|Industrial Hydraulics in Plastics
Key Rexroth Solutions
- Extent investment in existing equipment
- Increase productivity
- Increase reliability
- Increase ease of use
- Benefit from applying the latest electrohydraulic controls to proven mechanical molding equipment
- Increase competitiveness without major capital investments
VT-HACD controllers offer an unequaled combination of accuracy, repeatability, and load compensation. They give you more capabilities and flexibility in open- and closed-loop control, including the ability to nest loops. The controllers are available in application-specific configurations for clamping, injection, and transport.
SY-DFEE pumps save space and simplify design with a built-in open- and closed-loop proportional amplifier for precise control of flow and pressure.
HNC 100 controller is a programmable, bus-capable NC control for electrohydraulic drives using open- and closed-loop control algorithms specifically tailored to the special characteristics of hydraulics.
Proven Improvements Through Retrofitting
A typical example of a rebuild project was a mid-1980s 700-ton injection molding machine. This machine was rebuilt with the following components:
The goal for the project’s success was to meet "World Class Standards" for injection machine performance as defined by a third-party manufacturer of test and measurement equipment for the injection molding process.
- PLC using a DeviceNet™ network
- VT-HACD-DPQ and VT-HACD-DPC to control all major machine functions.
- A high-performance proportional valve for the injection cylinder.
- Existing clamp cylinder and ejector cylinder control valves were retained; both were determined to be adequate for closed-loop control.
- A clamp safety valve was added to meet new ANSI safety standards for plastic machinery,
- An additional fixed displacement pump was added to increase the injection and clamp speed.
Before the rebuild, only Ejector Repeatability could pass the world class test; after the rebuild all measured criteria exceeded world-class standards.
In addition, the rebuilt machine is running at 0.3% scrap rate, while the plant's average scrap rate is 3%. The calculated cycle time for the molded part is 40 seconds but this machine is producing the same part at a cycle time of 38 seconds. The reduced scrap and faster cycle time translates into additional annual plant savings of approximately $38,000!
World-Class Machine Criteria
|Hydraulic Injection Pressure Response (s) ||Failed ||0.20 ||0.145 |
|Injection Speed Linearity (%) ||28.28 ||10.00 ||8.41 |
|Injection Load Compensation (% kpsi) ||88.10 ||<3 ||0.610 |
|Clamp Repeatability (mm) ||7.188 ||2.540 ||1.676 |
|3-Stage Capability (Velocity Pack, Cavity Pressure, Transfer) ||No ||Yes ||Yes |
|Ejector Repeatability (mm) ||1.78 ||2.54 ||0.251 |
|Decompression Repeatability(cc) ||Not repeatable ||<25 ||9.940 |
|Injection Speed (cc/s) ||700 ||N/A ||900 |
More on Plastics Processing Productivity
Learn the full story on Bosch Rexroth’s advanced hydraulics solutions for plastics manufacturing.
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