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21 Ways to Maximize Your Odds At Lights Out Machining

May 31, 2016   //   by Bob Warfield   //   Blog, Business, Manufacturing, Techniques  //  2 Comments


Lights Out Machining: Huge Advantages But Hard to Achieve…

What is Lights Out Machining and Why Care?

Lights Out Machining: Holy Grail of productivity for some, scary unexplored territory for others.  Lights Out means manufacturing processes that are fully automated and require no human presence.  That’s the 100,000 foot view, but of course every process requires a human presence at some point.  It’s only a matter of how long it can run before that presence is required.  For many CNC job shops and manufacturers, Lights Out means putting on a an automated third shift in the dead of night after everyone has gone home.

Our 2013 analysis of Top Shops found that one of the things that makes Top Shops more productive and profitable than others is that they are 39% more likely to do Lights Out Machining.  This was the biggest difference in Machining Strategies versus other shops, with the second biggest being the use of 5-Axis machining with full contouring and the third being use of High Speed Machining.

Looked at as another shift, it’s a way to keep those spindles going for more hours in the day.  Even better, the spindles run without staff hours, so they’re some of the most profitable spindle hours that can be.  Suppose your shop runs two 8 hour shifts and then adds a 4 hour “Lights Out” shift.  It’s only 4 hours because that’s how long it can run without human intervention.  We’re now getting 20 hours of potential machine time (no, they won’t run the whole 20 hours of course) for a cost of only 16 hours of staff.  The effects on profit margin are huge, and we quickly see why Lights Out is so attractive to many shops.

But the productivity is not all.  We hear constantly about how hard it is to hire skilled labor for CNC shops.  Being able to get more hours out of the machines with the labor you’ve already got is also hugely helpful when it’s so hard to hire more labor.

What Makes Lights Out Difficult?

It’s tempting to think there’s some silver bullet that will instantly make Lights Out achievable or even easy.  Put your checkbook away–no such silver bullet exists.  No monitoring system, no robotic arm, no bar feed or pallet system can make Lights Out instant and easy.  Lights Out has been described by many who’ve climbed the learning curve as sheer misery.

The reason it gets called misery is because of the little things.  We constantly underestimate what the staff in the shop is capable of.  It all happens so fast and without much thought:

  • A chip jams a fixture from working correctly.  The operator sees it, clears the chips, and has things moving smoothly again before anyone can even notice.
  • An older machine has a balky sensor in the tool changer that cause a problem every few hundred tool changes.  Again, the operator spots the problem, recycles the switch, and we’re back in business without a second thought.
  • We get fines up into the coolant system, they clog the nozzle so coolant isn’t spraying correctly on the job.  No worries, the operator pauses the job, fishes the errant crud out of the nozzle and things start anew.
  • You get in some new material, a different batch, on that stainless job you’ve been running.  Suddenly tool life goes downhill in a hurry.  But, your operators hear when the inserts start to chip and they get them changed before anything too terrible happens.
  • A mistake was made loading tools and the wrong one is in one of the slots.  The operator catches this when he makes a routine check before turning the job loose to run.

This sort of thing and a hundred other similar things is happening constantly, all day, every day.  These things don’t cause much of a ripple because the operators are there to deal with them.  But we’ve all seen the results when the operator doesn’t catch one of these problems.  We hear the dreaded “Loud Red Button Noise” and heads turn in the shop.  Or there’s a lot of cursing as the operator dives and catches that E-Stop barely in time.  We come back from a break to find an expensive job scrapped because of some minor lapse in attention.


In this business, you can be the Hero and you can be the Loser all on the same day…

When the system works, it’s great.  But when it fails, it gets expensive and the boss starts screaming and yelling.  I had one CNC’er tell me they’ve never been in a business where you can be such a hero and such a loser in the eyes of management all on the same day, only to repeat it again and again on other days.

Lights Out is a Process of Continuous Improvement

With Lights Out, there are no operators.  All those little things the operators are catching?  You have to figure out how to prevent them in advance or deal with them in a completely automated way.  You have to realize that with operators present, you’ve mostly gotten by without fixing root causes–you’re simply using the operators to work around them.  Lights Out won’t tolerate that level of sloppiness–it forces you to focus on fixing root causes and on being very paranoid about what might happen.

