Copper CNC bending

Annealed copper takes a tight radius; half-hard copper will crack or craze on the outside of a tight bend. Copper picks up tool marks readily, so urethane or protected tooling is used for visible faces. Springback is low but not zero, and a bend on a wide busbar needs a die that supports the full width.

The commercial consequence is that copper is priced on its own material line, not blended into a steel rate. Material grade, thickness, tolerance and finish are quoted separately from conversion, so a change of specification is visible in the price.

Ganesh quotes to the drawing first and to ISO 2768 general tolerances where the drawing is silent. For copper CNC bending, the practical starting points are in the table below. They are starting points, not a guarantee: the part geometry, thickness and fixturing decide what can actually be held, and the quotation states the tolerance offered.

Flat length is calculated from bend allowance, not outside dimensions; a K-factor taken from a table rather than the actual material and die is the most common cause of a part that is 1 mm short across a box. Busbars and current-carrying parts are specified by conductivity, not just by grade name; ETP C11000 is the common baseline and oxygen-free copper is reserved for vacuum or brazing duty. The route is quoted as one sequence so the customer does not have to coordinate a cutter, a former, a welder and a coater.

For very thick busbars, a press brake is the wrong tool; a dedicated busbar bender or a machined radius is more controllable.

A manufacturability review before quotation is the cheapest place to find this out. Send the drawing, material, finish and annual quantity and the review comes back in writing.

• Busbars
• Flexible connector ends
• Earthing strips
• Heat sink clamps

Use press brake bending for almost every formed sheet part, including production parts, because the brake stores a program per part and needs no tool beyond standard punches and dies. A dedicated forming tool only makes sense when the geometry needs a feature a brake cannot produce: a coining operation, a closed hem, a very short flange on a high-volume part, or a form that must be identical across a million cycles. For copper the practical constraint is conductivity and heat: cutting parameters, bend radius and joint method are all set by the temper and the electrical requirement, not by the shape alone. Copper parts are often single-source by specification rather than by process, so the decision that matters is the temper and the edge condition, both of which should be on the drawing before a supplier is chosen.

Give the inside radius, the bend angle and its tolerance, the bend line dimensions and whether they are to the outside or the inside of the form. State the flat pattern expectation if the customer owns it, and the bend sequence if the part is boxed and the order matters. Mark the cosmetic faces. On a 4,450 mm panel, say whether the full length is a single bend or a stepped form.

Angular tolerance is checked with a protractor or against a fixture, and linear dimensions against the drawing. The stored program is the setup record. First article approval covers the first part off the program, not the drawing review.

Cost splits into setup, handling and stroke time. Setup is amortised across the batch, which is why 50 parts cost more per part than 500 off the same program. The number of bends, the part size and whether a second operator is needed to handle a long panel all move the price more than the tonnage does. On copper, material is quoted as its own line at the prevailing rate for the grade and thickness, so a change of specification is visible rather than hidden in a blended rate.