A supplier can receive every requested file and still lack enough information to price a die reliably. A hole may be easy to pierce in the flat blank but distort during bending; a bracket may meet its dimensions only when someone presses it flat for inspection.
DFM means design for manufacturability. At the quotation stage, the useful output is an agreed list of engineering decisions. Use the buyer RFQ checklist for files, quantities and commercial terms, and this guide to resolve the features that affect tooling and acceptance.
What should the review decide before a tooling quote?
A DFM review should establish how the part will be priced and which decisions remain open. Classify each issue by its effect on the process, tooling and acceptance. The three outcomes below are a practical way to organize a review, rather than a formal industry grading system.
- Ready to quote: the drawing revision, material, functional requirements and proposed process are sufficiently defined for the requested quotation scope.
- Quote with conditions: an option can be priced separately, such as a larger non-critical hole or masking an electrical contact. Write the exact assumption and its effect on scope in the quote.
- Clarify first: a conflict or missing requirement could change the tooling concept, such as a different sheet thickness or an undefined locating feature. Resolve it before confirming the affected tooling price.
Start with the assembled function and the inspection setup
Identify what locates the part in its assembly, which faces touch and which dimensions control fit. Those features guide datum selection and the inspection setup. A narrow tolerance without a clear reference or measurement condition can leave the buyer and supplier checking different things.
For a flexible bracket or cover, state whether a requirement applies in the free state or under defined restraint. If it is restrained, identify supports, clamping points and the agreed load or fastening condition. KEYENCE's guidance on non-rigid parts explains why free-state and restrained requirements need explicit drawing instructions. [3]
- Confirm which drawing and model revisions belong together, and identify the governing file if they disagree.
- Mark locating holes, mating faces and other functional features; retain an explicit general tolerance for the rest.
- State whether the checked part is flat, fully formed, deburred, finished or assembled. Use the state relevant to each requirement.
Which hole and slot details need a closer look?
Review the smallest hole diameter or slot width, the metal left between cut edges and nearby forming zones. As a punched feature becomes small relative to sheet thickness, punch loading and edge quality become more difficult to manage. Material strength, punch support and cutting clearance also affect feasibility; diameter alone is not a pass/fail test. [1]
For an illustrative 1.0 mm hole in 1.2 mm sheet, the diameter-to-thickness ratio is 1.0 ÷ 1.2 ≈ 0.83. Flag that feature for a tooling review. Ask whether the hole can be enlarged, whether the tooling can support the small punch, or whether another operation should be quoted.
Define distances precisely. A 4 mm diameter hole with its center 3 mm from a straight outer edge leaves only 3 − 4/2 = 1 mm of metal. That is an edge-to-edge distance, not a 3 mm ligament. For holes near bends, specify whether the reference is the bend tangent, theoretical sharp corner or a line on the flat pattern.
Review bends together with the operation sequence
A hole beside a bend may change shape or position during forming, even when it was pierced accurately in the blank. The review must consider the material moved by the bend, the required final hole location and whether the tool can reach and support the feature at the planned station.
Compare moving the hole, changing a relief or piercing after forming. Each option has a different consequence: a design change needs buyer approval, a relief can affect stiffness or appearance, and later piercing may need additional tooling and locating. Record the proposed route so the price includes the intended operations.
Review inside radius and flange height against the actual grade, temper and thickness range. Springback is elastic recovery after unloading, so a nominal 90° tool angle does not by itself establish a 90° finished bend. WorldAutoSteel explains how material properties and geometry influence this recovery. [2]
- Identify which bend angle, flange height or hole-to-face dimension controls assembly after forming.
- Ask whether tool access, part removal, opposing bends or a short flange changes the proposed die layout.
- If a trial is needed, name the feature to check and use the intended production material condition. Keep tooling compensation subject to that review.
What does the buyer need to explain about edges and finish?
Start by explaining how the part will be used. You do not need to choose a burr-height limit or a deburring process before enquiring. For example: “A wire passes through this hole, so the edge must not damage its insulation”; “These two panels need to sit flush”; or “This is an electrical grounding contact and must remain unpainted.”
A burr is a small raised edge that cutting can leave behind. Circle the relevant areas on a drawing or photo and include any existing drawing requirements, assembly photos or customer standards. HARVLAND can use that information to review suitable treatment options and agree the required result and inspection method with your team.
- Fit and wiring: show where parts touch and where cables pass through. Photos of a gap, snag or assembly problem can also help.
- Electrical contact: identify the area used for grounding or conduction. The supplier can propose the masking boundary for your team to confirm.
- Appearance: identify the faces visible after assembly and share a reference photo or sample if available. Inspection details can be agreed during the review.
Why does engineering also check dimensions after finishing?
Cutting clearance affects hole size and burr formation, while additional edge finishing can change a small feature. These are process details for the supplier to assess when recommending how to make the part. The buyer provides the functional requirements; the treatment and acceptance method are then agreed together. [1]
Finishing can also reduce a clearance. A deposited layer of thickness c on each of two opposing faces reduces their gap by approximately 2c, assuming both faces receive that thickness. Actual coverage and the resulting fit must be checked on the finished part.
Example: how to turn a bracket concern into a decision
Consider an illustrative steel mounting bracket made from 1.2 mm sheet, with a 1.0 mm hole, another locating hole near a bend and a powder-coated surface with a grounding contact. The question is what must be confirmed to price the intended part and verify its function.
For the small hole, ask the buyer whether its size is fixed by function. For the locating hole, check its final relationship to the mating face and compare the forming sequence. For the grounding contact, define the uncoated area. The example issue log below shows how to record those actions without treating every concern as a rejected design.
What closes a DFM issue before tooling and after sampling?
Before tooling starts, close the decisions needed to build the die: the approved drawing revision, accepted changes, selected process and inspection requirements. Some technical questions still need sample validation. Keep those listed as pending validation, with a check and approval owner, rather than marking them proven by a quotation.
After sampling, link the actual measurement or assembly result to its issue number, drawing revision, material and process. A sample made by a different route can help check fit, but it may not resolve a burr, springback or repeatability question for the intended production process.
- Give each issue an ID, a drawing location, an owner, a due date and a clear next action.
- Close a design decision with a revised drawing or written approval tied to that revision. A proposed change remains open until approved.
- Close a validation item with the agreed evidence: a dimension report, edge or finish check, or documented assembly result.
- List exclusions and open assumptions in the quotation. Keep quotation acceptance, tooling authorization and production approval as separate decisions.
| Issue | Why it matters | Next action | Who confirms | Status and closure evidence |
|---|---|---|---|---|
| D01 · Ø1.0 hole in 1.2 mm sheet | Small punch; edge quality and maintenance need review | Check if diameter can increase; assess the small-punch route if fixed | Buyer design engineer + tooling engineer | Open · approved diameter and selected route; sample hole check pending |
| D02 · Locating hole near bend | Forming may shift the final hole position | Define bend reference; compare hole movement with later piercing | Buyer design engineer + tooling engineer | Review required · approved feature/sequence; final hole-to-datum check pending |
| D03 · Flatness setup unspecified | Free and clamped measurements may disagree | Define supports, restraint and acceptance state | Buyer and supplier quality engineers | Clarification needed · agreed inspection instruction |
| D04 · Grounding area inside coated face | Coating may cover the electrical contact | Buyer marks the contact area; supplier proposes masking limits for approval | Buyer design engineer + finishing supplier | Can quote with conditions · written masking scope; sample coverage check pending |
| D05 · Model and drawing revisions differ | Tooling may be priced from the wrong geometry | Identify governing geometry and issue matching files | Buyer drawing owner | Clarification needed · aligned revision package |