Let’s assume there are eight potential glitches that can each stop a particular process.  You can easily make a list of a lot more than 8, but prioritize it to the 8 most likely.  Further, let’s assume that each of the 8 fails only 1 time in 20.  Guess what?  If those 8 are present, your Lights Out process will run successfully only two-thirds of the time.  Fully one-third of the time you’ll come in the next morning with something to be unhappy about.  In the best case, things just didn’t finish and now you’re behind where you thought you’d be.  The worst case?  Who knows, maybe a fire started and your whole shop burned down.

21 Ideas to Improve Your Lights Out Odds


Light Bulbs = Ideas.  But what about Lights Out Ideas?

I hope you’re starting to see that Lights Out is a Quality Game.  It’s an Odds Game too, and you want to work on Quality issues that will skew the odds in your favor.  You will probably never achieve perfection–the jobs will change too often for that.  But you can get very good at Lights Out and that will make you and your shop a lot of money.

Here are CNCCookbook’s Ideas about how to improve your odds:

  1. Start with “Don’t Care” goals.  Think of Lights Out as a margin sweetener, but don’t commit anything to it that has to be done.  Only commit work that it’d be nice to get done via Lights Out.  That way, if the results disappoint, it’s no big thing, and if they succeed, you can keep that big smile on your face.
  2. Run only proven jobs that have been tested with plenty of operators present during the day.  Until they run unattended, don’t relegate them to Lights Out.  One shop I talked to had a clever idea–they schedule a job so the last tool ran unattended on a job.  It didn’t run all that long, a little over one hour, but it was their first baby steps.  They made sure the cut got started in good shape and then headed out the door.  They had proven the job ran fully during the day, so all was well.
  3. Never run new code on a Lights Out job.  This is part of the proven job thing.  If you change a part program, you have to run it fully attended before it can go to Lights Out.
  4. Invest in simpler repeatable quick change setup.  Fixture plates, pallets, and that sort of thing.  You don’t want a shift to be hastily setting up a Lights Out job just as they’re in a hurry to clock out.  So make it as easy and foolproof as possible.  Quick change tooling like the Capto system can make tool setup for the Lights Out shift faster and easier too.
  5. Invest in monitoring.  Personally, I wouldn’t want to run a Lights Out job unless I had fire alarms and fire suppression on all the machines that would be run Lights Out.  Being able to tell via MTConnect our other technologies the status of a machine is also helpful.  Is the part program still running?  Can I determine that remotely?  How about video inside the machine?  How about video of the machine’s control panel?  Internet video is pretty cheap and cheerful to set up these days and might be well worth it.
  6. Keep one light on.  In other words, leave one operator at the plant.  Depending on the size of the plant, one guy to monitor and put things back on track is almost infinitely better than having nobody.  And that one guy may be just a small fraction of the normal staff so you’re still keeping most of the profit.  Having one person to walk the aisles, listen for Bad Noises, or check personally if a machine has stopped unexpectedly can really make Lights Out dramatically more likely to succeed.  If you rotate that job among your staff, they will all gain an appreciation for what sorts of things interrupt a Lights Out operation and they’ll be that much more diligent about preventing recurrences too.
  7. Reliable Equipment:  You know that one machine everyone hates?  I know, you have a soft spot for it–it was your very first VMC.  You bought it used and beat to death, but you’ve nursed it along and it still makes parts.  Sometimes.  How about we leave that machine out of the Lights Out rotation?  Maybe we want to use your newest machines instead?
  8. Preventative Maintenance is the cheapest and easiest path to reliability.  You have to train everyone as soon as there is a problem to deal with it and not just work around it.  You may not be able to afford to stop everything, but you need to at least note it down so someone will deal with it in short order.  Pilots keep a log of what they call “squawks” about their airplanes–every odd noise or slight misbehavior goes onto the squawk list.  Their goal is to fix those things before their next flight, if possible, and definitely before they can get bad enough to cause a real problem.  Add a log of some kind to every machine and encourage operators to write squawks down in the log.  Make it someone’s responsibility to gather than information and get things fixed at the root cause so the squawks go away.  Add to that log a program of preventative maintenance.  Operators need to turn to that page and perform any tasks required that day before they start using the machine to make parts in earnest.  Make them sign each item to signify they take responsibility for having done the work.
  9. Simulation: Can we run first time correctly every time?  There are shops that can throw a job on a machine and know it’ll run correctly the first time and every time.  They’ve invested heavily in simulation and other technologies and they know because they’ve proven out so many jobs during the day that ALL their jobs will run as expected the very first time on a machine.  This is an extremely difficult achievement, but very profitable if you can get there over time and ideal for Lights Out operations.  Even if you don’t have this degree of sophistication around your use of simulation, running a simple simulator on any g-code before it goes on the machine will save time and money and is good discipline.
  10. Coolant Management.  Suppose your coolant nozzles become clogged with fines 30 seconds after the last operator walks out the door for the night, what do you think is going to happen to that Lights Out job?  Add a filter to your coolant lines pre-nozzle so fines won’t clog your coolant nozzles.  Put pressure gauges coming and going from the filter and when the pressures are too far apart you know the filter is clogging up–get it changed. How about putting skimmers on all the machines to get rid of tramp oil?  Do you have a preventative maintenance regimen for coolant?  Who is responsible for checking coolant concentration, coolant levels, and how often does it get checked?  Most experienced Lights Out operations prefer High Pressure coolant.  It brings an extra margin for error that provides more safety cushion with chip clearing.  Lastly, prefer water based not oil based coolants as oil bases can catch fire.
  11. Chip Management can be just as important as coolant management.  Clearing the chips is one more thing the operator has been doing automatically when his Mark I Optical Sensors (i.e. his eyeballs!) tell him it’s time.  There’s not an awful lot you can do unless your machine is equipped to deal with the problem.  If it has a chip conveyor, you need to make sure it’s programmed to come on at some interval that will work.  Here’s a quick and dirty tip if you don’t (or even if you do it might be helpful)–rig a way for your spindle to at least clear the majority of the chips from the work area.  A compressed air or coolant blast may be all you need coupled with a spiral out pattern from center of table to wash the chips away from the immediate work area.  What about all those special chip clearing situations the operator deals with on a case by case basis.  Have a look at these ideas:

