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BUILT BY AUTONOMOUS SYSTEMS · WORK IN PROGRESS

Fabrication rules and prices for gyropup

Checked 2026-10-25. Every number has a source tag like [B1]. The sources are listed at the end. If a value was not published or could not be fetched, it says so. Values we calculated ourselves are marked derived or estimate, and their inputs are shown. The machine-readable version is catalog/fabrication.json.

Plan of record: gyropup is mostly 3D printed. The first build is PLA on the Bambu P1S. Later builds move to carbon-fibre-filled filament on an upgraded or newer Bambu printer. SendCutSend metal and CF tubes are optional upgrades for single parts. This report follows that order: printing first, upgrades after.


1. Rules the designer should apply

1.1 Printed parts (default)

  1. Orient leg links flat, so bending stress runs along the layers. In CNC Kitchen's test, PLA printed upright reached 31 MPa against 63 MPa printed flat, about 50%. Printing at 45° gave 40 MPa [K5]. Bambu's datasheets give the Z-to-XY tensile ratio as 0.89 for PLA Basic, 0.47 for PET-CF and 0.34 for PPA-CF (derived from [B1][B11][B14]). So the CF filaments are much weaker across layers than plain PLA.

  2. Stress allowables for PLA. Ezeh & Susmel suggest a conservative static reference strength of 22 MPa. They also give a fatigue limit at 2×10⁶ cycles of 10% of UTS (90% survival), with an S-N inverse slope of 5.5 [P1]. For PLA Basic (35 MPa XY [B1]), the cyclic stress limit is therefore 3.5 MPa (derived).

  3. Heat. PLA Basic softens at 54 °C (HDT at 1.8 MPa), with a Vicat temperature of 57 °C and Tg of 60 °C [B1]. In a loaded oven test, PLA started to give at 60 °C, PETG at 80 °C and ASA at 110 °C [K1]. No PLA part should touch a motor housing unless the housing temperature has been measured well below 54 °C. On a stock P1S, the fallbacks are:

    • PETG (HDT 68 °C [B5])
    • ASA (92 °C [B8])
    • annealed Polymaker HT-PLA Pro (HDT at 0.45 MPa rises from 56.3 to 107.6 °C after 30 min at 100 °C; no hardened nozzle or enclosure needed) [M3]

    We did not research motor temperatures.

  4. Fill the outer skin first. Bending and torsion loads are carried at the outside of a part. Gradient (outer-dense) infill was about 30% stiffer at equal weight [K2]. In tension-tension fatigue, 100% infill lasted 43,406 cycles against 28,325 at 50% infill, and its modulus was 2553 MPa against 2004 MPa [P2]. No cited source gives a wall count, so pick one by test.

  5. Threads in printed parts: use heat-set inserts.

    • M3 hole: 4.0 mm nominal if drilled. For an as-printed PLA hole, 4.2 mm worked best, because printed holes come out about 0.25 mm undersize [K6].
    • Pull-out strength is about 1400 N per M3 insert [K6].
    • Iron temperature is about 225 °C for PLA and 245 °C for PETG.
    • Make blind holes about 1 mm deeper than the insert [K7].
    • In PETG, torque-out was 3 Nm with an insert against 1 Nm for a screw driven straight into the plastic [K8].
  6. Pivots: use bearings in printed seats, with a shoulder bolt as the shaft. A printed hole should never act as the bearing surface. This is the Stanford Doggo five-bar pattern: two deep-groove bearings stacked in one link, with a shoulder bolt through them into the opposing link [D1]. Size the seats from a printed test coupon, then correct with Bambu Studio's XY hole compensation [B20]. Bambu publishes no press-fit allowance.

  7. CF-filled filament needs a hardened steel nozzle. Use 0.6 mm as the first choice. A 0.4 mm hardened nozzle is fine for Bambu PLA-CF and PETG-CF. Never use 0.2 mm [B19]. A P1S stainless nozzle showed visible wear after 10 h of PETG-CF [B21].

