CNC Machining Keyboard Shell: Detailed Explanation Of Customization Process And Cost

1. Why choose CNC processing keyboard parts?

When compared with 3D printing or injection molding, CNC processing of keyboard shells made of different materials such as aluminum alloy, brass and stainless steel demonstrates three unique advantages that will not be replaced and cannot be surpassed:

1. CNC machine tools can stably achieve IT6 level tolerances in terms of accuracy and consistency. The tolerance of the hole-axis fit can be controlled within plus or minus 0.01mm to ensure that the positioning plate and the shaft body can be accurately engaged without shaking.

2. The texture of the material is formed by directly cutting the solid metal blank, and then the surface of the finished product can be subjected to wire drawing process, emery cloth grinding, anodizing treatment, or PVD coating process, etc. The feel and visual effects achieved in this way are far better than those of plastic.

3. The whole body is processed and formed into an integrated shell. This integrated shell has no welding and has high torsional strength. It can achieve complex tilt angles through programming, complex step surfaces can be programmed, and complex internal stiffeners can also be shaped through programming.

There is such a real case. There is a small keyboard studio that once used CNC to process 10 sets of aluminum alloy casings with a 65% layout. Because the minimum radius of the tool was not confirmed in advance before doing this, too much material remained in the internal corners, which caused the PCB to be unable to lay flat. This problem was later solved by adding a 0.5mm corner-clearing tool path. What this case shows is that the design document must match the processing capability.

2. Standard process of CNC machining keyboard (5 required steps)

Step 1: 3D Model Design (CAD)

Use SolidWorks to create a 3D model, use Fusion 360 to manufacture the model, or use Rhino to shape the 3D shape of the keyboard shell. The key design points are:

Wall thickness, in the case of aluminum alloy materials, the thinnest part should not be lower than 1.5mm, otherwise, it will easily deform or break during processing.

For fillets, the radius of all internal corners must be greater than the minimum radius of the available tool. The recommended minimum radius value is greater than or equal to 1.5 mm.

The screw column is designed as an M2 or M3 threaded bottom hole. The diameter of the M3 bottom hole is 2.5mm, and the depth must be greater than or equal to 8mm.

Step 2: CAM Programming

Import the model into the CAM software to generate tool paths. Need to be explicitly specified:

Rough machining: Use an end mill with a diameter of 6-10mm to quickly remove most of the allowance.

For precision machining, use a tool with a spherical head diameter within the range of 2 mm to 4 mm, or a tool with a flat bottom, to achieve a surface finish with Ra less than or equal to 1.6 μm.

Drilling: Set individual peck drill cycles for screw holes, USB port slots, etc.

Step 3: Material selection and fixture fixing

Common keyboard CNC materials and their characteristics:

The fixing method adopted is to use precision vise or vacuum suction cup to ensure that there is no displacement of the device during the processing operation. For thin-walled shells, that is, those with a wall thickness less than 2mm, it is recommended to use the auxiliary fixation method of "sacrificial layer (it is not clear what the layer means and determine the layer by yourself)", that is, an additional 1mm thick special connection layer is left at the bottom of the blank, and finally the overall milling operation is performed.

Step 4: Actual processing and monitoring

Example of CNC machine tool operating parameters (taking 6061 aluminum alloy as an example):

Spindle speed: 8000-12000 RPM

The feed speed during cutting ranges from 800 mm per minute to 1,200 mm per minute during the roughing stage, and from 400 mm per minute to 600 mm per minute during the finishing stage.

As for the depth of cut, during rough machining, the depth of each tool ranges from 0.5 mm to 1.0 mm, while during finishing, the depth of each tool ranges from 0.1 mm to 0.2 mm.

Coolant: Use water-soluble cutting fluid or oil mist for lubrication to prevent aluminum chips from sticking to the tool.

[Prompt word: Tool path optimization]

During the finishing process, give priority to the "down milling" direction, and add a semi-finishing process (reserve a margin of 0.05mm) before finishing, which can significantly reduce the tool marks. If there are anti-slip grooves on the bottom of the keyboard, use a V-shaped engraving knife to complete the molding in one go. The use of punctuation marks is to split sentences so that they meet task requirements and facilitate reading and comprehension, rather than semantic repetition.

Step 5: Post-processing (deburring and surface treatment)

After the processing is completed, the operator must manually remove the sharp edges and corners, and then select the surface treatment according to the needs.

After it is sandblasted, it is then anodized: this is the most commonly used method and can be provided in a variety of colors such as silver, gray, black, red, etc. It is wear-resistant and non-conductive.

Brushed + clear coating: Shows metal texture, but easily retains fingerprints.

Polishing + PVD: obtain mirror or golden effect, the cost is higher.

3. Core factors affecting the cost of CNC keyboard

Knowing your cost components will help you make balanced decisions. It includes the following four items, which account for more than 85% of the total cost:

1. Aluminum alloy is the most economical in terms of material cost. The material cost of brass is about twice as expensive as that of aluminum alloy. The unit price of stainless steel is at a medium level, but its tool wear is large.

