Executive answer
Define the curve before comparing bend reports
- A 90-degree turn describes direction change, not a complete curve or an allowable material limit.
- Label radius, reference, angle and the actual supported region before comparing bend reports.
- Geometry, construction and movement history belong together in the acceptance plan; none substitutes for the others.
Current guidance context
What OEM engineers and sourcing teams should decide first
A drawing note might say 'bend tail 90 degrees,' while a sample report says it passed a stated number of bends. Those statements do not establish that the report represents the installed route. The missing information may be geometric before it is a material problem: where does the curve start, how tightly does it turn, and what supports the tail?
Start by marking the route on a housing section. Keep the tail construction and connector definition beside that section, then ask the responsible engineers to select the method and evidence. This guide narrows one RFQ gap: why angle, radius and curved length must not be treated as interchangeable values. It does not replace an installed-route assessment.
Check a legacy method before copying its designation
ASTM's public record marks F2750-16, concerning bending of a membrane switch or printed electronic device, as withdrawn in 2023 with no replacement. F2749-15, concerning creasing, is withdrawn in 2024 with no replacement. The older combined bending/creasing practice F1683-09 is withdrawn in 2018 with no replacement. These are historical references, not three current default requirements.
The public descriptions identify possible appearance, mechanical-integrity and electrical-function effects and warn that testing may be destructive. They do not establish a universal tail radius or authorize a numerical pass limit for the buyer's construction. If a drawing still cites one, record the edition and status and have the responsible team agree the contractual basis before testing.
Do not reconstruct a full test procedure from a catalog summary or rename a house test as ASTM compliance. Preserve any genuine historical method and fixture records needed for comparison, and identify deviations openly. Keep test specimens controlled for evaluation rather than treating a post-test continuity pass as permission to install them in finished equipment.
Work three reference arcs, not three material ratings
The following is a hypothetical HYR editorial geometry example, not measured product data or an ASTM fixture. Assume a planar circular reference line of zero thickness with constant radius R. The reference line is chosen on the drawing; it is not assumed to be a physical tail surface or mechanical neutral axis. No construction, supports, strain model or acceptance threshold is supplied.
For that ideal reference arc, curved length s = R × θ when θ is in radians. Convert the turning angle using θ = degrees × π / 180. Path A turns 90 degrees at R = 2 mm: θ = π/2 and s = π mm, approximately 3.142 mm. Path B also turns 90 degrees but uses R = 8 mm: s = 4π mm, approximately 12.566 mm. The angle is unchanged while both radius and curved reference length are four times larger.
Path C uses the same R = 2 mm as A but turns 180 degrees: θ = π and s = 2π mm, approximately 6.283 mm. A and C share a radius, not a turning angle or arc length. The three rounded lengths use three decimal places for the example only, not a manufacturing tolerance or required measuring resolution.
These calculations describe only the circular portion. They do not include straight leads, transitions, insertion length, a service loop or routing in three dimensions. They cannot determine the complete tail length or fixture clamp spacing. Nor do they show whether any of these hypothetical radii is permissible for a real multilayer tail.
Dimension the radius reference and supported region
Put the radius leader on an identified line or surface in the section view. If the project specifies an inner surface, say so. If the fixture is described by a mandrel diameter, retain that description and explain how the tail is positioned relative to it. Do not silently substitute that diameter for the radius of a drawing reference line or assume a multilayer tail's neutral axis lies at its mid-thickness.
Mark where the permitted bend region begins and ends relative to the panel exit, stiffener, connector and supports. Show which portions stay straight and which can move. A radius label that floats above the tail without an attachment point leaves the converter and test laboratory to choose different interpretations.
Resolve those definitions against the real assembly before a sample comparison. A reference arc can clarify available route space, but the responsible team still needs the actual construction and boundary conditions to assess material behavior. The FPC file-set guide addresses how released bend-area information remains aligned with the manufacturing outputs; it does not turn a geometry calculation into fabrication approval.
Separate an installed shape from a movement test
A tail installed once and held in a defined route answers a different use question from a tail moved whenever a cover opens. Record the actual sequence: initial routing, closure, service access, connector operations and repeated movement where applicable. Define one complete cycle before assigning a count, and retain the minimum and maximum shapes reached during that cycle.
A 180-degree circular turn is not, by angle alone, proof of a crease. The ideal semicircle in Path C has a finite radius throughout. Conversely, a note describing a smaller direction change does not rule out an unintended local fold elsewhere in the real assembly. Define the deformation and inspect the identified region rather than using the angle as the category.
Have the responsible test owner choose movement range, rate, dwell, environment, specimen history and electrical observations appropriate to the intended question. Specify whether a possible interruption during motion must be detected or whether the agreed output is a before/after reading. This guide sets no universal cycle count, monitoring bandwidth or safe radius, and a connector mating count remains a separate record.
Avoid five bend-report gaps
These are hypothetical drawing and acceptance failures, not reported HYR defects or customer cases. Each requires a controlled input or observation rather than a more confident product description.
- The RFQ gives an angle without a radius reference. Return a section with the curve, leader and permitted bend region identified.
- A mandrel diameter is compared directly with a tail radius. Reconcile the dimension type, reference and placement before declaring the geometries equivalent.
- An arc-length calculation is used as the complete tail length. Add the actual straight, transition, insertion and service-route portions on the assembly drawing.
- A held installation shape is used to approve repeated service movement. Record the distinct movement sequence and agree the additional evidence required.
- A withdrawn designation or a final continuity reading is treated as complete approval. Resolve the method status and the required appearance, mechanical and electrical acceptance records separately.
Release a bounded tail-bend RFQ
Send one controlled package to each quoting supplier: tail construction, housing section, connector, radius reference, angle and supported region. Mark unresolved dimensions as open decisions. Ask for a proposed sample and test plan that identifies what it can establish, rather than accepting an unspecified 'bend passed' statement.
Tie the returned report to the actual specimen revision, fixture and movement history. Keep raw electrical observations, visual or mechanical findings, deviations and the responsible disposition. When the enclosure, stiffener, tail stack, connector or route changes, decide which evidence no longer represents the assembly. A revision-controlled geometry record makes that review possible without claiming that geometry alone predicts damage.
Use HYR's secure engineering RFQ to share the available drawing and the intended installation or movement. The review can clarify component boundaries and missing inputs; it does not promise a particular minimum radius, flex life, test service, quotation outcome or delivery schedule.