Rerun DFMXpress after a change, but set your shop's limits first

Thu, 05 Nov 2026 · 7 min read · Written with an AI assistant

A design change can break a manufacturing rule on a feature nobody edited. DFMXpress will catch it, but only against the limits it has been given. Set those to your supplier's real limits, then compare violations before and after the change

A design change rarely touches only the feature it names. Thicken a plate by 20 mm and every hole through it gets deeper, even though nobody edited a hole, and the part that machined cleanly at the last revision may now need a longer drill or a second operation.

That is a manufacturability problem, and SOLIDWORKS already ships a tool for finding it. DFMXpress is an analysis tool that checks whether SOLIDWORKS parts can be manufactured, aimed at areas of a design that might cause problems in fabrication or raise production costs. The catch is in how it decides what a problem is. It checks against limits. If those limits are the defaults, a pass tells you very little about the shop that will cut the metal.

A small change can break a rule nobody touched

Most DFM violations introduced by a change are side effects. The engineer edits one parameter; the geometry downstream follows it. Some patterns worth recognising:

A deeper hole. A thicker section, or a hole extended to reach a new mating part, raises the depth-to-diameter ratio. The diameter did not change, so nobody looked at it.
A new or deeper pocket. Removing mass or clearing a new component often means a pocket that is deep relative to its width, which pushes the cutter further out of the holder.
A smaller corner radius. A slot widened to fit a new part, or a corner tightened to gain clearance, can end up sharper than any end mill that reaches that depth.
A hole moved towards an edge. Shorten a sheet metal flange and the holes in it are suddenly closer to the edge than the punch and the material will tolerate.
A thinner wall. On a moulded part, trimming wall thickness to save mass or make room can cross a minimum, or leave one wall much thicker than its neighbours.

None of these show up as a failed rebuild. The model is valid. The part is just harder or dearer to make.

What DFMXpress checks

The rules are grouped by process. The 2026 Help has a Rule Descriptions page for DFMXpress, so the tool is documented for the current release. The groups below come from a SOLIDWORKS tech tip on using DFMXpress, first published in 2020 and updated in 2025, so check the detail against your own version.

Drill rules: hole diameters, flat-bottomed holes, hole entry and exit surfaces, holes that cut into cavities, partial holes, linear and angular tolerances, and whether a hole matches a standard drill or punch size.
Mill rules: deep pockets and slots, features the tool cannot reach, sharp internal corners, and fillets on outside edges.
Turn rules: minimum corner radii and bore relief.
Sheet metal rules: hole diameter against sheet thickness, hole-to-edge distance, hole spacing, and bend radii.
Injection moulding: minimum and maximum wall thickness.

For a change review, map the changed features to these groups. A deepened hole belongs to the drill rules. A new pocket belongs to the mill rules. A moved sheet metal hole belongs to the hole-to-edge and spacing checks. That tells you which results to read closely and which are noise from features the change did not affect.

The defaults are not your shop’s limits

The important line in the tech tip is that the user sets the rules DFMXpress checks against, so it can enforce company standards for machining as well as general manufacturing guidelines. The same post’s worked example ran a machined part against the default Mill/Drill settings. That is fine for a demonstration. It is not fine for signing off a change.

Think about what each rule depends on in practice:

The standard drill size check only means something if the drill list matches the drills your supplier stocks.
The hole depth limit depends on the longest drill they run at that diameter, and whether they will gun drill at all.
The internal corner check depends on the smallest cutter they will run to the pocket depth you have drawn.
The bend radius check depends on their press brake tooling. The tech tip’s guideline is that for most materials the bend radius should be at least the material thickness. That is a reasonable starting point, but your supplier’s punch and die set decides.

So before you trust a pass, get the supplier’s real limits and set them in the rule parameters. Write down the values you used. A DFM result without its rule set is like a stress result without its load case.

Worked example: compare the violations, not the verdict

Take a hypothetical machined bracket. At revision B, the base plate is 20 mm thick with four 6 mm through holes for the mounting bolts. A field issue prompts revision C: the plate goes to 40 mm for stiffness. The engineer edits one dimension in the base extrude. The holes are still 6 mm and still through, so they look unchanged in the feature tree.

They are not unchanged. The depth-to-diameter ratio has gone from about 3.3 to about 6.7. Whether that fails depends entirely on the limit in the rule set, which is the point of the previous section. The same edit also deepened a lightening pocket cut from the opposite face.

Run DFMXpress on both revisions with the same supplier rule set, then compare rule by rule:

Rule set: supplier mill/drill limits (values recorded with the change)

Rule                       Rev B   Rev C
Hole depth-to-diameter       0       4    <- new
Deep pockets                 0       1    <- new
Sharp internal corners       1       1    existing, accepted at Rev B
Flat-bottomed holes          0       0

The counts are illustrative, but the pattern is the useful part. The overall verdict was “has violations” at both revisions, so a glance at the summary would miss the change. The diff shows two new problems, both caused by an edit to a different feature.

This is not unusual. In the tech tip’s own example, two holes broke the depth-to-diameter ratio rule, alongside sharp internal corners in a slot, a flat-bottomed hole, fillets on an outside edge and deep pockets. The sheet metal part in the same post failed mostly on hole-to-edge distance and standard hole size.

Each new violation then needs a disposition before the change moves on. For the holes, the options are familiar: drill from both faces, add a counterbore to shorten the drilled length, change the fastener, or accept a longer drill and its cost. For the pocket, reduce the depth or open up the width. Existing violations keep the disposition they were given last time. Anything that cannot be designed out goes to the supplier or the cost review with the DFMXpress report attached, so the conversation starts from named features rather than “the new part costs more”.

What this means for CAD and engineering tooling

Be clear about what a pass means. The Help overview describes DFMXpress as checking parts, and the tech tip calls it the “smaller brother” of DFMPro from HCL Technologies, included in every level of SOLIDWORKS. A pass means no rule in your set was broken. It does not mean the part is cheap, that the process choice is right, or that the supplier will quote what you expect. It supports the engineer’s manufacturability decision. It does not make it.

For tooling around a change, three habits follow:

Store the rule set with the result. Any automated check should state which limits it used.
Report the diff, not the verdict. New, removed and unchanged findings, per rule, between the released revision and the proposed one.
Make every new finding a decision. Each one gets a disposition from an engineer: fixed, accepted with reason, or sent to the supplier.

These are the principles we are building into AI-CAD, our engineering copilot for SOLIDWORKS, which is still a prototype. Its target workflow places verification, analysis, and cost and supplier review between the CAD change and the release package, with an engineer approving each decision. Whatever check runs at those stages, the engineer should see which limits it used and what changed since the last release.

DFMXpress costs nothing extra and takes a few minutes. The work is in the set-up: get your supplier’s limits into the rules once, keep them current, and run the check on both sides of every change. Then a pass means something. We will keep writing about the checks that sit between a CAD edit and a release; follow the journal, or get in touch if your shop handles this differently.