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Force Measurement Solutions for Bolt and Screw Fastening

Among the many applications of force measurement devices, one that appears to be a simple application can have a big impact on worker safety, productivity, waste reduction, assembly and product performance. In this new animated application note highlight, we take a look at the tools used for bolt fastening measurement.

Bolts and screws are used to secure different pieces or components together for nearly every product imaginable, especially when it comes to large machinery and even automobiles. The success of these products and the manufacturing of these components requires a strict level of detail that goes into the tightness of a bolt. It’s not like your typical “do it yourself” furniture where you just tighten a screw or bolt until you can’t anymore. The precision needed for certain objects to be tightened to the exact measurement is mandatory.

Interface provides measurement solutions for all types of industrial automation and toolset testing used in thousands of applications that ultimately are utilized in the building of products. In the example below, we provided devices that are used to determine the exact bolt force and tightness necessary. The goal of measuring the tightness is to avoid under or overtightening. As you can imagine, under tightening can cause components to come apart. However, over tightness can also cause significant damage to the pieces being bolted together.

Bolt Fastening Application

To show the process of measuring bolt tightness, check out this latest use case video demonstration.

For this bolt fastening application, the customer used an Interface Model LWCF Load Washer along with an Interface Model INF-USB3 Single Channel PC Interface Module to monitor force being applied during bolt tightening. The data transferred from the bolt clamping force load cell load washer with a thru-hole, to the instrumentation is displayed, logged and graphed directly onto a computer for analysis and performance testing.

This is a basic example of the test and measurement process, however, Interface also contributed to a number of real-world projects and created applications notes to provide an illustration. One of our favorites is when an industrial automation company was building an automated assembly machine for an automotive manufactur­ing plant.

The product engineers and testing team needed to tighten all of the head bolts on an engine on their assembly line to a specific torque value. Having the head bolts precisely and consistently tightened to the engine block is critical to the operation of the engine.

To measure this force, several Interface Model T33 Spindle Torque Transducers were installed in their new machine to control torque and angle and ensure the head bolt was properly tight­ened. The square drive of the T33 allowed the customer to fix their tool directly to the end of the torque sensor, streamlining the installation.

Using this solution, the head bolts were correctly installed according to manufacturer specifications, producing an engine that meets performance and reliability expectations of the auto manufacturing plant.

Here are additional solutions that showcase how Interface load cells, torque transducers, instrumentation and custom solutions are used for various tools and manufacturing processes across various industries.

Aircraft Screwdriver Fastening Control

Fastening Work Bench

Bolt Fastening Force and Torque

Interface Solutions for Robotics and Industrial Automation

Contact us to learn more how we can help you ensure the right fastening and machine control for your next projects.

 

 

 

Understanding Load Cell Temperature Compensation

The performance and accuracy of a load cell is affected by many different factors. When considering what load cell will work best for your force measurement requirements, it is important to understand how the impact of the environment, in particular the temperature impact on output.

An important consideration when selecting a load cell is to understand the potential temperature effect on output. This is defined as the change in output due to a change in ambient temperature. Output is defined as the algebraic difference between the load cell signal at applied load and the load cell signal at no load. You can find more detailed information in our Technical Library.

Temperature affects both zero balance and signal output. Errors can be either positive or negative. To compensate for this, we use certain materials that are better suited for hot or cold environments. For instance, aluminum is a very popular load cell material for higher temperatures because it has the highest thermal conductivity.

In addition to selecting the right material, Interface also develops its own proprietary strain gages, which allows us to cancel out signal output errors created by high or low temperatures.

In strain gage-based load cells, the effect is primarily due to the temperature coefficient of modules of elasticity of the force bearing metal. It is common in the industry to compensate for this effect by adding temperature sensitive resistors external to the strain gage bridge which drop the excitation voltage reaching the bridge. This has the disadvantages of adding thermal time constants to the transducer characteristic and of decreasing the output by 10%.

Our load cells are temperature compensated for zero balance. By compensating for zero balance, we can flatten the curve in the relationship between temperature and zero balance. An uncompensated load cell has a much more severe curve, which ultimately affects accuracy and performance.

Interface offers thousands of load cell designs, standard use and for hazardous environments. For instance, rocket engine tests subject our load cells to extremely high temperatures. For use in various maritime industry projects, they can be used in very cold coastlines and even submerged in cold water. No matter where you are, environment influences the load cells performance.

