Original Date: 07/09/2007
Revision Date: / /

The Inpro/Seal Company employs a remarkably efficient and continuous real-time production scheduling process. Using simple network-based software, the production queue is managed via shipping dates, which allows for priority same-day orders to be inserted at or near the top of the queue. Machine downtime is minimized by directing jobs to machine cells based on stock size and tooling similarities. The key to Inpro/Seal’s impressive flexibility is placing responsibility for completion of portions of the queue into the hands of the machine operators.

The Inpro/Seal Company in Rock Island, Illinois, produces bearing isolators for rotating machinery. Inpro/Seal has developed a simple and efficient yet highly flexible product planning process that turns out 40,000 units per month and is able to boast same-day shipping of 30% of the company’s output.

This pull process is initiated once a design has been translated into machine code for the CNC machine, released by the Production Programming Office, and enters the production queue. This triggers several events. First, the Production Control Office routes the design to one of seven CNC cells based on the material stock-size type and outer diameter to minimize retooling between jobs. Given that many jobs are single units or very small production runs, downtime for retooling is a critical metric at Inpro/Seal. Design release also triggers inventory staging of stock and O-rings at the appropriate production cell. Last, the process clock is started to measure the total time from design release to completion of packaging.

Production Control is responsible for managing the production queue and ensuring orders meet the requested shipping date by apportioning work in the queue to one of seven CNC cells based on stock size and tooling requirements. The simple computer-network-based queue is visible to virtually anyone in the sales and production offices, and any changes or additions are instantly posted. Each CNC cell consists of multiple machines (typically three) operated simultaneously by a crew of one to three operators. Three cells are unique in their orientation – one is reserved for manual machining, one is used for large quantity runs, and one is operated as a lean experimental cell. All three cells, however, can accept work from the queue like any other. The cell operators have the responsibility of managing their own queues. They have the freedom to reorder their queue and assign jobs to any of their machines based on stock size and tooling similarities, with the shipping date driving priorities.

This instant visibility of work in progress and the ability to resequence jobs is one of the key enablers to Inpro/Seal’s impressive responsiveness to same-day shipping of the priority orders that constitute 30% of daily production. Upon receipt of a priority order, Production Control inserts it into the queue using the same criteria as any other job. Since the shipping date drives the pull process, it instantly appears at or near the top of the queue. Associated paperwork receives a red “Must Ship Today” sticker to reinforce the priority status. This simple yet highly efficient handling of all orders – the so-called continuous real-time scheduling – eliminates perturbations in the production process.

As each job enters and leaves machining, milling, final assembly, and shipping, it is logged in and out using a simple barcode-based tracking system. The status of any job can be instantly determined; if adjustments are necessary to the design or production run, the job can be removed, altered, and reinserted into the queue. The tracking system also allows Inpro/Seal to determine and track several key metrics – machine time versus process time, and machine cell operation time versus operator work hours. The company’s goal is to drive overall process time as close to actual machine time (including final hand assembly), minimizing the time that partial assemblies sit idle. The second metric, the ratio of machine cell operation to operator work hours, currently stands at 2.8:1 for a three-machine cell. This means that for each hour an operator is on the job, a total of 12 minutes of downtime is spread across his or her three machines (or an average of only four minutes of downtime per machine per hour).

Inpro/Seal has reached a remarkably high level of efficiency in its production process by using simple software tracking tools, remaining flexible at all points in the process and placing control of the process and responsibility for meeting customer deadlines in the hands of the machine operators.

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