Setup Reduction & Quick-Change Workholding

Setup reduction is the discipline of cutting the time a machine spends not cutting, and it is the practice that ties together the quick-change workholding of this group. Every time a job ends, the machine must be stopped, the old workholding and tools cleared, the new workholding fitted, the new tools loaded and set, the work offsets found and the first part proved — and for all of that time the machine is making nothing. Setup reduction is the attack on that dead time: preparing the next job’s workholding, tools and settings before the machine needs them, so that the change itself is a matter of minutes rather than hours, and the machine returns to cutting sooner. This entry, the last of the workholding group, sets out how a shop reduces its setup time, drawing together the methods the earlier entries have described — the fixture plates, the soft jaws and the zero point systems — into a practice.

The two kinds of setup work

The first step in reducing setup time is to see that setup work is of two kinds, and that only one of them need stop the machine. Internal setup is the work that can only be done while the machine is stopped: removing the old job, fitting the new workholding to the machine, setting the new tools in the spindle. External setup is the work that can be done while the machine runs: preparing the new workholding, setting up a vice or a fixture on its plate at the bench, presetting the new tools in their holders, gathering the offsets and the program. The shop that reduces setup time moves as much work as possible from internal to external — so that when the machine stops, everything is ready, and the stop is as short as the change itself. The discipline is to ask of every step of a setup whether it truly needs the machine, and to do off the machine everything that does not.

Prepare the work off the machine

The greatest single saving comes from doing the setup where the machine is not, and off-machine preparation is the heart of the practice. A vice or a fixture is mounted on its own fixture plate or carrier at the bench, bolted down, indicated and proved while the machine is still cutting the previous job; when the machine is free, the prepared unit is moved to the table and fitted, already square and already known. The tools for the next job are set in their holders and their lengths recorded before the job begins, so the operator does not measure them against the machine. The program and the work offsets for the job are called up and checked, and the workholding is stored as a unit with its settings — the vice on its plate, the fixture with its offsets — so that a returning job is fetched as a prepared setup rather than rebuilt from scratch. The more of the setup that happens at the bench, the less the machine waits.

Standardise the setup

The shop that standardises its setups makes every change a variation on a familiar theme, and standardisation is the quiet partner of off-machine work. If every job uses the same style of vice, mounted the same way on the same plate at the same height, then the change from one job to another is a change of jaws and parts, not a re-layout of the table; if the soft jaws and fixtures are machined to a common datum height, the tools and the offsets carry over between jobs. The shop settles on a small range of standard workholders — a standard plate, a standard set of vices, a standard clamping kit — and fits its jobs to those standards. Standardisation turns setup from a fresh design problem into a repeatable routine, and a routine can be made fast, taught and improved.

Use quick-change workholding

Where the machine must accept the workholding itself, quick-change hardware makes the change a matter of seconds, and the methods are the ones this group has described. The zero point system is the exemplar: the workholding sits on a carrier that drops on to the machine’s receivers and locks at a repeatable position, so the whole setup — vice, fixture and parts — is changed as one unit in the time it takes to unlock one and lock the next. The pallet changer carries the idea further, exchanging one prepared pallet for another at the machine, and the quick-change vice and the fixture plate system let the operator unbolt one workholder and fit the next without re-indicating. Each of these is workholding designed for the change, and their common point is that the machine’s position for the new workholding is already known — set once, repeated by the coupling or the plate, so that the change needs no measuring and no first-part adjustment.

Cut the proving time

The last minutes of a setup are the proving, and they too can be reduced by preparation. A setup is not finished when the workholding is fitted but when the first part is good, so the shop shortens the road to the good first part: the work offsets are known and recorded from the last run of the job, the tools are preset, the program is proved and stored, and the first part is checked against the first-article standard that the job already has. A documented setup — the plate, the jaws, the offsets, the tool list, the order of the operations — lets the next operator repeat a proven setup instead of rediscovering it, and the shop that records its setups finds that the second and third runs of a job are set up in a fraction of the time of the first. The proof of the setup is moved off the machine too: where a setup is proved at the bench or on a previous run, the machine’s first cut is a good cut.

The payoff of short setups

Setup reduction pays in the coin that a machine shop values most: cutting time. Every hour saved on setups is an hour of cutting, and short setups make the small batch economical — a machine that changes in minutes can take the small order and run it when the part is wanted, and can keep its lights-out running without an operator to change it. The practice is cumulative: the workholding group’s own progress — from the vice and the soft jaw to the plate and the zero point coupling — is a history of moving work off the machine and making the change repeatable, and setup reduction is the discipline that uses them all. The shop that prepares off the machine, standardises, quick-changes and records its setups turns its changeover from lost time into a brief routine — and its machines spend their hours cutting, which is the whole point of setup reduction.