Orange-peel sphere

The surface is faceted or triangulated, so the pattern is an approximation. The error is known and printed as a number on the drawing — it is not hidden.

Dimensions are entered as: Inside dimensions. The flat pattern itself is always computed on the neutral fibre — at Ø800 in 3 mm sheet the difference between the inside and the outside dimension is 18.8 mm of developed width, and then the seam does not meet.

En hel kugle bygget af lige store gore-blade (lune-blade) i skiftevis to farver — som en melon eller en strandbold. Hvert blad er en smal kile af kuglefladen fra pol til pol.

Demonstrations- og dekorationskugler, kuglebeholdere og kuppellamper, hvor gore-princippet vises tydeligt. Samme udfoldning bruges på alle kugleflader i pladearbejde.

Smed og metalsmed — kugle- og kuppelemner: kupler, spir-afslutninger, dekorative kugler og kuglebeholdere.

Rustfri, kobber eller stål 1–3 mm i lune-blade (gores). Kobber til bygningsbevaring (kupler/spir).

Source: Materialelære + samlinger: metalsmed-artikler i src/lib/skoler/indhold/data.ts. Fremstillingsfælder: docs/PLAN-UDFOLDNINGSBIBLIOTEK.md §9.2/§4.

Radius — The radius

Kuglens radius R i mm; sætter både omkreds (2πR) og meridianlængde (πR).

Gores — Number of gores

Antal blade N kuglen deles i (lige tal, fx 12). Flere blade = rundere kugle.

Step by step with compass and square — in cardboard first, in sheet metal after.

1. 01Aflæs antal blade N direkte fra Gores-parameteren. Hvert blad dækker 360°/N rundt om kuglen og går hele vejen fra sydpol til nordpol.
2. 02Meridianbuen er en halv storcirkel fra pol til pol; dens sande længde er π·R. Tegn den som lodret midterlinje i fuld størrelse og del den i fx 12 lige stationer (én ved hver pol, resten imellem).
3. 03Hver station svarer til en breddevinkel φ målt fra ækvator (−90° ved sydpol, 0° ved ækvator, +90° ved nordpol). I hver station måles bladets halve bredde ud til begge sider: halv bredde = π·R·cos(φ)/N.
4. 04Bredden er størst ved ækvator (φ=0) og går mod 0 ved begge poler, så bladet bliver en symmetrisk 'appelsinbåd', spids i begge ender.
5. 05Klip ÉT blad og brug det som skabelon til alle N blade. Skift evt. farve på hvert andet blad for melon-effekten.
6. 06Buk hvert blad let på tværs så det følger kuglekrumningen, og saml dem kant-mod-kant hele vejen rundt; alle spidser mødes i de to poler.

Med kun 4–6 blade bliver kuglen tydeligt kantet (en 'lanterne'); 12 og opefter ser rund ud. Da bladet er symmetrisk om ækvator behøver du kun måle den ene halvdel og spejle den.

• ·En kugleflade har Gauss-krumning ≠ 0 og kan IKKE foldes rent fladt (Theorema Egregium) — den deles i lune-blade/petaler eller presses fra en ronde. Et «fladt mønster» af en kuppel lyver.
• ·Flere blade (16–24) giver en rundere kugle med mindre kantbukning, men mere svejsning; 12 er den klassiske afvejning.
• ·Husk svejsesvind på bladbredderne ved tyk plade — ellers bliver kuglen for lille i omkreds.

The words and formulas the trade uses for a flat pattern. The symbols are the same throughout Discebo: α is the bend angle in degrees, R the inside bend radius, t the sheet thickness and K the K-factor — all in millimetres.

Flat pattern (development)

The part's surface laid out flat as one continuous cutting outline — the way the sheet looks BEFORE it is bent or rolled. Only a developable surface can be unfolded exactly; a doubly curved surface cannot be laid flat without stretching the material.

