Category: Design & Engineering

Leverage Key Suppliers for Consolidation

Market trends are driving significant consolidation within the medical device industry. OEMs are collaborating with suppliers that can provide solutions for multiple steps in the supply chain thereby:

  • Freeing up capital
  • Reduce workload
  • Increasing quality control
  • Improving lead times

What’s driving this consolidation? Medical device OEMs are under heavy pressure to reduce costs in their highly complex supply chains. As such, cutting edge procurement professionals are seeking strategic supplier relationships that can reduce this complexity. Additionally, this industry is seeing increased regulation and increased competition.

The Burden of Increased Regulations

Over the years, regulatory bodies, including the FDA, have increased the requirements for supplier controls. This requires medical device OEMs to allocate additional time assessing and validating each supplier’s process controls in addition to all standard procurement activities. OEMs are burdened with the requirements of keeping increasingly detailed records, conducting additional audits and performing a larger number of on-site visits. The responsibility of these additional tasks falls to both procurement professionals and quality teams, both of whom are feeling the strain.

The Impact of Industry Pressures

In 2010, the Patient Protection and Accountable Care Act granted organizations providing Medicare services the ability to set reimbursement payments based on a measure of efficiently providing high-quality care. This is a migration from historically service-based pricing to a value-based model. As a result, innovation of medical devices is encouraged to increase patient recovery time and reduce hospital stays.

Additionally, within the healthcare industry, payer organizations are routinely adjusting the details behind medical device reimbursements. Over the past several years, the value of these reimbursements has been decreasing and the impact is felt throughout multiple places within the supply chain.

Rising Costs and Limited Manpower

Increased global regulations and changing industry pressures have left OEMs with rising costs and limited manpower. The additional activities to monitor quality and process controls throughout the supply case require additional personnel, but additional personnel would contribute further to rising costs.

The strategic answer for many medical device OEMs is to partner with suppliers that provide services in addition to basic manufacturing capabilities. Essentially, leading-edge procurement professionals are seeking suppliers who can take over a portion of the OEMs responsibilities and the responsibilities of multiple suppliers.

Leveraging Value-add Suppliers

Finding these unique suppliers reduces the supply base by consolidating the functions of multiple suppliers into one. A supplier review process can reduce an OEM’s approved supplier list by up to 30%.

Leveraging value-add suppliers also reduces the workload of the OEM’s procurement and quality teams who are already resource-limited, thus freeing up their time for strategic activities such as product innovation projects targeting cost reductions while maintaining quality performance.

With strategic suppliers actively participating in process controls and additional value-add services such as inventory management and collaborative product design, the risk of regulatory action against medical device OEMs is further reduced.

A consolidated supply chain with reduced complexity can also save OEMs significant time and money on the following activities:

  • In-house parts inspections,
  • Sampling inspections when receiving inventory,
  • Chain history for medical device records,
  • LTL shipping costs,
  • Shipping, purchase order and invoice paperwork,
  • Lead times and recommended inventory levels.

Conclusion

Industry pressures and increased regulatory requirements in the healthcare industry have driven up costs, increased manpower requirements and created a very complex supply chain for medical device OEMs. Leading procurement professionals are addressing these challenges by partnering with key suppliers who can provide additional services across multiple points in the supply chain.
OEMs who have partnered with these suppliers have seen a reduction in cost, a reduction in risk, a reduction in supply chain complexity and a reduction in internal resource requirements. Supplier consolidation has become an advantageous strategy for competing in this industry.

A Closer Look at Electrical Tests

A Closer Look at Electrical Tests

In one of our previous posts, we discussed the importance of product testing in manufacturing. In this article, we’ll focus on the most common types of electrical tests.

Hipot Testing

Although many of the tests required by safety certifications like UL or CSA are performed at outside testing laboratories, some can (and need to) be done at the factory. Hipot (short for “high potential”) testing is one of them. The most common type of hipot testing is the non-destructive dielectric withstand test. This test involves placing a large voltage (potential) difference between the product’s AC input wires and its enclosure. The current which leaks across the product’s electrical insulation is then measured and compared against an allowed limit.

Since the hipot tester subjects the product to voltages much higher than its nominal operating ranges, passing the hipot proves the product won’t present a shock hazard when properly used and maintained. Hipot testing is usually done on every single unit which is powered directly from the main supply, but can also be done on individual high-voltage components like transformers.

Continuity and Voltage Testing

Continuity testing is often used to verify that cable assemblies are built according to the drawing. This type of test can be done both manually and automatically. If done manually, a technician sets a digital multimeter (DMM) to resistance mode, touches one DMM probe tip to one pin of the assembly, while placing the other probe tip on another pin in the same cable harness. If those two pins are electrically connected, a very low resistance will be displayed by the DMM. Just like the hipot test, the measured resistance must fall below a specified value (usually explicitly stated in the cable drawing). Although the maximum resistance of a “good” connection is largely dependent on the length and gauge of the wire(s) connecting the two pins, good continuity is usually less than 2ohms.

Continuity testing can also be automated by using a cable tester fixture. These often use IC chips and custom made interface boards to very rapidly test every single electrical connection in the harness. As is the case with almost any automated process, the initial set-up costs for automated cable continuity testing can be high. However, if the volume of tested harnesses is high, the resulting cost per assembly can be quite low due to quicker testing compared to a manual pinout test.

