Careful planning is crucial for carrying out any kind of operation, whether dealing with the military or industrial machining. We can’t deploy machinists (troops) without knowing which operation will have the best effect (fewest casualties).
While it isn’t a life-or-death situation like war, deciding what goes into your CNC milling project can save greatly on both time and costs. But new entrepreneurs often make the mistake of skipping this crucial first step.
Why is planning so important? Put simply, CNC milling is an expensive process. Doing and redoing any operation can seriously disrupt your budget. After all, devising a war plan after you’ve already lost all your troops is futile.
Prototyping is good, but meticulously planned prototyping is, arguably, the best.
Identifying the design and development factors leading to high CNC costs is key. Equipped with the right insights, entrepreneurs can then adjust these factors, minimize their use, and eliminate any production-heavy aspects in the early stages of production. Some of the most common cost-increasing factors include overly specific tolerances, expensive materials, and elaborate surface finishes.
Below are some expert tips for saving on both time and costs during your next CNC milling project.
1. Select Raw Materials Wisely
Expensive doesn’t always mean better. Raw materials play a huge role in production cost inflation. You can save a lot by being smart with material selection. We’re not asking you to compromise on the quality, by any means; in fact, using cheap, substandard material often leads to unexpected expenses.
The trick is to choose materials that are:
- Inexpensive enough to suit your budget.
- Easily available.
- Able to meet your design requirements with desired precision.
Cheaper materials like aluminum, polymers, and cold rolled steel can serve as good bases for functional prototyping. If necessary, use expensive raw materials — such as stainless steel and exotic alloys — when milling medical equipment.
2. Reduce the Number of Setups — and Setup Time
You’ve listed your raw materials and selected the process. You already know what the end product will look like. Now come the intermediate steps: operations and setups.
Each machined part involves one or many operations. Every operation necessitates a series of setups. There is machine setup, of course. But there is also CAM programming (which will be different for cutting, milling, and drilling processes), part fixturing (if required), material setup, and more.
You can skip all the mess — and expenses — by cutting down on the number of setups. Most parts can be wrapped up in six setups or less. Try to get this number down to two necessary steps — or one, if possible.
Fewer setups will reduce setup time by half or more. And in this way, you’ll be able to machine CNC milled parts better and faster.
3. Specify Tolerances Only for Critical Features
Specifications are crucial for precision CNC machining. Entrepreneurs usually define what they want and how they want it. But part design — specifically, tighter tolerances — has a huge impact on production costs.
We recommend that you maintain standard tolerances for general features. You may specify tolerances for certain critical features and functions if absolutely necessary.
Similarly, maintain a specific dimension for holes for milling. Smaller (and deeper) holes take up a significant amount of machining time and may trigger tool breaks.
4. Maintain a Standard Radius of 3 mm for Inside Corners
The rule of standard specifications applies to inside corners as well.
Milling small, specific radii for inside corners is expensive, time-consuming, and often requires special setups — especially if you’re operating with very small cutters. This is because CNC machines generally run vertical milling operations on the workpiece.
The ideal inner corner radius for most of the machined parts is 3 mm, or ⅛ inch. You can save on setup time and expenses by following standardized radii for noncritical features.
5. Cut Down on Machining Time by Working With Feasible Materials
When it comes to cost savings, machining time — or the time in which actual production is taking place — is as important as material selection or defining the inner radius. Machining time is usually governed by two factors: raw material and part design.
We’ve already discussed the role of part design in tips 3 and 4, but navigating complex part designs with super-specific dimensions is a challenging — and expensive — undertaking. You can sort this out by simplifying your specifications as much as possible.
You can also save on machining time by selecting machinable materials like aluminum, low-carbon alloys, and brass. Hard metals like steel take longer to machine, and they often lead to tool breaks. Plastics are also harder to machine. They require slow machining for a smooth surface finish. And don’t forget: Plastics are often quite expensive.
Other Ways to Minimize CNC Milling Costs
- Reduce nonrecurring engineering costs (NRE) — one-time costs for researching, designing, developing, and testing new products — wherever possible.
- Avoid features involving nonstandard fixturing (soft jaws, sine bars, etc.). Setting each fixture requires a separate setup and CAM program.
- Bulk buying is another smart way to compensate for unit expenses.
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