Why Your CAD Design Is Difficult to Manufacture: Common DFM Problems

A valid solid model describes nominal geometry. It does not prove that a cutter can reach a pocket, a fixture can hold a thin wall or an inspector can verify a hidden feature. Manufacturability review translates the intended function into a feasible sequence of operations. Start with the manufacturing process and supplier capability rather than treating the CAD file as a finished production definition.

Check tool and holder access

For machined parts, review the approach direction, reach, corner radii, undercuts and collisions with the tool holder. A deep narrow pocket may require a long, flexible cutter and several finishing passes. A feature accessible in a CAD section view may be inaccessible on the proposed machine.

Discuss geometry changes in terms of function. Enlarging an internal radius or opening a pocket from another face may simplify machining, but verify clearance with mating components. Autodesk's prototype-machining guidance distinguishes functional tolerance needs, such as bearing locations, from less demanding clearance features.

Give the part a credible workholding strategy

Ask how the raw stock is located, clamped, machined and transferred between setups. Thin walls can deflect under cutting or clamping loads; a final feature may remove the surface needed to hold the part. Plan sacrificial stock, soft jaws or intermediate datums where appropriate.

The inspection state matters too. A flexible part measured while heavily restrained may pass a drawing but change shape after release. Define the required condition for critical measurements and coordinate it with the manufacturing plan.

Specify functional tolerances and datums

Identify the interfaces that locate and constrain the assembly. Allocate tolerances from those functional requirements instead of applying a tight general tolerance everywhere. A tolerance stack includes contributions from multiple parts and features, so an individually accurate component can still form an unacceptable assembly.

For example, three independent dimensions each allowed to vary by ±0.10 mm create a ±0.30 mm worst-case stack in a simple linear chain. Statistical treatment requires justified process and distribution assumptions; it is not an automatic reason to reduce the required clearance.

Check process effects beyond nominal geometry

Machining, welding, heat treatment, coating and assembly can change dimensions or material condition. Allow for finish thickness at fitted surfaces, distortion after material removal and the accessibility of deburring operations. The correct sequence may be as important as the final CAD geometry.

Where simulation is used to reduce mass, include manufacturing constraints and reassess stiffness, fatigue or contact after the change. A lighter shape with inaccessible internal features may be an unsuitable production design even when its structural response is attractive.

Release a coherent manufacturing package

Provide the controlled model, drawing revision, material, finish, functional tolerances, datum scheme and inspection requirements. Resolve conflicts between model dimensions and drawing notes before release. Autodesk describes DFM as aligning process capability with geometry and tolerances early; use supplier feedback while revisions are still inexpensive.

The review output should distinguish mandatory functional requirements from negotiable geometry. Fluxiss can connect CAD, analysis and manufacturing preparation around that decision list, with a record of why each accepted change preserves the part's intended use.