Ergometers: 3D Technology for Critical Parts Solves Design Challenges

Heart disease is the leading cause of death in the United States, accounting for approximately 20 percent of the nation’s deaths. With data showing a heavy impact across all racial and ethnic groups in the United States, it seems no one can afford to disregard this threat.

Worldwide statistics paint a similarly gloomy picture. The American Heart Association estimates that 244.1 million people globally were living with ischemic heart disease in 2020. “Cardiovascular diseases remain the leading cause of disease burden in the world. CVD burden continues its decades-long rise for almost all countries outside high-income countries, and alarmingly, the age-standardized rate of CVD has begun to rise in some locations where it was previously declining in high-income countries,” the Journal of the American College of Cardiology reported in 2019.¹

Amid this global health crisis, emergent technology is helping healthcare professionals detect cardiovascular disease. The race to develop equipment is a worldwide industry pattern, as manufacturers have mobilized in recent years to increase the pace of innovation and production. The need for speed has never been greater, especially in the medical community. Any innovation has the potential to save lives.

A German manufacturer of recumbent ergometers faced such a challenge. The units are designed for exercise, including the kind of exercise challenge used to diagnose heart disease. The company, ergoline, needed wear-resistant and lubrication-free bearings in a custom dimension so that the company could start production of a new series. Creating bearings from bar stock was too time consuming and expensive.

With the help of a German counterpart, ergoline found a quick answer. Igus, a German manufacturer of motion plastics, offered the customer its Fast-Line service, an innovative resource that features modern computerized numerical control (CNC) technology. The time from order to delivery was four days.

“Delivery time has been an issue since the early days of igus,” says Tom Krause, head of 3D printing at igus. “Our founder, Günther Blase, relied on a modular tool design in the first years. Over the years, however, the requirements became more and more time-critical and have become even clearer in the past 10 years.”

Experience with Ergometers

Ergoline is hardly an ergometer manufacturing newbie. The company is a major producer of these medical devices and has specialized in producing a wide variety of high-quality medical ergometer designs for more than 30 years. The company launched its first product, the ER 900, in 1986 and sold more than 25,000 devices — some of which are still in use. It distributes its products in more than 60 countries across all continents.

The company also manufactures and develops equipment and software for training and monitoring patients in cardiac rehabilitation. When it comes to getting smart on the heart, ergoline stands near the head of the class.

“These systems are especially common in rehabilitation clinics and sports medicine centers,” says Dominik Huber, head of design at ergoline GmbH. “All components — such as plain bearings — must be durable and able to withstand a wide range of loads, such as acceleration and high weight.”

One of ergoline’s products, the ergoselect 1200 model, is a reclining ergometer developed for the purpose of dynamic stress echocardiography. Essentially, the procedure evaluates cardiac structure and function during physical exercise or the pharmacologic simulation of exercise by measuring increased heart rate, cardiac output, and myocardial oxygen demand.² The procedure allows for echocardiographic images to be obtained anywhere along the continuum from rest to peak physiologic stress.

The ergometer can be electrically adjusted horizontally or laterally between 0° and 45°, allowing special ultrasound heart examinations during an ergometric stress test. In the ergometer, specially sized plain bearings are pressed into the bearing point where they ensure reliable, safe adjustment even with dynamic forces of 1.3 tonnes. The bearings are ideal for ergometers in that they are lightweight, corrosion-free, and resistant to dust and dirt.

Design Challenges

Several design issues arose with the product. First, Huber sought a plain bearing to support the adjustment mechanism for height and tilt. The company selected igus’ iglide P210 bearing, which works well in pivoting movements on various shaft materials.

The bearing, like all of igus’ components, requires no external lubrication and thus meets the stringent demands for the medical field. It is also extremely durable. Another issue developed when shaft modifications in the product resulted in too much clearance from items that had been selected from a catalog.

“Since production was about to begin, we initially decided to turn a small number of the parts from bar stock,’’ Huber says. Volume production, however, required an even faster solution.

“Six weeks for a regular tool was too slow for us and continuing to turn bearings from bar stock was too time-consuming and expensive,’’ Huber says.

The igus service hastened the turnaround time. “By investing in our tool shop with its own production line for round parts that features modern CNC technology, we were able to produce specially shaped plain bearings for ergoline within a very short time,’’ says Benjamin Haupt, technical sales consultant at igus GmbH.

