CNC press brake programming is the process of entering bend angles, material thickness, tooling parameters, and backgauge positions into a CNC controller (such as Delem DA66T or DA69T) to automate precise sheet metal bending operations. Modern CNC press brakes eliminate manual trial-and-error by using programmed sequences with springback compensation, multi-step bending routines, and real-time angle correction. This guide walks through the complete programming workflow — from controller setup to your first production-ready bend.
What Is CNC Press Brake Programming?
CNC press brake programming is defining a multi-step bending program in the machine controller that specifies:
- Bend angle (Y-axis depth) for each step
- Backgauge position (X-axis) for material positioning
- Tooling parameters (punch height, die width, V-opening)
- Material type and springback compensation value
Unlike manual press brakes that rely on operator judgment, CNC programming ensures ±0.1° angular accuracy and ±0.02 mm positional repeatability across high-volume production runs.
| Controller | Display | Programming Mode | 3D Simulation | Best For |
|---|---|---|---|---|
| Delem DA66T | 15" touch | 2D graphical + numerical | No | Mid-range shops |
| Delem DA69T | 21" touch | 2D/3D graphical | Yes | Complex parts |
| ESA S630 | 15" touch | Numerical + graphical | Limited | Budget CNC |
| Cybelec CybTouch 12 | 12" touch | Numerical | No | Entry-level |
Understanding Press Brake Axes
A CNC press brake has multiple programmable axes. Understanding each is essential before programming:
| Axis | Movement | Function | Typical Precision |
|---|---|---|---|
| Y1 / Y2 | Ram vertical (left/right) | Controls bend depth and angle | ±0.01 mm |
| X / X1 / X2 | Backgauge horizontal | Sets flange length position | ±0.02 mm |
| R | Backgauge vertical | Adjusts finger height for multi-step bending | ±0.05 mm |
| Z1 / Z2 | Backgauge lateral | Positions fingers for tapered/asymmetric parts | ±0.1 mm |
| W (crowning) | Bottom beam vertical | Compensates beam deflection for uniform angle | ±0.01 mm |
Step-by-Step CNC Press Brake Programming (Delem DA Guide)
Step 1: Power On & Calibrate
- Turn on main power → start oil pump → perform Y-axis homing (zero reference)
- On DA66T: Press "Manual" → "Calibrate" → step ram to top position
Step 2: Enter Material Parameters
- Open "Products" mode → "New Program"
- Input: Material type (mild steel / SS304 / aluminum), Thickness (e.g., 3mm), Width (sheet width)
- The controller auto-selects springback angle from its material database
Step 3: Select & Define Tooling
- Navigate to "Machine" → "Tool Library"
- Select punch: e.g., 90° standard punch, height 100mm
- Select die: e.g., 24mm V-die (= 8× material thickness for 3mm steel)
- V-die rule: V-die opening = 8× material thickness (standard rule)
- Save tool configuration before returning to program
Step 4: Program Each Bending Step
For each bend in the sequence, enter:
- Angle (Y1, Y2): target bend angle (e.g., 90°, controller adds springback automatically)
- X position: backgauge position = flange length + correction offset
- R position: set automatically or manually for complex parts
- Bending speed: approach speed 10-50 mm/s; bending speed 2-15 mm/s (slower = more accurate)
- Hold time: 0.5-2 seconds at bottom for springback stabilization
Step 5: Set Springback Compensation
- Check controller's material database for pre-set values
- Mild steel 3mm, 90° bend: typically +1.5-2° overbend
- Stainless steel: +3-5° (higher springback)
- Aluminum 5052: +2-4°
- Run a test bend on scrap material → measure actual angle → adjust Y-axis offset
Step 6: Simulate & Test Bend
- On DA69T: Press "Simulate" to preview 3D motion and check for collisions
- On DA66T: Run in single-step mode (press foot pedal once per step)
- Measure first part with protractor or laser angle gauge
- Adjust Y-offset in 0.1° increments until target angle achieved
Press Brake G-Code: What You Need to Know
Unlike CNC milling or turning, press brakes do not use traditional ISO G-code (G00, G01, G02). Instead:
- Delem uses proprietary
.daprogram files with numerical bend parameters - ESA uses its own format with step-based sequences
- ISO 14649 (STEP-NC) is an emerging standard for press brake code but rarely used in practice
A simplified "pseudo G-code" for a 2-step bend program looks like:
Where Y = ram position (angle), X = backgauge, V = V-die width, SPEED = bending speed in mm/s.
