Friday, May 30, 2008

Etching is a controlled corrosive process and Inconel has been developed with a high nickel and chromium content, specifically to resist corrosion. The Inconel 617 nickel-chromium-cobalt-molybdenum superalloy offers excellent high-temperature strength and oxidation resistance It also exhibits excellent resistance to a wide range of corrosive environments, which to date have largely prevented the material being photo etched

Etching is a controlled corrosive process and Inconel has been developed with a high nickel and chromium content, specifically to resist corrosion.

Processing thin sheet Inconel by conventional means (punching and slitting) has always given cause for concern as parts tend to come out wavy and the material has a tendency to roll at the edges after processing. Now, thanks to this by the Precision Micro Technical Team, perfectly flat, precision parts can be produced from 0.006in Inconel sheet, economically and with outstanding repeatability.

Wednesday, May 28, 2008

The new additions to IFM Electronic's efector T series are probably the only all-stainless steel sensors with an operating temperature as high as 100C. FM Electronic has released inductive proximity sensors with housings made from stainless steel, including the sensing face. They suit the food industry, as they can be used in wet areas and survive aggressive cleaning and high temperatures

The new additions to IFM Electronic's efector T series are probably the only all-stainless steel sensors with an operating temperature as high as 100C. The IFM devices suit true flush-mounting and normal spacing between sensors.

Complemented by the IFM EVT range of M12 stainless steel food-grade connectors, these stainless steel sensors are available in M12, M18 and M30 versions with sensing ranges optimised on stainless steel targets of 3, 5 and 10mm respectively. These food-grade sensors carry IP ratings of both 68 and 69K.

Wednesday, May 21, 2008

The digital output from the SX8273 allows manufacturers of industrial pressure/temperature sensing equipment to provide a cost-effective and complete solution to their customers. Solid State Supplies has released an ultra-small sensor interface device that uses low-power ZoomingADC signal amplification circuitry to connect directly to a wide variety of pressure, temperature and magnetic sensors Enabling electronics to be co-located with the sensor, the digital output from the SX8273 sensor, whether it is magnetic, pressure or chemical, allows manufacturers of industrial pressure/temperature sensing equipment to provide a cost-effective and complete solution to their customers.

Capable of operating from a single Li-Ion battery without loss of its 16bit precision, even with a depleted battery, the device features ZoomingADC, a 10bit preamplifier with a programmable gain of between 0.1 and 1000 and a 16bit ADC.

The preamplifier delivers the highest possible gain, giving designers the freedom to achieve a given level of sensitivity using lower-cost sensors. Four digital GPIO lines enable the component to read most Wheatstone bridge sensors.

Thursday, May 15, 2008

Cures to a tough, strong solid with excellent long term durability and chemical resistance even when exposed to adverse environmental conditions. Master Bond has developed a high-temperature-resistant epoxy-resin system called EP121CL for service up to 260C The two-component optically clear low-viscosity epoxy-resin system features high thermal stability, superior electrical insulation properties and outstanding dimensional stability for casting, sealing, potting, encapsulation and impregnation applications.

Especially noteworthy are its mechanical properties of 83MPa in tensile strength, 119MPa in compressive strength, and its exceptional electrical insulation properties including, a volume resistivity greater than 30Tohm-cm, a dissipation factor of 0.020 at 1MHz and a relative permittivity of 3.34 at 60Hz. EP121CL is an elevated temperature curing epoxy resin system that passes NASA's low-outgasing test.

It cures to a tough, strong solid with excellent long term durability and chemical resistance even when exposed to adverse environmental conditions. There is no cracking or separation of properly cured EP121CL resin from metal, glass etc, over a wide temperature range. Having excellent optical clarity it can be used in optical and fibre-optic applications. The two components are storage stable and after mixing have a working life of 2-3 days at ambient temperatures.

EP121CL is also available in one component and thermally conductive versions. It comes packaged in premixed bipacks and cartridge/gun applicators for convenient dispensing as well as in pint, quart, gallon and 5 gallon containers. Master Bond has developed various "low outgssing" epoxy resin based adhesive systems manufactured with exceptionally high quality standards.

Master Bond's speciality low-outgasing systems include those that are optically clear, cryogenically serviceable, electrically conductive, thermally conductive/electrically insulative and high temperature resistant. Some formulations have been tested by NASA authorised facilities, whereas others have been independently tested.