    • PA, PC, ABS and ASA, and their CF/GF versions, need an enclosed printer.
    • PLA, PETG and TPU print fine on an open frame. An enclosure is recommended for PETG [B19].
  8. Rescaling a part to another material (rectangular section, width fixed; table in §2.3). The new thickness is the larger of:

    • t_new = t_PLA·(E_PLA/E_new)^(1/3) for equal stiffness
    • t_new = t_PLA·(σ_PLA/σ_new)^(1/2) for equal strength

1.2 Metal and CF upgrades (optional)

1.3 Price model for the guide


2. 3D printing (primary path)

2.1 Printers and what each can print

Printer Price (US store) Build (mm) Stock nozzle Max nozzle Chamber CF filament? Src
P1S (current) $399; AMS Combo $549; AMS 2 Pro Combo $579 256×256×256 0.4 mm stainless 300 °C enclosed, passive (regulator fan, no heater) Not out of the box. Bambu: "not recommended… before an extruder and hotend upgrade" [B16]
P1S upgrade Hardened Steel Upgrade Combo $49.48 (0.4 hardened hotend + hardened extruder gears) – hardened 0.4/0.6/0.8 complete hotend $34.99 each (hotend only $14.99); gear assembly $19.99 320 °C (hardened hotend, retailer listing) – yes, PLA-CF/PETG-CF/PET-CF/PA-CF [B17][B18][B21][R1]
P2S $549; Combo $749 256×256×256 hardened nozzle and extruder gears n/p enclosed, no active heat, "50 °C chamber ready" yes [B22]
X2D $649; AMS Combo $899 n/p n/p on store page 300 °C 65 °C active heating, dual nozzle n/p [B23]
H2S $1,199; AMS Combo $1,399 340×320×340 n/p on store page 350 °C 65 °C active heating n/p [B24]
H2D $1,549–1,749 (two "standard" listings) 325×320×325 hardened 0.4 mm, hardened gear 350 °C 65 °C active heating, dual nozzle yes [B25]
H2C $2,199–2,499 330×320×325 0.4/0.6 hardened hotends 350 °C 65 °C active heating yes [B26]
X1C / X1E not sold new in the US store sitemap; refurbished X1C Combo $649 – – – – – [B27]

n/p = not published on the page we fetched.

Chamber temperatures from Bambu's datasheets:

Material Chamber Src
PET-CF, PA6-CF, PAHT-CF 45–60 °C [B11][B12][B13]
PPA-CF 50–80 °C [B14]
PPS-CF H2 series and X1E only [B19]

So: a P1S with the $49.48 combo, plus a $34.99 0.6 mm hardened hotend, can print PLA-CF, PETG-CF and (passively warmed) PET-CF and PA-CF. PPA-CF wants a heated-chamber machine (X2D, H2S, H2D or H2C).

2.2 Filament properties and prices

All values come from Bambu datasheets [B1–B15]: 100% infill printed specimens, ISO 527/178/75. Prices are from the Bambu US store on 2026-10-25, per kg, refill price where sold, otherwise the spool price [B1s–B15s].

Filament $/kg ρ g/cm³ Tensile XY / Z MPa E (tensile XY) GPa Flex mod XY GPa Flex str XY / Z MPa HDT 1.8 MPa °C Hardened nozzle Enclosure Src
PLA Basic 14.99 (spool 17.99) 1.24 35 / 31 2.58 2.75 76 / 59 54 no no [B1]
PLA Matte 15.99 1.31 30 / 22 1.96 2.36 53 / 29 52 no no [B2]
PLA Tough+ 20.99 1.21 34.9 / 20.9 1.86 2.14 65 / 54 58 no no [B3]
PLA-CF 31.99 1.22 38 / 26 2.79 3.95 89 / 49 54 yes no [B4]
PETG Basic 13.99 1.25 51 / 35 2.78 1.95 75 / 56 68 no recommended [B5]
PETG HF 15.99 1.28 34 / 23 1.81 2.05 64 / 48 62 no recommended [B6]
PETG-CF 31.99 1.25 35 / 29 2.46 2.91 70 / 48 68 yes recommended [B7]
ASA 29.99 (spool) 1.05 37 / 31 2.45 1.92 65 / 40 92 no yes [B8]
ABS 15.99 1.05 33 / 28 2.20 1.88 62 / 39 84 no yes [B9]
PC 39.99 (spool) 1.20 62 / 56 2.11 2.31 108 / 55 117 no yes [B10]
PET-CF 84.99 (0.5 kg $44.99) 1.29 74 / 35 4.73 5.32 131 / 49 182 yes yes [B11]
PA6-CF 79.99 (0.5 kg $42.99) 1.09 102 / 48 4.43 5.46 151 / 80 164 yes yes [B12]
PAHT-CF 94.99 (0.5 kg $49.99) 1.06 92 / 47 3.86 4.23 125 / 61 170 yes yes [B13]
PPA-CF 199.99 (derived: $149.99 per 0.75 kg) 1.25 168 / 57 11.8 9.86 208 / 63 196 yes yes, 50–80 °C chamber [B14]

