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  1. #21
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    Quote Originally Posted by Big B View Post
    I'm not a real experienced CNC guy like a lot of you but "hand near the emergency stop button" comes to mind.
    Nope... If it comes to hitting the big red button, you already screwed up.


    Not that I haven't done it, just saying that's not the right way to setup.

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    Quote Originally Posted by Jashley73 View Post
    I'm writing some work instructions for supervisors/operators, and just drafted a section on "Preventing a crash."

    I've practiced these "3 rules" for years, and looking back, every time I've crashed a machine, it's because I failed to follow these 3 rules.

    Those 3 rules are,

    Rule #1 - Set the Rapid-Override to 25% (Or whatever makes sense on your machine - 2% if we're talking a Brother Speedio, etc...)
    Rule #2 - Turn on Single-Block
    Rule #3 - Watch your Distance-To-Go



    What is your opinion of this idea of "The 3 Rules" ? Am I correct in preaching this to others, or am I missing something?


    Feedback is appreciated, and you're welcome to steal or borrow these if desired. Thanks
    Single blocking and monitoring the length of the tool over the material is a really good way to note XY position of the tool and the z distance of the tool to material. This list you have explains good solid caution and practice. It is good to write down everything you can think of as a full list.

    Plus instructions on the basics of tool setting along with G54 x and y location finding. The basics of good setup are also important.so many things can make a difference in reality.

    Assuming a good program can very often be a big mistake. I always run at least a path trace graphic before stepping it through.

    What a crash can do to the machine and it’s accuracy are important to be mindful of.

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    I confess since you ask I go back to first stressing the basics like the proper tool for the process and matched to features on the print. Tools sharp and inserts replaced or good to cut, rigid vise or Chuck. It can really be a big mistake putting in just one oversized drill.

    I have seen setup instructions and programs proven and run numerous times in a shop where similar mistakes and parts scrapped in setups usually will cost a part. Structural failure because the program or the setup sheet are not right and have been ignored in regard to updating the problems.

    In fact these kind of situations will just confirm that proving the setup instructions , program, and setup never actually was actually proven. These kinds of issues must be a priority to find and fix with recurring jobs.

    Any clarity at all to bring good practices into the whole process will reap benefits. Changing a procedure or having it followed will bring results. No question if the process is valid.

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    My programs are relatively short but on new programs, I always offset things 3" off the part and cut air. This lets us spot issues in the program as well. Its cheaper than a crash or destroyed tool. On proven programs, we always reduce rapids and single block each tool start to make sure we did not fat finger the offsets.

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    Quote Originally Posted by Big B View Post
    I'm not a real experienced CNC guy like a lot of you but "hand near the emergency stop button" comes to mind.
    Too drastic. All machines I have ran have a red feed hold button right next to the green cycle start button, use that one and then if needed turn the spindle off. A lot of machines don't like you hitting the E-stop if they are in motion.

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    Quote Originally Posted by Trueturning View Post
    Any clarity at all to bring good practices into the whole process will reap benefits
    Page 75 of the April 2012 edition of the Haas CNC Mill Operator's Manual: "Take tool 1 in hand and insert the tool (pull stud first) into the spindle."
    That reminded me of the rifle instructor in Basic demonstrating how to chamber a round: "Insert the bullet with the sharp end pointing towards the front." Now he was indulging in sarcasm but I doubt that is the case with the Haas manual. I err on the side of extreme caution by recommending air cutting above the part if the program is new. Trying to stop the action at depth with the tool approaching the part (or the fixture, or the vise) is begging for a big expensive noise—much more expensive than the time taken to be absolutely sure of avoiding a crash. OK, we aren't under the time pressures of a job shop but down time costs us just as much if not more...

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    I run my programs through Cimco and backplot the gcode real quick then to the machine and keep an eye on the first few movements at 25% and single block, then its off to the races

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    Quote Originally Posted by Big B View Post
    I'm not a real experienced CNC guy like a lot of you but "hand near the emergency stop button" comes to mind.
    You are right about knowing where the stop is. How many times a machine starts making noise with something that goes wrong where a operator froze and did not e stop the machine is more than I like remembering. Good reflexes will come eventually if you are alert they actually become lightning fast.

    When proving I watch the program, the location on the screen and the location and move of the right tool. On reflexes once my son and I were talking and he accidentally dropped his lighter. I caught it and gave it back to him quick and he was so surprised he dropped again and so by reflex I caught it again. It freaked him out and so I told him that is one reason never to take a swing at Dad it won’t work.

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    Lots of great advise, and I pretty much follow the three rules posted.

