Stepping motor example | 071 | I want to make the infusion pump used in the hospital room quieter!

Problem

The medical equipment industry is a global growth industry. Medical equipment manufacturers are required to develop products that meet the requirements of the field. As technological innovation advances rapidly, high performance and quality are required in areas such as automation, miniaturization, and low noise, and competition is becoming increasingly fierce.

Infusion pumps used in hospital rooms. The challenge in developing a new model was to make it quieter!

Company E, which develops and manufactures various medical devices, has recently begun the development of a new infusion pump. Mr. T, who is in charge of new product development, had this to say:

"Infusion pumps, which are used to administer medication accurately at a constant rate, are one of the most frequently used medical devices. A motor is used in the pump mechanism that controls the flow rate, but because these devices operate for long periods of time in hospital rooms, the noise caused by the vibration of the motor can make patients anxious and disrupt their sleep.
Although noise reduction had been an issue up until now, we had recognized that a certain amount of motor noise was unavoidable, since maintaining the accuracy of the infusion flow rate was a priority. However, in order to improve patient comfort and differentiate our products, reducing noise was an important development issue for the new model.

Want to avoid design changes that would require recertification

Company E uses a two-phase stepping motor in its pump mechanism. The first improvement that came up was to change the current stepping motor from two phases to five phases.

"Changing to a five-phase stepping motor would reduce the step angle, which would reduce vibration and noise. However, in this case, the driver would also need to be changed to a five-phase model. Medical devices are subject to mandatory certification, so making major changes to the system would mean re-certification. This would significantly extend the development period, including the evaluation period and the time it takes to obtain certification, so it wasn't realistic," said Mr. T.

Mr. T wanted to make the new model quieter while still maintaining the current certification, so he continued to look into the issue, but was unable to find a good solution.

assignment

We wanted to reduce vibration from the motor that controls the flow rate of infusion and improve noise reduction.
We want to avoid major design changes that would require re-certification.

Solution

Noise reduction of 25%! Effect of mounting damper

Mr. T asked several companies for information on how to make his infusion pump quieter, and received a proposal from SANYO DENKI CO., LTD. to attach a mounting damper to the stepping motor.

"Apparently, attaching an optional damper to a stepping motor can reduce motor vibration. I've heard that this method is commonly used in the FA industry, but this is the first time I've heard of it.
Furthermore, they provided us with comparative data on noise characteristics that quantitatively showed the frequency components of the motor alone, which gave us hope for a reduction in noise. Based on this, we decided to carry out an evaluation on an actual machine." (Mr. T)

The decision was made after evaluating the actual equipment and finding that it reduced noise by 25%. In this way, Company E was able to reduce motor vibration and achieve a quieter new model of infusion pump.
"SANYO DENKI CO., LTD. made precise proposals based on technology and know-how in the factory automation industry that we were not familiar with. Thanks to them, we were able to achieve our development goal of reducing noise without having to obtain certification again. The optimal proposals and support from SANYO DENKI CO., LTD., who understands our products, were very reassuring." (Mr. T)

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."

effect