Hardened-nozzle and enclosure columns are from [B19].

Two things to note:

TPU for tyres and bumpers [B15][B28][B29]:

TPU $/kg ρ Tensile XY / Z MPa E XY MPa Elongation XY Notes
TPU 95A HF 41.99 1.22 27.3 / 22.3 9.8 >650% tyre tread candidate
TPU 90A 41.99–44.99 1.24 12.5 / 10.1 5.3 >650% softer, grippier
TPU 85A 41.99–44.99 1.18 12.0 / 10.5 6.8 >700% softest
TPU for AMS (68D) 34.99 1.26 22.4 / 11.2 1190 >650% stiff; bumpers, not tyres

The 85A/90A/95A grades are not AMS-compatible; feed them from an external spool [B19].

Third-party filament prices, US stores on 2026-10-25:

Filament Price Notes Src
Polymaker PolyLite PLA $19.99/kg (3 kg $49.99) [M1]
Polymaker PolyLite PLA Pro $23.99/kg [M2]
Polymaker HT-PLA Pro $24.99/kg [M3]
Polymaker Fiberon PET-CF17 $44.99/kg [M4]
Polymaker Fiberon PA6-CF20 $52.99/kg product page claims 109 MPa and over 8.6 GPa XY [M5]
eSUN PLA+ about $20.99/kg third-party Amazon seller, 2026-08-01; no official price found [E1]

eSUN's published tensile figures conflict: 63 MPa on an eSUN-affiliated page against 53.3 MPa XY / 31.2 MPa Z at a retailer. The official datasheet was not retrieved.

PLA+ is not simply better than PLA. In CNC Kitchen's test, PolyMax PLA+ against PolyLite PLA gave 43 vs 57 MPa tensile and about 2200 vs 3000 MPa stiffness, with about 4× the impact toughness and the same 65 °C failure [K3]. Annealing PLA (100 °C, 45 min) added 7.5% tensile but shrank the part up to 10% in XY [K9]. Don't anneal precision PLA parts.

2.3 Material ladder: thickness factors for the designer (derived)

Inputs are the XY flexural modulus and strength from §2.2 [B1–B14], with standard beam formulas. Factors are relative to a PLA Basic part of the same width. "Mass" uses the governing thickness, which is the larger of the stiffness and strength factors. "Cost" means filament cost.

Material E ratio σ ratio Z-σ ratio t for equal stiffness t for equal strength t for equal Z strength Mass × Cost × HDT °C
PLA Basic 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 54
PLA Tough+ 0.78 0.86 0.67 1.09 1.08 1.22 1.06 1.49 58
PLA-CF 1.44 1.17 0.84 0.89 0.92 1.09 0.91 1.94 54
PETG Basic 0.71 0.99 1.13 1.12 1.01 0.94 1.13 1.06 68
PETG HF 0.75 0.84 0.74 1.10 1.09 1.16 1.14 1.21 62
PETG-CF 1.06 0.92 0.94 0.98 1.04 1.03 1.05 2.24 68
ASA 0.70 0.86 1.00 1.13 1.08 1.00 0.95 1.91 92
PET-CF 1.93 1.72 1.13 0.80 0.76 0.94 0.83 4.73 182
PA6-CF 1.99 1.99 1.55 0.80 0.71 0.80 0.70 3.73 164
PAHT-CF 1.54 1.64 1.52 0.87 0.78 0.81 0.74 4.69 170
PPA-CF 3.59 2.74 1.84 0.65 0.60 0.74 0.66 8.79 196

Recommended ladder for gyropup:

