April 2020 Design Notes

Varnish removal cleans up plastic injection molding

Hydraulic fluid is one of the most important components in an injection molding machine, which is why contaminated fluid cannot be overlooked. 80% of all hydraulic failures are caused by contaminated fluid. The common types of contaminants are solid particles and water, but varnish is just as destructive for hydraulic systems.

The constant pressure and temperature fluctuations of the hydraulic fluid can lead to mechanical and thermal stress of the fluid. This instability results in a breakdown of oil molecules leading to the creation of a sticky residue (varnish by-products). This residue, combined with other contaminants, can cause friction and wear, which can shorten component oil life and cause unnecessary downtime of the system.

Using a RMF varnish removal system from Des-Case improved uptime in an appliance manufacturer’s plastic injection molding machine.

Additionally, the forming of varnish can be accelerated by a chemical reaction between metal solid particles and water. This reaction results in corrosion of the components, changes in fluid properties, and oil degradation.

A large appliance manufacturer in the United States reached out to Des- Case regarding an increase in unplanned maintenance, blocked line filters, and frequent oil changes on their Toshiba plastic injection molding machine. All of these symptoms were in line with severe varnish problems and was further confirmed by an oil lab analysis. The results of the test showed a Membrane Patch Colorimetry (MPC) value at a critical level of 63.4 and an ISO cleanliness level of 25/20/14.

To solve the varnish problem, Des-Case offered its RMF Varnish Removal System, which acts as a kidney loop, continuously pumping fluid through the high-efficiency varnish removal cartridges.

The Varnish Removal System combines varnish removal with oil quality monitoring and prevents varnish from forming by removing solid contaminants and water.

Long fiber cellulose/PP cartridges in Des-Case's Varnish Removal System are specially designed for the removal of varnish by-products which are dissolved in the fluid.

The Long Fiber Cellulose/PP cartridges are specially designed for the removal of varnish by-products which are dissolved in the fluid. These cartridges adsorb polar acids through special compacted fibers, which create an intricate internal flow path. Unlike other technologies, the cartridges do not add water to the fluid. They remove water and other solid contaminants.

During the operation time of the system, samples were taken frequently and sent to a laboratory for analysis. Next to a standard fluid analysis, an MPC and gravimetric solids (MPC weight) test was done to measure the varnish potential. After three weeks of filtration, the varnish potential (MPC value) went from a critical level of 63.4 to 7.8, and the MPC weight decreased from 0.0182 to 0.0072 g. In the following five weeks, the MPC dropped even lower to 1.6 and weight down to 0.0038 g. The ISO cleanliness levels also dropped from 25/20/14 to 17/14/11 in three weeks. Five weeks after that, the ISO code dropped even further to the target level of 15/13/10.

As the data shows, the cleanliness and health of the lubricant improved significantly in a short time and will improve the uptime of the machine.

Des-Case | descase.com

New design overcomes piston-pump limitations

AX fixed displacement piston pumps and AXM motors are available in multiple sizes with displacements from 18 to 76 cc/rev.

Piston pumps and motors have been on the market for many years, and they are arguably one of the most important components in many a hydraulic circuit. The basic design behind a conventional piston pump usually has seven or nine pistons that convert mechanical torque into oil pressure. In a piston motor, the process is reversed.

Every project engineer has, without a doubt, experienced the limitations of piston pumps and motors: high-pressure ripple, and less-than-desired mechanical and volumetric efficiency, according to officials at Bucher Hydraulics, Elgin, Ill. In addition, the growing demand for electrically powered machines has exposed additional drawbacks such as noisy operation and minimum shaft speeds that must be fairly moderate when working at high pressure.

Applications that face the need for faster cycle rates, increased operating pressures, more-responsive dynamics and accurate flow and pressure control have already been handcuffed by the shortcomings of current piston pumps. Engineers normally compensate for these restrictions by using accumulators and valves with associated high energy losses and additional costs.

For these reasons, Bucher Hydraulics is introducing a new series of pumps that overcomes the limitations of conventional piston technology. Company officials say it is not just a further evolution of existing pump concepts, but rather it is a revolutionary design that offers better efficiency, excellent dynamics, low noise, and low minimum speed at high output torque.