Flat length

The flat length the part must be cut to so the dimensions come out right once it is bent. It is either the sum of the outside dimensions minus the bend deductions, or the sum of the flat legs plus the bend allowances — both routes must give the same number.L = Σ(udvendige mål) − Σ(BD) = Σ(flade ben) + Σ(BA)

Bend allowance

The length of material that sits in the bend itself, measured along the neutral fibre. The bend allowance is always positive and is added to the flat legs.BA = (π/180) · α · (R + K · t)

Bend deduction

The amount subtracted from the sum of the outside dimensions, because the two outside dimensions between them count the corner twice. Here the bend deduction is taken as POSITIVE and subtracted; DIN 6935 writes the same quantity as the compensation value v with the opposite sign.BD = 2 · OSSB − BA

Outside setback

The distance from the theoretical outside corner point in to where the bend starts. Above 90°, tan(α/2) is clamped to at most 1 per DIN 6935, so the number does not explode towards 180°.OSSB = tan(α/2) · (R + t)

Compensation value v to DIN 6935

The standard's own way of writing the same corner loss: the flat length is a + b + v, where v is negative. Our bend deduction is therefore the same quantity with the opposite sign — never flip one without the other.L = a + b + v ⇒ v = −BD

K-factor

Where the neutral fibre sits in the sheet, given as a fraction of the sheet thickness. DIN 6935 writes the correction factor k, which applies to the neutral line in the form (R + t·k/2); the American CAD convention writes (R + K·t), so K = k/2.k = 0,65 + 0,5 · log₁₀(R/t), k ≤ 1,0 ⇒ K = k/2

Neutral fibre

The layer in the sheet that is neither stretched nor compressed when the part is bent. The flat pattern is always computed on the neutral fibre — which is why it matters whether the drawing's dimensions are inside or outside.

Bend angle

The angle the material is turned through, not the angle between the legs. The bend angle is 180° minus the included angle, so a square corner is 90° and a seam fold is 180°.α = 180° − åbningsvinklen

Inside bend radius

The radius on the inside of the bend. It is set by the tooling and the material, not by the drawing — too small a radius cracks the part in the outer fibre.

Sheet thickness

The thickness of the material. It enters every single bend allowance, so sheet delivered 0.2 mm thicker than ordered shifts the flat length at every bend.

Fold line

The line on the flat pattern where the part is to be bent. It is drawn but never cut through — in a laser file it therefore sits on its own layer.

Test bend

A strip of known raw length, bent in the material and the tooling that production will use. Measure the two outside legs afterwards and the bend deduction and K-factor can be worked back. The machine's own measured bend table beats any table.BD_målt = (A + B) − L₀

DIN 6935 covers only cold bending of flat products in structural steel. Stainless, aluminium, copper, brass and titanium zinc are not included — there the formulas are an extrapolation, and a test bend in the actual material settles it.

6 fields. The starting values belong to the figure itself — they live in one place in the code, so the tool, the share link and the smoke test can never disagree about what «default» means.

A preset sets every dimension at once. The name is often the word the part goes by in the workshop — the library's search knows them all.

Read them before the part is cut. They are here because they cannot be calculated away — not as legal text, but as craft.

• Pressure-bearing spherical vessels (gas sphere, LPG sphere) are certified equipment and must be calculated and approved in accordance with DS/EN 13445 and PED 2014/68/EU. The figure gives the GEOMETRY — it does not size pressure, material thickness or weld class.
• The gore method is APPROXIMATE. Each gore is (π/n)/sin(π/n) − 1 wider than the chord it must span (n = 12 ⇒ 1.15%), and that difference must be rolled/drawn into the sheet. The gores do not fit flat.
• The thickness after rolling and drawing is not the sheet thickness: the material thins in the double-curved zones. Strength and weight calculations must use the FORMED thickness, measured on a finished blade.
• The sphere is built in two hemispheres with a circumferential seam at the equator; each physical melon segment is two half-gores welded together at the equator. A different division (e.g. three bands in height) is equally valid, but is not supplied by this figure.
• The circumferential seams (vertical + equator) do not carry an edge allowance on a sphere: the engine does not yet have a mapping from rim to cutting contour for ‘cap’. Bead, overlap and root gap must be added by hand there.
• The pole opening's nozzle, flange, blind flange or top rosette is NOT part of the figure and must be sized separately. The opening is only recorded as a truncation of the gores.
• The hygiene rules (no crevices, smooth seams, drainage, CIP) follow EHEDG's principles. They do not replace an approval under Regulation (EC) 1935/2004 or a HACCP assessment.