Detailed Explanation of Bending Dimension Calculation for CNC 3-in-1 Copper Busbar Processing Machine
(Compatible with FEIYING CNC 3-in-1 Copper Busbar Processing Machine, universally applicable to T2 copper busbars in high and low voltage switchgear, combined with machine tool CNC system logic, on-site practical version)
Important Prerequisite: The control systems of CNC 3-in-1 copper busbar machine tools on the market uniformly adopt the 【Bending Deduction Method (BD)】
I. Basic Concept Understanding
1. Flat Bending: Bending the copper busbar along its thickness direction (most common, bending the narrow side of the copper busbar)
2. Vertical Bending: Bending the copper busbar along its width direction (bending the wide side of the copper busbar)
3. Bending Inner Radius R: Standard value for the 3-in-1 standard bending upper die: R = t (copper busbar thickness)
4. Bending Deduction (BD): The metal in the bending area of the copper busbar undergoes tensile deformation. If all the outer dimensions of the finished product are directly added together as the blanking length, the overall size of the workpiece after bending will be too large. Therefore: Blanking length = Sum of all external dimensions − Sum of all bending point deductions
Core formula:
\(\boldsymbol{L_{Blanking} =\sum L_{External} – n\times BD}\) \(L_{External}\) = External dimension after bending n = Number of 90° bends BD = Deduction value for a single 90° bend
II. T2 Copper Busbar [90° Flat Bending] Standard BD Reference (Machine Tool Factory Calibration, R=t)
| Copper busbar thickness t | Single 90° flat bend BD |
| 3 mm | 2.8 mm |
| 4 mm | 3.7 mm |
| 5 mm | 4.6 mm |
| 6 mm | 5.5 mm |
| 8 mm | 7.4 mm |
| 10 mm | 9.2 mm |
⚠️Important Reminder: Vertical bend BD > Flat bend BD, the two cannot share parameters! Vertical bending results in greater metal stretch. For copper busbars of the same thickness, the bending deduction value for vertical bending generally increases by 10%~18%. Within the CNC system, it is recommended to establish two independent compensation parameter files for horizontal and vertical bending.
III. Case Study Calculation (Routine Factory Workpieces)
Case 1: Single 90° Horizontal Bending L-Shaped Copper Busbar
Material: 5mm T2 copper
Outer dimensions: Horizontal section 200mm, Vertical section 110mm
Number of bends: 1
Cutting length = 200 + 110 − 4.6 = 305.4 mm
Cut the 305.4mm sheet metal; the bent dimensions will meet the requirements.
Case 2: U-shaped busbar with two 90° bends
Material: 5mm copper
External dimensions: 80mm on both sides, 210mm in the middle horizontal section
Number of bends: 2
Cutting length = 80 + 210 + 80 − 2 × 4.6 = 370 − 9.2 = 360.8 mm
Case 3: Workpiece with three consecutive 90° bends
6mm copper busbar, three bends, external dimensions 150+90+160+70
Total deduction = 3×5.5=16.5
Cutting length = 150+90+160+70−16.5=453.5 mm
IV. Calculation method for non-90° bends (45°, 60°, 120°, 135° oblique bends)
Bend deduction is approximately proportional to the bend angle. Formula:
\(BD_\theta=BD_{90°}\times \frac{\theta}{90°}\) \(\theta\)= Actual bending inner angle. Example: 5mm copper busbar, 45° bend \(BD_{45}=4.6\times 45\div90=2.3\mathrm{mm}\) Practical advice: The formula is for theoretical reference only. Before mass production, trial bending and sampling are necessary. Fine-tune the compensation value in the CNC system to ensure high precision.
V. Two Operating Modes of CNC 3-in-1 Machine Tools (Core! Distinguishing Between Manual Calculation and Automatic Calculation)
Mode 1: External Dimension Input Mode [Recommended, Mainstream in Factories]
The FEIYING CNC system has a built-in bending compensation database. Operators directly input the finished product’s external dimensions and bending angle after bending. The machine automatically retrieves the corresponding thickness copper busbar BD parameters and automatically calculates the required cutting length. ✅Advantages: Reduces manual calculation errors, easy for beginners, suitable for large-volume standard busbars in switchgear.
Mode 2: Manual Cutting Length Mode
Manually calculate the total cutting length in advance and directly set the cutting length. The machine only controls the bending angle. Suitable for special irregular busbars and small batches of non-standard workpieces. Requires operators to be proficient in bending calculation formulas.
VI. Key Factors Affecting Bending Compensation BD Values (Essential Reading for Debugging)
1. Bending Inner Radius R: Changing the upper die increases R → reduces copper busbar stretch → decreases BD value; decreases R → increases BD. After changing the die, parameters must be recalibrated by trial bending.
2. Material Differences: The parameters in the table above only apply to T2 copper. Aluminum busbars and brass have different hardnesses, and all BD parameters need to be recalibrated; they cannot be directly applied.
3. Distinguishing Between Flat and Vertical Bending: It is absolutely forbidden to use the same parameters interchangeably; otherwise, continuous dimensional deviations will occur, resulting in a large number of scrapped parts.
4. Sheet Metal Temperature and Mold Wear: With long-term production, the molds experience slight wear; parameters require periodic spot checks and fine-tuning.
VII. Complete Machine Tool Debugging Standard Procedure
1. Based on the copper busbar thickness and whether it’s a flat or vertical bend, create a new parameter group in the system; enter the basic BD reference value.
2. Cut a short piece of material for a trial bend.
3. Measure the actual external dimensions after bending, compare with the theoretical dimensions, and slightly modify the system compensation parameters.
4. After parameter calibration, save the program number for subsequent workpieces of the same specification.
VIII. Common Errors in Production
❌ Error 1: Directly adding external dimensions without subtracting bending deductions → The total length of the bent workpiece is too large, making it impossible to assemble the cabinet.
❌ Error 2: Directly using flat bend parameters for vertical bends → Dimensional deviations continue.
❌ Error 3: Changing bending dies or copper busbar thickness without recalibrating compensation.
❌ Error 4: Directly using the 90° bending deduction value for oblique bends.