  1. PLA Basic. Cheapest; for parts away from motors.
  2. PETG Basic. Same price, +14 °C HDT. Make parts 12% thicker for equal stiffness.
  3. PETG-CF or PLA-CF on a P1S with the hardened combo. About the same stiffness as PLA, but PETG-CF has HDT 68 °C.
  4. PET-CF or PA6-CF. About 20–29% thinner and 17–30% lighter than PLA, at 3.7–4.7× the filament cost. HDT 164–182 °C, so these can sit next to motors.
    • PA6-CF has to be dried. It should also be annealed: un-annealed PA6-CF bolted joints crept and needed re-tightening almost daily; 8 h at 110 °C fixed it [K4].
    • PET-CF absorbs far less water: saturated absorption at 25 °C / 55% RH is 0.37%, against 2.35% for PA6-CF and 0.88% for PAHT-CF [B11][B12][B13]. That makes PET-CF the low-maintenance step up.

Caveat: datasheet specimens are 100% infill and dried or annealed. Real parts with walls and infill are weaker, so keep the safety factor from rule 1.1.2.

2.4 Structural PLA details

Creep

Fatigue

Layer orientation

Inserts

Bearing seats


3. Carbon-fibre tubes and plates (optional upgrade)

3.1 Tube prices

$/m is derived as list price ÷ length.

Seller OD×ID mm Type List $/m Mass g/m E GPa Src
Easy Composites (UK) 16×14 roll-wrapped (UD + 3k twill) £17.35/m ex VAT £17.35 (qty breaks £15.60/£13.90) 74.2 64 [C2]
Easy Composites 20×18 roll-wrapped £20.40/m ex VAT £20.40 (£18.35/£16.35) 86.5 64 [C1]
Easy Composites 25×22 roll-wrapped £33.65/m ex VAT £33.65 (£30.30/£26.95) 168.5 64 [C3]
Easy Composites 12×10 pultruded UD £12.50/m £12.50 n/p 28–40 [C4]
Rock West 17.96×15.88 roll-wrapped fabric $78.99 / 1.829 m $43.19 n/p n/p [C5]
Rock West 21.74×19.05 roll-wrapped std-mod twill (INFINITube V size 04) $129.99 / 1.880 m $69.15 n/p n/p [C6]
Rock West 24.31×22.23 roll-wrapped fabric $106.99 / 1.829 m $58.50 n/p n/p [C7]
Rock West 25.60×23.83 roll-wrapped fabric $98.99 / 1.524 m $64.95 n/p n/p [C8]
Rock West 18.03×15.88 roll-wrapped unidirectional $69.99 / 1.829 m $38.27 n/p n/p [C9]
Rock West 12×9.8 pultruded UD $40.99 / 1.829 m $22.41 n/p n/p [C10]
CarbonFiberTubeShop 17.78×15.88 roll-wrapped uni (SM7072U) $67.70 / 1.829 m $37.02 n/p n/p [C11]
CarbonFiberTubeShop 20.96×19.05 roll-wrapped uni (ME8272U) $75.61 / 1.829 m $41.34 n/p n/p [C12]
CarbonFiberTubeShop 25.27×22.23 roll-wrapped uni (ME9972U) $117.07 / 1.829 m $64.01 n/p n/p [C12]
DragonPlate – – not retrieved – – – –

Pultruded vs roll-wrapped. The largest pultruded round tube offered is 12 mm OD at both Easy Composites and Rock West [C4][C10]. Pultruded tubes give the most longitudinal strength but are "more vulnerable to crushing or torsional fracture". Roll-wrapped tubes are more resilient to crush and twist [C13].

Leg-sized tubes (16–25 mm) are therefore roll-wrapped. They cost $37–69/m in the US, or £17–34/m ex VAT from the UK.

Easy Composites roll-wrapped tubes:

3.2 20 mm CF tube against aluminium (derived, beam theory)

Tube EI N·m² Moment limit N·m Mass g/m Inputs
CF 20×18 roll-wrapped 172.9 175.6 (tension-based upper bound) 86.5 E 64 GPa, 650 MPa [C1]
Al 6061-T6 20×18 186.2 74.5 (yield) 161.1 E 68.9 GPa (10 Msi) [C14]; yield about 40 ksi; 0.0975 lb/in³ [S5]
Al 6061-T6 20×16 319.7 127.9 305.2 same
CF 16×14 85.2 108.2 74.2 [C2]
CF 25×22 491.2 399.1 168.5 [C3]
PLA Basic solid Ø20 rod 21.6 59.7 389.6 2.75 GPa, 76 MPa, 1.24 g/cm³ [B1]

A same-size CF tube is about as stiff as aluminium, at about half the mass. The CF moment limit is calculated from tensile strength, so it is an upper bound. In practice, crushing at the clamps and the bond fail first.