    All of my programs have option stops, and on the first run I use them. However, as toolmaker posted, a lot of my work is one piece, and can be long runs. I do stupid things, especially in the midst of doing 5 other things. So I will always watch the tool come in. Whether I set the wrong work coordinate, forgot to change tool numbers, whatever... it happens.

    I've had my fair share of bumps, growls, and shortened vise jaws, but the only real CRASH I had happened so fast I couldn't react, and your 3 rules wouldn't have helped. I was finishing up a 12 hr 3rd shift and had just changed out tools and went to rerun a section of the part and missed the tool call line. I do not know if all Heidenhain have this wonderful feature, but with the Hermle if you missed that call line, the spindle would rapid at full speed right into the table. I think I hit the red button 5 or 6 times, but I have no idea if I managed to stop the spindle with the estop or the machine stopped the spindle. All I can say is the slam was felt through the floor of the entire shop, which caused the whole shop to stop and turn. Since that set of $80k ceramic bearings and spindle rebuild had less than a year on them, I fully expected to be executed on the spot...

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    For me its mostly sticking to the same sequence of operations each time and not get disturbed or do anything else until that is all done. Too easy to come back and forget 1 step. Triple check all the offsets and make sure they make sense. For repeat jobs I have a basic sheet with where my normal offsets and tool order/lengths are for that part#.
    Last edited by SND; 10-03-2019 at 07:32 PM.

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    Quote Originally Posted by solidworkscadman View Post
    I run my programs through Cimco and backplot the gcode real quick then to the machine and keep an eye on the first few movements at 25% and single block, then its off to the races
    Yup.
    Mastercam verification
    NCPlot
    Set up.
    M01 on.
    Toolchange and check correct tool (LoL).
    Set rapid at 25% with hand on feed override.
    Cycle start and slowly watch tool come in using distance to go and visual the tool.
    Single block on and feed override down so it comes in slow to the clearance plane (check distance to go/screen)
    Keep single block on and feed in slow to the feed plane (usually 2mm for me) - check screen.
    Feed override 0, single block off, feed override gently wind up and let it get into cut and then let it go.
    Keep M01 on so end of tool machine toolchanges and sits waiting for me to continue.
    Repeat process above.

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    Here are my processes off the top of my head (I REALLY need to write these down as SOPs):

    3-axis VMC:
    1) Simulation in Fusion 360
    2) Kanban cards at the machine for tool and work offsets*
    3) If I am interrupted during tool or work offsets, and have to leave the machine, I start over, respectively.
    4) Call first tool, MDI the offset at a sensible distance from the WCS zero and check with a scale. Repeat if using multiple offsets.
    5) If I've got a tool coming very close to the workholding (vise jaw, talon grip, etc.) I will call that tool and that offset to the minimum Z value listed at the top of the program.

    4-Axis VMC:
    Same as the 3-axis except I verify that the rotation of the 4th won't cause problems

    5-axis VMC:
    Same as the 3-axis except CAMplete is used after CAM simulation and before posting.

    Lathe:
    Same as 3-axis VMC with the addition that I will MDI the cutoff tool offset and check the subspindle transfer prior to running the program. I will also do thisw for the bar exchange program, and I will make sure that the machine will not be unattended for the first bar change (use work counter to ensure an operator is cycle-starting the last few parts before the bar change).

    *I had these on little magnet holders at my old day job and moved them from machine to machine. No one liked the idea... but lots of guys crashed machines. Hmmmmmm... Anyways the cards are colored red on the other side and say the offsets are NOT set.
    img_20180219_155856_755.jpg

    The first time I run through a program I usually option-stop between tools (especially if I'm going to be setting up a tight tolerance part for a production run) but once I have that program marked as proven in the CAM software and in the file itself, I will just watch the first Z dive and walk away.

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    Mikron has a hardware solution to the problem of spindle crashes;


    And Haas has a software solution;



    IMO it's ridiculous that some machine brands charge the price of a new car just for the spindle assembly, and that those spindles tend to be very fragile in the first place. New matched sets of bearings cost under 1,000 dollars if they are steel and several thousand if they are ceramic. Hass, Brother, and Fadal are reasonable in cost and everyone else gouges.


    I always run a full simulation in CAM before posting, then run with the global Z offset up several inches, rapids on low and hand on the pause button. The first time for each tapping cycle, I have rapids on 1% and hands on both the E stop and pause button since tapping cycles don't get paused while they are doing each hole. I haven't crashed yet, but I have kicked a plastic part out of a vise and snapped two 0.25" long carbide end mills at 12,000 RPM, one of which fractured both my windows.

