Indexing systems remain the norm in many assembly applications, and those that involve dispensing a liquid into a product container are no exception. However, in many cases, continuous motion assembly may be a better way to go. This assembly technique offers faster speeds, a smaller footprint, and greater quality. Let's take a closer look at the differences between indexing and continuous motion systems — and which type might be right for your next assembly task.

Continuous motion offers faster speed, a smaller footprint, and greater quality compared to indexing, and is suitable for myriad dispensing applications.

Continuous motion vs. indexing

The primary differences between continuous motion and indexing assembly involve speed and precision. With indexing motion, products being processed start and stop at each station on the machine. With continuous motion, multiple processes can occur without interruption for every cycle, so that the jobs effectively overlap. The result is a faster process: 400 to 1,000 parts per minute (ppm) are possible with continuous motion versus up to 250 ppm with indexing motion. In addition, the tooling never loses contact with individual components, so part alignment is always maintained.

When to choose indexing motion

In most applications that require a complex assembly and speed of less than 100 parts per minute, an indexing system is likely to be more cost effective than a continuous motion setup. So if the application doesn't require high speeds — or the product can't handle it — an indexing system might be the appropriate choice. However, even for faster setups, many manufacturers don't evaluate the potential benefits of a continuous motion system, and ultimately specify an indexing system — simply because the technology is familiar.

Continuous motion outputs 400 to 1,000 parts per minute, versus up to 250 with indexing; because the tooling never loses contact with individual components, part alignment is also maintained.

When continuous motion is preferable

In applications where the target total net output exceeds the capability of a single indexing machine, continuous motion is probably a good choice. Why is the speed limit of an indexing system lower than that of a continuous motion system? Simple: It comes down to dwell time. The tooling of an indexing system can only complete its task while a part is stationary, which is approximately two-thirds of the time. The part is in motion the rest of the time. Therefore, an indexing system is subject to the constraints of target output speed. This constraint becomes particularly detrimental when working with viscous fluids that can't be forced out too quickly without encountering accuracy issues. For example: If output is 60 parts per minute, there is one second available for each part, but only two-thirds of a second to complete the task while the part is stationary.

Continuous motion, on the other hand, takes this time element out of the equation by using a platform that can be expanded to whatever the output dictates. It's simply a matter of sizing the continuous motion equipment appropriately. Other advantages of continuous motion include:

Smaller footprint

If an application requires multiple assembly processes with an output of 300 ppm, this can be accomplished by building five indexing machines, each with an output of 60 ppm. In contrast, a single continuous motion machine can execute the same job.

Less labor

In the same scenario, five indexing machines each require their own operator, whereas the continuous motion machine requires only one operator.