Stepping motor case study | 076 | The cause of misalignment and noise in the imaging diagnostic equipment cannot be identified!

Problem

In the medical field, the fusion of different fields is progressing by incorporating not only existing technologies but also new technologies. As a growing market that is expected to grow in the future, and because it is less affected by economic fluctuations, companies from various industries are actively entering the medical device industry.

Development of diagnostic imaging equipment begins, but images are blurred

Company A, which develops image processing software, has begun developing a medical imaging diagnostic device by utilizing its image analysis technology. First, they completed a prototype by referring to other companies' devices, but faced two problems while evaluating the device.

Mr. M from the Product Development Department had this to say about this challenge:
"As this was our first time developing hardware, we started production by referring to equipment from other companies, but after taking pictures repeatedly, we noticed that the images were blurred. After investigating the cause, we found that there seemed to be a misalignment in the photographing mechanism. Since the mechanism is the same as the reference device, we were unable to figure out what was causing the misalignment."

Medical equipment also produces unpleasant noises that should be avoided.

Additionally, noise was also an issue.
"There was a noise that was not present in other companies' devices. Because this is a device that is used near patients, it is undesirable for it to produce noise that is unpleasant. However, with little development experience or know-how, it was difficult to identify the cause of the noise, and we were at a loss." (Mr. M)

Mr. M inspected the prototype in detail to identify the cause of the blurred images and noise. However, he was unable to identify the cause, and the development schedule continued to fall behind schedule.

assignment

This causes misalignment and blurs the captured image.
Due to lack of know-how, they are unable to identify the cause of the noise.

Solution

Support from identifying the cause of misalignment to finding a solution

Mr. M, who was in a difficult position, went to a medical equipment exhibition in search of a solution and explained his problem to the person in charge at SANYO DENKI CO., LTD. booth. Later, the SANYO DENKI CO., LTD. person in charge visited Company A and discussed the problem in detail.
"The SANYO DENKI CO., LTD. staff explained to us in detail that the causes of the mechanism misalignment were electrical and mechanical, and then carried out an investigation." (Mr. M)

After some investigation, the cause of the misalignment was discovered. Mr. M recalls:
"The cause was that the part connecting the pulley and motor in the camera mechanism had loosened due to repeated back and forth movements. To solve this, they suggested machining a key groove into the motor shaft." (Mr. M)

Reduce unpleasant noise by changing to the optimal motor!

It was also discovered that the noise was caused by the over-specified motor that was used.
"I had heard that stepping motors lose steps when the torque is insufficient. Malfunctions caused by stepping out are unacceptable. So I chose a motor with plenty of torque to spare. But I never imagined that this would be the cause. I discovered that when a stepping motor is over-specified, the excess torque causes vibrations and generates noise." (Mr. M)

SANYO DENKI CO., LTD. staff investigated the load and operating conditions and provided an optimal motor sample to Company A. Mr. M immediately installed the sample motor in a prototype machine and performed an actual machine evaluation.
"When we changed the motor in the camera mechanism to a two-phase 56-axis motor with a keyway, the blurring of the captured images and the unpleasant noise disappeared. We were very grateful for the support we received from identifying the cause during the development stage." (Mr. M)

After that, Company A successfully completed the development of the medical imaging diagnostic device, and was able to enter the medical field for the first time. Mr. M said that he would like to rely on SANYO DENKI CO., LTD. for future medical device development.

For more information about stepping motors, please see "What is a stepping motor? An explanation of its structure, types, usage (drive system and control method), advantages and features."

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