Busbar Punching, Shearing and Bending Defects: What to Check

Start with the location and timing of the defect. A hole that is already out of position on the flat blank needs a different investigation from a hole pattern that only fails to align after bending. Save the affected part and record its drawing revision, material, tooling and operation sequence before adjusting the machine.

The checks below are diagnostic starting points, not a diagnosis from appearance alone. Use the machine-selection guide first if the part may be outside a station’s working range.

Match the symptom to a useful first check

Symptom	Possible cause to investigate	First check
Heavy burr around a punched hole	Tool wear or unsuitable punch/die clearance	Inspect the hole and slug; identify the punch, die and material thickness
Burr concentrated on one side	Uneven tool condition or alignment	Compare the full hole perimeter and have tooling alignment checked
Hole positions consistently shifted	Wrong datum, stop setting or drawing revision	Measure the first hole from the specified reference edge
Hole positions vary between parts	Inconsistent seating or bar support	Observe how each blank locates before the punch cycle
Sheared end is marked, distorted or not square	Blank seating, support or shear-tool condition	Check the blank against the stop and inspect the cut before deburring
Bend opens after unloading	Springback	Measure the unloaded angle using the agreed method
Cracking at the outside of a bend	Material condition or radius incompatible with the required bend	Check grade, temper, thickness and the actual inside radius
Contact surface has repeated marks	Debris, damaged contact surfaces or handling	Compare mark locations with tool and support contact points

Punch clearance affects the cut edge, burr and tool loading; the slug can help distinguish clearance and wear problems. These principles are described in Mate’s die-clearance guidance. Use clearance and maintenance instructions for the actual tool set, rather than importing a setting from another press.

Separate punching errors from bending errors

Measure a flat blank before forming it. Record hole size, hole-to-hole distance and hole position from the drawing datum. Then measure the finished part from its specified assembly references.

If the flat blank passes but the assembled connection does not align, investigate bend location, angle, radius and developed blank geometry. Moving the punching stop before making this comparison can hide the actual cause and produce a different error on the next part.

Include the full shape in the trial. A short coupon can establish one hole or bend, but it cannot show whether a previously formed leg blocks access to a later operation.

Check springback after releasing the load

Springback is the change in shape after the bending load is removed. Rittal’s busbar bending guidance identifies it as a factor in achieving the finished angle. Measure the free part, using the same reference faces and instrument for each trial piece.

Our WM-9400 has PLC, encoder and touch-screen control. Establish the working setting through the specified setup procedure and a measured trial; those control components alone do not demonstrate automatic measurement of the unloaded angle.

Copper’s ability to form a bend depends on its material condition and thickness. See Copper for Busbars, section 1.2.2.2.7. When a bend cracks, review the material and required radius before attempting a revised part.

Correct one variable and inspect the complete part

1. Confirm the drawing, material and selected station capacity. Record the original failed condition.
2. Identify the tool set and inspect its condition. Tool inspection and adjustment must follow the machine’s isolation and maintenance procedure.
3. Make one documented correction appropriate to the identified cause.
4. Measure the same features on consecutive parts, including the first part after reloading or a tool change.
5. Check the completed geometry and mating fit, not only the feature just corrected.

Agree whether cut-edge acceptance is measured before or after a specified finishing step. If deburring is required, include its time and its effect on dimensions in the process evaluation.

For support, send us the drawing and trial evidence: a whole-part photo, a close view of the defect, the measured value and tolerance, material details, and the operation where it first appears. Our busbar trial checklist gives a record format for comparing the correction with the original result.