What a straightening tolerance means
After flame cutting, plate parts may have waves or local deformation. A straightening requirement defines the shape condition needed after processing.
Surface flatness, edge straightness and the dimensional accuracy of the cut profile must be distinguished. A description such as “as straight as possible” is not sufficient for unambiguous acceptance.
Why there is no universal value
Achievable flatness depends on material, thickness, overall dimensions, cut-outs and initial distortion. A long, narrow flame-cut part presents different challenges from a compact plate. Its intended use also matters: an assembly surface may need different tolerances from stock for further machining.
Drawings and purchase orders should therefore specify the form tolerances actually required. Agreed standards, tolerance classes and their scope must match the supply and processing task.
Which DIN standards are relevant?
DIN EN 10029 specifies dimensional and shape tolerances for hot-rolled steel plate from 3 mm thickness, including normal and restricted flatness tolerances. It is relevant to the parent plate within its scope. Its requirements should not be transferred without assessment to the straightening tolerance of a flame-cut part made from that plate.
DIN EN ISO 9013 addresses geometrical quality and tolerances of thermal cuts, including oxyfuel, plasma and laser cutting. Cut quality must be distinguished from the flatness of the entire part surface. A reference to this standard alone does not replace an explicitly agreed flatness requirement after straightening.
State the applicable standard and edition, any tolerance class, required flatness and inspection conditions in your enquiry. BEB will agree with you what can be achieved for your workpiece.
Agree measurement conditions in advance
Comparable results require a known measurement method, assessment area and support conditions. For large or slender parts, self-weight and support can influence the result. Whether a part is measured free or clamped is also relevant.
When checking with a straightedge and gap measurement, specify the measuring length and positions. Such a check cannot automatically be treated as equivalent to every geometrical flatness inspection. Agree with the processor what evidence is required.
Match tolerances to the manufacturing chain
Very tight requirements can increase processing and inspection effort. They should therefore follow from the function of the part. If welding or material removal takes place after straightening, possible subsequent shape changes must also be considered.
Agree which condition is accepted immediately after straightening, which processes follow and at what stage another inspection is planned.
Information to include in your enquiry
Provide a drawing with material grade and condition, thickness, outside dimensions and cut-outs. State quantity, weight, existing distortion and the required form tolerance.
Include the assessment area or measuring length, support conditions and any inspection report required. BEB will assess feasibility and agree the intended result with you.
Your next step
Let’s talk about your workpiece.
A drawing, material grade, dimensions and required result help us assess your enquiry.
