How to Choose a Hydraulic Press for Stamping Gold Bars and Bricks

The key to selecting a hydraulic press for stamping gold bars and bricks lies in accurately calculating the pressure (tonnage) based on the product specifications and ensuring the equipment possesses the high precision and adjustability necessary for the stamping process. This is a decision requiring comprehensive consideration. Below, Jianlong Hydraulic Technology will provide a clear selection guide from four dimensions: tonnage calculation, core configuration, model comparison, and key parameters, for your reference!

1. Core Step: Accurately Calculate the Required Tonnage

Tonnage is a core performance indicator of a hydraulic press. Choosing too small a press will result in unclear stamping, while choosing too large a press will lead to waste. Gold bar stamping belongs to die forging in the "forging process." You can refer to the following formula for estimation:

1.1 Core Formula: Required Pressure (tons) = (Forging Stress of Material × Projected Area of Mark × Shape Factor) / 9800

1.2 Forging Stress of Material (σ): This is related to the material and deformation temperature. For pure gold at room temperature, the forging stress can be taken as 50-100 MPa; for gold-silver alloys or platinum, the value needs to be increased accordingly.

1.3 Projected Area of Marking (S): Refers to the maximum outline area on the mold that contacts the gold bar; the unit needs to be converted to mm².

1.4 Shape Factor (K): Used to compensate for the additional resistance caused by the complexity of the pattern and the depth of the relief. For simple markings (such as shallow lettering), 1.5-2 is suitable; for fine or deep relief patterns, 3-5 is recommended.

1.5 Unit Conversion: /9800 in the formula is used to convert the mechanical unit Newton (N) to the commonly used engineering unit "ton" (t).

2. Key Configurations: Three Elements to Ensure Imprinting Quality After determining the tonnage, the following configurations also need attention, as they directly determine whether the imprinted markings are clear and consistent.

2.1 High Rigidity Structure (Four-Column Three-Plate Type Preferred)

This structure uses four precision guide sleeves to control the vertical accuracy of the moving plates, ensuring that the parallelism between any point on the lower and upper working surfaces is less than 0.1mm. This is crucial for gold bars, preventing uneven markings (one side darker than the other) or deformation of the gold bar itself due to uneven force.

2.2 Precise Speed Control (Requires "Fast Down-Slow Press-Fast Return")

• High Idle Stroke: Idle stroke speed is recommended to be above 150mm/s to improve production efficiency.

• Slow Feed Speed: Pressing speed is recommended to be adjustable to below 25mm/s. Slow extrusion allows the metal to flow fully into the fine texture of the die, ensuring a clear and full pattern, while avoiding impact damage to the die.

• Adjustable Holding Pressure: The control system must be able to precisely adjust the holding pressure time to ensure the gold bar is fully plastically shaped under high pressure.

2.3 Intelligent Control System (PLC and Dual Mode)

It is recommended to choose equipment equipped with a PLC, which can achieve the following two key control modes:

• Constant Pressure Pressing: The pressure stops when it reaches the set value (accuracy up to <1T), ensuring consistent force on each product.

• Constant Stroke Pressing: The slide stops when it reaches the set position (control accuracy <0.2mm), ensuring consistent thickness on each gold bar.

3. Comparison of Mainstream Models: C-Type Machine vs. Four-Column Machine

Depending on your production scale and needs, you can choose from the following two mature models:

3.1 C-Type Open Hydraulic Press

The C-type open hydraulic press has a C-shaped body, open on three sides, providing a large operating space and good visibility, facilitating workpiece placement and observation of the pressing process. Common tonnage is 10T - 50T. Its rigidity is relatively weaker than that of a four-column machine, and slight deformation may occur at high tonnage, affecting accuracy. Suitable for small-batch, multi-variety customized production, such as commemorative gold bars, personalized gold medals, etc., with very convenient mold replacement.

3.2 Four-Column Three-Plate Hydraulic Press 

The four-column three-plate hydraulic press boasts high rigidity and precision (parallelism <0.1mm), and operates extremely smoothly. Common tonnage ranges from 60T to 300T. However, its operating space is not as spacious as that of a C-type press; it is suitable for large-volume, standardized continuous production of gold bars, ensuring a high degree of consistency in the depth and clarity of markings on each product.

4. Quick Reference Checklist of Selection Parameters

To facilitate communication with equipment manufacturers, I have compiled a list of key parameters for you:

4.1 Tonnage: Select the required tonnage of the hydraulic press based on your product, allowing for a 20%-30% margin.

4.2 Structure: Four-column three-plate type or C-type open type

4.3 Effective worktable area: Must be larger than your mold size.

4.4 Opening height: Must be greater than (mold height + gold bar height + operating space).

4.5 Stroke: Must be greater than gold bar height + loading/unloading space.

4.6 Speed requirements: Idle speed ≥150 mm/s, working speed ≤25 mm/s

4.7 Control accuracy: Parallelism ≤0.1mm, pressing tonnage accuracy <1T, position control accuracy <0.2mm

4.8 Control system: Must have PLC, constant pressure/constant stroke mode, adjustable pressure and time.

4.9 Safety features: Two-hand start, emergency stop button, infrared light curtain protection.

4.10 Power Supply: Three-phase 380V

We hope this selection guide will help you make a more accurate decision. If you can provide the most common length and width dimensions of gold bars or gold bricks, as well as your expected daily output, we can provide you with a more specific analysis for your reference. For more information/advice on hydraulic presses for stamping and forming gold bars and gold bricks, or to purchase other high-quality hydraulic presses, please contact us (or scan the WhatsApp QR code below). Jianlong Hydraulic Technology will provide you with personalized and customized professional solutions and is dedicated to serving you.