Springback Compensation in CNC Programming
Springback is elastic recovery — after bending, material springs back 1-7° depending on material and thickness.
| Material | Thickness | Target Angle | Typical Springback | Program Angle |
|---|---|---|---|---|
| Mild Steel (S235) | 2mm | 90° | 1.5° | 91.5° |
| Mild Steel (S235) | 4mm | 90° | 2° | 92° |
| Stainless Steel 304 | 2mm | 90° | 3.5° | 93.5° |
| Stainless Steel 304 | 4mm | 90° | 5° | 95° |
| Aluminum 5052 | 2mm | 90° | 3° | 93° |
| Aluminum 6061-T6 | 3mm | 90° | 4.5° | 94.5° |
Three compensation methods:
- Overbending (most common): program angle = target + springback value
- Bottoming/Coining: apply 3-5× more force to eliminate springback (wears tooling faster)
- Step bending: decompose >120° bends into multiple smaller steps
Delem DA66T vs DA69T: Controller Comparison
| Feature | DA66T | DA69T |
|---|---|---|
| Screen size | 15" touch | 21" touch |
| Programming modes | 2D graphical + numerical | 2D + 3D graphical |
| 3D simulation | No | Yes |
| Axes supported | Up to 17 axes | Up to 21 axes |
| Offline programming | Yes (DA-PC software) | Yes (DA-PC software) |
| Angle measurement | External option | Integrated option |
| Best for | Standard shop bending | Complex multi-step parts |
| Typical machine class | Mid-range electro-hydraulic | High-end CNC press brake |
Recommendation: For shops producing standard profiles (brackets, enclosures, channels), the DA66T provides excellent ROI. For aerospace, automotive, or complex multi-bend parts, the DA69T's 3D simulation prevents costly collisions and scrap.
5 Common CNC Press Brake Programming Mistakes to Avoid
- Ignoring springback — Programming exact target angle without compensation. Fix: Always add springback offset from material database or test bend.
- Wrong V-die width — Using too narrow a die increases tonnage and risks cracking; too wide reduces accuracy. Fix: V = 8× thickness for mild steel; V = 10× for stainless.
- Incorrect X-axis offset — Forgetting to account for material thickness in flange length calculation. Fix: X position = flange length + (material thickness / 2) for air bending.
- Not running simulation first — Skipping simulation leads to tool-workpiece collisions on complex parts. Fix: Always simulate on DA69T or use step-mode on DA66T.
- Skipping test bend — Going directly to full production without verifying actual angle. Fix: Always bend one test piece, measure with protractor, and fine-tune Y-offset before running batch.
Frequently Asked Questions
What is the standard programming unit for CNC press brakes?
CNC press brakes are programmed using degrees (°) for bend angles, millimeters (mm) for backgauge position and ram depth, and mm/s for bending speed. The Delem DA series displays all parameters in metric units by default, with imperial (inches/degrees) available as an option in Settings mode.
How long does it take to program a CNC press brake?
A simple 2-4 step program takes 5-15 minutes on a Delem DA66T using graphical programming mode. Complex parts with 8+ bends and collision checks on DA69T may take 30-60 minutes. With offline programming software (DA-PC), programs can be prepared in the office and uploaded to the machine in seconds, eliminating setup time on the floor.
Can CNC press brake programs be saved and reused?
Yes. Delem DA controllers store programs in internal memory with alphanumeric IDs. Programs can also be exported via USB as .da files, backed up to PC, and loaded for repeat jobs in seconds. Most shops maintain a library of hundreds of programs organized by part number, dramatically reducing setup time for repeat orders.
What is the difference between air bending and bottoming in CNC press brake programming?
Air bending (the most common method) programs the ram to stop before the sheet touches the die bottom, achieving the angle through die geometry. The bend angle is controlled by Y-axis depth, and springback must be compensated. Bottoming (or bottom bending) drives the sheet fully into the die, with the programmed angle matching the die angle exactly — springback is minimal but tonnage is 3-5× higher, requiring more careful force calculation.
CNC press brake programming is a skill that combines machine knowledge, material understanding, and systematic programming discipline. By mastering Delem DA controller setup, proper axis configuration, springback compensation, and bending sequence logic, you can consistently produce accurate parts with minimal scrap and setup time.
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