Undercuts and Side Actions: What the Quote Assumes
The First Click Prices the Solid, Not the Wish
An undercut quote starts from the solid you upload. List each snap, port, and internal hook, say keep, redesign, or open to DFM, and mark show-face keep-outs. The first number prices the geometry. Review may add a slide or lifter later. A feature that blocks ejection is scope, not a surprise.
Read injection mold tooling cost for how side actions sit in the tooling line. This page only covers the quote assumption.
Undercut is geometry that will not release in the main pull
The STEP file is the assumption. The meeting note is not. An undercut is geometry that will not release in the main pull direction. The first click assumes the pull implied by the solid and any note you typed. It does not assume a slide you mentioned in a meeting.
Slide, lifter, or shut-off redesign are scope words
Side actions are the steel that releases an undercut: a slide for a side hole or a snap that opens outward, a lifter for some internal hooks, or a shut-off redesign that removes the undercut. This page does not publish adders for them. The honest move is to name the feature and say keep, redesign, or open to DFM.
A DFM flag is a note, not a refusal
A DFM flag is the quote catching up to geometry you already sent. Tell sourcing a flag on a snap is a decision, not a bait-and-switch. If they must keep the snap, write keep. If they can open the hook, write redesign and send a new revision. If they want the reviewer to pick, write open to DFM. Read design for manufacturing review for what follows a flag.
A worked example: a handheld housing has two side ports and a battery-door snap. The engineer uploads a STEP named housing_simple. The ports and snap are in the solid. Review then flags a slide at each port and a lifter or slide at the snap. That flag is not a new requirement invented after you clicked.
What the Quote Can and Cannot See
Modeled snaps and side holes are visible
Modeled snaps, side holes, internal hooks, and wrap-around lips are visible when they exist as solid faces. The engine reads those faces. A reviewer can point to them. That is the first-click set.
Email intent and markup PDFs are not in the solid
A note that says ports will be drilled later is not in the solid if the ports are already modeled. A note that says ignore the snap is not a delete. Export a solid that matches the intent, or write the intent on the RFQ in the same sentence as the feature name.
Ambiguous pull direction needs a show-face note
If the part could split two ways, the first click picks one. If you already chose a split because of a show face, write that show face and the keep-out. Otherwise review may pick the easier pull and place a witness where you cannot accept it.
A worked visibility example: the CAD has a rectangular side window. Marketing wants the window as an open port. The solid still has a thin wall across the window. The first click sees a closed wall, not a port. Cut the window in the solid or write that the wall is a to-be-removed shutoff and attach a screenshot.
Another miss: an internal hook modeled as a shallow groove. If you know it is a hook that must catch a lid, write internal hook, keep, Face 27. If it is only a styling groove, write groove, straight pull, witness allowed.
How to Write the RFQ So Scope Stays Honest
Census: list snaps, ports, hooks, side holes
Simple tool is not a scope word. Feature list is. Walk the part the way it will eject. Write each feature that cannot slide off in the main pull. If you are unsure, list it and mark open to DFM.
Decision per feature: keep, redesign, or open to DFM
Keep means the snap, port, or hook is required and a release path is in scope. Redesign means you will change the solid and re-quote. Open to DFM means the reviewer may propose a shut-off change or a mechanism, and you will decide on that note. Mixed decisions are normal. You can keep two ports and redesign one snap.
Cosmetic keep-outs near every release path
A keep snap with no keep-out leaves the witness line as a guess. A slide parting line on a show face is a witness. If that face is camera-facing, write no slide witness on Face A. For the face list pattern, read mark cosmetic vs functional faces.
Export the current solid if pull direction changed
If you already rotated the split or opened a hook, that is a new solid. Export it. A note that says we will add draft later is not the new solid.
A worked note: Ports at Face 8 and Face 9, keep, witness allowed on the hidden side. Battery snap at Face 14, keep, no witness on Face A show. Internal hook at Face 27, open to DFM. That block is honest. No sliders in the project title is not.
RFQ Paste Block
Use this list on the revision you upload. The list is the assumption the next reviewer will inherit.
- List snaps, ports, internal hooks, and side holes.
- Say keep, redesign, or open to DFM.
- Mark cosmetic keep-outs near those features.
- Export the current solid if you already changed pull direction.
- Upload CAD through the injection molding instant quote platform.
A worked submit block: Rev D housing. Pull from Face A. Ports Face 8 and 9 keep, witness allowed. Snap Face 14 keep, no witness on Face A. Hook Face 27 open to DFM. That is a complete undercut note. See drawing is not, unless the drawing is attached and the balloons match the solid.
For the file set around that note, read what to upload for a molding quote.
What to tell sourcing: send the census with the CAD. If a later DFM flag adds a slide, compare the flag to this list. If the feature was listed as keep, the flag is confirmation, not a surprise. If the feature was not listed, the next package should add it.
Common mistakes at submit:
- Uploading Rev C after you already opened the snap in Rev D.
- Writing open to DFM on a snap marketing already locked.
- Attaching a mechanism catalog and asking the quote to pick a brand of slide.
- Writing must be a simple tool next to a keep-all-snaps list.