Friday, May 02, 2008

Dan Schimelman explains how innovative miniature solenoid valves and diaphragm pumps enable advances in portable medical devices. Medical therapies are being driven to reduce hospital costs by administering treatments at home or even on the go. This demand has launched new generations of portable devices. Since most of these systems incorporate modules consisting of miniature diaphragm pumps and solenoid valves, these fluidic components need to be tailored according to the system criteria that best achieve the market demand objectives.

Medical Device developers benefit from understanding how these components can be optimised to best meet their specific application requirements. Both employers and payers have exerted pressure to contain health care costs by shifting skyrocketing hospital care to less costly outpatient procedures. There is an increase of procedures that are being performed in an outpatient and ambulatory procedures that once were performed only on an inpatient basis.

Advancements in medical technology and the development of noninvasive and minimally invasive surgical procedures have contributed to growth in outpatient ambulatory care. In many cases, surgeries once requiring several days of postoperative observation and care have become same-day procedures. The trend for medical practitioners to have patients reduce hospital stays and continue treatments at home has required medical device companies to engineer systems to be more portable, quieter and cost effective. Several high technology diagnostic and therapeutic services now available in the home include transfusion therapy, dialysis, oxygen therapy, mechanical ventilation, compression therapy and wound therapy.

This changing healthcare landscape is driving the medical device field to experience explosive growth. The market will continue to accelerate as demographics and market drivers increase their pressure for new and innovative product offerings. To successfully support speed to market of new and innovative products, Hargraves Technology Corporation, a leading innovator of miniature, high efficient diaphragm pumps and solenoid valves, has been working closely and earlier in the development process with medical device companies to identify key system requirements. Miniature diaphragm pumps and solenoid valves have become popular with fluidic system engineers to provide the pressure and vacuum transport of air and gas in a cost efficient manner.

By understanding how key components such as these can be tailored for optimum system performance, medical device developers can speed their time to market by identifying earlier exactly what they need. The marketplace for portable medical devices is becoming more segmented and competitive with each having their own distinct requirements for success to meet specific end user demands. The first step in the development process should be to gain clear definition from the marketing team the criterion for a successful product release.
Then, it is important to prioritise these capabilities and select the components and their respective performance specifications needed to best meet the ranked criteria.

Since there are usually tradeoffs, this will help to ensure that major product objectives are met and that development timelines don't suffer from project scope creep. For portable medical device developers, the following criteria and how they are prioritised can make a significant difference on the specific components that should be selected. For medical devices to be truly portable, they need to be much more compact and lighter than their desk mounted predecessors. The maximum envelope that the fluidic module can fit into needs to be determined. This will have an impact on determining the maximum size of the pump and valves that will determine fluidic performance.

Should space be very limited, smaller pumps and fewer valves will be needed which either will limit performance or increase noise if smaller pumps are to run at maximum motor speeds to achieve similar performance of a larger pump that is run slower. The required flow at pressure/vacuum at the key operational points of the medical therapy and how they need to be controlled (analogue control, PWM control, PWM with tachometer output etc) should be determined for to set baselines for key components. Increasing the performance while shrinking the size of the miniature solenoid valves and diaphragm air pumps has posed several interesting challenges.

Advanced designs, materials, and motor technologies have launched new innovative pumps and valves that can achieve more performance in a smaller package. Medical therapies taking place next to a patient while sleeping or while they are in public will need to take noise into account.
Diaphragm pump manufacturers can minimise noise by reducing the stroke, optimising diaphragm shape and durometer, and lowering chamber efficiencies. Depending on the level of these actions, tradeoffs may impact pump efficiency and fluidic performance. Another tactic noted earlier is to use a larger capacity (for example a dual head pump versus a single head pump) running at lower speed.

The performance stays the same but the noise level drops significantly. The negative tradeoff, of course, is a larger pump envelope. If it is a battery powered device, what is the desired target operational life from the battery?. Would there be a market advantage to have the portable medical device run longer from a battery that its competition?. As will be discussed later, the proper selection of motor technology for the diaphragm pump will contribute greatly in the efficiency of the system. In addition, properly matching the orifice size of the solenoid valves will ensure that they are not acting as a restriction thus forcing the diaphragm pump or miniature compressor to work harder.

Will this device be disposable or requiring the fluidic components to run intermittently or will it be required to be having proven high reliability under demanding cyclic operation that can exceed 10,000 hours of operational life?. Operational life requirements are affected by selection of the motor technology, diaphragm elastomer, and fluidic loads and cycling in addition to the maximum temperature environment to which the components will be exposed. The priority that cost is placed on the decision criteria for fluidic components will greatly impact the ability to maximise the advantage of each of the preceding factors.