Tests show an 80% reduction in pressure pulsations in an AX size-24 pump running over 1 rev and 400 bar, compared to a conventional bent-axis pump.

The new AX piston pump and AXM piston motor work on the principle of balancing internal forces by having two rotating barrel plates facing each other, and each having 12 pistons. Thus, the units achieve a high power density all while limiting the axial forces, which need only a light bearing to handle the loads.

The models come in displacements from 18 to 76 cc/rev, and the company plans to extend the range up to 115 cc/ rev in the near future. Maximum operating speed for the units is 3,600 rpm.

Sights on electrification

The characteristics of the Bucher Hydraulics AX pump were developed with a particular focus on construction machines powered by electric motors. The high volumetric and mechanical efficiency, low noise, lowpressure ripple, and minimum permissible speed of only 2 to 3 rpm, together with the possibility of bidirectional operation, make the AX pump well-suited for electrical and hybrid machines of the future.

For example, because as there is virtually no minimum speed limit, they are ideally suited for matching fixeddisplacement AX units with variable-speed electric drives. Further, this high level of efficiency in electric-drive mobile machines is essential, as low power losses mean valuable battery capacity can be conserved.

Likewise the AX pump, with a balanced design and more pistons, produces a low pressure ripple and generates minimal noise over a wide range of speeds and pressures. In contrast, conventional axial-piston pumps produce considerable noise as alternating and widely fluctuating internal pump forces result in housing vibrations that ultimately transmit to the machine. When traditional hydraulic pumps are used with diesel engines, the problems of physical pulsation are barely noticeable. In inherently quiet electric-drive applications, that’s no longer acceptable.

The large, non-compensated forces in typical bent-axis motors need to be absorbed by extra-large ball or roller bearings. This increases the space required and makes integration into a machine more difficult.

The advantages offered by these models also come into play in winch applications. Winch operations, in general, are problematic because torque-ripple issues can hurt performance. Efficiency at start-up can be poor. And high-pressure performance can be poor at low rotary speeds.

Standard AX pumps and motors can reach a working pressure of 450 bar. And with a low-speed range of just a few rpms, the AX motor has a starting efficiency of 99% versus the 60 to 65% of a conventional axial-piston unit. Performance can significantly increase thanks to precise and accurate crane movements. Crane slew drives can take advantages of these attributes, too.

Other industry applications can also benefit from the Bucher AX hydraulic pumps and motors characteristics of excellent energy efficiency and performance when the unit must start and run slowly under high load and pressure. In wheel motors, for instance, high power density and working pressure coupled with low permissible speed make the AXM motor the perfect alternative to gear motors. The minimum speed of 2 rpm brings new possibilities to mobile machines. New software lets engineers conduct multiple iterations during the design phase, offering several options in different and lower gear ratios. For straight travel in vehicles such as crawler excavators, the volumetric efficiency of approximately 96% will permit an increase in ground speed.

Bucher Hydraulics | bucherhydraulics.com

Mechanical joining tools for secure, leak-proof joints

The Monaghan Mechanical Joining Tool (MJT) is suitable for applications where joints loosen due to changes in temperature, altitude changes, vibration, and where high pressure is present — including those common in the automotive, fluid power, and aerospace industries.

Monaghan Tooling Group’s Mechanical Joining Tools join tubing to flanges and fittings to create secure, leak-proof jointsthat withstand up to 20,000 lb of hydrostatic pressure. Superiorto welded, brazed, or crimped joints, mechanically joined partswill not leak, pull apart, or loosen from pressure, vibration, ortemperature changes. This proven method allows joints to be rolled to a torque or diameter spec.

Rolling to a torque ensures consistent results, regardless of tolerance and variations of the tube OD, wall thickness, and component ID. Rolling to a consistent diameter guarantees a consistent ID of the tube, which makes it possible to “iron out” and round up the ID of the tube. Any annealed or ductile product can be mechanically joined, including mild steel, stainless steel, aluminum, titanium, copper, cupronickel, Inconel, and more. Monaghan Mechanical Joining Tool (MJT) is suitable for applications where joints loosen due to changes in temperature, altitude changes, vibration, and where high pressure is present — including those common in the automotive, fluid power, and aerospace industries.