PCBAs can also benefit from continuity testing, particularly when it comes to finding electrical continuity where there shouldn’t be any. Sometimes defects occur during PCBA manufacturing which can create an unwanted path for current and even short circuits. These assembly defects include solder splash, solder bridges and unremoved flux which has become conductive. If these short circuits occur between a voltage rail and a point connected to ground, overheating and irreversible damage can occur if that board is powered on. Checking for shorts between a board’s ground and voltage supplies can save a lot of money in repair and rework costs.

Continuity testing on PCBA’s, just like with cable harnesses, can be performed both manually and automatically. Both methods are made a lot easier when the PCBA includes test points, which can take the form of either empty vias or metal posts. Test points are also good for another kind of electrical test which is performed when the unit under test (UUT) is powered on: confirming that all the board’s self-generated voltages are present and within the design specifications.

For low volumes of PCBAs, both resistance and voltage checks can be performed manually by a test technician and DMM, or semi-automatically with a custom test fixture equipped with pogo pins which make electrical contact with the UUT’s test points. When large volumes of boards need to be tested, flying probe automated tests are used.

Although flying probe testing is automated, the process can still take some time, which is why almost all electrical testing, including flying probe, is done on only a sample of units. Sampling and statistics can help you make wise trade-offs between the cost of testing, probability of failure, and the cost of failure. Due to high volumes and extensive use of automation, modern manufacturing relies heavily on validating the processes by which the products are made as opposed to testing every single unit which rolls off the line. This validation involves verifying the production and testing equipment work (by calibrating them to some standard) and proving that the processes are repeatable, consistent and verifiable.

Hipot, continuity and flying probe testing are just some of the electrical testing capabilities we at Providence provide our customers. By combining board and box assembly together with testing, we provide a complete electronics contract manufacturing solution under one roof.

From design to delivery, Providence is ready to take on your next contract manufacturing project. What can we do for you?

Moving Down the Line: Electromagnetic Linear Actuators

Moving Down the Line: Electromagnetic Linear Actuators

In a recent post, we discussed the main categories of electric motors and how they operate. While those electric motors fulfill an important need any time you have to convert electricity into rotational motion, sometimes rotation is not the type of movement needed for an application. In this article, we’ll discuss electro-magnetic linear motors and actuators, which produce linear motion.

Linear Motors: Gliding Along
Let’s first talk about linear motors, that can be thought of as conventional rotating motors whose stator has been unrolled, and laid out flat. Specifically, linear motors are operating by the same principles as their rotating analogues, the AC induction motor and the AC synchronous motor. Maglev trains are an example of large-scale linear motors, where powerful magnetic fields provide both the forward propulsion and the friction-free magnetic cushion that allows these massive trains to reach high speeds with minimal vibration.

Solenoids: Pushing and Pulling with Fields
Another, more familiar type of linear electro-magnetic actuator is the solenoid. A solenoid is a hollow coil of wire that forms an electromagnet, inside of which an armature (the linear equivalent of a rotor) made from a magnetically soft material, is free to slide in and out. These are very useful for on/off mechanical devices, and like fluid valves are easy to build, maintain and operate.

Solenoids are great for applications that need shorter durations of linear movement since once the armature is fully inside the energized coil, it cannot move any further, and thus the solenoid essentially becomes an electric heater. This means that the circuitry that drives the solenoid is usually optimized for supplying large current pulses, in addition to including protection from the counter-EMF produced when the solenoid is turned off.

As we’ll discuss below, a variation on the solenoid design, one which uses a magnetized rod as the armature, has found a niche in low-pressure air pumping.

Advantages of Linear Actuators

Linear motors and solenoids are used in applications where limited linear motion, long operating lifetime and low maintenance are all necessary but a linkage converting rotary motion into linear motion (like a flywheel and crankshaft combination), is not practical or desired.

One such device that showcases the advantages of electro-magnetic linear actuators is the linear air pump. We didn’t discuss these in our recent article on pumps, because linear pumps aren’t a separate category of pump. “Linear” simply refers to how the mechanical energy is transferred to either a sliding piston or a flexing diaphragm and thus already belongs to those two pump categories.

Linear pumps work by using electromagnets (the stator) to generate an alternating magnetic field which alternately push and pull on a magnetized rod (acting as the armature). It’s the movement of this rod that provides the motion needed for a piston or diaphragm pump.

Linear pumps have a very long life, since they use neither bearings nor oil, both of which deteriorate over time and thus require maintenance (and the associated downtime) to replace them. Fewer moving parts also mean fewer potential points of failure. Also, linear pumps are quiet when running and can be highly energy efficient. The AC that energizes the stator can be taken straight from the residential (or industrial) mains, making linear pumps very simple to construct and thus very economical to purchase.

Linear pumps also highlight the main drawbacks of these types of actuators: the outlet fluid pressure is limited to the forces acting on the rod and the strength of the magnetic field, which in turn is limited by the magnetic materials used and the number of loops on the coils. This means linear pumps are limited to low differential pressure applications, like pumping or evacuating anesthesia gas in biological laboratories.

Considerations Specific to Linear Actuators

One of the most important questions to ask if you’re considering using a linear motor or solenoid in your application is, “What are my weight constraints?” In addition to the heavy copper coils in the stator, the armature material is almost always composed of heavy magnetic alloys. If the actuator will be stationary, you’ll have a lot more leeway in your design than if something (or someone) must move the device.

