Brain teaser- A well running job will not run the next morning.
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  1. #1
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    Default Brain teaser- A well running job will not run the next morning.

    I took in a nice job with 304SS truebar. Since it ran slow I split the delivies. 1st of 3 ran fine...when I went to release the 2nd material was no longer available...from them or anyone...except Parker Steel had a metric crossover that was close...but it's a premium plus shipping.
    With little choice I had to have 304SS plate sheared and edged...wonderful stuff to be drilling, tapping and milling.

    A good amount of dialing in the speeds, feeds and edge prep on tools to get it to run consistently. But by days end I'd be running lots of 8 parts in two machines trouble free. I had warning a drill was on its way out when a squall turned to a squeal...end of that cycle just change drill out and continue. Easily 1000 tapped holes between changing a tool with a telltale notification from tool that it needed to be changed.

    Now comes the part I do not understand. I come in next morning, warm up machine 15-20 minutes, cycle through program with no parts a few times as the guys come into work. They load up machine and I go in to get office work started only to have them standing at my door, drill broke, which took out the tap. Sure enough the tip twisted off on the drill.
    Now I hear the drill in the other machine squealing like a pig and both machines are down. New tools are put in and they just don't last I have to start tweaking the programs speeds and feeds dialing it in again...finally both machines are producing parts again consistently.
    End of the day it's running good I stay a fewours to get up to speed, change out tools for fresh before I leave so in the morning All is fresh. Run a few parts all is good.

    Next morning drill is squealing on the first part, tap breaks in the other machine,

    This went on every day for a week...ran great at the end of the day and wasted at least an hour or two the following morning till machines just ran...

    So, any ideas why?

    I thought machine being colder it may have lagged a few split seconds hardening work surface...material work hardened very easily.
    Yes, with every worn or broke tool I pulled out all just the parts, replaced with new blanks
    But machine was warmed up and my playing around trying to dial it in didn't have machine doing much warming up with my changing tools and tweaking program.

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    Sounds like variations in material. A lot of this stuff comes from places all over the earth and material variance can be a real issue. Every try Carpenter for stainless?

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    Quote Originally Posted by SIM View Post
    This went on every day for a week...ran great at the end of the day and wasted at least an hour or two the following morning till machines just ran...
    Are you sure your operator isn't messing with the override buttons?

    A few years ago we had an operator running production that liked to turn the rapid override down to 50% because it made the job last longer. I noticed the number of parts ran versus the number he should have ran.

    So I went into the program and used some G and M codes that locked out the override switches without telling him. He was none the wiser and ran more parts the next day miraculously.

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    A strategically aimed coolant nozzle knocked slightly out of place can have that sort of mystery effect.

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    Quote Originally Posted by SIM View Post
    So, any ideas why?
    I have fought this fight before, and I figured out the answer: it is because it is 304

    I'm sorry, that is the answer.

    Seriously have seen that a few times, and it is usually 304 or 316 giving me the issue, and it makes NO sense. Could it be there's a few tenths more play in the spindle axially causing the problem? Could it literally be that the coolant and machine are 10 degrees warmer later on in the day, causing less of a shock to the tool?

    NO. The answer is that it is 304 and you just deal with it. Fun!


    However, I have an idea for you in case you don't believe me (or in the unlikely scenario that I'm wrong). Try leaving one (or both) of your machines on overnight. Maybe have it run a program that jogs it around and turns on the coolant every 5 minutes. It doesn't have to be running the whole time, just enough to keep everything at operating temperature. see if it still does it when the machine never shut down.

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    Just a random thought. What if the drills being cold at start up are the issue. You wouldn't think it would matter but possibly slightly more prone to break when cold. I may be all wet on this thought if so just overlook.
    Hodge

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    Thanks for the answers so far.


    Yes it's 304SS and sheared from plate so it has hard with some easy to machine with real hard parts and everything in between. I know this works against me, I get it and paid more for truebar not to deal with that aspect. But unless I want to machine face and sides, this is what I have to deal with . Dealt with, jobs done...

    That said, I'd get machine dialed in to run all the crap by the end of the day. Yes I lost time on the easy stuff..but machine ran for hours without intervention. In my shop that is important.


    One or two days catching a bad batch of material is possible, but every morning for several consecutive days says to me that is not the reason.


    I think the oddest part is I rarely snap drills, I tend to run very conservative for longevity, unattended operations. To have multiple drills snapping, edges breaking off is not what I am used to seeing...but happened with regularity in the mornings.


    Machine was warmed up...maybe overly so....but tools? Is it possible tool is not warmed up...do tools warm up?.
    This job ran best with HSS tooling over cobalt if that means anything. Cobalt drills had edges ripping off on new drills after only a few parts. HSS at 135, split point did not last...HSS at 118 degree and a light hone on edges ran over a 1000 holes before needing a light touch up. Carbide was a forgetabout it...few parts and gone.

    I'm back to slight variations in machine due to warm up or tools themselves...odd, very odd... in my opinion.

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    Are you using hydraulic work holding that maybe has a leak and air is getting in the lines overnight until it cycles a few times the next morning?....on both machines....only on this job......nevermind.

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    I guessed 304 stainless before even opening the thread.

    The material is notorious for being inconsistent, and similar questions pop up here a few times a year.

    316 is superior to 304 in just about every way other than price, and it machines consistently. I think the only purpose of spec'ing 304 is to save money, at your (the machine shop's) expense.