If you are concerned about temperature, Interface provides specifications for every load cell we manufacture. The Interface specification datasheet, as see referenced here, is available for download by product. It always includes all the necessary data required to understand the load cell’s ability to perform at the highest-level including compensation range, operating range, effect on zero balance and effect on span.

One thing that is also unique about our products is that while most competitors only compensate for hot temperatures (60 to 160 degrees Fahrenheit), Interface covers both hot and cold thermal compensation from 15 to 115 degrees Fahrenheit, including adjust and verify cycles.

Be sure to tune into Load Cell Basics, where Keith Skidmore discusses temperature compensation.  He notes during this informative presentation that if the temperature is changing during a test that can affect the zero and the output of the load cell. How much effect depends how much temperature is changing and how well the load cell is compensated against the errors, which can be either positive or negative. Good news is they are repeatable from test to test so if you have large temperature swings you can characterize the system and then subtract out the shift if you know the temperature effect on zero.

Interface Application Engineers are available to answer questions regarding the effect of temperature on force measurement data, or the different ways we can help design a solution to compensate for your environment.

Load Cell Basics Sensor Specifications

When selecting a load cell, it’s critical to understand the major factors impacting sensor accuracy. These factors are determined by the materials and components used in the construction of the load cell, the calibration, instrumentation, the accessories such as cables, and mounting installation. Each must be considered in the specific use cases for the load cells.

During our virtual event, Load Cell Basics, applications expert Keith Skidmore detailed everything you need to know about load cells and how to choose the right load cell.  First, Keith highlighted four vital application considerations:

Mechanical – Dimensions and Mounting

Electrical – Output and Excitation

Environmental – Temperature and Moisture

Performance – Accuracy and Thermals

Taking a deeper dive into performance, an important consideration when selecting your load cell are the sensor specifications and how they impact accuracy. The sensor specifications relate to the max error of various parameters. The specifications are always included in product spec sheets and are expressed using the following values – %FS, %RO, %, %/°F, time-related. Specifications listed relate to the max error for accuracy and temperature.

Interface provides all sensor specification data for our load cells in the product datasheets found on each product page for easy download.

The information we provide for every load cell typically includes:

Accuracy:

  • Static Error Band
  • Non-linearity
  • Hysteresis
  • Non-repeatability
  • Creep
  • Side Load Sensitivity
  • Eccentric Load Sensitivity

Temperature:

  • Compensated Range
  • Operating Range
  • Effect on Zero
  • Effect on Span

Further definitions can be found in our online technical glossary.  Here are a few that we highlighted in the Load Cell Basics webinar.

Static Error Band: A band encompassing all points on the ascending and descending curves centered on the best fit straight line. It is expressed in units of %FS.

SEB Output: The output at capacity based on the best fit straight line.

Non-repeatability: The maximum difference between output readings for repeated loadings under IDENTICAL LOADING AND ENVIRONMENTAL CONDITIONS. In practice, there are many factors that affect repeatability that ARE NOT included in the non-repeatability specification. It is normally expressed in units of %RO.

Non-linearity: The difference in the output from a straight line. It is normally expressed in units of %FS.

Hysteresis: The difference in the ascending versus descending curves. This is normally expressed in units of %F.

Understanding these factors and the maximum error for your specific project is critical to selecting a load cell and getting the best possible data out of it.

To learn more about sensor specifications for load cells, review the product specs on each datasheet or in our product catalogs. For additional help, call to speak with our application engineers at 888-557-2533.

To view additional online events, please go to our events page.

 

Load Cell Basics Webinar Recap

Interface applications and load cell expert Keith Skidmore was the featured presenter at the latest ForceLeaders Forum hosted event, Load Cell Basics. In his comprehensive presentation, he highlights key subjects including fundamentals of load cell design, sensor specifications, use cases, troubleshooting and valuable performance related topics.

The entire event is now available on the Interface YouTube channel.

In this 60-minute virtual event, Keith highlights commonly asked questions from both new load cell users as well as for advanced engineers and force measurement pros.

What will you learn watching the online Load Cells Basics event?