Other important design considerations involve the amount of travel the actuator will need to move, whether you’ll be able to use springs instead of sliding seals (and thus avoid the use of oil lubricant entirely), and whether or not you’ll need to contain all the magnetic fields generated by the actuator.

Linear air pumps, motor assembly and electro-mechanical assemblies are three areas of expertise here at Providence Enterprise. Let us show you how partnering with our team can improve your quality, throughput and cost structures.

From design to delivery, Providence is ready to take on your next contract manufacturing project. What can we do for you?

The Basics of Stepper Motor Control

The Basics of Stepper Motor Control

Due to their durability, reliability, efficiency and availability in standardized sizes and mounting options, stepper motors are widely used in industrial automation, robotics, and new niche consumer products like desktop 3D printers. In this article, we’ll talk about the basics of how these motors work and how to control them.

Steppers: A Perfect Choice for Precision Motion Control

In our recent article on electric motors, we gave a broad overview of the different families of AC and DC motors based on how they convert electrical energy into rotating mechanical movement. Broadly speaking, stepper motors fall into the synchronous category, meaning that the rotor moves in lock step with orientation of the applied magnetic field generated by the stator. This synchronous operation is precisely why steppers are frequently used in applications that require precise motion control. But a feature unique to steppers—a gear like rotor with many magnetic teeth—divides one full rotor rotation into many small angular steps, allowing small, precise amounts of movement. This plus the fact that stepper motors are brushless (and thus have a long lifetime), have made them the motor of choice for industrial automation and robotics.

Although all stepper motors share this many-pole rotor, in some steppers each tooth is a pole of a permanent magnet, thus making them permanent magnet synchronous motors. In another type (variable reluctance stepper motors), these teeth are not magnetized but instead made of a magnetically soft material.

How Steppers Operate

Although the individual stator coils (phases) in a stepper motor are driven by DC pulses, stepper motors are best classified as AC permanent magnet synchronous motors (PMSMs) since the DC voltage applied to the phases is pulsed at such a high frequency (“chopped”) that the current waveform in the phases more accurately resembles a sine wave (since the current inside an inductor can’t change instantly). This results in the same rotating stator magnetic field found in PMSMs and is especially true when stepper motors are micro stepped. This method of using a high-frequency modulated DC waveform to recreate a smooth AC waveform, is the same one used by audio electronics such as high-efficiency Class D amplifiers and some digital to analog converters (DACs).

Great for Open or Closed-Loop Control

Although they are great for open loop control, it’s easy to implement a closed-loop control by adding limit switches, Hall effect sensors, and optical sensors. This is a good idea in applications where small cumulative positioning errors are likely (due to backlash, micro stepping, vibration, stalling). The control loop can account for and correct this error.

Basic Requirements of Stepper Motor Control

A stepper motor controller and driver (often integrated into the same PCBA) must perform 3 main things:

Provide current to the phases. The components that are directly connected to the motor phases (almost always power transistors) must be able to source and sink the required current, quickly switch the phase voltage on and off, and withstand any counter-EMF produced by the stepper’s coils. The power supply that feeds the controller and drive circuitry, must be able to handle the anticipated maximum currents (including stall currents) without sagging and causing a brownout of all attached circuitry. This can wreak havoc in real stepper motor control systems since the same power supply often powers the digital control circuitry as well as the stepper motors themselves.

Turn the phases on and off in the right sequence. The sequence in which the individual phases are turned on and off (stepping) determines not only the direction of rotation, but also the torque and the amount of vibration, noise, and mechanical resonances. Keeping the latter to a minimum is crucial to avoiding positioning errors due to step loss, not to mention adverse effects on the rest of the mechanical system. Micro stepping achieves this while at the same time increasing the angular precision of the stepper motor.

Generate the right waveform voltage. This includes generating the chopping frequency (often around 30 kHz) and sending it to the power transistors which then modulate the DC current waveform which feeds each of phases. The stepper motor controller modulates the voltage applied to the phases to maintain the current in them, close to a constant value. After all, it’s the current in the coils that determines the strength of the field and thus the torque acting on the rotor.

Modern Stepper Motor Controllers: Integration and Miniaturization

It is commonplace to purchase a single stepper motor control PCBA that includes the drivers, controllers (including chopper) and industrial interface like RS-485, CAN, and even USB. These all-in-one integrated solutions are becoming smaller, cheaper and more powerful, which in turn makes stepper motors even easier to use and integrate into your own designs.

With a motor design and assembly group of more than 400 highly skilled personnel, we excel at the design and production of permanent magnet stepper motors, as well as their components, drives and controls.

From design to delivery, Providence is ready to take on your next contract manufacturing project. What can we do for you?

Sealing the Deal: A Primer on Rubber Injection Molding

Sealing the Deal: A Primer on Rubber Injection Molding

Injection molding isn’t just for thermoplastics. The same process, with a few minor tweaks, can also be applied to synthetic rubbers. Having largely displaced natural rubber for almost all uses except automobile tires, modern elastomers (short for “elastic polymers”) are as specialized as thermoplastic resins are. Some are low cost, good versatile performers. Others are more expensive, but excel at chemical resistance or working temperature range. As a result, synthetic rubbers are used to make products for a lot of different sealing applications in industrial and consumer products.

And how are those products made? Largely by rubber injection molding, which makes this an important manufacturing process.