    There have been frequent power outages in my shop since it's right next to the port, and the Fanuc control deals with this by pulling up the spindle and locking the servo brakes as part of the "brown out" protection. This would normally be a good thing but I run a huge T slot cutter on many parts and if it were to yank the spindle up when the T slot was going 6,000 RPM, it would probably break the inserts and the pull stud, then launch the entire tool and tool holder through the window at me. Luckily it hasn't happened yet.

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    Quote Originally Posted by Jashley73 View Post
    Rule #1 - Set the Rapid-Override to 25% (Or whatever makes sense on your machine - 2% if we're talking a Brother Speedio, etc...)
    Rule #2 - Turn on Single-Block
    Rule #3 - Watch your Distance-To-Go

    What is your opinion of this idea of "The 3 Rules" ?
    That pretty much covers it to me...I always tell my guys, "POS screen...'Distance To Go' is your friend!" I just thought of this - maybe you could put something like:

    G43H1Z6.0;
    M01; OR /GOTO N1;
    M00; (only use this block with the "GOTO" option above)
    ;
    N1;
    ;
    Z.1;
    ;
    ;

    after each tool change? That way you could tell them (on the first part) to use Opt. Stop or Block Skip during the first part and just check with a 6" scale when each tool stops above the part. The idea being that the tool could still be off by like 5" and you'd be safe. I can only imagine how crazy my eyes look when going back and forth between looking at the cutter and the "distance to go" screen as my life approaches Z.1 and then when it stops me being like, "yeah...that looks about like .1 to me"...cycle start!

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    For me alone. I do my own programming, set up and operating (most of the time).

    That said; I'm pretty confident in my own program. Once it goes to the Machine and I do record all the offsets--methodology, methodology, methodology. I do the same things in the same order EVERY time. If I'm interrupted, I take measures to insure my righteousness. My Tools are set off a "master tool", so if it's right, the rest are too. I let it go.

    R

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    I appreciate everyone's feedback. I admit, I hadn't considered other possible, applicable scenarios of different shop environments, machinery, programming method, part volumes/mix, etc... (Sometimes we assume that the world revolves around us, and expect others to be reading our mind, even if we aren't aware. I guess we'll call that a blind spot?)


    Quote Originally Posted by Jashley73 View Post
    Those 3 rules are,

    Rule #1 - Set the Rapid-Override to 25% (Or whatever makes sense on your machine - 2% if we're talking a Brother Speedio, etc...)
    Rule #2 - Turn on Single-Block
    Rule #3 - Watch your Distance-To-Go

    In my specific case, it's production only, 2-axis lathes only. These "Rules" will come into play when our operators/supervisors are doing change overs, or after some simple troubleshooting. For a staff of good character, but very low technical skill & experience level.

    Were I writing these rules for even a semi-experienced machinist, working across several machines, new programs & setups, I'm sure the instructions would be different. (As the feedback in this thread has obviously highlighted to me...)

    Training has been a real low-priority issue for our company, despite the heavy need for it. Writing some things down & building good, simple habits seems like a good way to begin with the training. These "3 Rules" are part of another training document.


    Thanks again for the replies.

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    Process is everything in a production environment, especially with lower-skill laborers. People are not perfectible, but processes are (or at least are to a greater degree).

    I was appalled when I talked to a lead in a lathe department and he indicated that crashes were just something that was going to happen, especially with new people. I spoke to others in milling departments that indicated the same. WHAT?! If that tact had been taken in my first career, people would have died because of it.

    Process, process, process.

    If I can have a highschool dropout safely handling hydrofluoric acid, I can have one not crashing machines.

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    One thing I did do for both the Siemens control lathes, and the Fanuc mills, was change the rapid override "0" setting to be 400mm/min.
    25% rapid will still smack something pretty hard if you're careless.
    400mm is slower and less likely to damage - easier to spot if there's an impending car crash
    In doing this, you have to make sure that the machine (talking Fanuc) stops rapid when the feed override is on 0 (parameter change).
    We did have an issue where the business partner had the rapid on 0, feed down around 50% and went out for a smoke, thinking that the machine won't move when it went into rapid.
    Nope, it moved and there's was a small car crash - this was all while proving out one of his own programs...

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    Quote Originally Posted by Jashley73 View Post
    I appreciate everyone's feedback. I admit, I hadn't considered other possible, applicable scenarios of different shop environments, machinery, programming method, part volumes/mix, etc... (Sometimes we assume that the world revolves around us, and expect others to be reading our mind, even if we aren't aware. I guess we'll call that a blind spot?)





    In my specific case, it's production only, 2-axis lathes only. These "Rules" will come into play when our operators/supervisors are doing change overs, or after some simple troubleshooting. For a staff of good character, but very low technical skill & experience level.

    Were I writing these rules for even a semi-experienced machinist, working across several machines, new programs & setups, I'm sure the instructions would be different. (As the feedback in this thread has obviously highlighted to me...)

