DFM Checklist for Indian Manufacturing: Catch These Issues Before Tooling, explained simply.
DFM is what separates a part that releases on schedule from a part that bounces between design and tooling for three months. This is the checklist we run on every CAD before recommending it to an Indian vendor.
Core idea
What this blog covers
Indian vendors will quote your CAD and accept the order even if the part has DFM issues — they'll figure it out at the tool stage and bill you for changes. By then you've burned weeks of timeline and lakhs of rework. A 4-hour DFM review before vendor handoff prevents almost all of this.
Main discussion
Injection molding DFM checklist
(1) Draft angles — minimum 0.5° on all walls, 1° preferred, 2° on textured surfaces. Without draft, the part can't release from the mold. (2) Parting line — choose it deliberately, not by accident. Place where flash will be hidden. (3) Wall thickness — uniform, typically 1.5-3 mm. Variation causes sink marks and warpage. (4) Ribs — height ≤ 3x wall thickness, thickness ≤ 0.6x wall thickness. Otherwise sink. (5) Undercuts — eliminate or design slides / lifters into the mold. Each adds significantly to tooling cost. Catch these in pre-tooling DFM and tooling cost stays manageable.
Sheet metal DFM checklist
(1) K-factor matched to the vendor's press brake. (2) Bend radius matches available V-dies (6, 10, 16, 22 mm common). (3) Minimum flange length — typically 4x material thickness, otherwise the flange can't be held during bending. (4) Hole-to-bend distance — minimum 2.5x material thickness from the edge of a hole to the start of the bend, otherwise the hole deforms. (5) Bend reliefs — included on intersecting bends to prevent material tearing. (6) Material grade and finish specified explicitly.
CNC machining DFM checklist
(1) Tool access — every machined feature has to be reachable by a tool. Deep narrow pockets are expensive (long endmills) or impossible. (2) Internal radii — minimum 2x the cutting tool radius, typically 3 mm or 6 mm. Sharp internal corners aren't machinable. (3) Tolerance stacks — don't over-specify. ±0.025 mm tolerance is 4x more expensive than ±0.1 mm. Reserve tight tolerances for surfaces that actually need them. (4) Threads — specify standard (M3, M4, M5 etc.), not exotic. (5) Surface finish — specify Ra value (e.g. Ra 1.6 µm) not 'smooth' or 'polished'.
3D printing DFM checklist
(1) Wall thickness — minimum 1.2 mm for FDM load-bearing, 0.6 mm for SLA structural. (2) Overhangs — keep below 45° from vertical or design as supportable. (3) Print orientation — tell the bureau which face needs the strongest layer adhesion. (4) Hole sizes — design 0.2-0.4 mm oversize on FDM to compensate for melt flow. (5) Wall-and-infill thickness consistent across the part — variations cause warping. (6) Heat-set inserts vs printed threads — printed threads strip; specify inserts for any threaded interface that mates more than once.
Tolerance stacking and assembly fits
Across all manufacturing processes, the most expensive DFM mistake is over-specified tolerance stacks. A part with five tolerance dimensions, each at ±0.05 mm, ends up with worst-case assembly tolerance of ±0.25 mm — and a manufacturing cost that's 5-10x higher than necessary. Audit every tolerance: 'does this dimension actually need to be this tight?' Loosen everything that doesn't need to be tight.
How we run DFM review at Yantrix
Every CAD project we deliver gets a DFM review pass before final handoff. Output is a one-page report with annotated CAD screenshots, specific issues flagged, and fix recommendations. For client-supplied CAD, we offer DFM review as a standalone service — typically ₹15,000-50,000 for a complete product review depending on part count and complexity. Send us the CAD and target manufacturing process; we'll come back with the DFM report within 3-5 business days.
Key takeaways
What readers should remember
- Injection molding: draft, parting line, wall thickness, ribs, and undercuts are the top-five issues.
- Sheet metal: K-factor, bend radius, minimum flange length, and hole-to-bend distance.
- CNC: tool access, internal radii, deep pockets, and tolerance stacks.
- 3D printing: wall thickness, overhang angles, support strategy, and print orientation.
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