Design for Manufacturing (DFM) Guidelines

Introduction to DFM

Design for Manufacturing (DFM) is a systematic approach to designing parts and assemblies that are efficient, cost-effective, and high-quality to produce. By adhering to MetalCore’s DFM guidelines, you can:

• Reduce production costs by 15–40%
• Accelerate lead times and time-to-market
• Improve part reliability and dimensional consistency
• Minimize tooling iterations and post-processing

General Design Principles

1. Minimize Part Count: Combine features where possible to reduce assembly complexity.
2. Standardize Features: Use common hole sizes, radii, and thread standards.
3. Avoid Tight Tolerances: Specify GD&T only where functionally required.
4. Design for Accessibility: Ensure tool paths, bends, and ejection are unobstructed.
5. Modular Design: Favor interchangeable components for easier maintenance and scaling.

Material Selection Guidelines

Choose materials based on mechanical requirements, environment, and manufacturability. Common stock materials are optimized for our processes.

Standard Tolerances & Surface Finishes

Unless otherwise specified, MetalCore applies the following default standards. Tighter tolerances increase cost and cycle time.

Surface Finish Options: Anodizing (Type II/III), Powder Coat, E-Coat, Passivation, Plating (Zn, Ni, Cr), Vibratory Tumbling, Bead Blasting, Mirror Polish.

CNC Machining Guidelines

Recommended Design Features

• Use standard end mill radii for internal corners (1/8", 3/16", 1/4", 3mm, 4mm, 6mm).
• Maintain minimum wall thickness ≥ 1.5 mm (0.060") for aluminum, ≥ 2.5 mm for steel.
• Provide relief pockets for deep cavities to prevent tool deflection.
• Use chamfers or radii on external edges to reduce stress concentrations.
• Standard thread depths: ≤ 2.5 × nominal diameter (tap limit), ≤ 4 × diameter for die threads.

Design Avoidances

• Sharp internal 90° corners without radii (tools are cylindrical).
• Deep, narrow slots (depth-to-width ratio > 4:1 causes breakage).
• Undercuts requiring expensive 5-axis or EDM processes unless critical.
• Over-specifying tolerances on non-mating or cosmetic surfaces.

Sheet Metal Fabrication

• Minimum Bend Radius: 1× material thickness (T) for aluminum, 1.5×T for steel.
• Bend Allowance: Use K-factor ≈ 0.44 for standard materials. Let our CAM team calculate net dimensions.
• Flange Width: Minimum 3×T to prevent cracking and ensure proper tooling clearance.
• Hole/Mount Clearance: Maintain ≥ 1.5×T from edge to avoid deformation during bending.
• Laser/Waterjet: Taper is ~0.5–1.5° depending on thickness. Design critical alignments to accommodate.
• Welds: Avoid tight corner joints; use lap or fillet welds where possible. Specify weld size & class.

Injection Molding & Die Casting

Injection Molding (Plastics)

• Wall Thickness: Aim for uniform walls. Standard: 1.5–3.0 mm. Avoid sudden transitions.
• Draft Angle: Minimum 1° for shallow features, 1.5°–2° for deep cavities.
• CornerRadius: Internal: 0.2×T, External: 0.5×T to prevent sink marks.
• Ribs: Thickness ≤ 0.6× nominal wall. Add fillets at base.
• Snap Fits: Use flexible tabs with ≤ 30% deflection of material yield.

Die Casting (Aluminum/Zinc)

• Minimum Wall: Aluminum: 1.0–1.5 mm, Zinc: 0.6–1.0 mm.
• Draft: 1:50 (1.15°) for aluminum, 1:100 (0.57°) for zinc.
• Gating & Runners: We optimize automatically; avoid overly thin or complex internal flow paths.
• Knockout Holes: Provide relief holes for deep cavities to prevent trapped air/cold shuts.

File Submission & Documentation

Proper file formatting ensures accurate quoting, faster DFM analysis, and zero production delays.

DFM Review & Support

Not sure if your design is optimized? Submit your files to our engineering team for a structured DFM review. We evaluate:

• Manufacturability & tooling feasibility
• Tolerance stack-up & GD&T optimization
• Material & finish recommendations
• Cost drivers & value-engineering opportunities
• Alternative process suggestions (e.g., machining vs. casting)