In CNC, computer instructions guide mills and lathes that control the precision of the instruments. The process enables the development of parts and components that would usually be impossible to create manually. The four-day delivery time at a cost-effective price surprised Huber. “We had expected to pay three times as much,’’ he says. “Of course, we were very pleased. It gives us the possibility to work flexibly in design.”

Speed Is Essential

The service was created to meet the needs of manufacturers with high product demand. Customized parts, such as plain bearings in unique shapes, have to be delivered without complications. Injection molding can require several weeks. An expanded inhouse toolmaking department enables delivery of plain bearings in special dimensions in a few days and at affordable prices.

“By investing in our toolmaking department with its own production line for round parts with modern CNC technology, we are now able to respond even faster to our customers’ needs,’’ says Stefan Loockmann-Rittich, business unit manager of iglide at igus GmbH. “In addition to our large catalog range of polymer plain bearings, which are available from stock, we can produce customized parts cost-effectively in just a few days using the appropriate injection molding tool.”

Customers can determine whether injection molding or another production method is more cost-effective with the iglide Designer. The online tool allows the customer to enter the dimensions of the plain bearing, select the desired material, and define the quantity. The program shows an overview of the manufacturing processes with the appropriate costs.

Customized and Quick

The German manufacturer of ergometers is among the growing legion of manufacturers that want customized products delivered quickly. While reducing downtime is still a major focus for manufacturers, they are also demanding that suppliers of components to get materials delivered in record time. Now more than ever, if a company is not moving forward, it is standing still.

“There are different reasons,’’ Krause says. “A common one is that part of a machine is broken down and it needs to be replaced, so it’s imperative to get the machine running again. Other reasons include failed sourcing methods or an expectation of getting individual parts in a few days.”

Igus’ focus on speedy delivery did not begin with FastLine. It previously manufactured molds from aluminum for time-critical developments and later added in print2mold (3D printing).

“The advantage of FastLine is that we have a mold that is 100 percent suitable for series production and is not limited in the number of shots in injection molding,’’ Krause says.

In 2014, the company introduced its first 3D printing filaments, which are made especially for moving applications because of the solid lubricants, Krause says. In 2016, it introduced its first SLS material, iglide i3, and started with its SLS 3D print service. “Since then, our customer interest was constantly growing, so that we now have 10 SLS machines worldwide,’’ he says. “We are able to produce special wear parts very quickly in Boston, Shanghai, and Cologne. Last year, we made more than 200,000 special wear parts by 3D printing.”

More than Ergometers

Ergoline is one example of just how 3D printing innovations can speed up industrial processes. The technology can also be used in energy chain applications, for instance. In one case, mounting brackets and moving ends for the energy chains were developed in a large-scale 3D printer.

In another application, iglide i6 material was used to develop glide pad adapter clips for energy chains. The clips serve as a ramp to relieve the glide pads, extending their service life. The material improves the lifetime of bearings by six times compared to its predecessors, even for temperatures over 212 °F.

“Mostly we produce parts for our customers with their own design,’’ Krause says. “Bearings, gears, sliders, and other friction parts are the most printed parts. For energy chains, 3D printing is already used in the prototyping phase and in the start of the series. For the bigger quantities, injection molding is still more cost effective. When a special design is needed and quantities are not big enough for molding, 3D printing is used as a bridge technology to move things along faster.”

Like advancements in the medical field, innovation in the design and manufacturing of medical equipment and the products incorporated in them is moving more rapidly. The timeline for design and development to production to market has shifted considerably. The movement toward faster production does not come without risks, which is where calculable service life, testing, and predictive maintenance of manufacturing equipment can also support the movement.

Just as engineering expertise has resulted in faster speeds for race cars in the Indianapolis 500, everything will continue to get faster in manufacturing. How fast is the question. “We do not know the limits, but we are sure we have not reached them yet,’’ Krause says. “There are many approaches and ideas, as our customers need it now and in the future.”

Reference

1. GA Roth, et al., “Global Burden of Cardiovascular Diseases and Risk Factors, 1990-2019: Update From the GBD 2019 Study,” J Am Coll Cardiol., 2020 Dec, 76 (25) pp. 2982-3021.
2. L Gilstrap, et al., “Dobutamine stress echocardiography: a review and update,” Dove Press, 5 April 2014 Volume 2014: 5, pp 69-81.

This article was written by Thomas Renner, who writes on building, construction, engineering, and other trade industry topics for publications throughout the United States. For more information on igus  , contact Tom Krause, head of 3D Printing at igus, e-mail This email address is being protected from spambots. You need JavaScript enabled to view it.. For more information about ergoline, visit here  .

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