  • Load cell designs and how they work
  • Capacities, models and how to choose the right load cell
  • Factors that can impact sensor accuracy
  • Performance, moment compensation, creep, and eccentric load sensitivity
  • Calibration and troubleshooting
  • Use Cases and FAQs

The team concluded the event by answering a series of questions from the participants. They addressed advanced technical and set-up questions, as well as frequently asked inquiries about common troubleshooting issues.

Here is a sample of questions that you can find answered in the Load Cell Basics recorded event:

  • Is the temperature compensation achieved using dummy gauges?
  • Does Interface offer or have their own software to read the TEDs?
  • Can we assume that all load cells are intrinsically safe for hazardous locations?
  • What is the IP protection rating for the electrical connection?
  • What is better way to tare load cells, by electronics or mechanical preload?
  • Which is the frequency measurement limit and how fast does the load cell respond?
  • What are recommended amplifier instrumentation brands?
  • What is the most frequent problem when installing a load cell?
  • Does the cables and amplifiers affect the results of the load cell calibration?
  • For an application to 10 kN (2250 lbf), is it too much to use a 2000 lb load cell or should we use the next higher capacity?
  • What is the maximum sampling frequency for strain gage load cells?

WATCH THE EVENT AND Q&A HERE: https://youtu.be/_oHvfAzHMig

If you have additional technical questions or would like to talk about your specific application requirements, contact our Interface Application Engineers here. 

Additional resources for troubleshooting can be found here.

Our Interface Load Cell Field Guide is also helpful for troubleshooting and advanced technical support references.  You can order here.

Interface Outlook for 2021

Interface CEO Greg Adams shares his outlook for the coming year.

Never in our collective lives have we faced so much uncertainty and turmoil! The year 2020 will make history, that much is certain. Between the COVID-19 pandemic, social unrest, and a year of political strife for the ages, I think we’re all ready to turn the chapter on the start of this decade.

Despite the challenges we’ve faced in 2020, I’m still very optimistic about our future, and for Interface. My optimism is fueled by the amazing people we have here at Interface.

As a family, we’ve gotten through this together and are only growing stronger. I couldn’t be prouder of our people for their resilience and hard work in the past year. We have continued to provide the same excellent service our customers appreciate. In fact, our Net Promoter Score® remained above 60 again in our latest 2020 Customer Satisfaction Survey.

Additionally, product quality is higher than ever and we even had a few major product launches this year, including ConvexBT, our most advanced load button load cell ever, and the G Series, a new international Mini Load Cell product line. And most importantly, we’ve done all of this by ensuring that the health and safety of everyone is our number one priority.

Our ability to remain successful in the past year is a product of how diversified our end markets remain. We continue to serve a wide variety of critical technology-focused industries including aerospace and defense, automotive, medical, industrial, T&M and more. We have benefited from global diversification as well, stepping up our focus on market leaders around the world. It’s also a testament to our engineers who continue to be future focused on innovation. We’ve developed new and groundbreaking ways to serve customers, and we’ve identified trends to keep us at the bleeding edge in our industry and continuously moving forward.

The last point I’ll make on the year 2020 before looking ahead is that we’ve also taken some of the downtime to improve our internal processes and dedicate time to skills training for our team. Not only have we improved our product lines and capabilities, but we’ve also ensured that our skillsets remain strong going into the next year.

And as we finally make the turn to 2021, I’ve spent some time looking ahead to what I believe the next year will hold for our industry and for Interface:

A heightened focus on pre-sale and post-sales service is one thing that we’ve heard from customers in the last year through our semi-annual surveys. We’re upgrading our sales process to ensure our engineering teams are more involved in assisting the customer select and configure the products and systems that are right for their application. Enhancing our after-sales service will include capturing and distributing instructions, guides, and other technical services into a more accessible and easier to find outlets like our robust website.

Another trend we’re seeing requested from our customers is a desire for force measurement providers to migrate from components to systems. World-class componentry will always be important, but our experience working with customers to provide total system solutions that meet their specific needs is critical. In addition, the demand for higher performance and more customization options continues. One of the biggest improvements Interface has made in the past year is updating our production lines to include more automation capabilities. This allows us to provide high-performance, customized products at high volume while still being able to offer competitive costs. This change is helping us expand our sales with the OEM customers.