    Training has been a real low-priority issue for our company, despite the heavy need for it. Writing some things down & building good, simple habits seems like a good way to begin with the training. These "3 Rules" are part of another training document.


    Thanks again for the replies.
    Maybe add


    "#4. Stop and think - What is the worst thing that can actually happen here ? … No really ! "


    (as soon as complacency sets in / "Got this" "Easy-peasy" that's when the crashes and accidents happen. ).

    Although ~ The use of the word "Stop" could cause all kinds of confusion (in that context, you mean actual stop, cycle stop, pause and think hit e-stop and "Think"... "No , it doesn't mean literally stop it means you (the operator "Pause for thought" - "cycle pause then think ??? " " No ! " " I mean..." ) … Hmmmm not so easy is it …

    Interesting that some crashes are caused by over focusing on something not realizing that something else is just about to go slam, bump or bang into something else. Sort of a broader spatial awareness of what's going on rather than over-focusing on just the path of the tip of the next tool. [It's not two axis lathe but thinking more B axis mill turn where you smack the back end/top of the milling spindle into the counter spindle chuck whilst over focusing on the path of the tool tip (business end of the B axis milling spindle) at the main turning spindle.].

    [For serious snafu's (more generally) and industrial accidents / disasters it seems three things have to happen in a combination that no one normally anticipates. The so called "Perfect storm".].


    ________________________________


    Quote Originally Posted by Jashley73 View Post
    For a staff of good character, but very low technical skill & experience level.
    ^^^ I had a good laugh (not maliciously) at this turn of phrase … Kind of imagining someone dressed in tweeds and a cravat from the 1940's … Like from Downton Abbey or something,

    "Me and my wife are of good character and posses low levels of technical skill and experience... Can we help with the war effort building these Lancaster Bombers you speak of ? We'd love to help " (smiling enthusiastically with nervous anticipation.).

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    Quote Originally Posted by Jashley73 View Post
    I'm writing some work instructions for supervisors/operators, and just drafted a section on "Preventing a crash."

    I've practiced these "3 rules" for years, and looking back, every time I've crashed a machine, it's because I failed to follow these 3 rules.

    Those 3 rules are,

    Rule #1 - Set the Rapid-Override to 25% (Or whatever makes sense on your machine - 2% if we're talking a Brother Speedio, etc...)
    Rule #2 - Turn on Single-Block
    Rule #3 - Watch your Distance-To-Go



    What is your opinion of this idea of "The 3 Rules" ? Am I correct in preaching this to others, or am I missing something?


    Feedback is appreciated, and you're welcome to steal or borrow these if desired. Thanks

    IDK about the SINGLE BLOCK, but I tell guys to hit the FEED HOLD soon before you get to your expected Ref Plane.
    Now look at your DTG on the CRT.
    Then, does the DTG value look valid compared to where your tool is right now?



    edit:

    I've read a few comments about "not looking for the FEED HOLD", or have your hand near the E-stop or RESET....

    I have had to tell new guys that you need to have your thumb on that feed hold switch when running through the first time.
    There's no time to look for it.
    By the time you decide that you need to hit it, you're already too late, but we certainly don't need to add 2 more seconds to the ordeal!

    Being close to the RESET or the E-STOP can cause issues.
    Hitting either during a tool change for example, could cost you the rest of the day to git that all straightened out - depending on the machine and how well the ladder is coded.
    Stay close to the FEED HOLD!




    edit II:


    Quote Originally Posted by Oldwrench View Post
    Page 75 of the April 2012 edition of the Haas CNC Mill Operator's Manual: "Take tool 1 in hand and insert the tool (pull stud first) into the spindle."
    That reminded me of the rifle instructor in Basic demonstrating how to chamber a round: "Insert the bullet with the sharp end pointing towards the front." Now he was indulging in sarcasm but I doubt that is the case with the Haas manual. I err on the side of extreme caution by recommending air cutting above the part if the program is new. Trying to stop the action at depth with the tool approaching the part (or the fixture, or the vise) is begging for a big expensive noise—much more expensive than the time taken to be absolutely sure of avoiding a crash. OK, we aren't under the time pressures of a job shop but down time costs us just as much if not more...
    If I am going to be running a piece of code that I am concerned may not be right - I will set it to maybe Z-.05 or maybe even cut air, enough to qualify that the code is right FOR THAT MACHINE.

    Getting into G2, 3, and tapping codes, and even G83 and the different retract full or partial codes, being different between controls.
    Is the I/J on this machine ABS or INCR? I have ones that default both ways.
    Air is your friend while proving code.

    -------------------------

    Think Snow Eh!
    Ox


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