6061-T6 Aluminum CNC Machining for Open-Frame Parts

A compact aluminum component can become difficult to machine when most of its internal material has to be removed.

This 120 × 40 mm custom part features two rectangular openings, narrow connecting sections and several projecting mounting tabs. Its open-frame design reduces weight but also leaves less material to support the component during machining.

We produced 300 pieces from 6061-T6 aluminum for a customer in the United States. The complete project—from material sourcing and CNC machining to polishing, sandblasting and anodizing—was completed within three weeks.

The main production challenge was not the overall size of the part. It was maintaining the shape and position of the narrow frame sections throughout machining, manual surface preparation and final finishing.

Project Specifications

Why the Open Structure Changed the Machining Plan

When the material inside the two windows was removed, the remaining frame became less rigid. This made the part more sensitive to clamping pressure and cutting forces than a solid aluminum bracket of the same size.

Clamping the part too tightly could distort the narrow sections. Providing too little support could allow vibration during milling, affecting the openings, edges and small mounting features.

The projecting tabs also required special attention. Because they extend away from the main body, they could not be used as primary clamping areas. Their positions nevertheless had to remain consistent because they are likely to influence how the finished component fits with mating parts.

The machining plan therefore focused on:

• Supporting the stronger areas of the workpiece;
• Removing material from the openings in controlled stages;
• Avoiding excessive cutting forces as the frame became thinner;
• Maintaining the relationship between the openings, holes and tabs;
• Limiting repeated clamping of delicate finished features.

The objective was not simply to machine the part quickly, but to create a repeatable process for the entire 300-piece batch.

Maintaining Consistency Across 300 Parts

Producing the first acceptable component confirmed the machining approach, but batch consistency required continued process control.

During production, changes in tool condition, fixture positioning or clamping pressure could gradually affect the narrow sections. The main profile, rectangular windows, side details and mounting holes were therefore machined in a planned sequence.

Material was removed progressively so that sufficient support remained during the earlier operations. The smaller features were completed after the main geometry had been established, without applying unnecessary pressure to the projecting tabs.

Dimensional checks were carried out during production rather than only after all 300 parts had been machined. Inspection focused on the overall profile, window geometry, mounting-hole positions and the relative location of the side tabs.

This intermediate inspection reduced the risk of sending a dimensional problem into surface treatment, where rework would become more difficult and could affect the delivery schedule.

Preparing the Parts for Sandblasting and Anodizing

The specified surface-treatment process included polishing, sandblasting and anodizing. In this project, polishing was used as a controlled preparation step rather than as the final decorative finish.

After CNC machining, burrs, sharp edges and noticeable tool marks were removed. Particular care was taken around the internal openings, narrow walls and small tabs. Excessive polishing in these areas could round the edges or alter the profile.

Once the surfaces had been prepared, the parts were sandblasted to create a uniform matte texture and then anodized.

Sandblasting can make the surface appearance more consistent, but it cannot conceal deep scratches, dents or uneven manual finishing. Anodizing may make some imperfections more visible. For that reason, the parts were visually checked before being released for surface treatment.

This step helped avoid spending additional time and cost on anodizing components that did not yet meet the required surface condition.

Completing Material, Machining and Finishing in Three Weeks

The three-week schedule covered the entire order, not only the CNC machining stage. It included 6061-T6 material sourcing, process preparation, batch production, polishing, sandblasting, anodizing and inspection.

To keep the project moving, machining and surface-treatment arrangements were coordinated from the beginning.

The production sequence included:

• Reviewing the customer’s 2D and 3D drawings;
• Ordering and confirming the 6061-T6 material;
• Preparing fixtures and CNC programs;
• Machining the profiles, openings, holes and mounting features;
• Deburring and polishing the machined parts;
• Sandblasting and anodizing;
• Completing dimensional and appearance inspections;
• Packing the finished parts for export to the United States.

Scheduling the surface treatment in advance helped reduce waiting time between processes and left sufficient time for final inspection before shipment.

For projects with a fixed delivery date, this coordination can be as important as the machining cycle itself.

Inspection After Anodizing

The parts were inspected both before and after surface treatment.

Before anodizing, the inspection concentrated on dimensional features and surface preparation. After anodizing, the focus shifted to appearance and handling condition.

The finished components were checked for:

• Visible distortion of the frame;
• Damage around the projecting tabs;
• Burrs inside the rectangular openings;
• Scratches or dents on visible surfaces;
• Uneven sandblasted texture;
• Anodizing defects or noticeable color inconsistency;
• Marks caused by part-to-part contact.

Because the tabs extend beyond the main profile, they are more exposed to impact during handling and transportation. The parts were therefore separated and protected during packing to reduce contact between anodized surfaces and prevent damage before delivery.

Custom Aluminum CNC Machining for Lightweight Structures

This project demonstrates why machining difficulty cannot be judged by dimensions alone. Although the component measured only 120 × 40 mm, its large openings, narrow frame sections and projecting tabs required a stable workholding method and a carefully ordered machining process.

It also shows the importance of considering surface treatment during machining—not after production is complete. Edge preparation, manual polishing, sandblasting and anodizing all have the potential to affect delicate aluminum features.

We manufacture custom aluminum parts from customer-supplied 2D and 3D drawings, supporting prototypes, small-batch production and repeat orders. Available services include material sourcing, CNC milling, deburring, polishing, sandblasting, anodizing, inspection and export packaging.

For open-frame components, thin-wall brackets and other non-standard aluminum parts, we review how the geometry will behave during machining, how the required finish will affect exposed features and how the completed parts should be protected during delivery.

Request a Review for Your Aluminum Part

If your project involves a similar 6061-T6 aluminum frame, mounting component or sandblasted anodized part, send us your drawings together with the required quantity, tolerances and surface specification.

Our engineering team can review the workholding, machining sequence and finishing requirements before production, helping identify potential deformation or appearance risks at an early stage