A solid printed PLA rod is about 8× less stiff than the CF tube and 4.5× heavier. Tubes pay off on the long links.

3.3 Joining CF tubes

3.4 CF plates


4. SendCutSend (optional upgrade)

4.1 Materials relevant to robots

Thicknesses are from the materials page [S8] and the quoter JSON [S1].

Material Process Thicknesses (in) Bend Density g/cm³
5052-H32 Al fiber laser .040 .063 .080 .090 .100 .125 .187 .250 .313 .375 .500 yes, ≤ .250 2.685 (0.097 lb/in³) [S4]
6061-T6 Al fiber laser .040 .063 .080 .100 .125 .187 .250 .313 .375 .500 .625 .750 no 2.699 (0.0975 lb/in³) [S5]
7075-T6 Al fiber laser .125 .190 .250 no 2.796 (0.101 lb/in³) [S9]
Mild steel A36/1008 fiber laser .030–.500 (12 sizes) yes, ≤ .250 7.83 [S10]
304 stainless fiber laser .030–.500 (10 sizes) yes, ≤ .250 8.00 (0.289 lb/in³) [S11]
316 stainless fiber laser .060 .125 .187 .250 yes n/p
4130 chromoly fiber laser .050 .063 .125 .190 .250 yes 7.83 [S12]
Ti-6Al-4V grade 5 fiber laser .040 .063 .125 .187 .250 no; no tap/hardware 4.43 [S13]
Carbon fibre waterjet .040 .063 .079 .118 .157 .197 .315 no; no services about 1.66 (about 0.06 lb/in³) [S6]
G10/FR-4 waterjet .063 .125 .187 .250 .375 .500 no n/p
Delrin CO₂ laser (.125) / router (.270) .125 .270 no; tap + countersink n/p
UHMW router .375 .500 no n/p

Densities in g/cm³ are converted from lb/in³ where the page gives lb/in³.

The CF page's figures (500+ ksi, 20–30 Msi) describe the fibre, not the laminate. Don't design with them [S6].

4.2 Holes, edges, tolerances, sizes

4.3 Bending (fixed tooling; values from the quoter JSON [S1])

Rules from the bending page [S3]:

5052 t (mm) K Inside R (mm) Min flange (mm) Keep features from bend CL (mm)
1.02 0.45 0.61 6.45 6.0
1.60 0.42 0.89 6.45 6.0
2.03 0.48 0.97 6.45 6.0
2.29 0.37 0.81 6.45 6.0
2.54 0.40 3.18 9.32 8.0
3.18 0.44 3.18 9.32 8.0
4.75 0.43 6.35 15.72 12.5
6.35 0.42 6.35 29.19 20.0

K-factors for steel (0.32–0.40), 304 stainless (0.34–0.38) and 4130 (0.36–0.43) are per thickness in the JSON.

4.4 Services and lead times

Lead times are from the rush-production page [S16] and the shipping page [S17].

Base lead time: cutting 2–4 business days; CNC 2–5.

Added time by service:

Service Added time (business days) Notes
Bending +1–2 the shipping page says 2–3
Tapping +1–2 metric M2–M16 by thickness: e.g. 5052 3.18 mm takes M2–M12 [S1]
Countersinking +1–2 5052/6061/7075 from .125 in
Hardware (PEM nuts/standoffs/studs) +1–3 Al from .040 in; part 1×1.5 to 36×46 in [S18]
Deburring +0
Tumbling +1–2
Anodize (Type II, 5052/6061/7075) +1–3 clear/black, +5–7 colours 1×3 to 23×23 in [S19]
Powder coat +3–5
Plating +7–10

Rush tiers:

Tier Ships
Fast 1–3 days
Faster 1–2 days, with overnight shipping
Fastest within 24 h; order by noon PT

Rush prices are not published [S16].

