9.3 Editing, Rollback & Parent-Child

9.3 Editing, Rollback & Parent-Child

Quick Answer: CSWA advanced items expect you to edit an existing model—not rebuild from zero. Use Edit Sketch / Edit Feature, the rollback bar for mid-tree work, and parent-child awareness to fix dangling relations. When mass is wrong after a change, run a fixed checklist: units → material → rebuild errors → missed features/patterns → end conditions → dimensions/relations—not random redraws.

Building a clean first-pass model is only half of intermediate and advanced part scoring. Many prompts ask for an initial mass, then modify a key dimension (thickness, length, hole diameter, offset, fillet radius) and report a second value. Candidates who only know “draw forward” lose points when Edit Sketch feels slower than starting over—and starting over under a time box is how you fail assemblies later in the exam.

Edit Sketch vs Edit Feature

Workflow for a modification prompt:

1. Identify whether the changed value lives in a sketch or a feature dialog.
2. Edit the correct object; type the new value with correct units.
3. Exit sketch / OK feature.
4. Rebuild (Ctrl+B / Ctrl+Q as needed) until the tree is clean.
5. Confirm no new errors; visual check.
6. Mass Properties again—do not reuse the previous number from memory or a sticky dialog.

Editing the wrong object is common: changing a sketch vertical line when the thickness is really Extrude Blind depth, or editing a cosmetic fillet when the problem changed a cut depth.

Rollback bar — mid-tree insert and diagnosis

The rollback bar in the FeatureManager moves the “present” state of the model to just after a selected feature. Features below the bar are rolled back (not in the current solid).

Uses on CSWA:

1. Insert a missing feature in the right order — e.g., you forgot a cut before a pattern. Roll to after the seed face exists, add the cut, roll forward, retie the pattern if needed.
2. Diagnose failures — roll just before a red feature; inspect parents; fix; roll to end.
3. Avoid children while editing a parent face — temporary rollback can make selection clearer (practice this before exam day).

Exam caution: Leaving the model rolled back while measuring mass reports an incomplete solid—mass will be wrong. Always roll to the end of the tree before Mass Properties for a final answer.

Parent-child relationships

Every sketch on a face, convert on an edge, pattern of a feature, and fillet of an edge creates a child that depends on a parent. When you edit or delete parents, children must update or they fail.

Healthy design intent

• Sketches on planes (Front/Top/Right or stable reference planes) survive face deletion better than sketches on faces that later get cut away.
• Up To Surface cuts/bosses track faces that still exist after size changes.
• Through All holes survive thickness edits.
• Offset from converted edges tracks perimeter changes.

Unhealthy links

• Sketch on a face that a later cut completely removes.
• Fillet on an edge that a later chamfer or cut eliminates—order problem (see 9.1).
• Pattern instances counted from a seed you deleted and replaced instead of edited.

Dangling relations

A dangling relation or dimension points to geometry that no longer exists (edge ID lost, face replaced). Sketch geometry may turn a dangling color/indicator; External References show broken links.

Repair pattern:

1. Edit Sketch / Edit Feature showing the error.
2. Delete the dangling relation or use replace/reattach tools when available.
3. Recreate the relation to current valid geometry (same design intent).
4. Fully define again; rebuild.

Do not stack a second extrude “to fix mass” on top of a broken sketch—tree debt multiplies under the next modification.

Freeze vs rebuild (practical exam view)

SOLIDWORKS offers rebuild tools and, in some releases/workflows, Freeze bar capabilities that lock early features from rebuilding to save time on huge models.

For CSWA-sized parts:

• Prefer a full rebuild after edits so mass reflects current geometry.
• Do not leave features frozen/suppressed if they belong in the graded solid.
• If a feature is suppressed for diagnosis, unsuppress before the scored measurement.
• Ctrl+Q (force rebuild) helps when a lightweight or deferred update leaves graphics looking updated but Mass Properties still off—rare but worth one try if values look stale.

Freeze is a performance tool, not a substitute for correct parents. Rebuild commits the parametric result; freeze postpones work on locked history.

Strategy when mass is wrong after modification

Use this ladder in order. Random undo/redo wastes the time box.

1. Units

Confirm Document Properties → Units still match the problem (often MMGS, g, mm). A dimension typed as 10 in IPS while the sheet is mm—or vice versa—orders-of-magnitude mass errors. Modification steps sometimes reopen files or templates; re-check units if the number is absurd.

2. Material

Mass = density × volume. Wrong material (or no material with default density assumptions) fails even with perfect geometry. Re-apply the specified alloy; confirm density in Mass Properties options if the problem states a custom density.

3. Rebuild errors and warnings

Red/X features mean the solid is not what you think. Yellow warnings can still change edges. Expand the tree; fix top-most error first (parents before children).

4. Missed or suppressed features

Compare FeatureManager to the drawing checklist: every cut, pattern instance count, mirror, fillet radius. A suppressed pattern or forgotten second mirror leaves mass high.

5. End conditions

After thickness changes, Blind holes that should be Through All leave plugs. Pockets accidentally Through All remove floors. Up To Surface references may have been lost—edit feature and reselect faces.

6. Dimensions and floating/dangling sketch state

• Did you edit the dimension the problem named, or a look-alike on another feature?
• Is the sketch still fully defined?
• Did a floating profile shift off midplane and change CoM even when volume looks “close”?
• Did offset side flip during an edit?

7. Section and measure

Insert a temporary section view or use Measure on a critical thickness/hole. If geometry is wrong, mass cannot be right.

8. Last resorts

Rollback and rebuild a single failed branch; replace a hopeless sketch while keeping downstream features if possible; only full rebuild from scratch if the tree is irretrievably corrupted and time remains—usually a sign to move on and return if points allow.

Parent-child debugging table

Multi-step item discipline

Advanced part questions often: build → answer1 → modify → answer2.

• Save mental (or on-paper) note of which feature holds answer1’s critical dims so answer2 is a one-edit change.
• Do not “clean up” by deleting history between answers unless required—you need the parametric path.
• After answer2, ensure you did not accidentally leave an extra test cut or suppressed fillet from debugging.

Worked modification scenario

Model correct: base 10 mm, offset pocket wall 3 mm, four patterned Through All holes Ø6, R2 fillets last, material set, mass1 accepted.

Prompt: change base to 12 mm, holes to Ø8, wall to 4 mm.

1. Edit Feature base extrude → 12 mm; rebuild.
2. Edit hole seed sketch → Ø8; pattern updates; rebuild.
3. Edit pocket sketch offset → 4 mm; rebuild.
4. Fillets rebuild on existing edges; if an edge failed, reselect.
5. Confirm not rolled back; material still Aluminum; Mass Properties → mass2.

If mass2 is high: check each hole still Through All at 12 mm thickness; check pattern still 4 instances; check offset side still inward.

If mass2 is low: check pocket not Through All; check fillet radii not accidentally increased; check no extra cut added while editing.

Exam habits that prevent tree disasters

1. Fully define sketches before features.
2. Prefer plane-based sketches for profiles that outlive faces.
3. Edit instead of delete-and-recreate when a child depends on the feature.
4. Roll to end before every scored mass read.
5. Fix errors top-down.
6. Use the mass-wrong ladder once—methodically—before panic redraw.

Editing, rollback, and parent-child fluency turn the hardest CSWA part category into controlled updates. Combined with construction order (9.1) and offset/complex profiles (9.2), you can deliver both initial and modified masses inside the advanced-part time budget and protect the larger assembly share of the exam.