8 Vital Considerations to Know When Selecting CNC Tooling
8 Vital Considerations to Know When Selecting CNC Tooling
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It's simple to outline what you need a tool to do. The challenge for many CNC machine shop engineers is picking the correct tool to ensure a job is completed effectively.
Although the tool's performance is imperative, it's not the only aspect to consider. The experience of the CNC machine shop, alongside cost, also contributes significantly. We will delve into these elements below.
When selecting CNC tooling, engineers should consider:
- Workpiece Material and Features
- Production Volume
- Combo Possibilities
- Machine Capacity
- Tool Material
- Toolmaker Selection
- Planning
- Experience of the Shop
1. Workpiece Material and Features
The workpiece material significantly influences tool selection. For example, if a shop mostly deals with aluminum, ductile iron, and gray iron castings, engineers will typically select their preferred CNC machining metal cutting tools for each material. Proven standardized tooling is often the first choice to mitigate risks, manage inventory, and cut costs.
Different CNC toolings such as drills, mills, and taps are tailored to machine various features, and standard tooling is available for each tool type and material. For instance, a shop specializing in three standard 90° square shoulder face mills may use different tools for aluminum, ductile iron, and gray iron. Aluminum, being highly machinable, demands tooling with higher surface feet per minute (SFM) specs, enabling faster operation.
2. Production Volume
Specialized, high-end cutting tools are often selected for high-volume tasks, whereas low-volume jobs might utilize more economical tools. This approach reflects the economy of scale, wherein the cost of high-end tools is justified by the high number of parts produced.
Like much of manufacturing, CNC machining revolves around production-focus, with machining centers playing a significant role in enhancing a shop’s efficiency.
3. Combo Possibilities
Tools with multiple features can drastically reduce costs and labor in CNC machining. If a single tool can perform several tasks — be it three, four, or more — it not only speeds up cycle time but also minimizes the need to replace the tool.
For example, a well-designed insertable combo tool can both drill and chamfer in possibly three different ways, completing the task in one pass with a single tool instead of requiring six tools (and passes). Though a custom, multi-feature tool might cost up to $3,000, the quick savings during high-volume projects can make up for the upfront cost.
4. Machine Capacity
While most CNC tools can be used in various CNC machines, not all will operate with the same efficiency. Machines with greater horsepower and larger tapers allow for the use of combo tools that can handle multiple functions.
Unlike large castings which require hoists for movement, smaller castings do not pose this challenge. In fact, creating a fixture that allows multiple small parts to run simultaneously on a larger machine may increase efficiency. This counters the typical belief that large machines are only for large castings.
Optimizing efficiency largely depends on aligning the right tool with both project needs and machine’s capability and availability. Operating multiple parts at once and changing out several simultaneously can significantly reduce time.
Running multiple parts on a pallet cuts down on the number of pallet and tool changes per part, optimizing overall time. For instance, running three parts instead of one can save 1/3 of the tool change and pallet change time per part, enhancing rapid motions across the three parts in the machining center.
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5. Tool Material
The same cutting tool can be manufactured from various materials, some more durable or costly than others.
Solid carbide tools are reliable, but PCD-tipped tools offer even greater durability. PCD (polycrystalline diamond) is the hardest cutting tool available, created by sintering diamond particles with a metallic binder.
A PCD-tipped drilling tool typically has about four times the tool life of a solid carbide tool (10,000 pieces vs. 2,500) and can operate 25% faster. Despite the higher initial cost ($960 for PCD compared to $180 for carbide), production savings justify PCD's cost.
PCD tools can also be retooled multiple times, preserving their diameter compared to solid carbide tools, which lose diameter after multiple regrinds. CNC shops often employ cutting monitors and tool life counts to predict failures and ensure proper cuts.
A cost-effective alternative to solid carbide involves using a steel tool body with brazed carbide inserts, potentially reducing costs by up to 75%. Other commonly used materials include high-speed steel tools and carbide-tipped tools, especially advantageous for smaller CNC shops.
6. Toolmaker Selection
A strong bond between a CNC machine shop and its toolmakers fosters familiarity. Large shops strategically collaborate with around seven or eight toolmakers, each specializing in particular challenges like solid carbide, combo tools, or PCD-tipped tools. This partnership results in increased buying power, faster project delivery, and a commitment to customer satisfaction, particularly benefiting well-established CNC shops.
For high-end CNC shops, engineers may design over 75% of all tooling required within the shop. If a project needs an insertable combo tool, an engineer collaborates with the toolmaker rep to finalize the design, resulting in a more reliable project. Smaller CNC shops typically rely more on their toolmaker reps for design and engineering support.
7. Planning
When planning a new project, engineers often devise a best-case scenario, utilizing the best tooling, highest cycle times, and top-end fixtures. They also prepare a "Plan B" with cheaper tooling and less powerful machines, though such alternatives can lead to additional costs and lost time.
Experienced CNC machine shops recognize the value of selecting high-quality materials and processes from the outset, defying competitors who opt for cheaper alternatives. This recognition helps maintain their leading position.
8. Experience of the Shop
Experience varies among CNC machine shops. Those with more seasoned staff possess an irreplaceable insight built through decades of successful projects. Such shops manage everything from design to assembly and have established processes and the right CNC tooling.
So, how does a new entrant establish itself amongst experienced shops? Choosing tools is a skill often passed down from engineer to engineer in high-end shops, embodying tribal knowledge.
Evaluating a shop’s capabilities in selecting CNC tooling without firsthand project insight can be tricky. Look for experience and ask for references. Additionally, three signs indicating a CNC shop’s proficiency in choosing the right tools for complex parts should be considered.
Now, you understand what CNC tooling entails and key considerations for selecting CNC machining cutting tools. Maximize your CNC tooling practices by exploring CNC Tooling Improvements and Partnerships: A Guide to Solving Specific Tooling Issues. Click the link below for your copy.
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