The injection molding process of an injection molding machine is a process that operates according to a predetermined cycle, that is, by closing the mold, locking the mold, advancing the injection nozzle, injecting glue, maintaining pressure, cooling the pre molding injection table, retreating, opening the mold, and taking out the product, etc., to achieve the molding of a certain product.

The losses in general injection molding processes mainly come from the following points:

1. Overflow loss. The hydraulic pressure, flow rate, and pressure required for each process vary depending on the product and processing steps. So, regarding the oil pump motor, the load during the injection molding process of the injection molding machine is in a changing state. The flow rate of the pump is planned according to the maximum required flow rate. When the oil pump operates, it provides hydraulic flow at a stable speed. When the required flow rate of the injection molding machine is less than the maximum flow rate, excess hydraulic pressure will flow back through the relief valve, and this part of energy will be lost.

2. Save losses. When hydraulic oil flows through the saving port of the valve, there will be a certain pressure drop, which is called saving loss. Due to the large saving area of directional valves, most of the saving losses occur on proportional valves. Due to long-term full speed hydraulic cycle activity and severe mechanical friction of hydraulic components, adverse phenomena such as high oil temperature, excessive noise, and shortened mechanical life are formed.

3. Plan for residual losses. In planning, commonality is usually considered, and the maximum capacity is used as the basis for planning. Therefore, the planned capacity of the user's oil pump motor is much higher than the actual need, resulting in a phenomenon of "big horse pulling small car" and a lot of waste of electrical energy.

A plan has been developed to equip the Sifang V560 series frequency converter with a dedicated expansion card for the molding process and process characteristics of injection molding machines. The system composition is shown in Figure 1, as follows:

1. The dedicated expansion card integrates four analog input channels, two voltage type and two current type, providing input interfaces for different types of flow and pressure commands;

2. Integrated multi-stage speed control, which can be combined with flow and pressure setting signals to determine the operating frequency of the frequency converter;

3. Bottom flow can be set to improve the response speed and stability of the system.

Plan advantages:

1. It has a dedicated operating frequency channel for injection molding machines, with short acceleration and deceleration time and rapid system response;

2. The system has strong current suppression ability, effectively preventing the occurrence of overcurrent and other faults, and the system operates stably;

3. The function of superimposing multi-stage speed, flow rate, and pressure commands facilitates the completion of different process requirements for operating frequency;

4. The temperature rise of the hydraulic oil in the injection molding machine has significantly decreased, effectively extending the service life of the hydraulic oil;

5. The system has high energy efficiency, generally reaching 20% to 50%.

This article introduces a driving plan for an injection molding machine based on the Sifang V560 frequency converter. The plan has the advantages of short acceleration and deceleration time, rapid system response, and stable system operation. The hydraulic oil temperature rise of the injection molding machine is significantly reduced, effectively extending the service life of the hydraulic oil. It has now been successfully applied to multiple injection molding machine energy-saving renovation sites.