Injection Molding: Resins vs. Rubbers
 There are a lot of similarities between rubber injection molding and thermoplastic injection molding. Both processes begin by squeezing hot, liquid material into a mold under extreme pressure. Both are automated processes that use a sprue, runners, and cavities to make high-quality parts in large quantities at a low price per part.

Also, many of the same design considerations we’ve discussed in previous posts apply to both processes: the benefits of multi-cavity tooling, the tradeoffs between the different types of gates, and importance of designing for manufacturing (DFM).

Injection rubber molding, however, is different from thermoplastic injection molding in two key ways:

Pressure: generally, higher pressure is required when injection molding synthetic rubber parts because the elastomers are usually more viscous than molten thermoplastic resins.

Heating: For the liquid elastomer to solidify, it must cure by vulcanization (heating the synthetic rubber so that the polymers cross-link). Therefore, rubber injection molds are heated. This contrasts with plastic injection molding where one of the main jobs of the mold is to cool the resin-filled cavity as quickly as possible. In fact, the uncured rubber is pre-heated before it enters the mold, as this decreases both the required cure time and the viscosity of the molten rubber. Decreasing the viscosity of the rubber allows it to fill the mold quicker and completely.

Common Materials Used for Rubber Injection Molding

From gaskets and grommets to seals and O-rings, rubber injection molding is used to make parts that require more “give” than can be expected from a plastic. Here are a few elastomers which are used in rubber injection molding:

Teflon Rubber is very resistant to almost all industrial chemicals, including solvents like MEK and xylene. Teflon rubber is also tough, and being Teflon, has low friction. This elastomer also has a very wide working range. This combination of characteristics makes Teflon rubber an ideal O-ring and gasket material for chemical seals.

EPDM is very resistant to heat, ozone and weather. This synthetic rubber is a great fit for electrical insulator applications due to its high electrical resistance. Weatherproofing products like weather-stripping and roof coatings are often made of EPDM because it has good water resistance.

Chloroprene (e.g. Neoprene), like EPDM is weather resistant, but its niche application is for refrigeration seals due to its excellent resistance to both ammonia and Freon. This tough and economical elastomer is also FDA approved for food and beverage industry use. However, chloroprene is losing a lot of ground to nitrile, due to the latter’s competitive price and generally superior properties.

Fluoroelastomers (including Viton) have a wide range of uses and the properties of a specific rubber depend mostly on the fluorine content and base polymer(s) used. Generally, Viton is compatible with hydrocarbons, making it a good O-ring material choice for engine seals.

Nitrile (e.g. Buna N) is very widely used due to its exceptional oil resistance and low cost. Nitrile’s high abrasion resistance, high tensile strength and low compression set make it a good versatile synthetic rubber.

Liquid Silicone Rubber (LSR) is great for static seals that are subject to extreme temperatures. Even at low temperatures, parts made from LSR retain their flexibility. LSR’s low viscosity makes it great for filling molds with complex profiles.

A Rundown of Runners

A Rundown of Runners

Before molten resin can fill the part cavity, it must first wind its way from the sprue (the inlet of the mold) to the gate(s). In between those two end points, the molten resin is distributed through channels, called the runner system. Think of the sprue as the highway, the runners are streets and the gates are driveways to the individual homes. Runners must be bigger than the gates they feed because the runners must be capable of delivering resin flow to every attached gate.

In some cases, multiple parts can be fed by one runner. To complicate matters further, a single part can have more than one gate, thus requiring more runners. In multi-cavity or family molds, there’s more than one part per cavity (but still one sprue). Thus, the runner system (the distribution network of molten resin from the sprue to every gate) can be quite large and labyrinth-like.

Cold Runners vs. Hot Runners

There are actually two types of runners:

Cold Runners: these runners are filled at the same time as the part cavity. The resin in these runners is also cooled at the same time as the part. This means that the runners, gates, and sprue often get ejected as one piece (unless you are using automatically trimmed gates after each completed cycle). The part is then either manually or automatically separated from the gates and runners. Runners are tossed as scrap, except in the cases where that resin can be reground and reused. Process sheets should dictate the allowable percentage of regrind allowed back into the injection molding process.

Hot Runners: The runner channels are kept hot by heating elements and thus never solidify. The section of the mold that contains the hot runners is kept thermally insulated from the section that houses the cavities (since one of the main jobs of that part of the mold is to cool the resin). When it’s time for the part cavity to be filled, valves open up and allow the resin to flow into the gates and cavity. Then those valves close and the resin solidifies in the mold.

Each type has its advantages and disadvantages. Molds with cold runners have a lower upfront cost, are simpler, and easier to maintain. The main drawback for cold runners is the problem of wasted plastic mentioned earlier. Although it is true that the runners can often be reground and reused on-site, this isn’t true for all plastics. For the expensive resins, the cost from this waste can be significant, especially if the runners are large or numerous, like the multi-cavity setups mentioned above.

Hot runners have several advantages over cold runners. In addition to less scrap due to plastic in the runners never solidifying, the cycle time is often shorter since you don’t have to wait for that section of resin to cool. Shorter cycle time means lower price per part. Hot runners can also help prevent sink marks. They are however, more expensive to machine, more complex, have higher maintenance costs, and require precise temperature control and control of their valve timing. This is why hot runner systems are not recommended for small production runs, as they can cost anywhere from $2,000 to more than $100,000. Another disadvantage is the fact that some resins are temperature sensitive and may not be compatible with this process.