    – Chip fans can help clear chips and coolant out-of-the-way and off the table. Mounting a wire brush somewhere on the table allows the program to be set up to swipe the wire brush over a tool in order to pull chips off of it. Running the spindle in reverse while the tool is working against the wire brush will clear the chips handily.

    – You may need to clear chips from holes between operations, for example before trying to tap a blind hole. You can fabricate a nozzle affixed to a tool holder in such a way that the through-spindle coolant can blast the hole clean, or remove chips from deep pockets and the like.

    – Another shop mentions brazing corkscrews to an extension and using that rig to pull chips out of holes.

  12. Conservative Feeds and Speeds.  Most experienced Lights Out operations dial back the feeds and speeds for Lights Out shifts.  It slows down the jobs but increases tool life creating a safety margin against tool breakage during Lights Out running.  The amount to slow down varies, but G-Wizard’s Tortoise Hare slider makes it easy to calculate more conservative settings.
  13. Full Time Tool Monitoring.  We talked about some forms of monitoring above, but I saved Tool Monitoring for its own item because it is one of the most if not the most important things to be able to monitor.  Your goal is to detect tool breakage or excessive wear.  Various types of sensor can be placed on the machine to do so.  You will want to check each tool with code in the part program before it runs every time you change tools.  For the next level of sophistication, provide redundant tools in your tool changer that are automatically selected if a problem is detected with a tool.  For even more sophistication, use a machine that has tool wear monitoring and management built in.
  14. Bar Feeders and Pallet Changers:  How are you going to get new workpieces into the machine with no operator present?  Initially, you may not, but eventually you will need to be able to get new material to machine automatically.  Bar Feeders for lathes and Pallet Changers for mills are the usual approaches.  With a sophisticated pallet changing system, you can even allow for completely different fixtures and process multiple different jobs during the Lights Out shift.
  15. Parts Catcher and Parts Segregation.  This was a clever idea I picked up from an article over on Production Machining.  Having a parts catcher is a good idea–it prevents parts from banging around too much on each other as they’re parted off on a lathe.  But these guys went one better–they created a segregated parts catcher.  They can use it in two ways.  First, if they’re making more than one kind of part, they segregate by part type.  But the second idea was the really clever one–they segregate the same parts into time segments.  For example, on segment per hour.  This way, if something happens, the scrapped parts will be grouped together.  By the way, if you don’t want to fabricate your own segregated parts catcher, Royal Products has a product called Rota-Rack that can do it for you:


