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6 design recommendations to optimize CNC machining costs

Introduction

Before the parts are mass-produced, whether you want to customize a simple prototype or low volume production, reasonable control of manufacturing costs is an important part of CNC machining. Fortunately, the decision you make as a designer directly affects the final pricing of the product. Through the design of the machining technique, you can help you optimize the parts you want to produce, and satisfy you with the least cost and the most suitable production process. The design and market requirements make your products more competitive and advantageous. Here are some suggestions from us. If you are still not sure which one is the best for your process, sales@zxmade.com.

Do you know what factors affect the cost of CNC machining?

The price of CNC machined parts depends on the following:
T Processing time:The longer it takes to machine a part, the higher its cost. Processing time is often the main cost driver for CNC machining.
T Cost:These are related to CAD file preparation and process planning and are important for low volume production. This cost is fixed and there is an opportunity to reduce unit prices by leveraging "economies of scale."
T Other manufacturing costs:When you design parts with special requirements (for example, when you define strict tolerances or design thin walls), special tools, more precise quality control, and more processing steps may be required - at lower Processing speed. This of course affects the total manufacturing time (and price).
It is now clear where the cost of CNC machining cost comes from, let us see how to optimize the design to reduce the cost of this process..

Tip 1: Add a Radius in Internal Vertical Edges to reduce the cost of sharp edge.

Because CNC machining tools are cylindrical and cannot be directly machined into perpendicular, we recommend adding a circular arc radius at the corner of the cavity. The smallest milling cutter diameter for CNC machines is 1.0mm, so the smallest rounded corner that can be machined is R0.5. With a machining depth of 5.0 mm, the corner radius can be reduced by using a tool with a smaller diameter. This means that although it takes a long time to perform multiple milling, it increases processing time and cost. To minimize costs:
1. Add the radius of the arc at the corner of the cavity (moderate).
2. Try to use the same radius in all internal edges.

Professional Tip: Ideally, the R-angle radius should be slightly larger than the tool radius that will be used to machine the cavity. This reduces the load on the tool and will further reduce your manufacturing costs. For example, if your design has a 12.0mm deep cavity, add a 1.5mm (or larger) radius to the corner. This will allow a ø3.0mm tool to be machined for better efficiency

Tip 2: Limit the depth of the cavity

The depth of the depth of cut affects the cost of CNC parts because it takes a lot of material to remove, which is time consuming.
It is very important to remember the limitations of the cutting length of CNC tools. The depth of the cutting pin is usually the best in the range of the toughness of the milling cutter. Of course, it can be milled deeper. Each tool is reserved to 25.0mm for clamping, or Use the extension rod to lengthen the length of the milling cutter, so that the product parts can be cut deeper. The disadvantages are that the tool is too long, the force is not enough during the machining process, the processing is not smooth enough, and the efficiency is reduced.

Tip 3: Increase wall thickness

Unless weight is a major factor, thicker solid parts are more stable (lower machine costs) and should be prioritized. In order to avoid deformation or breakage when processing thin walls, it is necessary to perform multiple cuts at a low depth of cut. Thin features are also very prone to vibration, so accurately machining them is challenging and greatly increases processing time.

To minimize costs:
1. For metal parts, the design wall thickness is greater than 0.8 mm (the thicker the better).
2. For plastic parts, keep a minimum wall thickness of more than 1.5 mm.
Note: The minimum wall thickness that metal can achieve is 0.5 mm and the plastic is 1.0 mm.
It is important to keep thin holes (and threads) when they are placed very close to the edge of the part. When placing holes in your design, be sure to follow the above guidelines.

Tip 4: Limit the length of the threaded hole

Specifying a length that exceeds the necessary threads can increase the cost of the CNC part because special tools may be required.
Keep in mind that threads that are 1.5 multiple longer than the hole diameter do not actually increase the joint strength.
To minimize costs:
1 Design a thread with a maximum length of 3 multiple the hole diameter.
2 For threads in blind holes, it is best to add at least 1/2 diameter of unthreaded length at the bottom of the hole. For blind hole threads, it is best to add at least 1/2 unthreaded length at the bottom of the hole.

Tip 5: Design Holes with Standard Size

With standard drills tool, drilling allows for fast CNC machining and high precision. For non-standard size holes, a custom milling cutter must be used for machining, which may increase the cost.
In addition, the depth of all holes is limited to 4 times its diameter. Deeper holes (10 times the diameter) can be made, but they can add cost.
To minimize costs:
1. The design hole has a diameter increment of 0.1mm, the diameter can be from 1-10mm, and the diameter of 10.0 is 0.5mm per increment.
2. When designing in inches, please use the regular inch drill size table.

Tip 6: Mark only the required and most important tolerances

Defining strict tolerances will increase the cost of CNC machining process because it increases machining time and requires manual inspection. Tolerances should be carefully defined and tolerances determined only when necessary.
If specific tolerances are not defined on the technical drawings, the parts will be machined using standard tolerances (DIN ISO 2768 or better), which is sufficient for most non-critical features.
To minimize costs:
1 Specify tighter tolerances only when necessary.
2 Define a single datum (for example, the cross section of two sides) as a reference for all dimensions with tolerances.

Additional tips: The most economical and cost-effective processing method is low volume production

In CNC machining, the quantity greatly affects the unit price. This is because installation costs are relatively high, and they account for a large percentage of the cost for a single prototype or a small number of parts. As the number increases, setup costs are almost eliminated because they are distributed across many artifacts. This means that even a small increase in the number will cause the unit price to drop significantly. Please note that the very high order quantity (> 1000 copies) can reduce the unit price by 5 to 10 times!
The effect of quantity is outstanding even in small batches. in fact:
Increasing the number from 1 to 5 can reduce the unit price by more than 25%!
In order to minimize costs: it is the most cost-effective to order more quantities.

Conclusion: Keep it simple...

The complexity of CNC machining is the most important factor influencing costs: the need for special tools or fixtures, the need for multiple machining or complex shapes of special materials requires more cost.