Which One is Right for Your Part?

Like so many other decisions in injection molding that can increase cost, using a hot runner system can more than pay for itself if you’re making hundreds of thousands or millions of parts. The higher upfront costs are made up by the reduction in scrap and the shorter cycle time. For prototype and smaller production runs, however a cold runner system may actually make more economic sense. This is especially true if you’re using a cheaper resin, the runner system isn’t that big and you’re using automatically trimmed gates, and the design of the cold runner system is simple.

The decision to use a hot or cold runner system should be made in close consultation with your injection molding contract manufacturer. You can take advantage of their experience, knowledge of their machines, and in-house engineering talent, thus avoiding the potential to be locked into bad design choices.

Whether you’re weighing hot vs. cold runners for your mold or any other design decision, Providence has the engineering staff, CAD tools, and experience to make sure your injection molding project runs smoothly from design to delivery. Contact us at today to discuss if a hot runner system is right for you. Because of the Hot Runner System is cost from couple thousand dollar up to more than hundred thousand dollar. Therefore it is not recommend to use for less production.

Whether you’re weighing hot vs. cold runners for your mold or any other design decision, Providence has the engineering staff, CAD tools, and experience to make sure your injection molding project smoothly flows (pun intended) from design to delivery.

From design to delivery, Providence is ready to take on your next contract manufacturing project. What can we do for you?

How to Successfully Contract Out Cable Harness Assembly

How to Successfully Contract Out Cable Harness Assembly

A lot of OEMs (particularly smaller ones) use cable assemblies in their products built in-house and usually do the assembly by hand with the help of tools like crimpers, strippers, and heat guns. Building these harnesses by hand is very labor intensive, so eventually OEMs hire a contract manufacturer with the aim of lowering costs and increasing volume.

Unfortunately, there are a lot of ways for this outsourcing to backfire. It can result in late deliveries and increased costs due to scrapped cable assemblies, reworking harnesses, and/or time spent fixing documentation.

One of the key reasons for this is that cable assemblies can become complex, as the system they’re used in matures and changes over time. For high-technology products such as scientific instruments and medical devices, the addition of new features very often requires new wires and connectors to send the signals and power to the components that makes those new features work. This is especially true for products whose designs are modified well past the prototype stage in order to meet safety requirements (such as those from CSA or UL).

Another common reason stems from how the documentation and testing of wiring harnesses are sometimes maintained within an OEM. The wiring can get neglected because some companies mistakenly believe there’s not much focus necessary there. On the contrary, there can be a lot of labor costs built into wire harness assemblies that have layer upon layer of modifications: needing to use jump wire; sending some of a cable’s wires to one connector while terminating the other wires somewhere else; use of multiple cables with the same wire colors in a harness, etc. These are all symptoms of cable assemblies that have accumulated a series of quick and easy “band aid” fixes instead of a more thorough redesign.

But there are a myriad of other ways OEMs sabotage their own success when it comes to outsourcing cable assemblies.

Mistakes OEMs Make

Specifying too many particulars of the assembly instead of the final product: Your focus should be on things like: overall length (with reasonable tolerances), jacket strip length, etc. Your contract manufacturer should know enough about things like cable stretch, to be able to factor those in and meet your overall requirements. If not, then you shouldn’t be working with them.

Using the wrong cabling: Do you really need a foil shield or a ground wire? Can you use discrete wires instead of jacketed cable? Does the cable you’re using have 8 conductors but you’re now only using 6? Working around these things adds time and ultimately cost.

Ambiguity in connector orientation and pinout: Make abundantly clear the pinout of all connectors; especially connectors whose front and back look almost identical. In the drawing, use views which clearly show the correct orientation by relying on asymmetric features (locking ramps, locking tabs on panel mount connectors, etc.).

Speaking of connectors, whenever possible, stick with the numbering scheme on the connector itself (like the pin #1 indicator). We all know that assemblers should follow the drawing and nothing else, but in real life this causes real headaches.

Inconsistencies between the BOM and drawing: Like all other drawings, put the BOM directly on the cable harness drawing. In SolidWorks, you can automatically generate the BOM from the drawing. When the cable drawing and BOM are separate documents, there is a tendency for the BOM to fall out of sync with the drawing, which in turn causes problems for your cable assembly vendor who is more likely to gather the required terminals and cable lengths according to the BOM.

Your own assemblers however, often start with the drawing (and inside knowledge), then work backward to determine the quantity of raw materials needed. This is why, of course, inconsistencies between the BOM and drawing are seldom caught before the documentation is handed off to an outside vendor: no one was working off the BOM when you were building the cables in-house.

Ambigious or Conflicting Crimping Specs: Give detailed specifications and examples of crimp terminal quality, especially if your needs deviate from the terminal manufacturer’s specs or industry standards for crimp quality. A bad crimp can easily cause intermittent contact opens which are hard to catch, even via electrical continuity tests.

Tips for Smoothly Outsourcing Cable Assemblies

There are things you can do as an OEM to ensure a smooth and successful transition from in-house cable assembly to buying finished harnesses (for less cost) from your contract manufacturer.

Make it easy for your CM to get it right the first time: Share and document any custom jigs/fixtures that you are currently using in making the harnesses in-house. Also, give your contract manufacturer good example cables. Yes, as we said above with pin out we all know that the drawing should be enough, but the end goal is an acceptable finished product, not to test your vendor’s ability to correctly interpret ambiguities in your documentation.