It should be noted that too strong an emphasis to cut costs of the diaphragm pumps and solenoid valves could actually increase overall costs and marketability of the device. For example, the selection of advanced, high efficiency and high reliability motor technology and solenoid valves will significantly decrease power consumption; sometimes in half. This can result in battery requirements being greatly reduced; giving development engineers the flexibility to design an even lighter and more compact device or elongating battery capacity.

The following are technology drivers greatly affecting the above decision criteria for miniature air diaphragm pumps and miniature solenoid valves. The motor of the miniature diaphragm vacuum pump or compressor is probably the biggest driver affecting the overall performance, efficiency, expected operational life and cost. Since the motor is the highest cost component of a diaphragm pump, it is a major cost driver impacting the overall cost of a fluidic module.
Two major motor technology designs, DC brush and DC brushless, can be configured on the pump with their respective advantages and disadvantages.

DC brush motors have been common with many diaphragm pressure and vacuum pump applications when low cost is critical but operational life is not important. Iron core brush motors typically use carbon brushes to conduct the electrical input from the lead wires to the motor's commutator. The constant rubbing of the brushes on the commutator causes the brushes to wear down like the lead in a pencil. Brush motors are designed to last from 500 hours to 5000 hours, depending on the quality of the motor and how it is used. The motor brushes experience an electrical arcing on each startup.

Frequent arcing will heat up the carbon brushes causing them to wear out more rapidly.
Therefore, brush motors that experience frequent on/off cycles per day wear out more quickly.
A top quality brush motor can be expected to last no more than 3000 hours with frequent on/off cycles. Brush motors used in high duty applications with more continuous operation can last longer. It must be stated that few applications allow a pump to run continuously.
Frequent starts and stops are the norm. Occasional cycling may lead to motor stall due to carbon dust build up between the brush base and commutator. Tapping the outer housing to clear these deposit from the brush tips can usually restart the motor.

In addition to limited life, brush motors can introduce unwanted electrical or RFI noise into a system's circuitry. Coreless motor technology differs from the standard brush motor in that the winding is wound onto itself on the rotor. The brushes are made from a highly conductive and efficient precious metal. No iron is on the rotor, making the lighter, coreless (or ironless core) rotor spin at a given performance level with less required input energy. These results in lower current draw required to power the respective diaphragm pump. Due to the precious metal brushes and the complexity to manufacture the wound rotor, coreless motors come with a price premium.

As a result, coreless motors are commonly used in portable, battery-operated systems requiring exceptional efficiencies to achieve longer battery operation. Brushless DC motors eliminate these problems. In a brushless motor, the magnets are on the rotor, and the windings are wrapped around poles on the stator. Instead of brushes and a commutator bar, the windings are switched on and off sequentially by solid-state electronics. Brushless motors require less maintenance and are smaller, lighter and more efficient than brush motors with comparable outputs. With motor designs that focus on performance, reliability and endurance, operational life can be expected to exceed 10,000 hours with a high precision bearing cage design to take out any play that causes bearing fretting.

This precision design also can produce a quieter motor as the mechanical noise common with brushless motors was significantly reduced. Brushless motors do have a limitation though since they incorporate slotted stators. The stator consists of slotted iron laminations that are fused to form a solid, uniform stack. The slots form rows that extend the length of the stack, and the windings are inserted into each row. As the rotor turns, the magnets are more attracted to the stator's teeth than the gaps between them. This uneven magnetic pull, called cogging, reduces the motor's efficiency and makes it difficult to produce smooth motion at low speeds.
With typical operating pressure and vacuum loads, current technology brushless motors today can see efficiencies in the 50-60% range.

Hargraves has introduced a new and innovative design variation the brushless motor that incorporates a slotless stator (one that has no slots to keep the windings in place). Instead, the windings are attached to the inside surface of the stator with adhesive. With no teeth to attract the magnets, cogging is eliminated, and the motor produces smooth, quiet rotation. The absence of teeth also provides room for larger magnets in the rotor and more wire in the windings, which means that slotless motors can generate more torque without a corresponding increase in size.
Additionally, the slotless design significantly reduces damping losses.

