal powder to fuse it.

Metal 3D printing is beginning to see many applications, especially in creating metal prototypes. With it, you can create prototypes with highly complex geometries quite easily.

√ Material Selection Available

Not so long ago, there weren’t many metals that could be 3D printed, but that is changing now. New interest in the field is broadening the material selection available.

Now, you can 3D print prototypes with common metals like Aluminum and stainless steel, high-grade alloys like Inconel and Titanium, and even some precious metals.

√ Pros of Metal 3D Printing

• We can use it to manufacture parts with complex geometries
• 3D printed metal parts have excellent mechanical properties
• We can modify the internal structure (topology) of 3D-printed parts.

√ Cons of Metal 3D Printing

• The cost of 3D printing remains relatively high
• The maximum part size is limited by the build chambers of the 3D printing machine

√ Design Tips for 3D Printing Metals

• Minimize the use of supports to save on materials costs.
• Always optimize the topology (internal structure) of parts to save both money and reduce the weight of the part.

3. Sheet Metal Fabrication

Sheet metal fabrication is a low-cost method for creating metal prototypes rapidly. It involves creating prototypes by shaping sheet metal into any desired geometry or design. We can create both functional prototypes and end-use parts using sheet metal fabrication.

To create a prototype using sheet metal fabrication, you can use many metalworking processes. These processes include welding, punching, laser cutting, bending. To create the final shape, we can use one or a combination of several of these processes.

The sheet metal can have thicknesses ranging from 0.006 to 0.25 inches. With these, we can create parts for a wide range of applications.

√ Material Selection Available

We can use sheet metals made out of various materials like copper, steel, aluminum, zinc, etc.

√ Pros of Sheet Metal Fabrication

• It produces durable parts
• It is cheap
• There is a wide material selection available

√ Cons of Sheet Metal Fabrication

• The parts require additional finishing processes
• It cannot be used for complex designs or geometries.

√ Design Tips for Sheet Metal Fabrication

• Maintain a constant sheet metal thickness throughout the part.
• Keep holes and slots away from bends and edges

4. Metal Extrusion

Metal extrusion is another metal forming process that we can use for metal rapid prototyping. Metal extrusion involves forcing a metal billet through a die to create a metal product with a consistent profile.

The metal- usually Aluminum- can be forced through the die, either hot or cold. As the metal goes through the die, it attains the die’s shape through plastic deformation.

Metal extrusion can create both one-off parts and can also be employed for low volume production. Disregarding the setup costs of the die, it is an economical method of rapid prototyping.

√ Material Selection Available

To keep production costs down, the material we use for metal prototyping with metal extrusion is aluminum alloy. It is cheap and it exhibits suitable plastic behavior for the task at hand.

√ Pros of Metal Extrusion

• It is a cheap method of metal rapid prototyping
• It produces good surface finishes
• The die can be re-used for a low volume production run
• The parts obtained have good mechanical properties.

√ Cons of Metal Extrusion

• It can only be used for parts with consistent cross-sections
• It requires a high setup cost.
• There can be structural variations in the final product.

√ Design Tips for Metal Extrusion

• It’s always good practice to maintain a uniform wall thickness throughout.
• Remove sharp edges from the die before extruding. You can round them off.

You can find more design tips here.

How To Select The Best Metal Rapid Prototyping Process?

A key part in the product design stage lies in selecting the right metal prototyping method. Selecting the right metal prototyping method involves balancing cost with quality while also satisfying the manufacturer’s requirements.

Here are some factors to consider when selecting a metal prototyping process.

√ Material Selection

Like we saw in the preceding section, different metal prototyping methods have different material selections available. The sort of material you want to use for your project will influence the metal prototyping method you’ll select.

√ Part Size and Complexity

Not every metal prototyping process can handle large or geometrically complex projects. Some processes are constrained by their machine sizes and their capabilities. So, to make sure you get the best quality, select a machining process that suits your project’s size and geometry.

√ Lead Time

The lead time refers to the time between the start and completion of a project. When choosing a metal prototyping method, you’ll have to choose one that best aligns with your timeline. For example, if you need the parts delivered quickly, you can go with a faster method like CNC machining, or 3D printing.

√ Production Volume

Whether you require a one-off part or you want a low-volume production run also factors into your decision. Some metal prototyping methods have low unit costs but high setup costs, while others have it vice-versa. To save costs, it’s best to go with the most cost-effective method.

How Much Does Metal Prototyping Cost?

Metal prototyping is often seen as an expensive venture especially when compared to other prototyping methods. That isn’t necessarily true.

Although there is no standard cost we can quote for metal prototyping, we can give you a look into some of the things that add to the final cost. Let’s look at them:

√ Materials

The sort of material you specify in your PMI is one of the main factors contributing to the final cost. Materials like Aluminum are usually cheap to source and work, while metals like Titanium and Inconel are on the higher end of the scale.

√ Prototyping Process Selected

The sort of prototyping process the engineer selects also plays a role in determining the magnitude of the final quote. The cost of manpower, consumables, and even equipment depends on the prototyping process.

All this goes towards the unit or part cost of the final product.

√ Post-Processing Activities

The post-processing activities required to get the product to its final form also adds to the cost. Processes like anodizing, painting polishing and even additional machining can increase the final cost.

FAQs

Q1: Why make a metal prototype instead of a plastic prototype?

A: The main reason why we use metals is to create a prototype with a high degree of similarity to the final product.

We can create metal prototypes with the same materials we want to use for full-scale production. This results in a prototype with the same functional and mechanical capabilities as the final product.

Q2: How do metal prototypes compare with mass-produced metal parts?

A: Metal rapid prototyping methods produce high-quality parts. Prototypes made using methods like CNC machining are stronger, more precise, and have superior surface finishes compared to mass-produced parts.

The Conclusion

Metal prototyping is a powerful tool that can help transform and accelerate your product development process. It can unlock many capabilities, not just for the engineers but for designers and others on the team. Let us help you do it right.

At RapidDone, we pride ourselves on being one of the best rapid prototyping companies in China. With a track record of working with several industry heavyweights to great success, you can be sure that we have all it takes to deliver the best quality possible.

So, contact us today with your designs and let our in-house team help you bring your products to life.