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Design for Manufacturing
If the shop could read your mind, what would it ask you to change on this drawing?
Design for Manufacturing is the set of habits that turns a drawing that works into a part that is easy and cheap to make. This section has eight pages: the fundamentals, then CNC machining, sheet metal, welded structures, assembly, tolerances and GD&T, whole automation machines and cost estimation. Each page has tools you can use on a real design, from a bend allowance calculator to an ISO fit calculator and a lifecycle cost comparison.
8 pagesInteractive calculatorsChecklistsIndicative figures
1Start where your problem is
Pick the situation that sounds like yours.
2The learning path
1. Start hereDFM FundamentalsWhat DFM is, the principles, cost drivers, a scorecard and a redesign saving tool.2. Machined partsDFM for CNC MachiningTool radius, pockets, holes, walls, machining time and tolerance.3. Bent partsDFM for Sheet MetalBend allowance, flat length, reliefs, hole-to-bend distance, springback.4. Welded framesDFM for Welded StructuresFillet weld size and capacity, access, symbols, distortion, allowance.5. AssemblyDesign for Assembly (DFA)Part count, design efficiency, poka-yoke, fastener access, impact.6. DrawingsTolerances, Fits and GD&TISO fits, stack-up, GD&T frames, gauge choice.7. Whole machinesDFM for Automation MachinesStandard parts, modular layout, plates, cable bend radius, air use.8. MoneyManufacturing Cost EstimationPart cost build-up, batch size, make or buy, lifecycle cost.
3The one-page version of DFM
| Question to ask | Why it matters | Where to go |
|---|---|---|
| Can a standard tool, stock size and process make this? | Standard means cheap, quick and replaceable. | CNC, Sheet metal |
| Can any of these parts be combined or removed? | Each part adds machining, handling, fasteners and failure points. | DFA |
| Is every tolerance something the function needs? | Tight tolerances are the quiet cost multiplier. | Tolerances |
| Can the process reach and hold every feature? | Tool reach, bend rules and weld access decide what is possible. | Welded structures |
| Could it be bought instead of made? | Catalogue parts usually win below high volumes. | Automation machines |
| What does one cost, and at what batch size? | You cannot reduce what you have not measured. | Cost estimation |
4Test yourself
Remember
- Design for the shop that will make it, not for the CAD model.
- Cut part count, then standardise, then relax tolerances.
- Measure the cost; it tells you what to change.
- Involve the manufacturer early, when change is cheap.
Related
ReferenceProcess vs ToleranceWhich process can hold a tolerance.CalculateStructural Frame AnalysisCheck frames, base plates and gussets.CalculateLM Rail & Block SelectorStandard linear guides for machines.LearnMES IntegrationTake the machine data into production systems.
Sources and notes
- Boothroyd, Dewhurst and Knight, Product Design for Manufacture and Assembly (CRC Press), for the DFM and DFA method.
- Machinery’s Handbook (Industrial Press), for machining, sheet metal and welding practice.
- Each page lists its own standards and sources.
All values are indicative guidelines. Your own shop and supplier capability always takes priority.