Design for Manufacturability (DFM): A Practical Checklist for Engineers

Design for Manufacturability (DFM) is one of the most important, and most overlooked, parts of product development.

A part can look perfect in CAD and still become a production nightmare once it hits manufacturing. Excessive machining time, warped molded parts, failed prints, tight tolerances that drive cost through the roof, many of these problems start long before production begins.

DFM helps engineers avoid those issues by designing parts around the realities of manufacturing processes from the start.

At its core, DFM is about creating parts that are:

• Easier to manufacture
• More consistent in quality
• Faster to produce
• More cost-effective at scale
• Less likely to fail during production

Whether you’re working with CNC machining, injection molding, or additive manufacturing, good DFM decisions can dramatically improve lead times, pricing, and part performance.

This guide walks through a practical DFM checklist engineers can use before sending a design out for quote or production.

What is Design for Manufacturability (DFM)?

Design for Manufacturability (DFM) is the process of designing parts in a way that simplifies manufacturing while maintaining performance and functionality.

The goal is not just to make a part manufacturable, it’s to make it manufacturable efficiently, repeatably, and economically.

DFM considerations can include:

• Material selection
• Wall thickness
• Draft angles
• Feature accessibility
• Tolerances
• Surface finishes
• Assembly requirements
• Tooling limitations
• Support structures
• Machine capabilities

A strong DFM review identifies manufacturing risks early, before they become expensive engineering changes, scrap, delays, or tooling modifications.

Why DFM Matters

Poor DFM decisions can create major downstream problems, including:

• Longer lead times
• Higher tooling costs
• Increased scrap rates
• Difficult assembly
• Cosmetic defects
• Warping or sink marks
• Excessive machine time
• Print failures
• Quality inconsistencies

For example:

• A CNC part with deep internal corners may require specialty tool and additional setups.
• An injection molded part without proper draft may stick in the mold.
• A 3D printed part with unsupported overhangs may fail during printing.

Good DFM helps avoid all of these issues before production starts.

A Practical DFM Checklist for Engineers

1. Review Wall Thickness

Wall thickness is one of the most important DFM considerations across nearly every manufacturing process.

Inconsistent or overly thick walls can lead to:

• Warping
• Sink marks
• Long cycle times
• Poor dimensional stability
• Increased material usage

Injection Molding

For injection molding, uniform wall thickness is crtical.

Best practices include:

• Keep wall thickness consistent whenever possible
• Avoid thick-to-thin transitions
• Use rib instead of bulky solid sections
• Core out thick areas to reduce sink

Typical wall thickness ranges:

• Most thermoplastics: 0.040″-0.150″
• Thin-wall applications: below 0.040″
• Structural applications: may require thicker walls depending on material

CNC Machining

For CNC machining:

• Extremely thin walls can chatter or deform during machining
• Deep think walls increase machining complexity
• Internal features may require longer cutting tools, reducing rigidity

General guidelines:

• Metal walls: ideally above 0.030″
• Plastic walls: ideally above 0.060″

Additive Manufacturing

In additive manufacturing:

• Walls that are too thin may fail during printing or post-processing
• Very thick walls increase build time and material consumption

HP MJF and SLS nylon parts often support thinner walls then FDM processes, but minimum thickness still depends on geometry and orientation.

2. Add Proper Draft Angles

Draft angles are essential for injection molded parts.

Draft helps the part release from the mold without dragging, scuffing, or damaging the tool.

Without enough draft:

• Parts can stick in the mold
• Ejection forces increase
• Cosmetic defects become more likely
• Tool wear increases

Recommended Draft Angles

A common starting point is:

$1^\circ \text{ to } 2^\circ \text{ draft per side}$

Additional draft may be required for:

• Deep features
• Textured surfaces
• Soft materials
• Complex geometries

DFM Tips for Draft

• Apply draft early in CAD modeling
• Draft all vertical faces, not just exterior walls
• Increase draft for textured Mold-Tech or SPI finishes
• Avoid zero-draft shutoffs when possible

Even aluminum tooling benefits significantly from proper draft design, especially for production repeatability.

3. Eliminate or Minimize Undercuts

Undercuts are features that prevent straight tools or mold removal.

Examples include:

• Side holes
• Snap fits
• Internal hooks
• Reverse geometries

Undercuts are sometimes unavoidable, but they almost always increase manufacturing complexity and cost.

Injection Molding

Undercuts may require:

• Side actions
• Lifters
• Hand-loaded inserts
• More complex tooling

These additions increase:

• Tool cost
• Lead time
• Maintenance requirements

CNC Machining

Undercuts in CNC machining may require:

• Speciality cutters
• Additional setups
• 5-axis machining
• EDM operations

Additive Manufacturing

Additive manufacturing handles undercuts much more easily then traditional methods, making it ideal for complex geometries.

