The short answer
For high-temperature electronics housings, **PEEK** and **aluminum 6061** are not drop-in substitutes on a CNC RFQ. PEEK buys chemical resistance, dielectric behavior, and continuous-use temperature headroom in polymer form; 6061 buys stiffness, thermal conductivity, and familiar chip-cutting economics. Silence on **which material family** and **why** is what widens many [quote-new.php](https://3dwk.com/quote-new.php) **rates.v1.1** estimate bands—not the envelope size alone.
This guide is for buyers packaging CNC housing RFQs where notes say “high-temp plastic or aluminum OK.” Illustrations use an **Example part** only—not a customer enclosure. ULTEM/PEI is omitted here because formal Batch1 pSEO inventory on 3dwk.com does not currently expose ULTEM combo pages; we compare **live** materials only. Related notes: [choosing engineering plastics PEEK POM nylon](https://3dwk.com/resources/choosing-engineering-plastics-peek-pom-nylon), [POM vs PEEK CNC functional prototypes](https://3dwk.com/resources/pom-vs-peek-cnc-functional-prototypes); here we focus on **PEEK vs aluminum labeling** for electronics-thermal housings.
What each material means for quoting
PEEK machines differently from soft acetals—feeds, tool wear, and chip control change the minute band. Aluminum 6061 is the default prismatic housing metal on many electronics-thermal pages ([CNC 3-axis PEEK electronics-thermal](https://3dwk.com/en/cnc-3axis/peek/electronics-thermal.html), [CNC 5-axis PEEK electronics-thermal](https://3dwk.com/en/cnc-5axis/peek/electronics-thermal.html), [CNC turning PEEK electronics-thermal](https://3dwk.com/en/cnc-turning/peek/electronics-thermal.html), plus [CNC 3-axis Al 6061 electronics-thermal](https://3dwk.com/en/cnc-3axis/al-6061/electronics-thermal.html)). Name the alloy/grade on the PDF: **PEEK (unfilled)** or **6061-T6**, not “high-temp plastic / Al OK.”
Do not bury material choice inside a vendor note cloud. Put the grade in the title block and RFQ text. Background: [DFM checklist before an online CNC quote](https://3dwk.com/resources/dfm-checklist-before-online-cnc-quote), [materials](https://3dwk.com/materials.php).
Temperature, conductivity and finish intent
If the housing must sink heat into a chassis, aluminum usually wins on conductivity; if the housing must isolate electrically or survive aggressive chemistry, PEEK may win. Anodize, chem-film, and paint notes apply to aluminum—not to PEEK—see [as-machined before Type II anodize](https://3dwk.com/resources/as-machined-before-type-ii-anodize) and [how anodize choice changes CNC RFQ cost](https://3dwk.com/resources/how-anodize-choice-changes-cnc-rfq-cost). For PEEK, say whether faces stay as-machined or need controlled Ra only.
Bar $/kg planning bands (estimates only): aluminum commodity vs engineering PEEK are different decades of cost; under **rates.v1.1** the material line and the machine-time coefficient both move. Saying “either OK” forces the wide band.
Wall thickness, threads and inserts
Thin PEEK walls and fine threads need different keep-outs than 6061. Helicoil/insert notes that assume aluminum confuse a PEEK path. Soft-jaw strategy also changes—see [soft jaws vs vise CNC production lots](https://3dwk.com/resources/soft-jaws-vs-vise-cnc-production-lots) and [how workholding changes CNC quote](https://3dwk.com/resources/how-workholding-changes-cnc-quote).
EMI, grounding and fastener strategy
Aluminum housings often double as EMI shells and ground paths; PEEK housings usually need separate shields or conductive coatings that must be named if required. Fastener torque and boss design differ—do not copy aluminum boss diameters onto PEEK without restating pull-out intent. If you need both dielectric walls and a grounded lid, say which components are PEEK and which are metal rather than leaving a dual-material cloud on one body.
Related process context for electronics-thermal aluminum also appears on [CNC 3-axis Al 6061 electronics-thermal](https://3dwk.com/en/cnc-3axis/al-6061/electronics-thermal.html); keep the RFQ to one primary body material so **rates.v1.1** planning does not fork.
Tolerance and inspection traps
Copying aluminum ±0.05 mm habits onto large PEEK faces without stating temperature of inspection invites disputes. Default non-critical envelope to ISO 2768-m and put functional tolerances only on connector lands and seal faces. Related: [surface roughness Ra for machined parts](https://3dwk.com/resources/surface-roughness-ra-for-machined-parts), [GD&T callouts that raise CNC quote bands](https://3dwk.com/resources/gdandt-callouts-that-raise-cnc-quote-bands).
Illustration 1 shows an **Example part** housing envelope labeled PEEK path versus 6061 path with finish keep-outs.
Example part walkthrough
**Example part:** ~100×70×25 mm electronics housing, connector cutouts, internal boss pattern, ISO 2768-m general. With STEP + **MATERIAL PEEK UNFILLED; NO ANODIZE; RA 3.2 GENERAL / 1.6 CONNECTOR LANDS**, expect a usable polymer planning band on [quote-new.php](https://3dwk.com/quote-new.php). Same geometry with **6061-T6 + TYPE II CLEAR ANODIZE + MASK CONNECTOR LANDS** is a different finish pack—not a silent “either.” Vague “high-temp plastic or aluminum” often lands **needs_manual**—without inventing any customer PO.
Illustration 2 contrasts a vague dual-material RFQ versus a single-grade pack and the clearer estimate path.
What widens bands fastest
“PEEK or ULTEM or Al OK,” missing fill grade, aluminum finish notes left on a polymer drawing, and ultra-fine Ra all-over on PEEK. Quantity breaks help unit minutes but do not erase material ambiguity—see [what needs_manual means](https://3dwk.com/resources/what-needs-manual-means-preliminary-quote) and [prototype vs production CNC quotes](https://3dwk.com/resources/prototype-vs-production-cnc-quotes).
What to do next
Pick **one** live grade (PEEK or 6061-T6), attach finish/mask only where it applies, 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.
Common questions
Why not compare ULTEM here?
Formal EN Batch1 pSEO pages currently inventory PEEK and POM plastics prominently; this guide only links materials that curl to HTTP 200 on 3dwk.com. If you need PEI/ULTEM, name the exact grade in RFQ text and expect manual review.
Is PEEK always more expensive than 6061?
Material $/kg usually yes; total **rates.v1.1** estimate also depends on cycle time, tool wear, and finish. Do not assume without a packaged RFQ.
Can POM replace PEEK for “high-temp”?
Often no for continuous high-temp duty. POM is a different trade—see [POM vs PEEK CNC functional prototypes](https://3dwk.com/resources/pom-vs-peek-cnc-functional-prototypes).
Do anodize notes belong on PEEK drawings?
No. Keep aluminum finish packs on aluminum RFQs only.