Technical Verification of a Used Press Brake
Successfully purchasing a used press brake requires a rigorous analysis of the frame's geometry, the hydraulic system's leak-tightness, and the precision of the CNC control. The most important parameters are pressing force, the number of controlled axes (typically Y1, Y2, X, R), and the crowning system. Choosing machines from brands like Amada, Trumpf, or Bystronic minimizes the risk of a lack of spare parts.
Companies looking for efficient solutions often analyze used CNC metalworking machines, as the secondary market offers devices with high structural rigidity for 40-60% of the price of a new model. However, without a thorough inspection of mechanical components, the investment can generate service costs exceeding the purchase value.
Types of Press Brake Drives on the Secondary Market
The type of drive determines not only energy consumption but, above all, the method of servicing and typical faults you might encounter after purchase.
Hydraulic Presses (Conventional and CNC)
This is the most popular category of machines. They use piston or gear pumps to generate pressure in the cylinders. In older models (over 15 years old), pay particular attention to the proportional valves. Their regeneration is costly, and failure prevents maintaining beam parallelism. Check the condition of the main cylinder seals – oil leaks under the upper covers indicate the need for costly repairs.
Servo-Electric Presses
These machines eliminate the hydraulic system in favor of servo motors and drive belts or ball screws. They are much faster and consume up to 50% less energy than hydraulic models. When buying a used electric press, focus on inspecting the transmission belts and rolling bearings. Any play on the ball screw disqualifies the machine from precisely machining parts with tolerances below 0.004 inches.
Hybrid Presses
They combine the advantages of both systems. A servo motor drives a small hydraulic pump placed directly above the cylinder. This solution reduces the amount of oil in the system (often from 50 gallons to 5 gallons) and reduces noise. These are usually newer machines, manufactured after 2010, making them a safer choice in terms of the availability of control electronics.
Key Technical Parameters and Their Significance
Analyzing the nameplate is just the beginning. You need to verify how the machine behaves under full load.
- Tonnage and working length: The standard in SMEs is 110 tons/10 feet machines. Remember that working at 95% of the nominal tonnage drastically shortens the frame's lifespan. Always choose a machine with a 20% margin of pressing force.
- Number of backgauge axes: The basic configuration is the X (depth) and R (height) axis. If you produce complex parts, look for machines with Z1 and Z2 axes (finger spacing) and X1, X2 for conical bending. The backgauge precision should be +/- 0.002 inches.
- Approach and working speed: Older machines work at a working speed of 0.3-0.4 inches/s. Modern systems reach 0.6-0.8 inches/s, which increases efficiency by 30% in large production runs.
Verification of Mechanical Condition and Geometry
Frame geometry is an irreparable parameter. If the frame is permanently deformed (“stretched”), the machine will never maintain the bending angle along its entire length.
Frame Deflection Measurement
Use a precision machinist's level and dial indicators. Perform a bending test on a long strip of sheet metal (e.g., 10 feet). If the angle at the ends differs from the angle in the middle by more than 1 degree (with the crowning off), it may indicate frame material fatigue. Also, check for microcracks on the frame welds – especially around the throat (side cutout).
Crowning System
Without a working crowning system, you will not be able to perform a straight bend on long elements. In used machines, you will find two systems: - Hydraulic: A set of short cylinders in the lower table. Check if the CNC controller correctly modulates the pressure in this system. - Mechanical (e.g., Wila system): Wedges moved by a motor. It is more precise and less prone to failure than hydraulic systems.
CNC Control System – The Heart of the Machine
Electronics are the weakest link in used presses. Controllers from brands like Delem (e.g., models DA-66T, DA-69T), Cybelec (ModEva), or ESA are market standards. Avoid machines with proprietary systems from manufacturers who have disappeared from the market. The inability to purchase a new motherboard or LCD monitor turns the machine into useless scrap metal.
Check if the controller has a 2D or 3D visualization function. This makes the operator's job easier and reduces the number of errors during the first bend. Network communication is also important – the ability to send DXF files directly from the technology office to the machine shortens setup time by several minutes per job.
| Feature | Hydraulic Press (Used) | Servo-Electric Press (Used) | Hybrid Press (Used) |
|---|---|---|---|
| Energy consumption | High (continuous pump operation) | Very low (only during movement) | Low (optimized) |
| Positioning precision | +/- 0.0004 inches | +/- 0.0002 inches | +/- 0.0002 inches |
| Service costs | Medium (oil and filter changes) | High (electronic parts) | Medium (closed system) |
| Noise during operation | 75-85 dB | 60-65 dB | 65-70 dB |
Tooling and Clamping Systems
When buying a machine, pay attention to the tooling clamping standard. The most popular is Amada/Promecam (Euro Style). Thanks to it, you have access to thousands of readily available die and punch replacements. If the machine has a Wila/Trumpf system, you gain in the speed of tool changes (often hydraulic), but you must take into account the higher prices of tooling.
The technical condition of the tool holders is equally important. If the upper beam has dents in the punch mounting location, precise bending will be impossible without costly beam surface planning. Check if the machine has hardened holders – they increase resistance to mechanical wear during frequent setup changes.
Safety and CE Standards
A used machine imported from outside the EU may not meet local safety requirements. A key element is the laser system for protecting the operator's hands (e.g., Fiessler, Lazersafe). Working on a press without a working safety system is unacceptable and exposes the company to huge penalties and the risk of accidents. Check the date of the last technical inspection of the safety system and the correct operation of the light curtains.
If you plan to automate production, check if the machine controller allows integration with a robot. For example, systems using Yaskawa Motoman robots require appropriate communication protocols (e.g., Profibus, Ethernet/IP), which are not always available in older press models.
Operating Costs and Hidden Expenses
The price visible in the advertisement is only part of the budget. Prepare for the following expenses: - Oversized transport: A 110-ton press weighs about 6-8 tons. It requires specialized transport and unloading with a heavy crane. - Foundations: Press brakes require a stable base. A standard 6-inch floor may crack under vibration. It is often necessary to make a 12-20 inch thick foundation with vibroacoustic insulation. - Hydraulic oil: Replacing 50 gallons of HLP 46 class oil along with filters costs around $500-$1,000. - Operator training: If you are switching from manual to CNC control, a budget for training in graphic programming is necessary to maintain production continuity.
Investing in a used press brake is a strategic move for companies increasing production capacity. The key to success is choosing a machine with a documented service history and performing tests under full load before finalizing the transaction. Remember that the cost of regenerating one hydraulic cylinder can be up to $3,750, which is a strong argument for a thorough pre-purchase inspection.
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