Finally, a big trend we’ve been following is miniaturization and the desire to pack more sensor technology into a single load cell or torque transducer. We’ve already begun to address this in some of our products by designing accelerometers into load cells. In industries like automotive, we often use a torque transducer to measure rotation with components like car engines. By adding an accelerometer, we can measure both rotation and acceleration through a single device.

As this desire for more data and less convoluted test systems grows, Interface will continue to find ways to customize our load cells and add more sensor types like temperature and humidity. We’ll also do this by using electronic miniaturization manufacturing methods to improve capability without increasing the overall size of the package.

In conclusion, I’m extremely pleased with the level of talent, the strength of the brand and the depth of our commitment to customer satisfaction. We’ve overcome the challenges presented to us this year and remain stronger than ever. Our renewed focus on the future will also help us identify opportunities for innovation to serve customers in more unique and beneficial ways.

I hope that everyone in our community, from our partners to our customers and employees, has a wonderful holiday season and comes back in the new year refreshed. We’re not out of the woods yet with the pandemic, but there is light ahead and we are speeding to be the Interface you can always rely on.

Interface Differentiator is Proprietary Strain Gage Manufacturing

Interface products have been heralded for their accuracy, reliability, and quality for more than 50 years. We credit our vertically integrated approach to manufacturing as the most significant factor in our development of industry-leading force measurement products, meaning we control every part of the design, manufacturing and testing of our products before they are shipped to our customers.

The process for how we differentiate ourselves begins with Interface strain gages. By manufacturing our own proprietary strain gages here at our headquarters in Scottsdale, Arizona, we can optimize our load cells to a quality level very few providers can match.

Think of strain gages as the heart and soul of a load cell. These components power every aspect of the device and their quality dictates a significant portion of the load cells’ overall quality. In addition, customization of the strain gages is a critical factor in ensuring the load cell is meeting the specific requirements of a customer’s project.

The last point is critically important because Interface does not just provide one size fits all products. Yes, we have a large standard product line ready to ship. There are many times when we collaborate directly with our customers to understand their application and the challenges that may be present during a force measurement testing program or OEM design. This allows us to offer modified and custom products that are engineered to order.  Whether that comes in the form of an off-the-shelf product within our catalog of more than tens of thousands of options, or a new model using our strain gage technology to meet the needs of a unique application.

An example of our commitment to meeting customer needs is the way we develop our strain gages to compensate for temperature, an environmental factor that can drastically affect the accuracy of force data. Our strain gages are designed and manufactured to counteract the temperature characteristics of the modulus of the load cell structural material.

The benefit to this is that our load cells are temperature-insensitive and do not require modulus compensation resistors, ultimately producing a simpler and more reliable circuit with higher output signal. It also means no dynamic thermal mismatch errors from modulus compensation resistors which cannot be thermally connected with the load cell’s surface at the strain gage location.

In addition, our proprietary strain gages provide several key benefits. Included below are a few of the differentiators available with Interface strain gages:

  • A higher output of 4mV/V, while competitors provide 3mV/V or less, which provides superior performance, flexibility, and accuracy.
  • The ability to perform hot and cold thermal compensation, from 15˚ – 115˚F, while competitors typically only provide heat compensation (60˚ – 160˚F).
  • Eight strain gages per load cell compared to our competitors four gages, which provides superior compensation of eccentric loads to further minimize resulting errors.
  • Our strain gages also offer:
    • Higher signal-to-noise ratio
    • Higher resolution in precision measurement applications
    • Superior fatigue life

Another factor in the development of our strain gages is our expertise and knowledge of the manufacturing process. We have always developed our own strain gages going all the way back to 1968. Therefore, we have learned everything there is to know about it and can guarantee the quality of our load cells in any environment based on this tenured expertise and having manufactured and calibrated millions of force measurement devices.

To learn more about our vertically integrated manufacturing process and the various forms of product and system customization we offer, contact our specialized application engineers.

 

Interface Engineered to Order Solutions

Load cells and torque transducers come in many different capacities, sizes and capabilities. They are used in nearly every industry that manufactures any type of hardware device or component. From testing minute forces on miniaturized medical devices, all the way up to measuring force in the construction of enormous suspension bridges or even rocket engines. The point is, there is no one size fits all in the force measurement world when performance matters.