However, unsupported overhangs may still require:

• Support structures
• Reorientation
• Additional finishing work

DFM Tip

Ask this question during design review:

“Can this feature be simplified without affecting functionality?”

Many undercuts can be redesigned into more manufacturable geometries with minimal impact on performance.

4. Avoid Overly Tight Tolerances

One of the most common DFM mistakes is applying tight tolerances everywhere.

Tighter tolerances:

• Increase machining time
• Require additional inspection
• Increase scrap risk
• Raise overall cost

Not every feature needs aerospace-level precision.

Use Tight Tolerance Strategically

Apply critical tolerances only where necessary:

• Mating surfaces
• Bearing fits
• Sealing interfaces
• Functional assemblies

Allow looser tolerances elsewhere

Typical Manufacturing Tolerances

Process	Typical Standard Tolerance
CNC Machining	±0.005″
Precision CNC Features	±0.001″–0.002″
Injection Molding	±0.005″–0.010″
HP MJF/SLS	±0.010″–0.015″
FDM Printing	Larger variation depending on geometry

Tolerance requirements should align with:

• Part function
• Material behavior
• Manufacturing process capability
• Production volume

5. Design Around the Manufacturing Process

A design optimized for one process may be inefficient for another.

For example:

• A geometry perfect for additive manufacturing may be impossible to mold.
• A CNC-friendly part may require unnecessary material removal compared to a molded design.

DFM should always consider the intended production method from the beginning.

CNC Machining DFM Considerations

• Avoid deep narrow pockets
• Use standard drill sizes when possible
• Increase internal corner radii
• Minimize setups and tool changes
• Design for workholding accessibility

Injection Molding DFM Considerations

• Maintain consistent wall thickness
• Add proper draft
• Plan gate and ejector locations
• Reduce undercuts
• Consider material shrinkage

Additive Manufacturing DFM Considerations

• Optimize orientation
• Reduce support structures
• Use lattices where appropriate
• Avoid trapped powder areas
• Design assemblies as consolidated parts when possible

6. Simplify Part Geometry

Complexity adds cost across eery manufacturing method.

Simplifying geometry can:

• Reduce cycle time
• Improve repeatability
• Lower scrap rates
• Improve relaibility
• Reduce inspection requirements

Areas to simplify include:

• Excessive cosmetic detailing
• Unnecessary surface finishes
• Tiny features
• Sharp internal corners
• Extremely deep pockets
• Complex assemblies that could become single parts

In additive manufacturing especially, part consolidation can significantly reduce assembly labor and hardware requirements.

7. Consider Material Behavior Early

Different materials behave differently during manufacturing.

Factors to consider include:

• Thermal expansion
• Shrinkage
• Warping
• Moisture absorption
• Brittleness
• Heat resistance

For example:

• Glass-filled nylons may warp differently then unfilled materials
• Aluminum dissipates heat differently then stainless steel during machining
• Flexible TPU behaves very differently than rigid PA-12 in additive manufacturing

Material selection should always be part of the DFM process, not an afterthought.

8. Think Beyond the Part Itself

DFM should also account for:

• Assembly
• Inspection
• Pacakging
• Serviceability
• Post-processing
• End-use environment

Questions engineers should ask:

• Can this part be inspected easily?
• Will finishing operations affect tolerances?
• Is assembly intuitive?
• Can operators handle the part safely?
• Does the geometry create bottlenecks later in production?

Good DFM considers the entire lifecycle of the product.

Common DFM Mistakes Engineers Make

Some of the most common manufacturability issues include:

• Over-tolerancing
• Ignoring draft angles
• Designing impossible internal corners
• Creating unnecessary undercuts
• Using inconsistent wall thickness
• Selecting the wrong process for production volume
• Designing without considering fixturing or tooling
• Prioritizing aesthetics over manufacturability

These mistakes often result in expensive redesigns later.

The Best DFM Strategy: Collaborate Early

One of the best ways to improve manufacturability is involving manufacturing engineers early in the design phase.

A collaborative DFM review can help identify:

• Cost-saving opportunities
• Production risks
• Better material options
• Faster manufacturing methods
• Design simplifications

Even small geometry adjustments can significantly improve manufacturability without affecting performance.

Final Thoughts

Design for Manufacturability is not about limiting engineering creativity.

It is about designing smarter parts that can move efficiently from prototype to production.

The best designs balance:

• Performance
• Cost
• Speed
• Reliability
• Scalability

By reviewing wall thickness, draft angles, undercuts, tolerances, material behavior, and process limitations early, engineers can avoid costly production issues and build parts that are truly production-ready.

At Uptive Manufacturing, our engineering teams work closely with customers across additive manufacturing, CNC machining, and injection tooling to help optimize designs before production begins, helping reduce delays, improve repeatability, and accelerate time to market.