Include simple tests in the drawing itself: Include a simple point-to-point resistance test as a note or step on the drawing. Not only will this allow the assembler to verify the pinout, but they may also be able to spot a bad terminal crimp. Also, a visual check using the wire run list (pin out table) and wire colors will help too. You won’t need to create and maintain a separate testing document, and your contract manufacturer will be able to catch problems before products hit your incoming inspection.

Pick a contract manufacturer who can automate most of the assembly: Automation, not necessarily lower labor costs, will be what ultimately saves you money on wire harnesses. Look for a contract manufacturer that has wire processors and automated crimping machines suitable for the terminals you are using in your wiring harnesses. Otherwise, you’re not going to save much (if at all) by farming it out.

DFM applies to cable harnesses too: Use pre-molded cable assemblies or terminated wires that you can buy off the shelf and simply drop ship to your vendor. Whenever possible in a cable assembly, use wires with different colors, as this will make visual inspection and continuity tests much easier.

Whether your cable assemblies are simple or complicated, ready for production or need some design refinement, Providence has the expertise and assembly capabilities to take your production to the next level.

From design to delivery, Providence is ready to take on your next contract manufacturing project. What can we do for you?

Choosing the Right Motor Can Really Move Your Application Forward

Choosing the Right Motor Can Really Move Your Application Forward

By converting electrical energy into motion, electrical motors literally keep our modern world turning. From compressors to ceiling fans, vacuum pumps to vacuum cleaners and dialysis machines to drones, motors are everywhere. They are so significant that entire books have been written about the different types of motors and advancements in motor control technology. In this post, we’ll discuss just some of the motor types we design and assemble here at Providence, along with the strengths and weaknesses of each type.

Many of the motors we make for our customers are in the fractional (less than 1) horsepower range and span different alternating current (AC) and direct current (DC) motor types. Let’s begin with a popular DC motor design: the PMDC motor.

Permanent Magnetic DC (PMDC) Motors

PMDC motors are used in applications that require a small, inexpensive motor in places where only DC current is available, like in battery operated toys or in automobiles where precise speed control is not required. Their construction is simple. Since they use permanent magnets for the stator field there’s no need for the additional energy or circuitry required in other DC motors that use electromagnets for the stator (hence the smaller size and higher efficiency advantages of PMDCs). Larger PMDCs may augment the stator’s permanent magnets with coils, to provide a stronger field.

PMDCs use brushes and a split ring commutator in order to deliver a reversing electrical current to the rotor, which in turn pushes and pulls against the stator field to rotate the rotor. Thus, the same drawbacks that affect all brushed DC motors including arcing and jerking at low speeds (from cogging torque), disturb PMDC motors as well.

The characteristics of PMDCs have recently made it a popular choice for fractional horsepower applications, since high-intensity rare-earth permanent magnets (like those containing neodymium) have opened the door to high-power DC motors in a reasonable size.

Now let’s discuss a few types of AC motors that have the advantages of being powered directly from mains voltage (whether single-phase residential or industrial three-phase). Since the current is already reversing, there’s no need for brushes and split commutators or their associated problems of friction, arcing, coasting through the gap in the commutator, electrical noise fed back onto the power supply, etc.

Permanent Magnet Synchronous Motors (PMSM)

Like the PMDCs we described above, this type of AC motor also uses permanent magnets. In a Permanent Magnet Synchronous Motor (PMSM) however, those magnets are built into the rotor. The AC current (usually three-phase) is applied to the stator coils, creating a rotating magnetic field in the area of the rotor. This motor type is called “synchronous” because the rotor spins at the same rate as the frequency of the AC supply. The use of permanent magnets alleviates cost, complexity and inefficiency incurred by supplying DC to electromagnets in the rotor. PMSMs powered by a three-phase AC, require a variable-frequency power source and usually use position sensors to detect the positions of the rotor poles. This is to ensure that the rotating magnetic field polarity is matched to the rotor’s field so that the motor spins in the correct rotation, produces the most torque, and operates at high efficiency. Some PMSMs are designed to run off of single-phase residential power and are used in applications like timers and water valve controllers, where they are commonly combined with a gearbox to leverage their ability to spin at a constant speed.

The next motor type on our list is “asynchronous”, meaning the rotor spins at a slower rate than the power supply frequency.

Inductive Asynchronous Motors

Induction motors work by relative motion of the stator’s rotating field moving across the rotor coils. When the rotor speed is low, the rotating field spins much faster than the rotor which induces a lot of current into the rotor, generating a strong rotor field that seeks to catch up with the rotating stator field until it is limited by a mechanical load. As the rotor’s rotational speed catches up to that of the stator field, the relative speed between the two decreases resulting in less induced current in the rotor, less torque, and thus less gain in speed. The rotor of asynchronous motors then, is always slower than the speed of the rotating stator field.

One common type of AC induction motor is the Squirrel Cage Induction Motor (SCIM) that gets its name from the loops of thick copper or aluminum bars embedded in the rotor which serves as the rotor coils. Three-phase SCIMs are very common in industrial applications because they are reliable, durable and cost-effective.

In an induction motor, speed is determined by the frequency of the AC applied to the stator coils, and thus variable frequency drives (VFDs) are necessary for changing an inductive asynchronous motor’s speed.

