Sheet Metal DFM Design Review Checklist (Free)

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8 critical items still open - these are the highest-risk gaps.

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Material and drawing basics

Material, alloy, temper and thickness are stated on the drawingCRITICALThickness is given in millimetres or inches, not only as a gauge numberCRITICALGrain direction is specified where appearance or tight bends require itFinish, coating and masking requirements are called outRevision and part number match the model and the ERP itemGeneral tolerance note is present and realistic for sheet metal

Cutting features

Hole diameters are not smaller than material thickness unless approvedCRITICALSlot and tab widths are at least about one times thicknessDistance from a hole edge to the part edge is at least about two times thicknessHole spacing leaves enough web between features to avoid distortionInternal corners have a radius or relief rather than a sharp cornerPart can be laser cut or punched without thermal distortion of thin features

Bending

Inside bend radius suits the material and temperCRITICALOne bend radius is used throughout where possibleFlange length meets the minimum for the V die in useCRITICALHoles and slots are far enough from bend lines to avoid distortionCRITICALBend reliefs are present where a bend meets a flat edgeBend order is feasible with no collision against the brake or return flangeBend angles are achievable and tolerances are not tighter than the processHems, jogs and offsets have enough clearance for the tooling

Hardware and assembly

Self-clinching hardware has the required edge distance and panel hardnessCRITICALHardware part numbers and installation side are called outWeld joints, symbols and heat distortion allowances are definedFasteners and tapped holes are accessible after bending and finishingMating parts have clearance for coating thickness

Quality and cost

Critical dimensions are identified and measurable after formingCRITICALTolerances stacked across bends are reasonableCosmetic surfaces and acceptable marking are definedPart nests efficiently, or standard sheet sizes are consideredQuantity breaks and annual usage are noted for the quotePackaging and handling needs for coated or polished parts are stated

Mark each item as you review the drawing. Resolve every critical item before releasing to quote or production. The distance rules are common shop guidelines, so confirm limits with your own fabrication process.

Track DFM findings by revision

Optional: a short chat on linking review findings to part revisions in your ERP.

Optional. The tool and every export work without this. No spam.

How to use the checklist

Open the drawing and model side by side, then check each group in order: material and drawing basics, cutting features, bending, hardware and assembly, and quality and cost. Items marked critical usually stop a part from being made or quoted correctly. Anything unchecked should become a question to the designer, with the answer recorded against the part revision in your PLM or ERP.

Review at quote time and again at first article.
Record resolved items against the revision.
Use the export to attach the review to the job.

Rules of thumb behind the checklist

Hole diameter of at least one times material thickness avoids punch breakage and poor edge quality. A hole edge two times thickness from the part edge, and a hole placed at least two to three times thickness plus the bend radius from a bend line, avoid distortion. Reliefs allow the material to deform without tearing at the corner of a bend. These are guidelines shops use, and your equipment and tooling may allow more or less.

Tolerances in formed parts

Sheet metal accumulates tolerance across every bend, including thickness variation, springback, angle and flat pattern accuracy. Dimensions that cross two or more bends cannot be held as tightly as a dimension on a single flat feature. Call out critical dimensions on the formed part, define the datum scheme, and avoid tolerances tighter than the process delivers unless a secondary operation is planned and priced.

Common mistakes

Frequent issues are bend lines running through holes, flanges shorter than the die allows, missing relief at bend ends, radii that do not match any available tooling, and gauge numbers without a material. Hardware placed too close to a bend or an edge also fails often because the clinch needs undeformed material.

Frequently Asked Questions

Why must hole diameter be at least the material thickness?

Smaller holes load the punch beyond its strength, causing breakage, burrs and poor hole quality. Laser cutting handles smaller holes but heat and dross can reduce quality, so the guideline is still a useful default.

What is a bend relief?

A small notch or cut at the end of a bend line where the bend meets a flat edge. It prevents tearing and bulging at the corner and lets the flange form cleanly.

When should DFM review happen?

At quoting, before releasing a new revision to the shop, and when the first article is inspected. Catching a flange problem at quote time costs a phone call, while catching it at the brake costs a scrapped part.

Do these distances apply to every shop?

They are common starting guidelines. Actual limits depend on tooling, equipment, material and tolerance. Ask your fabricator for their own design guide and align your checklist to it.

If your drawing review notes never make it into the item or routing record, we can help connect them to your ERP.

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