In both slotted and slotless motors, eddy currents are induced as the magnets pass the stator.
However, these currents are weaker in slotless motors, because the distance between the stack and the magnets is greater than in slotted motors. This makes slotless, brushless motors more efficient than slotted motors. Compared with slotted brushless motors, miniature diaphragm pressure and vacuum pumps can expect to see improved efficiencies up to 70% coupled with the exceptional life that the brushless design produces. The diaphragm in miniature diaphragm pumps and micro compressors are stretching and flexing under load and sometimes elevated temperature conditions.

Due to limitations of standard EPDM elastomers, many current technology miniature diaphragm pumps and compressors are only rated up to 40C and have limited elastic properties to endure the rigorous cyclic stretching required for higher output applications. Pumps configured with EPDM and operating at higher ambient environments typically will endure ripped diaphragms before they achieve 3000 hours. To extend diaphragm life past 10,000 hours under operating conditions that new generation portable medical devices require; innovative research by the Hargraves materials research team was conducted to develop an advanced performance elastomer that could withstand up to 70C with improved mechanical capabilities.

This research project resulted in the development of an advanced EPDM, or AEPDM, a proprietary elastomer material configuration that has been tested to last ten times longer than standard EPDM. Depending on the fluidic loads and ambient operating temperatures that the miniature diaphragm pump will be operating at, AEPDM diaphragms have been found to exceed 20,000 hours of operational life The shape of the diaphragm itself has been evaluated and optimised to improve vacuum, pressure and flow performance efficiencies. Typical flat diaphragms are performance limited by the amount that it can be stretched. High performance air and gas pumps require increased pump stroke beyond the stretch limits of the flat diaphragm.

Higher vacuum or higher flow performance requires that either a larger flat diaphragm be used (which would require a larger pump head design) or an increased diaphragm surface area by using a shaped diaphragm. Shaped diaphragms allow the pump stroke to increase by as much as 80%. By optimising the pump's diaphragm shape, significant increased performance output can be achieved in a much smaller, compact envelope size. Miniature solenoid valves are required to direct and control the flow in many portable medical devices that require miniature diaphragm pumps or micro compressors. To fit in these new generation enclosures, the valves typically cannot exceed a 10mm package size.

The new design trend has challenged component manufacturers to produce smaller, lighter components, specifically miniature solenoid valves, to fit these new products. With these smaller valves came smaller orifices and restricted throughput, effectively giving up higher performance for a smaller package. The typical 10mm solenoid valve has up to one-sixth the throughput area when compared with the pump output capacity. Due to the restrictions of these small, ineffective valve orifices, the pumps in a fluidic system have been required to overcome significantly large pressure differentials. A common practice of fluidic systems engineers to overcome this reduction in throughput has been to use a pump with up to 200% more capacity than necessary.
Even with the higher output pumps, minimal performance gains were achieved while adding unnecessary weight, increased power consumption, increased heat, noise and size.

Additionally, as portable medical devices designers develop smaller instruments with more functions, more solenoid valves are required compounding the increased heat, noise and power consumption problems. Recent advances in solenoid valve technology have focused the valve design to be small in overall size but having a much larger orifice. By using finite element analysis to analyse the fluid flow throughput and the flux efficiency of the magnetic field created by the solenoid, Hargraves was able to increase the flow up to two times the current capabilities with its Magnum series of solenoid valves. Due to much higher efficiency achieved in the solenoid design, power consumption and heat generation have been able to be significantly reduced.

In addition, advanced manufacturing processes can lock in exact, optimised orifices that will enable fluidic tailoring for application specific flow, resulting in a revolutionary advancement in solenoid valve technology. In addition, the new generation Magnum miniature solenoid valves can be mounted individually, on a manifold or soldered directly to a printed circuit board, giving fluidic module design engineers the most flexibility available. Typically, the weak link in a fluidic circuit has been the small valve with its small, restrictive orifice.

Instead of specifying larger, higher output pumps, fluidic designers are working with advanced fluidic solution providers to provide a tailored solution optimising the solenoid valve orifice to an optimised diaphragm pump to best meet their system criteria. Advantages are great including smaller, lighter pumps, less noise and greater pump life since the differential load pressures significantly decrease, and overall size and weight are also reduced. Portable medical devices that seek to achieve higher flow, longer battery operation and longer device life while in a smaller but cost effective fluidic module are benefiting from tailored configurations of advanced miniature diaphragm pumps and valves. Properly ranking the overall system criteria and the respective component requirements will help ensure the project success with quicker time to market.