Rota-Rack segregated parts catcher.

16. Which Parts?  Take some time to choose which parts to make on a Lights Out shift–not all are equally suited.  For example, big complex parts are high risk.  The problem that scraps the part can happen late in the game maximizing the cost of scrapping.  Choose families of similar parts that can share the same tools.  For bar-fed lathes, choose parts that can all be made from the same sized bar.

17.  Think about tolerances.  There’s no operator to take a measurement and make mid-flight corrections with wear offsets.  With in-process probing, you may not care, but without it, you’ll have to avoid those parts.  Thermal stability is another issue.  If you machine has features to increase thermal stability, that’s a good thing because running the machine for so much longer will mean great variations in operating temperatures.  Alternately, there are strategies like RAMTIC that can compensate on the fly.

18. Compressed Air: we take it for granted, but our machines are stuck without it.  Make sure all is well with your compressor.  Preventative maintenance is key here too.  Also, are you set up to automatically drain water from the tank?  Do you use an aftercooler to help cut down on moisture in the lines?  How about a pressure switch with an alarm that will make sure someone comes running if there’s no air during the Lights Out run?  Police your air leaks so the compressor won’t have to run so hard too.

19.  Fancy GCode tricks for Lights Out.  I could probably write another list of 21 that was just about gcode tricks appropriate to Lights Out machining.  Peruse our list of 37 things you can do with custom gcode that you can’t with CAM and you’ll find many ideas.  Custom gcode is handy for all kinds of things.  With the right DNC setup, for example, you can have your machines confirm every time they change a tool to a log file.  That’ll help you narrow problems down if there is one.  You can write macros that will send messages that may tell exactly what the problem was–tool wear alarm was tripped, for example.  You’re going to need to master g-code to play all these tricks, so why not check out our Free G-Code Tutorial today?

20.  Lights Out tapping?  Ooooh sounds scary, no?  Tapping often works better with a good tapping fluid, like Moly-D. You can program your g-code so it dips the tap into a reservoir mounted on the table before tapping each hole.  That’ll give you a lot better safety margin over fluid alone.  Want even more margin?  Use thread milling instead of tapping.  If you break the thread mill, it won’t be jammed solidly in the hole.

21. Get smart with probes for inspection.  With Lights Out, you may want to do a little more inspection than when the machine is attended.  Probes are one way to manage this.  Consider probing the last feature each tool on the job machines on each part.  You’ll know in a hurry exactly where things when wrong if your probe decides to stop the job.  In many cases, knowing where to start looking for a problem is a huge part of the job of fixing Lights Out problems.

There you have 21 ideas to improve your odds of Lights Out manufacturing.  There are many more available, but if you follow as many of these as you can you’ll be way ahead of the game.  Just remember, take it step by step, walk before you run, and be relentless about continuous improvement, fixing root causes, and preventative measures.  Those are the keys to a successful Lights Out program.


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21 Ways to Maximize Your Odds At Lights Out Machining
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  • Excellent article about creating high reliability in critical operations. Contrary to popular belief, this is how aircraft stay in the air. Aerodynamics only plays a small part in keeping a plane in the air.

    Some articles on G-code for things such as stock feeders and other auxiliary machining operations would be interesting.

  • […] and Five Axis, along with Lights Out Machining are coming on strong for Top […]

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