Volume adders:

Shipping and minimums:

4.5 Pricing behaviour

Cost drivers [S20][S21][S7]:

Bending minimum: the blog's table implies a $19 minimum for 1–2 bent parts. An older version of the same post said $9 [S20].

Published examples. SendCutSend labels all of these as estimates that may be out of date.

Part Qty 1 Qty 100 Src
5052 .187 in, 3.5×2.5 in, laser + deburr $9.90 $3.70 [S7]
CF .039 in, 3.35×3.25 in, waterjet $53.42 $29.60 [S7]
ABS .125 in, 3.5×3.5 in, router $7.42 $2.99 [S7]
5052 .100 in, 2.5×4.75 in, laser + deburr + tap $12.09 $4.40 [S22]
HRP&O .187 in, 4×4 in, laser + tap $23.32 $5.77 [S22]
Delrin 2.5×3 in, route + tap $15.16 $5.66 [S22]
HRP&O .188 in, 3.5×1 in, laser + PEM $14.14 $3.24 [S18]
CRS .135 in, 3×3 in, laser + bend + PEM $27.05 $6.44 [S18]
5052 .063 in, 5.5×6 in, laser + bend + deburr + PEM + anodize $44.51 $19.48 [S18]
G90 .059 in, 5.4×6 in, laser + bend + PEM $31.76 $8.32 [S3]
CRS .119 in, 6.3×7.4 in, bend + others $73.33 $16.21 [S3]
Polycarbonate .118 in, 4×5.5 in, route + bend $24.98 $7.84 [S3]
5052 .125 in, 4×3.25 in, laser + bend + csk + deburr + anodize $41.58 $12.86 [S19]
5052 .090 in, 6.5×7.5 in, laser + bend + tap + dimple + deburr + anodize $72.63 $24.62 [S19]
6061 billet 2.5×2.5 in, CNC + blast + anodize $357.23 $73.32 [S19]
Same sprocket: 304 .060 in vs Ti .063 in $6.76 vs $19.60 – [S20]

Derived from these examples:

API and quoting access:


5. Alternatives (one line each)


6. Bearings, pivots and fasteners

Single-unit prices from VXB on 2026-10-25, with load ratings from the VXB listings [V1]. McMaster and Misumi block automated fetching, so their prices were not retrieved.

Bearing d×D×B mm $ each Cr / C0 N Max rpm (grease)
6800-2RS 10×19×5 7.77 1380 / 585 22,000
6801-2RS 12×21×5 7.77 n/p n/p
6802-2RS 15×24×5 9.99 2080 / 1260 17,000
6804-2RS 20×32×7 7.77 4000 / 2640 13,000
6805-2RS 25×37×7 7.77 4360 / 2600 11,000
6806-2RS 30×42×7 9.99 4490 / 2900 9,500
6900-2RS 10×22×6 7.77 n/p n/p
6902-2RS 15×28×7 9.99 4300 / 2250 17,000
6904-2RS 20×37×9 9.99 6350 / 3700 12,000
6000-2RS 10×26×8 7.77 4750 / 1960 19,000
6001-2RS 12×28×8 7.77 5400 / 2360 n/p
6002-2RS 15×32×9 9.99 5850 / 2850 14,000
RU42UU crossed roller 20×70×12 199.99 7350 / 8350 –
CRBH3510AC1 crossed roller 35 bore, 10 wide 313.99 n/p –

10-packs of the 68xx, 69xx and 60xx sizes cost $29.99–49.99 (about $3–5 each) [V1].

For the knee and hip pivots, a pair of 6802 or 6902 bearings in a printed seat is the cheap default. Check the real joint loads against the Cr/C0 values above. Crossed-roller bearings cost 20–40× more (derived from the prices above).

Shoulder bolts. VXB sells a 20-pack of M6×1.0 thread, 8 mm shoulder × 12 mm, for $49.98, about $2.50 each [V2].

Five-bar legs (Stanford Doggo) [D1]:

The DDT Diablo's leg mechanism was not researched here.


7. Gaps


Sources

Bambu Lab (US store, datasheets and wiki; fetched 2026-10-25)

Other filament

Tests and papers

Carbon fibre

SendCutSend

Alternatives

Bearings and fasteners