The short answer
On hollow SLM RFQs, **escape holes** (drain or powder-evacuation holes) are not the same note as **lattice infill** or “print hollow to save mass.” A closed cavity traps unsintered powder; the buyer must say hole **size**, **location**, **count**, and whether holes stay open, get plugged, or are welded shut after evacuation. Silence on the drain path, on residual-powder allowance, and on whether a later CNC plug is in the pack, is what widens many [quote-new.php](https://3dwk.com/quote-new.php) **rates.v1.1** / powder estimate bands—not the wall cubic centimeters alone.
This guide is for buyers packaging AlSi10Mg RFQs where CAD shows a closed hollow fitting with no drain holes, or a notes cloud that says “remove powder as needed.” Illustrations use an **Example part** only—not a customer flight manifold. Sibling notes live in [lattice-infill notes for SLM structural parts](https://3dwk.com/resources/lattice-infill-notes-slm-structural-parts) and [powder-reuse notes for SLM buyers](https://3dwk.com/resources/powder-reuse-notes-slm-buyers); here we focus on **escape-hole packaging** so estimators do not guess a sealed cavity with no legal drain, or a 0.4 mm hole that cannot empty a 40 mm pocket.
What escape holes mean for quoting
**Escape holes** are designed openings that let loose powder leave a hollow or semi-hollow region after the build, often with a shake, blow, or vacuum step. **Lattices** are a different DFM family: they are intentionally open cells, not a closed skin with a hidden drain. A hollow with no legal path either ships with trapped powder (mass, rattle, and contamination risk) or forces the shop to invent holes. Process pages for aerospace aluminum powder ([SLM AlSi10Mg aerospace](https://3dwk.com/en/slm/alsi10mg/aerospace.html), [SLM AlSi10Mg](https://3dwk.com/en/slm/alsi10mg.html), [SLM Ti-6Al-4V aerospace](https://3dwk.com/en/slm/ti-6al-4v/aerospace.html)) assume cavity notes when lots mix solid bosses with hollow bodies.
Do not bury “hollow as CAD” inside a notes cloud. Put **TWO Ø4 ESCAPE HOLES ON FACE B, THROUGH TO CAVITY, POWDER MUST BE EMPTY TO BUYER WEIGH NOTE; HOLES LEFT OPEN UNLESS PLUG M3 IS NAMED** on the PDF and mirror it in RFQ text. Background: [SLM build orientation notes for buyers](https://3dwk.com/resources/slm-build-orientation-notes-for-buyers), [support-strategy notes for SLM thin walls](https://3dwk.com/resources/support-strategy-notes-slm-thin-walls).
Size, placement, and plug plan
Hole diameter has to pass powder and, if required, a plug or weld prep. A 1 mm cosmetic hole may not empty a long cavity; two Ø3–Ø5 holes at opposite ends of the pocket usually plan more cleanly. Placement should avoid thin walls, sealing faces, and support keep-outs, and should stay reachable after cut-off—see [build-plate removal notes for SLM parts](https://3dwk.com/resources/build-plate-removal-notes-slm-parts) and [SLM support removal and skim notes](https://3dwk.com/resources/slm-support-removal-and-skim-notes). If a later CNC thread or press plug is required, say the after-build operation and the finish state; hybrid notes live in [SLM vs CNC hybrid part strategies](https://3dwk.com/resources/slm-vs-cnc-hybrid-part-strategies).
AlSi10Mg powder and machine-time planning bands under **rates.v1.1** sit below titanium but still well above a simple wall-thickness story; trapped-powder risk and a plug operation are often the quote drivers.
Hollow skin versus lattice
Use a **named hollow + escape-hole pack** when you want a closed skin for fluid, appearance, or wipe-down, and you accept drain holes or plugs. Use a **lattice** when open cells are structurally acceptable and you do not need a sealed cavity. Promoting every mass-reduction request into a sealed hollow with no drains over-controls the job and can make the part un-evacuable. For most aerospace buyers, labeled drains (and a residual-powder mass or “empty” method) are clearer than “remove all powder.”
Tolerance and inspection traps
Calling “no trapped powder” without a hole, forbidding any witness on plug faces, mixing a 0.5 mm drain with a 50 mm blind pocket, or asking for 100% CT to prove emptiness on every cavity without a weigh or borescope method, all force **needs_manual**. Default non-critical skins to a general wall thickness and put functional seals only on faces that must stay closed. Related: [minimum wall CNC vs SLM](https://3dwk.com/resources/minimum-wall-cnc-vs-slm-for-buyers), [what files to send for a CNC quote](https://3dwk.com/resources/what-files-to-send-for-cnc-quote). Orientation of the drains relative to the build should sit next to the hole note, not in a separate unmarked chat.
Illustration 1 shows an **Example part** hollow fitting with two labeled escape holes at opposite ends of the cavity versus a sealed CAD body with no legal drain.
Example part walkthrough
**Example part:** AlSi10Mg SLM fitting ~60×35×28 mm, 2 mm nominal skin, one closed internal cavity ~40×18×12 mm, datum A on the flange. With STEP + **TWO Ø4 ESCAPE HOLES ON FACE B, THROUGH TO CAVITY, EMPTY BY WEIGH ±0.5 G VS SOLID MODEL MASS; HOLES LEFT OPEN; NO CT UNLESS NAMED**, expect a usable automatic planning band on [quote-new.php](https://3dwk.com/quote-new.php). Same geometry with silent CAD and “hollow, no holes, zero residual powder” often lands DFM notes or **needs_manual**—without inventing any customer PO.
Illustration 2 contrasts a vague RFQ (“remove powder as needed”) versus a labeled escape-hole pack and the clearer estimate path.
What widens bands fastest
Sealed hollows with no drain path, 0.5 mm holes on long pockets, “zero powder” with CT on every unit, and plug or weld-shut work mentioned only in email. Quantity breaks help unit minutes but do not erase an un-evacuable cavity—see [how quantity breaks change CNC unit cost](https://3dwk.com/resources/how-quantity-breaks-change-cnc-unit-cost) and [what needs_manual means](https://3dwk.com/resources/what-needs-manual-means-preliminary-quote).
What to do next
Mark **escape-hole size, count, and faces**, say open versus plugged, and name the residual-powder check, then upload on [quote-new.php](https://3dwk.com/quote-new.php). Service pages: [3D printing](https://3dwk.com/3d-printing-service.php), [materials](https://3dwk.com/materials.php). Treat **rates.v1.1** min/mid/max as estimates, not invoices. If the UI shows **needs_manual**, answer the escape-hole questions rather than forcing a fake firm price.
Common questions
Is a lattice always better than a hollow with drains?
Not as a silent default under **rates.v1.1** / powder estimates. Lattices evacuate naturally but change stiffness and cleanability. A closed skin with sized escape holes is the right pack when you need a wipe-down or a sealed look after plugging.
Can I write “remove all powder, no holes”?
Almost never for a truly closed cavity. Either add legal drains, open a face after the build, or accept a residual-powder allowance. “No holes, zero powder” is a common **needs_manual** trigger.
When should I plug the escape holes?
When the cavity must be closed in service (fluid, appearance, or contamination). Name the plug method (threaded, press, weld) and whether a flush witness is allowed.
Do escape holes change orientation notes?
They can. Drains that point down after cut-off empty more easily; holes hidden against the plate may stay packed. Put orientation and drain faces in the same pack.