# Sheet Metal Design for Manufacturability (DFM) Checklist > Source: https://netray.co/tools/sheet-metal-dfm-design-review-checklist > Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems. > Section: Free Tools ## Short answer A pre-release checklist for sheet metal parts covering cutting, bending, hardware, tolerance and finishing issues that cause rework and quote changes. ## Category engineering-plm ## Industry Sheet Metal Fabrication ## Audience - Design engineer - Fabrication engineer - Quoting engineer ## Tool **Kind:** checklist **Groups:** #### Material and drawing basics **Items:** **Text:** Material, alloy, temper and thickness are stated on the drawing **Critical:** true **Text:** Thickness is given in millimetres or inches, not only as a gauge number **Critical:** true Grain direction is specified where appearance or tight bends require it Finish, coating and masking requirements are called out Revision and part number match the model and the ERP item General tolerance note is present and realistic for sheet metal #### Cutting features **Items:** **Text:** Hole diameters are not smaller than material thickness unless approved **Critical:** true Slot and tab widths are at least about one times thickness Distance from a hole edge to the part edge is at least about two times thickness Hole spacing leaves enough web between features to avoid distortion Internal corners have a radius or relief rather than a sharp corner Part can be laser cut or punched without thermal distortion of thin features #### Bending **Items:** **Text:** Inside bend radius suits the material and temper **Critical:** true One bend radius is used throughout where possible **Text:** Flange length meets the minimum for the V die in use **Critical:** true **Text:** Holes and slots are far enough from bend lines to avoid distortion **Critical:** true Bend reliefs are present where a bend meets a flat edge Bend order is feasible with no collision against the brake or return flange Bend angles are achievable and tolerances are not tighter than the process Hems, jogs and offsets have enough clearance for the tooling #### Hardware and assembly **Items:** **Text:** Self-clinching hardware has the required edge distance and panel hardness **Critical:** true Hardware part numbers and installation side are called out Weld joints, symbols and heat distortion allowances are defined Fasteners and tapped holes are accessible after bending and finishing Mating parts have clearance for coating thickness #### Quality and cost **Items:** **Text:** Critical dimensions are identified and measurable after forming **Critical:** true Tolerances stacked across bends are reasonable Cosmetic surfaces and acceptable marking are defined Part nests efficiently, or standard sheet sizes are considered Quantity breaks and annual usage are noted for the quote Packaging and handling needs for coated or polished parts are stated **Scoring Note:** 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. ## Content **Intro:** Most sheet metal problems are cheaper to fix on the drawing than on the shop floor. This checklist walks through the points that cause rework, quote changes and delayed deliveries so you can review a part before release. **Sections:** #### How to use the checklist **Body:** 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. **Bullets:** - 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 **Body:** 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 **Body:** 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 **Body:** 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. **Cta:** If your drawing review notes never make it into the item or routing record, we can help connect them to your ERP. **Faq:** #### Why must hole diameter be at least the material thickness? **Answer:** 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? **Answer:** 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? **Answer:** 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? **Answer:** 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. ## Search terms sheet metal dfm checklist, design for manufacturability sheet metal, sheet metal design guidelines, bend relief checklist, sheet metal drawing review, hole to bend distance, sheet metal design rules, dfm review fabrication --- Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json