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Application of the Month

Customized Right Angle Servo Gearhead Solves Space Problem
November, 2013 - View all Application Examples

Today’s automated machinery is becoming more flexible and compact. One of the results is that the space available for drive components keeps shrinking. Creativity in selecting solutions to achieve the desired envelope size is a necessary attribute for suppliers of these types of products.

One of our customers approached us with a dilemma they were facing. They had a servo driven mechanism that required a specific amount of torque but had a strict space limitation in which to integrate a servo motor and gearhead. Because of the positioning motion profile they required a low backlash solution as well.

The customer had interest in our Dynabox servo worm. A right angle configuration was imperative because they had limited room along the axis of the driven shaft. With this configuration they could shaft mount the gearhead to eliminate the space needed for a coupling. The Dynabox is perhaps the best and highest quality design available in the world for right angle gearhead positioning applications.

After calculating the torque required to accelerate the load at the specified rate and speed, along with adding a factor for the number of cycles in a given period, the servo motor and gearhead sizes were selected. Unfortunately this is where the customer realized his dilemma.  His motor was too long to fit where it needed to fit.

At the risk of getting off track, I'd like to insert a teaching point about gearheads that has some relevance to the issue's problem and it's resolution.

Gearheads are designed with a specific output torque capacity, which can vary slightly depending on the gear ratio and number of cycles, or stops and starts, required for the designed motion profile. This is primarily a function of bearing life.

Continuous duty, designated S1, would allow a lower value due to the bearings being under constant load. Intermittent duty, designated as S5, would allow higher torque capacity as the bearings would see the load for shorter periods over a given lifetime rating.

Based on a relatively similar output torque rating for all ratios offered within a gearhead size, different motor sizes can be accommodated depending on the ratio selected. Theoretically, with gear efficiency aside, a gearhead with a 10:1 ratio could handle a motor with nine times the torque as one with a 90:1 ratio. Of course, gearhead output speed and inertia matching determines which gear ratio is best for the application.

In our customer’s case he needed fast acceleration. So a 10:1 ratio was the best choice for multiplying the motor torque while achieving the reaction time he needed. But to generate the necessary input torque he needed a relatively large servo motor. None of the options he looked at would fit in the space he had available.

This is where a little creativity came to the rescue. It was determined that there was some space available on both side of the gearbox. Our suggestion was to integrate two smaller servo motors that in combination would be able to provide the input torque required to achieve the motion profile. Because synchronizing servo motors is a relatively common tactic used by automation specialists, this solution had merit.

The Dynabox, like most servo gearheads, is optimally designed for a single input source. However, because of it’s right angle, single stage, gear configuration it is possible to extend the input shaft through the box and out the other side.

Typically we offer this customized option to drive another box down line, connected by a line shaft. This allows multi axis control with a single motor. But, because of the internal backlash adjustment components, two motor inputs was not a typical option.

However, customizing standard assemblies is a particular strength of DieQua and our manufacturing partners. The key design element we had to keep in mind was how to stay under the maximum backlash target while integrating a second motor adapter flange. Without revealing any secrets, let’s just say the Dynabox engineers performed their magic and the design was born.

After some relatively simple (for them, at least) programming changes to simultaneously control and synchronize two servo motors, the customer was thrilled with the solution. It saved them from some desperate moments. The customer bought several units for this application, then more of a larger size for a subsequent application. While this design isn’t often needed they come back to us when it is.

It isn’t only for space savings that this design is useful. Another customer came to us with a similar configuration request but for an entirely different reason. In their case they were driving a mission critical application, which absolutely couldn’t go down. They wanted a redundant drive system so any motor or control failure could be overcome.

For them we upsized the gearbox to provide extra service factor and provided the same dual motor input adapters so they could incorporate a reserve motor. When not required, the back up motor, on the left side of the gearhead, is driven by the primary motor on the right side of the gearhead. Should something happen to the primary servo motor, the backup motor would kick in to maintain production.

So, you see, a customized design for one customer can often solve a different problem for another customer. Its why after satisfying thousands of unique applications like these over the years that DieQua can repurpose past solutions to help solve your existing problems. Or perhaps come up with new ones all together for you.

Give us a call with your next design challenge. You may be surprised when we come up with exactly what you want or something you may never have thought about. Its what we do.

Chris Popp
Director of Marketing

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