How it works A tube is inserted into the flange; then, a mechanical joining tool is inserted into the tube. A generous chamfer or radius should be provided on the backside of the flange. The opposing end should include a shoulder that the tube can bottom out against to ensure proper position. Flange grooves with sharp corners at the top edge and the bottom of the groove are required. The width of the groove can be 0.062 to 0.375-in. (1.6 to 9.5mm), with depths from 0.005 to 0.0320-in. (0.13 to 0.81 mm) — both dimensions are dependent on flange width, thickness, and the hardness of the tube.

When the tube has been rolled to about 25% of total MJT expansion required, it makes metal-to-metal contact with the flange.

At approximately 50% MJT expansion, the tube metal begins to flow into the grooved serrations of the flange.

When the Mechanical Joining Tool is completely expanded, grooved serrations are now filled to the predetermined groove fill percentage of the tool. (Groove fill percentages vary by industry as well as applications.)

Once the correct joint has been completed, the rotation of the tool is reversed so that it can be extracted from the assembly and the cycle can be repeated with new components.

Monaghan MJT is suitable for a variety of applications, including hydraulic fittings, fitting and block assemblies for hydraulic components, hydraulic lines, tube installation into transmissions, differentials on large equipment, and all types of fluid lines in aircraft. Monaghan engineers are available to assist with tooling selection and other aspects of the mechanical joining process.

Monaghan Tooling Group provides the engineered tooling and services, including application-related consulting, to solve machining challenges. They have partnered with standard and custom tooling manufacturers including Elliott Tool Technologies, Diatool, UC Tools, RE-AL, MK-Tools, Reamtec, and Axis, to address the challenges of precision metal finishing and high-performance cutting. FPW

Monaghan Tooling Group | monaghantooling.com

Vacuum lifting systems maximize safety

The adapter includes a flow-control block for easier adjustment of hydraulics.

Vacuworx, Tulsa, Okla., manufactures innovative heavy-duty material-handling systems based onhydraulic-powered vacuum lifting. The equipmentis used in the oil and gas, water and sewer, highwayand heavy construction, concrete construction, landscaping and manufacturing industries.

The company announced at Conexpo/IFPE that it has engineered significant updates to its line of RC series vacuum lifting systems. All changes are designed to maximize safety while minimizing down time on the job. In addition, the lifters are “smarter” than ever before by incorporating a CAN bus system to provide real-time diagnostics and enhanced safety features.

Although the installation for RC series lifters is said to be quite simple, Vacuworx engineers have made several enhancements to the adapter (the part that connects the lifter to the host machine, such as an excavator) which improve the process.

The adapter now features removable top caps, which lets an installer position and secure the adapter pin easily. Standard pin size is 110 mm, but the adapter will also accommodate pin sizes down to 50 mm using bushings. Vacuworx also offers an adapter for 120 mm pins and larger.

A flow control block has been incorporated into the adapter to allow for safer and more convenient adjustment of the hydraulics. This puts the flow controls within easy reach, rather than higher up on the arm of the excavator. In addition, the part of the adapter that connects to the base plate on the lifter, referred to as the “tombstone,” is now a replaceable part of the assembly rather than being welded to the adapter. This is designed to minimize time and overall cost of repairs.

In a similar vein, the traditional gear box has been replaced with a belt drive. This will provide longer service life and drastically reduce repairs, said company officials. The belt drive requires virtually no maintenance and is environmentally friendly with no oil to replace. In addition, the system design keeps engine bay temperatures cooler.

Vacuworx has also implemented CAN bus technology for its vacuum lifting systems. Commonly used in passenger vehicles and other equipment, a Controller Area Network (CAN bus) lets internal devices communicate with each other without a host computer. Using a central logic controller, the system is designed to monitor for faults and quickly diagnose specific problems.

CAN bus gauge shows pressure levels and error codes.

The new dashboard gauge on one side of the lifter shows error codes, oil and fuel levels, pressure level, number of lifts and engine hours. The logic controller increases safety by ensuring that the electronic components are operating correctly.

The simplified wiring design of the system has fewer components and no mechanical switches. The system incorporates pressure transducers instead of a vacuum switch for greater accuracy. All circuits can be monitored and diagnosed through the logic controller. There are no fuses to repair or replace — all faults are reset electronically. In addition, the design helps promote safety by identifying any incorrect repairs or environmental damage.

Vacuworx | vacuworx.com