The short answer
On aluminum plate RFQs, **when to specify stress relief after CNC** is not the same decision as [when to specify heat treat after CNC](https://3dwk.com/resources/when-to-specify-heat-treat-after-cnc), [heat treating steel after machining](https://3dwk.com/resources/heat-treating-steel-after-cnc-machining), or a general flatness cloud. 6061-T6 is already tempered; a post-machine stress-relief note is a request to reduce residual stress from heavy stock removal—without quietly over-aging the temper. Silence on whether you want a thermal stress relief, a rough-then-finish sequence only, or just more finishing stock, is what widens many [quote-new.php](https://3dwk.com/quote-new.php) **rates.v1.1** estimate bands—not a furnace cycle alone.
This guide is for buyers packaging aluminum RFQs where CAD or a notes cloud says “stress relieve as needed” on a T6 plate with heavy pockets and a tight datum. Illustrations use an **Example part** only—not a customer automation plate. Sibling notes live in the generic heat-treat timing guide (hardening or temper changes) and the steel HT article; here we focus on **post-machine residual-stress packaging for aluminum** so estimators do not have to guess whether T6 properties must be kept.
What stress relief after CNC aluminum means for quoting
**Stress relief after CNC aluminum** is a sequence note: rough machine, optionally thermally or naturally stabilize, then finish datums. It is not a request to re-solution-treat or to “make it T6 again,” and a general heat-treat cloud on a 6061-T6 drawing often reads as a temper change. Process pages for automation aluminum ([CNC 3-axis Al 6061 automation](https://3dwk.com/en/cnc-3axis/al-6061/automation.html), [CNC turning Al 6061 automation](https://3dwk.com/en/cnc-turning/al-6061/automation.html), [CNC 5-axis Al 6061](https://3dwk.com/en/cnc-5axis/al-6061.html)) assume sequence and remaining-stock notes when lots mix heavy pocketed plates with tight flatness.
Do not bury “stress relieve if it warps” inside a notes cloud. Put **KEEP 6061-T6; ROUGH POCKETS, STRESS RELIEVE WITHOUT DROPPING TEMPER, THEN FINISH FACE A / BORE C; LEAVE 0.3 FINISH STOCK** on the PDF and mirror it in RFQ text. Background: [DFM checklist before an online CNC quote](https://3dwk.com/resources/dfm-checklist-before-online-cnc-quote), [what files to send for a CNC quote](https://3dwk.com/resources/what-files-to-send-for-cnc-quote), [how stock size changes a CNC quote](https://3dwk.com/resources/how-stock-size-changes-cnc-quote).
Heavy stock removal, plate versus billet, and movement
Residual stress shows up when a thick blank loses a lot of material on one side, or when pockets open a rolled or sawn plate. [Plate vs billet stock](https://3dwk.com/resources/plate-vs-billet-stock-cnc-aluminum) can change how a plate wants to move; it does not replace a written sequence. If you only need the shop to rough, rest, and finish—without a thermal cycle—write that. If you do want a thermal stress relief, say that the original temper must be retained and that any hardness or conductivity check, if required, is named. Do not invent a furnace recipe or a certificate.
Aluminum 6061 plate $/kg planning bands sit in the mid-commodity range under **rates.v1.1** material tables; material cost is rarely the stress-relief story—extra setups, finish stock, and a possible furnace step are.
When a stress-relief note is worth calling
Call it when a thin remaining web, a large one-sided pocket, or a tight [flatness or parallelism](https://3dwk.com/resources/flatness-vs-parallelism-callouts-cnc-plates) on a datum is likely to move after heavy roughing. Skip a blanket SR when stock removal is light, when the datum already has generous tolerance, or when you are actually asking for a different temper—that belongs on the [heat-treat after CNC](https://3dwk.com/resources/when-to-specify-heat-treat-after-cnc) path. [6061 vs 7075](https://3dwk.com/resources/6061-vs-7075-aluminum-for-machined-parts) still matters for strength, but it does not replace a sequence note.
Tolerance and inspection traps
Calling “stress relieve as needed,” mixing a tight face-A flatness with zero finish stock, or asking for 100% pre- and post-furnace CMM on every pocket, all force **needs_manual**. Default non-critical plates to a single finish pass and put a rough-finish (and optional SR) sequence only on datums that must stay put. Related: [ISO 2768 general tolerances on CNC RFQs](https://3dwk.com/resources/iso-2768-general-tolerances-cnc-rfq), [flatness, parallelism and perpendicularity](https://3dwk.com/resources/flatness-parallelism-perpendicularity-machined-parts).
Illustration 1 shows an **Example part** plate with labeled 0.3 mm finish stock on datum face A after a stress-relief or stabilize step versus a thin cosmetic pocket that is allowed to stay as-roughed.
Example part walkthrough
**Example part:** Aluminum 6061-T6 plate ~200 × 150 × 20 mm, deep one-sided pockets, keep T6, rough pockets then stress-relieve without dropping temper, finish face A and bore C with 0.3 mm stock left for the finish pass, ISO 2768-m general except a named flatness on A. With STEP + **KEEP 6061-T6; ROUGH, SR WITHOUT DROPPING TEMPER, FINISH FACE A / BORE C, 0.3 STOCK**, expect a usable automatic planning band on [quote-new.php](https://3dwk.com/quote-new.php). Same geometry with silent CAD and “stress relieve if it moves” often lands DFM notes or **needs_manual**—without inventing any customer PO.
Illustration 2 contrasts a vague RFQ (“stress relieve as needed, hold flatness”) versus a labeled sequence-and-stock pack and the clearer estimate path.
What widens bands fastest
Unlabeled SR on already-T6 material, zero finish stock on tight datums, thermal cycles that would over-age the temper, and 100% inspection before and after an unnamed furnace step. Quantity breaks help unit minutes but do not erase sequence ambiguity—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 whether you need a **keep-temper stress relief**, a rough-then-finish sequence only, and the finish stock on each datum, then upload on [quote-new.php](https://3dwk.com/quote-new.php). Service pages: [CNC machining](https://3dwk.com/cnc-machining-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 sequence questions rather than forcing a fake price.
Common questions
Does every pocketed 6061-T6 plate need stress relief?
No. Light pockets and generous flatness often machine in one finish path. SR or a rough-then-finish sequence is worth calling when one-sided stock removal is heavy and a datum must stay put.
Can I write “stress relieve as needed” and keep the T6 callout?
Only if you also say the temper must be retained and how much finish stock remains. A silent furnace note on a T6 drawing can be read as a temper change. Update the sequence so the shop and the estimate see the same intent.
Is this the same as heat treat after CNC?
No. [Heat treat after CNC](https://3dwk.com/resources/when-to-specify-heat-treat-after-cnc) is for changing or restoring a temper or hardness. This note is about residual stress from machining an already-tempered aluminum part. If you actually want a different temper, say so on the heat-treat path instead.
What if I only want the shop to rough, rest, and finish—no furnace?
Write that sequence and the finish stock, and omit a thermal stress-relief verb. Leaving “SR as needed” leaves the estimator guessing whether a furnace step is in the pack.