2. When time is used for processing, complex structures, such as bottom grooves and side openings, require multiple tool changes and different angles for processing. A 4-axis CNC takes an average of 45 to 90 minutes to process a single 60% keyboard shell.

3. The treatment method of the surface of the object: The cost of anodizing is calculated on a piece-by-piece basis. Normally, the cost per piece is between three US dollars and eight US dollars. The hard oxidation treatment method is more expensive in comparison, but it is wear-resistant.

4. The requirements for tolerances are as follows: If all dimensional tolerances marked on the drawings are plus or minus 0.02 mm, then the time required for processing will be extended by 30%, because this requires slower feeds and more inspections to achieve.

A common misunderstanding is that you want to design multiple parts, such as housings and positioning plates, as a whole to save assembly. However, in fact, this will greatly increase the cost of five-axis milling. It is better to process them separately and then connect them with screws.

4. How to ensure the success rate of CNC machining keyboard? (4 core checks)

Before sending documents to the processing factory, please verify item by item:

Sizing: Make sure the units are millimeters, not inches, as common mistakes can cause products to shrink by a factor of 25.4.

If a five-axis machine tool cannot be used, then it is necessary to avoid designing any structure that has a "dovetail" shape or a concave inside, which is an undercut area.

There should be clearance space. There should be a via hole with a diameter of at least 6mm next to the USB-C interface, and the depth should be enough to allow the plug to be fully inserted.

The specification of the thread is that if tapping operation needs to be performed directly on the aluminum alloy, the depth of the thread should be 1.5 times the diameter of the screw (if M2 screws are taken as an example, a depth of 3mm is required).

[Prompt word: Fixture design strategy]

For mass production (quantity ≥ 50 pieces), it is recommended to design a special pneumatic clamp or zero-point quick change system to reduce the time spent on each clamping from 5 minutes to 30 seconds, and at the same time reduce errors caused by manual positioning. For single-piece prototypes, double-sided tape or hot melt adhesive can be used to fix it on the backing plate.

5. Frequently Asked Questions (Q/A)

Q1: How much does it cost to CNC machine an aluminum alloy keyboard shell?

A: The price of a single prototype is between US$200 and US$400. If it is a small batch, that is, ten pieces, the price of each piece is US$80 to US$150. This is mainly determined by the complexity and surface requirements.

Q2: What format file do I need to provide for my design?

A: Provide a 3D model presented in STEP format or IGES format, and provide a 2D engineering drawing (PDF format) with complete tolerance annotations.

Q3: What is the minimum order quantity?

Person A said that there is no minimum quantity limit, and a single piece can start the processing process. However, the unit price is obviously higher, so it is recommended to process at least three pieces to share the costs of programming and clamping.

Q4: How long will it take to receive the finished product after processing?

For A, it usually takes three to five working days for a single prototype, and about seven to ten working days for a small batch (less than twenty pieces), which does not include surface treatment and transportation.

Q5: Will the aluminum alloy keyboard shell oxidize and discolor?

A: After anodizing treatment, a dense oxide film is formed. Under normal use, it will not fade for more than five years, but contact with strong acids and alkalis should be avoided.

Q6: Can the bottom case with complex curves be processed?

A: Three-axis CNC can only process vertical surfaces or small-angle inclined surfaces. As for the truly extremely complex curved bottom case, it requires a five-axis CNC, and its cost will at least double.

Q7: What is the minimum radius of the designed fillet?

For conventional tools, the minimum radius is 0.5mm. If it must be less than 0.3mm, then EDM must be used, and conventional CNC is not recommended.

6. Action suggestions and core conclusions

The core point is repeated: the key to the success rate of CNC machining of keyboard parts is 90% determined by three actions. First, determine the minimum radius of the tool and the undercut limit with the processing factory in advance; second, set a reasonable roughing and finishing allowance in CAM; third, specify clear and clear surface treatment standards in the post-processing link, such as "sandblasting to a roughness of over 180 mesh, plus anodizing to appear black and a film thickness of 15 μm."

Suggestions for action :

1. Immediately export your keyboard 3D model as a STEP file, and then use the measurement tool to check whether all inner corner radii are ≥ 1.0mm.

2. Select materials according to the table in Section 3 of this article, and contact at least two CNC machining services to discuss quotations and delivery requirements.

3. Request the supplier to provide a first-piece inspection report after processing, focusing on testing the flatness of the mounting surface of the positioning plate. This flatness should be less than or equal to 0.1mm.

According to the process and parameters given in this article, you can get a completely customized CNC machined keyboard shell with industrial-grade precision within two to three weeks. If there are any requirements in your design that exceed normal wall thickness or tolerances, be sure to indicate the "critical characteristics" symbol in the 3D model and communicate with the programming engineer individually.