Sometimes the squirrel cage design is combined with another motor technology, which allows squirrel cage motors to be powered from single-phase AC. Single-phase AC applied to the stator coils would just produce an alternating magnetic field in the stator, and not the rotating field necessary to spin the rotor. Modifying the design of the stator poles however, can in fact generate the second phase needed.

Shaded pole motors

Shaded pole motors have an auxiliary one-turn coil covering part of each stator pole. This coil gets current passing into it by the reversing polarity of the pole it is shading. This current, lags the pole current (i.e. has a delayed phase relative to the pole current), so that you have two alternating magnetic fields whose phases are different enough to give you a 2-phase rotating magnetic field. Since this type of AC induction motor generates its own 2nd phase, it can be powered from single-phase AC.

Shaded pole motors have low starting torque and are limited to less than one horsepower since other motor designs offer better performance at higher output powers. This means they are best used for fans and other loads without a lot of inertia.

Motors are an important part of the modernized world and power many of things that we use or interact with on a daily basis so we often take them for granted. That’s why with over 400 skilled employees in our motor assembly department and expertise in many motor types, Providence can keep your motor design, components, controls and drive assemblies running smoothly and efficiently, to solve even your most challenging supply problems.

From design to delivery, Providence is ready to take on your next contract manufacturing project. What can we do for you?

Are You as Pumped about Pumps as We Are?

Are You as Pumped about Pumps as We Are?

Out of the three normal states of matter—solid, liquid, and gas—pumps can move the last two and pressurize the last one. Pumps not only force fluids to flow, but can also create a vacuum by compressing gas to a high pressure, evacuating air from a container.

Pumps move fuel from your car’s tank to the engine. They also can dispense life-saving fluids from an IV bag into a patient’s veins.

We at Providence have a lot of experience designing and assembling custom pumps for our customers who span across many industries: Industrial, Marine, Medical, and Food & Beverage to name a few. There are a lot of different types of pumps, but ultimately every pump is a device that converts mechanical energy into a fluid’s motion energy, or the potential energy of a pressurized gas.

In this post, we’re going to highlight just a few of the fundamental pump designs we’ve manufactured for our customers.

Rotary Vane Pump

There are entire families of pump designs that utilize one or more rotating parts. That is convenient considering almost all electric motors output rotational mechanical energy, and that makes the coupling between the electric motor and pump very simple, resulting in a pump assembly that can be plugged into an electrical outlet. Here, we’ll discuss only one type of rotary pump: the rotary vane pump.

A rotary vane pump contains a circular internal rotor that spins inside the circular pump housing, but the center of the rotor is offset from the center of the housing. The rotor makes contact with the pump housing wall between the inlet and outlet ports, thereby ensuring flow in only one direction. The rotor has vanes (walls, fins) that slide in and out, and maintain contact with the pump housing. These vanes are spring-loaded so that they are always pressing against the wall of the housing. The vanes also sweep the fluid and segment the flow into separate compartments with expansion happening at the inlet and compression occurring at the outlet.

The rotary vane pump is popular for high-pressure hydraulic applications such as a car’s power steering and automatic transmission pumps. They can also be used in lower pressure applications, such as carbonators for soda dispensing machines; one of Providence’s initial key industries and product lines that helped the team develop extensive experience with pumps. Rotary vane pumps are also a common design for vacuum pumps, especially in two-stage designs, where they perform such functions as evacuating refrigerant lines of an air conditioning system.

Since the vanes must consistently maintain a tight moving seal, mechanical tolerances and material choice are critical for a long operating life and great overall product lifecycle performance. Maintaining tight tolerances and other mechanical specifications, like the k-factor of the spring pushing the vanes, are also of great importance.

Piston Pump

There are some pumps that don’t rely on rotational motion. One type, the piston pump, uses a sliding piston inside a cylinder. There are actually two main designs of piston pumps: lift pumps and force pumps.

Force pumps draw in water through a one-way valve on the inlet when the piston moves up, and expands the empty volume creating a partial vacuum in the cylinder. When the piston moves down and pushes the fluid, another one-way valve located on the outlet opens up and allows the fluid to flow out of the pump. Once the piston has reached the bottom of the cylinder and squeezed out all of the fluid, the piston then moves back up, creating the partial vacuum that closes the outlet valve and opens the inlet valve. Force pumps only push out gas or liquid on the downward stroke, as the upward stroke refills the cylinder. This is analogous to the separate intake and exhaust strokes in a four-stroke engine.

Lift pumps refill during the downward stroke, and discharge the fluid during the upward stroke when the piston “lifts”, hence the name. During the upward stroke, fluid is squeezed out the top of the cylinder as the piston travels up. At the same time, the upward stroke of the piston creates a partial vacuum at the bottom of the cylinder that pulls in fluid through the inlet. When the piston makes its downward stroke, valves inside the piston open up, allowing the fluid to pass through the piston into the upper compartment of the cylinder. When the piston travels back up, those valves close, and the volume of the compartment above the piston gets smaller as it rises. This allows the fluid to be discharged through the outlet attached to the upper compartment. One-way valves on the inlet and outlet are also present on lift pumps.

The piston pumps manufactured today are often double-acting, which means that suction and discharge happen in both cylinder compartments (above and below the piston). Double-acting piston pumps thus require two pairs of inlet and outlet one-way valves; one pair at the top of the cylinder, and one pair at the bottom.

