CNC machining is a complex process that involves many different facets, from high-tech software and state-of-the-art tooling equipment to heavy-duty machines and optimized designs. To create an accurate finished product, designers must come to the table prepared.
Knowing your limitations as a designer can help you develop better ideas without as much trial and error. That, in turn, can reduce manufacturing costs, increase productivity, and boost morale. That’s why it’s important to understand the common design restrictions in CNC machining before drawing up your blueprints.
Understanding common design restrictions in CNC machining
Machinists don’t want there to be any restrictions when it comes to designing and fabricating parts. However, the laws of nature say otherwise. Therefore, the design limitations imposed are the natural byproduct of mechanical and technological limitations.
Designing for machinability significantly reduces the cost of a project. It also helps with lead times and allows the entire manufacturing team to work more efficiently. So,use these three considerations to design parts that are optimized for rapid prototyping and/or CNC manufacturing.
#1. Access to Tools
It’s crucial to work alongside a CNC machine shop that’s well-equipped with industry-leading tools. It also helps if there’s a licensed machining expert available to handle those tools.
TIP: Choose a company that uses ProShop ERP software to help you streamline your designs even further.
#2. Geometry of Tools
A majority of CNC cutting tools are cylindrically shaped with either a cylindrical or flat end. There are specialty cutting tools, but their geometries dictate what they can produce.
TIP: Ask your team about NDT fabrication and prototyping techniques for more options.
#3. Material Properties
The stiffness of the workpiece determines how much quick-turn CNC machining it can handle. Furthermore, the material’s properties affect temperature tolerances and aspect ratios as well.
NOTE: The vertical corners on the inside of any CNC machined part will have a radius regardless of the tool’s size or shape. So, either try to incorporate that into your design or consult a Pioneer Cuts expert for more ideas.
To prevent your workpiece from warping or deforming during the manufacturing process, coordinate its design with the available tools, techniques, materials, and talent.
The 3 golden rules of CNC machined designs
Here are some actionable guidelines to help you translate those restrictions into your next design:
Rule #1. Mind the cavities and pockets.
Deep cavities in the workpiece will be machined with large-diameter cutting tools to affect the internal edge fillets. Therefore, designers need to take that into account when creating parts with tight tolerances.
Rule #2. Pay attention to the internal edges.
Larger fillets are almost always better for machining internal vertical edges, especially when it comes to BUE accumulation and tight geometrical tolerances. Ask about minimum wall thicknesses to create more accurate designs and prototypes.
Rule #3. Consider the work holding options.
A part’s geometry dictates how it gets held in the machine, plus it affects how many steps are required to finish it. This is why multi-axis CNC machining can be such a lifesaver when designing new parts or updating old ones.
By understanding, respecting, and implementing this knowledge, you and your manufacturing team can come up with better designs at a faster pace, and usually for a lot less money.
What you need to know about manufacturing materials
It’s also important to become familiar with the primary characteristics of popular manufacturing materials. That’s because CNC machining uses a wide variety of different resources to create customized designs and finishes. Plus, your intended purposes depend on getting this right.
Meanwhile, just about any sufficiently hard material can be machined, although high-quality CNC machining typically involves specific options. For example, most engineering projects generally use heavy-duty, lightweight metals and/or durable, malleable plastics. Let’s take a closer look at each one:
METALS
Aluminum
Stainless-steel
Alloy steel
Mild steel
Tool steel
Brass
Iron
Titanium
PLASTICS
ABS
PEEK
Nylon
Polycarbonate
Silicone*
POM (Delrin)
Many materials can be manipulated in several ways, making them easy to work with during complex projects. However, it’s vital to speak with a certified CNC machinist to ensure proper compliance with industry standards and production regulations.
A note about surface finishing
Quick tips for cutting CNC machining design costs
You can keep your project on a tight budget even if you’re unsure about the final design. Here’s how:
1. Reduce the machine time by simplifying your design complexity.
a. Minimize machine orientations.
b. Use larger fillets.
c. Add undercuts to sharp edges.
2. Use rapid prototyping to save time and money on new design concepts.
a. Get quick online quotes before initiating an order.
b. Discuss cost-effective changes.
3. Consider the total cost of materials and labor combined.
a. Try similar, cheaper materials.
b. Opt for competitively-priced CNC machining.
The takeaway
There’s no limit to the human imagination, especially when it’s given tailorable tools and expert machinists to turn designs into working parts. However, there is a limit to what CNC machine shops can do because of the laws of nature. So, follow the rules and work with a team of educated and experienced experts to create something from nothing.
