How to Measure Rework Rate, Setup Time, and Parts-Per-Shift on Your Production Floor — and Use Those Numbers to Justify Your Next Machine

By Centex Automation Editorial Team

Your shop can be busy all week and still struggle to finish the jobs that matter. Cabinet sides get cut twice. An edgebander waits for the next setup. A skilled employee spends the afternoon correcting parts instead of moving a new order toward assembly.

Before buying another machine, put numbers on those losses. Rework rate, setup time, and accepted parts per shift give cabinet and casework manufacturers a practical starting point for deciding whether the next improvement should be equipment, maintenance, tooling, training, or a different production method.

The goal is a purchase decision tied to a measurable production problem. Here is a shop-floor method you can start with a simple shift log.

Define what you are counting

Choose one process boundary, such as cabinet-side machining through inspection, and one unit, such as an individual cabinet side. Write down the acceptance criteria: dimensions, hole locations, edge condition, and any other requirement needed by the next operation.

Give every part a unique identity or traceable batch position. A component that returns for correction remains the same component. A replacement for a scrapped part is a new production attempt and needs its own record.

Start with a representative baseline of about two working weeks. Extend it if that period misses important materials, shifts, or job families. Separate repeat rectangular work from complex custom parts; a shift producing shelves is not directly comparable with a shift machining detailed doors.

These are explicit working definitions for your log. Use them consistently, and document any differences from a software vendor’s definitions.

Measure rework without hiding it in final output

A part that eventually passes inspection still consumed extra resources if it needed correction. ASQ’s definition of first-pass yield excludes parts requiring rework or repair on the first attempt. See ASQ’s first-pass yield definition.

Rework rate (%) = unique parts requiring rework ÷ parts completing their first attempt × 100.

Count the affected part once in the rate, even if it needs two corrections. Record both correction events and their labor separately. Otherwise, a small group of troublesome parts can make the rate misleading while the real cost remains invisible.

Worked example: one completed production cohort

Assume 500 parts complete their first attempt. Of those, 450 pass immediately, 30 require rework, and 20 are scrapped without a rework attempt. All 30 reworked parts are subsequently accepted. This is an illustrative example, not a Centex customer result.

If some reworked parts are later scrapped, the rework and scrap categories overlap. Keep first-attempt status and final disposition in separate fields rather than assuming all percentages must add to 100%.

For an open job, show unresolved parts as pending. Do not compare a fully resolved batch with one whose difficult parts are still waiting for inspection.

Time the entire changeover

Use a consistent clock: last accepted part of Job A to first accepted part of Job B. Include the adjustment and verification needed to produce that first acceptable piece. Record the reason for each delay so a material shortage does not get mistaken for a mechanical setup problem.

Also record setup labor. Two employees working for 20 minutes represent 40 labor-minutes, even though the machine loses only 20 elapsed minutes.

Separate preparation that requires a stopped machine from work that can be completed safely in advance. The Lean Enterprise Institute describes this distinction between internal and external setup activities as central to SMED, a changeover-reduction approach. Read the SMED explanation.

For a cabinet shop, advance preparation might include checking the next program revision, staging the correct panels, and making the required tooling available. Tool changes and adjustments still follow the machine’s approved procedures.

Compare like-for-like transitions. Changing panel thickness may take a different amount of time from changing an adhesive system or machining fixture. Track the median and the slowest recurring cases for each transition type. A single average can hide the setup that repeatedly derails the schedule.

Count accepted parts at a clear handoff

Accepted parts per shift = unique accepted parts leaving the selected process during that shift.

Count each accepted part once at that handoff. Do not count every machining pass as new output. Mark parts carried in from earlier shifts so you can explain why accepted output and new first-attempt counts differ.

In the example above, if all 480 accepted parts leave during an eight-hour staffed shift, output is 480 parts per shift, or 60 accepted parts per staffed hour. The latter includes that shift’s interruptions. A machine-running rate using only active machining time is a different measure.

Record shift length, staffing, planned breaks, downtime, and job mix alongside the count. For mixed production, group comparable part families or use documented standard minutes of work. Do not treat a small shelf and a heavily machined cabinet side as equal workloads simply because each counts as one part.

Identify the loss your next machine must remove

Rank recurring problems by labor consumed, material lost, and time taken from the process that limits completed orders.

Improving a station with spare capacity can still help quality or labor, but it may add little shipment capacity. Identify where the shop is constrained before pricing extra speed.

Turn recovered minutes into a defensible business case

Suppose three daily setups fall from 25 to 15 minutes each. That recovers 30 machine-minutes per day. At a demonstrated rate of 1.5 accepted parts per running minute, the theoretical opportunity is 45 additional parts daily.

That opportunity becomes useful output only if materials, labor, downstream capacity, and customer demand are available. If the time is recovered at an unconstrained station, the added shipment benefit may be zero.

Likewise, reducing rework can free labor without reducing payroll. Identify whether the benefit will appear as lower overtime, reduced outsourcing, more saleable work, or capacity held in reserve. ASQ treats rework and scrap as internal failure costs within the broader cost-of-quality framework. See ASQ’s cost-of-quality guidance.

For an initial screening calculation, use:

Annual net operating benefit = avoided cash costs + contribution from additional saleable output − incremental operating costs.

Simple payback = total installed investment ÷ annual net operating benefit.

An illustrative $180,000 installed investment with $18,000 in annual avoided costs, $36,000 in additional contribution, and $6,000 in added annual operating costs produces a $48,000 annual benefit and 3.75-year simple payback. At a $24,000 annual benefit, payback becomes 7.5 years.

Use contribution after variable costs, rather than sales revenue. Do not count the same recovered time as both an avoided labor expense and additional production benefit unless both can actually occur. This simple screen excludes financing, taxes, discounting, and resale value; evaluate those separately in the final capital plan.

Make the demonstration match the purchase case

Bring a repeat job, a typical mixed job, and the job that creates the most trouble. Ask for a trial covering setup, production, inspection, handling, and the agreed downstream handoff.

Record the tooling, software, material, staffing, and automation used. A result demonstrated with an automatic offloader should be tied to a quotation that includes that equipment.

Build the decision around a conservative case, an expected case, and a stronger case. Then establish an acceptance plan for installation and repeat the same measurements after the process stabilizes.

Schedule a demo call now

Your shift logs can become the starting point for a better equipment decision. Bring your rework records, setup times, accepted-part counts, and production goals. Centex Automation can help you evaluate machinery, tooling, handling, service, and financing around the improvement your shop needs.

Schedule a demo call now with Centex Automation.

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