Optimization of CNC Machining Process and Time Through Lean Manufacturing

When you organize your CNC machine shop to reduce waste, downtime, and inefficiencies, that’s called lean manufacturing.  The underlying principles of lean manufacturing were formed almost a century ago at Toyota Motor Works.  In the years since, countless books and papers have been written on the topic and it has become the dominant system in manufacturing.  Like so many things, the key is how you implement it.

The Focuses of Lean Manufacturing

It can be harder than it sounds (which is why so much effort goes into discussing it).  Inefficiencies creep into any system over time as the products change, new machines are introduced, and new people come in.  It’s almost axiomatic that whatever system was set up ten years ago is less efficient today just due to tiny system changes.  The CNC machining processes now run much faster because of the new mills, so the operator has downtime he didn’t use to have.  Instead of taking finished parts here for inspection, he now must take them across the shop to the new CMM machines.  That eats time.  Non-productive time is created by one change.  Another change comes along and uses up that spare time, but typically not in a productive way.  Lean manufacturing is concerned with those little gaps in actual productivity.

These “just-in-time” principles extend to inventory control as well.  The idea is to have the parts needed on hand as they’re needed.  Part shortages or surpluses equally point to inefficiencies in productivity.  Our clients rely on us to get parts to them, but they don’t want to warehouse huge quantities.   That puts the onus on us to work closely with them and plan well ahead to ensure they stay properly stocked -and no more.

Lean Manufacturing on the Shop Floor

Macfab has long used the ideas underlying lean manufacturing.  Back in the day, a CNC operator could run a mill or a lathe -one machine at a time.  Machining a part demanded the operator’s full attention.  With the advent of the CNC machining processes, operators wound up with spare time on their hands.  If a mill is going to take 5 (or a hundred) minutes to carry out operations on a piece, the operator has time to do other things.  He can get another job set up on another CNC machine, pull finished work off a machine, or run tests on the piece just finished.  Depending on the job, one operator may be able to keep several CNC machines busy.  That’s a principle of lean manufacturing.

If you want to reduce non-productive time and want operators to run more than one machine, those machines need to be set up so the operator can move from one to another easily.    They need to be arranged so it’s easy for raw stock, castings, tools, etc. to be delivered where needed.  That typically means the stock room and tool crib should be somewhat centrally located.

Lean manufacturing also calls for careful monitoring of workflows.  Ideally, we try to make sure as few people as necessary are involved as a specific part moves through the CNC machining processes.  That saves time, improves consistency, and avoids confusion during the completion of the part.

Lean Manufacturing in the Offices

Lean manufacturing doesn’t begin (or end) on the production floor.  Our ERP software monitors customer inventories for low levels or new jobs that come in, triggering orders for raw stock or castings.  If it’s an item that we stock for a client, that stock is delivered, and production begins to replenish our inventory.  The volumes of parts at each production step are monitored, watching for bottlenecks in the manufacturing process.  We go beyond tracking inventories of consumables, looking for anomalies.  Are more end mills wearing out on a particular CNC machine than any other?  Is that a function of the jobs it’s doing, do the milling parameters need to be adjusted, or does it indicate a problem with the machine itself?

Diligence is Always Due

We’ve learned if we’re consistent about watching for these inefficiencies, we can prevent them from becoming real headaches.  Just because an issue seems trivial doesn’t mean we shouldn’t focus on it.  A worn part on a CNC machine today will become an additional worn part if it’s not replaced.  Lean manufacturing is the key to catching those issues while they’re manageable and keeping downtime to a minimum.

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