Case Study: Linear Ball Screw

3DEO | Innovate. Design. Scale.

Linear Ball Screw Application

A linear ball screw is a mechanical actuator that creates high-performance, low friction linear motion at high speeds and duty loads. Essentially, it is a high-efficiency method of converting rotary motion to linear motion by using a recirculating ball mechanism between the screw shaft and the nut. Compared with a conventional sliding screw, the ball screw requires driving torque of one-third or less, making it ideal for saving drive motor power. From motors in robots to automobile power steering motors, and in aerospace and defense, and semiconductors, linear ball screws are widely utilized in a variety of industries.

NOTE: this case study is based on 3DEO’s production of the ball return tube for a US-based Tier 3 aerospace supplier in the aerospace and aviation industry. 

The Challenge

Ball bearings in the assembly facilitate this low-friction linear motion, and must be recirculated within the nut assembly. One of the legacy designs that recirculates the ball bearings requires a small, precision bent tube. This tube is particularly difficult to fabricate because of precision requirements on the inner diameter of the tube and the very small size (recirculates 0.080” ball bearings).

In this particular linear ball screw application, the ball bearings are incredibly small at 0.080”, and the tube is less than 0.65” in its longest dimension. It is very small, with incredibly tight tolerances.

According to our customer, they could only get a few suppliers to even attempt the part. Conventional suppliers attempted to bend tubes, which would result in crimping the elbows of the tube, preventing recirculation of the ball bearings. Since the aerospace company could not find a supplier, they turned to 3DEO and metal 3D printing as a last alternative.

“We wanted 17-4PH in the application because it is a premium material. The performance of the material in the application really impressed our customer.” – Lead Engineer

The Solution

3DEO approaches every project as a collaborative partnership, taking a holistic view of our customers’ pain points, objectives, and development needs. The team is driven by its commitment to help engineers solve their toughest problems or do things that haven’t been done before.

In this case, 3DEO’s applications engineering team spent many hours with the aerospace customer to review the design of the ball nut assembly and understand the requirements of the application. They brainstormed pain points, specifications, and creative solutions. In the end, they co-designed and fabricated a superior ball return tube to solve the problem.

“This was a critical component in the assembly that we could not make any other way. 3DEO partnered with us to deeply understand the application and help us solve the problem, and this collaboration was essential to our success.” – President, Tier 3 Aerospace Manufacturer

3DEO worked directly with the customer’s engineering team starting at the design stage to ensure their designs were optimized for 3DEO’s technology. In the course of the collaboration, the teams came up with a creative solution to leverage the geometric freedom of 3DEO’s printers to eliminate an expensive post-machining step.

Conventional Process vs. 3DEO Process

Conventional Process: 3 steps – Bend tube, fixture part, machine part

3DEO’s Process: 1 step – Print part

Results of Fatigue Testing

After many iterations, the customer used 3DEO’s first articles–printed on the same machines and of the exact same quality as their parts in high volume production–and tested them against the legacy part in simulations.

“Our customer specified that the minimum number of cycles of one ball return tube needed to be 12,000. Legacy ball return tubes were failing around 12,000 cycles. 3DEO cruised to 20,000 cycles without a single issue and we just turned the machine off to end the test. The quality of 3DEO’s parts in the test was exceptional.” – Lead Program Engineer, Tier 3 Aerospace Manufacturer

Testing threshold:

Minimum 12,000 cycles

Legacy part:

Failed at 10,000 cycles

3DEO part:

No failure, even after 20,000 cycles

In fact, when the fatigue testing was complete and the assembly analyzed, 3DEO’s ball return tube showed less wear than the ball bearings.

Benefits of Working with 3DEO

3DEO is an award-winning design, engineering and manufacturing service specializing in complex metal 3D printed components produced in high volumes. We help companies at every stage of their product lifecycle from ideation to scale, partnering with our customers to design for additive manufacturing.

A next-generation American manufacturing technology company, 3DEO is working with many aerospace companies today to replace MRO investment cast components. 3DEO is a quality supplier of mil-spec aerospace components. In addition to ISO 9001, the company is certifying for AS9100.

3DEO is driven by its commitment to help engineers solve their toughest problems or do things that haven’t been done before. Whether you need in-house design expertise to build prototypes that seamlessly transition to scale or are seeking innovative solutions to a complex supply chain, 3DEO can help.

  • Early-stage design for additive manufacturing
  • Component functionality optimization
  • Transition from prototyping to production
  • Production at scale

3DEO is an indirect supplier to

Linear Ball Screw Components Benefitting from 3DEO’s Technology & Services

  • Crossover components
  • Ball return pipes/tubes
  • Ball nuts
    • Deflector-type
    • End cap-type

Sizes

  • Length – 1” to 8’ typical
  • Diameter – 5mm – 1000mm typical

Pitch

Representative of the angle of the threads. Often represented in distance traveled linearly per revolution of the screw.

Start Count

Commonly 1 to 4 starts, meaning the number of individual bearing races operating in parallel. Related to the pitch and impacts how much operating torque is required and the translation speed of the carriage.

Tolerance

Defined in units of error per unit of distance traveled. For example, if offered in imperial units would typically be inches of error per inch: 0.001”/1” for a 0.1% linear travel error specification.