What makes Interface uniquely the leader and is a true differentiator in the force measurement industry is our ability to provide engineered to order solutions to meet our customer’s exact application requirements.

Innovation across multitudes of industries has provided the opportunity to be more creative in utilizing Interface proprietary technology and engineering talent in the development of new force measurement devices. More and more we find ourselves leaning on our experts using our proprietary strain gages and product designs to develop solutions that meet the needs of our customer’s unique projects and end-products.

Through our work on modifications and custom solutions, we have expanded our product offerings to more than 37,000 uniquely designed products spanning across 52 years of development. Once initiating as a custom solution, many of these products have made their way into our catalog as standard products based on growing trends and larger demands.

There is also another form of customization, or more accurately termed modification, that we are seeing more and more as Interface grows our engagement with OEM customers. We call this “engineered to order” solutions. These solutions are different from full customization and critical in serving our diverse customers.

Designers and builders of high-volume products may have opted in the past for simplistic testing technology that lacks consistency, quality, accuracy and reliability. As product failures or customer satisfaction wanes based on performance, OEMs are driven to find force measurement solutions they can depend on for precise measurement and performance. This is also indicative of the times we are in utilizing advancements in production, technology and even robotics to produce products.

It is essential for product makers and engineers to find reliable solutions for accurately monitoring and testing product performance in real-time. In short, they need sensor capabilities that meet their product manufacturing volume, safety requirements and overall robust product performance standards. This is very typical in industrial markets where OEM customers want to monitor machines in the moment and more accurately predict fatigue or when a machine will need to be repaired, reducing overall downtime and saving money.

To best serve OEM customers and testing engineers with premium and affordable force measurement solutions, Interface offers engineered to order capabilities for the masses. Engineered to order means Interface can deliver force measurement solutions from our massive catalog that are modified to meet the features and specifications that our customers require, while still retaining the premium accuracy, quality and reliability Interface is known for across every industry we serve.

Interface Application Engineers work closely with our customers to determine the exact specs their product requires and deliver a manufacturing plan that meets their volume, accuracy and reliability needs through an engaged process. We plan, coordinate and team together to build the right product, for the right time and right price. Most importantly, we can modify most of our products in our entire catalog, giving flexibility within a precision line of solutions.

OEMs, product designers, and testing experts do not need to compromise performance. Interface’s engineered to order process combined with our automated production lines allows us to provide the same great quality force sensor our customers expect from an industry leader.

Interface excels when we partner with our customers in the earliest phases of development to ensure we provide the best solution, based on size, capacities and performance capabilities. By sharing design plans, we can collaborate with our customers to provide the best outcome. Ready to engage our experts?  Contact us here.

Advancing Load Button Load Cell Capabilities with ConvexBT

Demands for high precision testing utilized for compact designs and in confined spaces is growing. The requirements for quality, accuracy and most importantly reliability are what has driven the experienced engineers at Interface to create the newly released ConvexBT™ Load Button Load Cell product line.

The revolutionary design of the ConvexBT is a first of its kind load button load cell, providing better temperature resistance and more enhanced eccentric load rejection. Miniature load cells categorized as load buttons have been sensitive to off-axis, eccentric or misaligned loads. This means if the load is not exactly perpendicular to the surface it is resting on, the data could become skewed or inaccurate.

Interface designed the ConvexBT™ Load Button Load Cell to confine misaligned loads to the primary axis of the cell providing superior performance in comparison to similar products on the market in repeatability, better data and reproducible results.

As technology advances, there is a growing demand to make devices and products more compact and convenient. This trend is happening across industries and is especially prevalent in medical, industrial automation and products reliant on advanced communications technology. To design and validate these products, our customers need force-sensing solutions that can fit in confined spaces and provide extremely accurate data. This is the driving force behind the development of ConvexBT, the next generation in force measurement device.” – Ted Larson, VP product management and marketing, Interface.

CONVEXBT FEATURES AND SPECIFICATIONS

The newly released ConvexBT product comes in two different sizes: 3/8-inch, and 1/2-inch, which are all manufactured using 17-4 PH heat treated stainless steel. These options provide a wide measurement range from 10 to 250 lbf, a compensated temperature range of 60° to 160°F, and an operating temperature range of -40° to 175°F.

