Key layout considerations
During initial circuit layout, it’s important that ports be identified by the 1, 2, 3, 4 naming convention, which represents the numbering of ports starting from the bottom-most port. This convention ties the hydraulic port on the symbol with the physical port in the hole. It ensures that the manifold designer won’t connect the valve backwards. Most manufacturers have standard common cavity sizes of 8, 10, 12, 16 and 20. A large degree of interchangeability exists between manufacturers (except for Sun Hydraulics, which has a proprietary cavity standard).
A common problem with cartridge circuits is that designers overlook the additive effect of pressure drop across cartridge valves in series. This can be a source of unintentional energy inefficiency.
It’s important to proceed cautiously when specifying flange ports on manifolds for high-pressure and high-flow applications. If a Code 62 flange is called out, it must be clearly communicated to manifold designers, or you could end up with a Code 61 flange.
Care also must be exercised with high-flow SAE O-ring ports. As these ports grow, they get de-rated for pressure. Similar care needs to be exercised by the manifold designer — neither a de-rated SAE construction plug port nor a Code 61 flanged construction port should be used in the manifold when the pressure calls for Code 62.
At the interface between the schematic and manifold design, it’s critical to provide complete component information. It’s not sufficient to either show D03 on the circuit, or even draw a four-way, two-position, spring-offset valve. The ports must be labeled P, T, A, and B, and the model code must be specified. Without this kind of detail, the manifold can be vulnerable to errors or over-designed to compensate for lack of detail.
For example, the manifold designer needs to know whether to leave enough space for an ac coil (which is short), or a dc coil (which is longer). If a spool feedback is used but not shown symbolically, and the model code isn’t called out, chances are good that the manifold will become scrap upon arrival.
When designing an HIC, it’s good practice to provide pressure-measurement ports with each of the work ports. It also helps to identify any other part of the circuit that may need pressure monitoring to set a differential valve for calibration or troubleshooting. A measurement port is especially valuable for a prototype. If the manifold goes into production, the measurement port can be eliminated. A good manifold designer will make a construction hole as a measurement port.
Role of software
When designing HICs, it’s best to use specialized circuit design software. Some manufacturers offer it for free, and other suites are commercially available. Such software ensures a strong tie-in between the symbol, model-code, geometry, cavity, and port numbers and names. In turn, such circuit intelligence is communicated to manifold designers and manifold design software, thus greatly reducing interpretation errors.
After completion of the circuit and creation of a bill of materials (BOM), the manifold is designed either in-house, by a valve OEM, or by an independent manifold manufacturing house that offers design capability. AutoCAD ruled the roost in manifold design until about 2000. But 3D CAD began to emerge in the 1990s, which ultimately led to the widespread adoption of Autodesk Inventor 3D and SolidWorks 3D platforms. Most U.S. manifold designers now use these two platforms that have been equipped with specialized manifold design software. A few valve OEMs use Pro-Engineer and Unigraphics CAD platforms.
These CAD platforms allow vivid visualization of the manifold as it’s being created, resulting in efficient and compact designs. Specialized manifold design software ensures correct connectivity, sufficient clearance between holes, and produces accurate and automated machining instruction.
Migration to HICs
Three macro trends have enabled the rapid growth of HICs. The first is the cartridge valve’s rise from being low-duty-cycle, low-pressure, mobile technology to a more mainstream industrial hydraulic segment. The second trend has been the arrival and widespread adoption of 3D CAD and specialized manifold design software, which has facilitated design. The third has been the adoption of computer numerical control (CNC) machining for manifolds, which has driven down the cost and increased the availability of manifolds.
The upsurge occurring in this sub-segment drives technology and innovation, which further drives growth. This cycle will continue, with the emergence of better cartridge valve and application engineering software tools and the adoption of highly automated, web-based, while-you-wait manifold design software.
Yudhishthira (Yudi) Raina is president and co-founder of VEST Inc. For more information, call (248) 649-9550 or visit www.vestusa.com.