Both types of piston pumps can be driven by hand, motor, or engine and the construction is quite simple and can be built inexpensively. They can be found in applications such as liquid soap dispensers or bicycle pumps. A syringe is also an example of a single-use medical grade piston pump. They are all reciprocating, meaning they pump out the same volume of fluid/air every cycle.

Diaphragm pump

Imagine modifying the force piston pump, but instead of the sliding piston increasing and decreasing a chamber’s volume, a flexing diaphragm is what draws in and pushes out the fluid. That, in a nutshell is diaphragm pump. The diaphragm, or membrane, is often made out of an elastomeric material. Diaphragm pumps don’t require lubrication, yet operate with little friction and maintain a high-quality hermetic seal with little or no maintenance.

The diaphragm itself can be flexed via compressed air, hydraulic fluid or even manually. Since there are no sliding seals like in piston or rotary vane pumps, no oil lubrication is required, which in turn means no contamination from oil vapor of the air expelled from the outlet. This also means that diaphragm pumps are a really good choice for air compressor applications requiring very pure air. They’re a great fit for removing air in low-vacuum applications.

Regardless of the underlying design, your air compressor or pump project requires the stringent quality control, pump design expertise and mechanical assembly capabilities from a partner like Providence Enterprise. Contact us today to learn how we can keep your project flowing smoothly from design to mass production!

From design to delivery, Providence is ready to take on your next contract manufacturing project. What can we do for you?

Overlooked Thermal Considerations for PCBAs

Overlooked Thermal Considerations for PCBAs

Although we immediately think of electronics when printed circuit board assemblies (PCBAs) are mentioned, good PCBA design is in fact a multidisciplinary endeavor spanning electrical, mechanical, and even chemical engineering. However, one area where technology companies can run into trouble with PCBA designs, is the impact of elevated temperatures and heat flow through their boards during production, use and rework.

The Problems of Running Hot

There are a lot of thermal problems that a PCBA can run into. One of the more obvious issues is inadequate heat sinking of active components which produces considerable waste heat, like FETs operating in their linear region (i.e. not being used as solid state on/off switch). For example, if a MOSFET is being used to limit current in a control system, its heat sink must be able to disperse enough heat to keep it under the maximum operating temperature specified in its data sheet. This includes the worst-case scenario: when the gate voltage is halfway between VGS(OFF) and fully on.

By extension, this applies to linear voltage regulators as well. If your design forces you away from switching regulators due to electrical noise requirements (like in the high-sensitivity analog chains found in scientific measuring instruments), additional heat sinking and airflow beyond passive cooling in still air, will most likely be required.

Keeping temperature sensitive components cool is only one facet of good thermal design in a PCBA. Another necessary aspect is ensuring that the heat you are removing from those components, doesn’t find its way to another part of the assembly where it can cause problems.

This is harder than it sounds because electronic components cool via convection, by the transfer of heat into the surrounding air, and also through conduction by dispersing the heat into the PCB. If a warm part is cooling itself passively by conducting heat into the copper pours of your PCBA, then that heat can travel throughout the entire board and trickle into a temperature sensitive component. If you have a temperature sensor on the board, then that heat can conduct into it and artificially raise its temperature through the sensor’s leads. As a result, that sensor will erroneously read higher than the actual air temperature as the board warms up from a cold start. On the other hand, if that same sensor is downline from a warm component, then that sensor will also read higher than the ambient air temperature due to the additional heat in the air which then blows across the sensor.

Thermal Issues Affecting Rework

If you don’t pay close attention to the layers and traces of copper in your PCBA, you could end up designing a board that can be very hard to repair or rework. Thick copper layers are great for carrying large amounts of current and lowering IR drop, but they can make rework much harder due to that copper wicking away heat from a soldering iron tip or the heated air from a hot air rework station.

Although you could compensate for this by throwing more heat at the part, the risk of lifting a pad, melting a header connector, or damaging other parts on the board increases. For expensive PCBAs, the inability to quickly and easily replace soldered parts could mean large costs due to scrapping the entire board when only one component fails.

How to Avoid These Problems During Design

All of the problems mentioned above can be avoided by following these design tips:

Use thermal relief on your pads. This applies to both through hole and surface mount parts whose performance won’t be adversely affected by the increase in resistance (which will still be low in absolute terms).

Air Temperature sensors should never be directly attached to any PCBA. Use long, small diameter wires to put some distance between the sensor and the board to decrease measurement error from heat trickling up the board. Most high-accuracy air temp sensors now are current source sensors that are meant to be used remotely for this very reason.

Split your PCBA into separate boards for high power & I/O, and control. Restrict heavy copper pours to the high-current board. You will have to spend time and money reworking layouts and adding connectors (and maybe cables), but in practice, this tends to work a lot better than splitting planes in a monolithic PCBA.

Be smart about air flow in the box. Design the enclosure so that air moves from the coolest part of the PCBA to the warmest. Direct the air flow so that it moves faster across the parts that generate the most heat, because the more heat the air can remove, the less will conduct into the board.

Providence’s extensive PCBA testing capabilities and board assembly experience can help you identify and remedy these and many other thermal issues in your PCBA design. Contact us today to learn how we can help keep your boards cool!

From design to delivery, Providence is ready to take on your next contract manufacturing project. What can we do for you?

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