Additional specifications for ConvexBT include:

  • 2.00 ± 20% mV/V rated output
  • ± 0.25 non-linearity as a percentage of full scale
  • ± 0.25 hysteresis as a percentage of full scale
  • ± 0.50 static error band as a percentage of full scale

Other load cell load buttons designs have also been extremely sensitive to temperature conditions. Interface has redesigned its ConvexBT ultra-precision product line of load buttons to ensure that this is no longer something the user has to account for by taking the sensing technology disrupted by temperature out of the cable, and designing it directly into the load button.

The new available ConvexBT models include the following capacities:

  1. ConvexBT Model LBSU-10 lbs 3/8″
  2. ConvexBT Model LBSU-25 lbs 3/8″
  3. ConvexBT Model LBSU-50 lbs 3/8″
  4. ConvexBT Model LBSU-100 lbs 1/2″
  5. ConvexBT Model LBSU-250 lbs 1/2″

Additional model capacities will be available this year.  You can view the complete product specifications as well as technical guide by visiting the product page here.

ConvexBT was developed through a combination of intense research into growing technology trends in force measurement and actively collaborating with our customers to understand their unique challenges, By introducing the industry’s most advanced and versatile ultra-precision load button load cells, we are solving the test and measurement challenges associated with miniaturization of existing and new technologies.” – Greg Adams, CEO at Interface

The revolutionary ultra-precision line of ConvexBT™ Load Button Load Cells uniquely uses multi-point calibration for testing force on miniaturized products and within confined spaces where accuracy is paramount to success and safety. The requirements are critical to common buyers of miniature load cells, especially for use in medical devices, robotics and in industrial automation applications

In addition to its ability to solve test and measurement challenges with compact devices, another key benefit of ConvexBT is its versatility in that it can be used as a traditional test and measurement solution. It can also be installed into OEM components and devices as an advanced miniature sensing solution to collect accurate real-time force data on the product as it is in use.

ConvexBT is available now under the product family of Interface Mini® Load Cells. The product is part of a growing line of Interface Load Button Load Cells. The new ConvexBT model LBSU specifications are available here: /product-category/load-button-load-cells/.

Read more about Off-Axis Loads and Temperature Sensitive Applications here.

Understanding One-Cell Force Measurement Systems

When it comes to load cells and force measurement systems used to test and validate product designs, the options for different configurations is nearly endless. In fact, Interface has tens of thousands of force measurement products in standard, modified and custom-made configurations.

In our recent post, Considerations for Steel, Stainless Steel and Aluminum Load Cells, we detailed materials used in load cell construction. These considerations are important based on the project specifications for accuracy, quality and reliability in test and measurement.

Similarly, understanding the system configuration is another critically important factor to setting up the correct test for receiving accurate data.  A simple system configuration used for less-complex testing is known as one-cell or single load cell system.  They are popular for performance and durability testing.

How do one-cell systems work and what are the benefits and trade-offs?

One-cell systems are developed by using a tension cell and mounting it through a rod end bearing and clevises. If the cell is properly oriented with the dead end going to the support, the only other major consideration for this system is the elimination or reduction of possible parallel load paths. This type of simple system is attractive to some testing engineers and product designers because it is cost effective and can provide very accurate measurements when using Interface precision load cells.  It is important that the load meets the criteria for the test system.

In this figure, it shows a high-impact one-cell system platform. This one-cell system can withstand the high impact of rough treatment from certain applications such as large drums, LPG tanks and more.

The downside to using a one-cell system is that the center of gravity of the load must be placed directly on the mark for the system to work properly. However, this can be accounted for by positioning the fences as shown in the high-impact one-cell platform diagram, so that the center of gravity is located properly when the application you are measuring is shoved up against fences.

The actual load at the center of gravity for your application will be factored by the lever arm (as shown below):

The one-cell system works simply because the location of the center of gravity is under control. If the force on the primary axis of the load cell bears the same relation to the location of the center of gravity and the load under all conditions, the scaling will be correct. Whether using a one-cell or two-cell system, the system must be designed to retain its integrity.

This has been a brief overview of a one-cell system, which is detailed in Interface’s Load Cell Field Guide.

To learn more about these systems and to determine if your application test can utilize the simplicity and cost savings of a one-cell or two-cell system, contact our systems experts and application engineers.