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    And, like you say yourself, 304 plate is the worst of both worlds. Hardness, tensile, specific cutting force, work hardening all extremely inconsistent from one cubic inch to the next. Absolutely horrible stuff to work with from the perspective of process reliability.

    If you're still absolutely convinced it's not the material, I'd look at getting your machine ballbar'd to make sure there is no problems with jerky motion or anything like that that might cause a drill to break. You can do a quick check yourself with a long travel dial indicator, just program a feed in at the same feedrate you use for your drill and make sure the needle moves smoothly.

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    Another observation, would it be worth it to run the job continually (provided you have the manpower) until it's done rather than shut it down at the end of the day. Of course you may need the break from it.
    Hodge

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    Quote Originally Posted by Mtndew View Post
    Are you sure your operator isn't messing with the override buttons?

    A few years ago we had an operator running production that liked to turn the rapid override down to 50% because it made the job last longer. I noticed the number of parts ran versus the number he should have ran.

    So I went into the program and used some G and M codes that locked out the override switches without telling him. He was none the wiser and ran more parts the next day miraculously.
    I didn't think of this. Way back when, at dad's place, we had an operator that LOVED to do this.

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    Inconsistent material, a very common occurrence these days. I get certs on everything these days, and ask where it came from before I buy. I try to stick with the same brands if it worked well before. I also order more tooling than before as far as in different varieties. I have often been blown away when what tooling has worked well on a job the last 5 times it ran all of a sudden doesn't work, and drill and tap life go way down. Recently drills TINI coated cobalt drills would barely make 10 parts in some 4140 annealed. I was used to getting 100-150 parts. I went and tried some cheap black oxide coated HSS, the first one made 200 parts, I was blown away.

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    Quote Originally Posted by Mtndew View Post
    Are you sure your operator isn't messing with the override buttons?

    A few years ago we had an operator running production that liked to turn the rapid override down to 50% because it made the job last longer. I noticed the number of parts ran versus the number he should have ran.

    So I went into the program and used some G and M codes that locked out the override switches without telling him. He was none the wiser and ran more parts the next day miraculously.
    And if a part gives you trouble, first instinct is to turn the feed down. 304, wrong answer

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    Could it be your machine coolant pressure/ flow is different. Maybe not hitting the holes in the same manner. Maybe the chips have been removed allowing better coolant return to the tank and a slightly different pattern . Just a WAG.

    Sent from my SM-G960U using Tapatalk

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    304SS was not my choice and I charge more to deal with it. 316SS was offered at virtually the same price by me and kicked down. That's neither here nor there.

    304 runs inconsistent for sure, but I dialed machine in to run the worst of the material with lower speeds and higher feeds. After tweaking the machines would run several hundred parts each on the same tooling.

    Maybe a few part blanks outside the worst of the worst that coincidentally happened to be the first parts run in the morning...ok, it's possible.

    But on a 1000+ pieces what is the chance of both machines having these worst of the worst loaded every morning several days in a row.

    If just 1 machine, I'd blame on the machine, but its two machines one early 2000 and the other a couple years old.

    My guys tweaking the feeds...no, I'm 99% past that with them. Besides, after tools broke it was me standing, loading and running with same results on new tooling.

    ...and yes, I pulled all parts out loading fresh blanks with the new tools. Best way to ruin a new tool is have it try to rerun a surface from a prior dull worn tool.

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    Right outta the gate - when I read the title - I have to say coolant.

    How fresh is the coolant?
    Have you checked your PH level?

    I fight this on old coolant when running alum for deep holes / surface finish. Alum really wants the lubricity, and older coolant can settle out over night, and not throw as much "oil" on the glass as it will after it's been ran a while. 304 needs all the lubricity it can git as well.

    "First thing in the morning and then all goes well after that."
    THAT is a coolant thing fer sure from my experience!


    I don't cycle the machine, but I will call up a deep hole drill and just let the HP coolant pump burn a while in the morning.


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

    Think Snow Eh!
    Ox

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    Quote Originally Posted by Ox View Post
    Right outta the gate - when I read the title - I have to say coolant.

    How fresh is the coolant?
    Have you checked your PH level?

    Ox


    Coolant...now that is an angle I never considered.

    How fresh is it? let's just say it is not close to being fresh. One machine I changed it out 11 or 12 years ago and the other has been in since new a few years ago.
    Ph check is easy, I've never checked. I have only checked the concentration levels.

    I can say the coolant still looks and tests great, but maybe on some level it needs to mix a bit more.

    Almost kinda wish I had more parts left to run...I'd turn on coolant during warm up to see if it made a difference.

    ...it's an idea I'll add to the memory bank for future use.

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    Well, the Ph aspect is basically it's ability to hold in suspension.
    Ph gits too low - the oils will settle out. (also if too high of "hardness" of the water - like you keep topping it up with hard water)

    With 304 - I would think that you would want your concentration level abnormally high, but I don't run enough of it to say fer sure.
    But when I run even 303, I will tend to mix my make-up at 2x or whatnot and then I can cheapen out next week when running sumpthing less taxing.
    (ass_u_ming that it doesn't all go out with the chips in the meantime)


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    Ox

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    Heres something else to think about.
    Dont knwo what type of machines your running or how new,you may want to look into your drawbars.
    older machines get alot of gunk and grim over time in the bevelle washers. if there cold they might be enough pressure do to the greese, when they warm up things are back to normal. had that happen on a older fadal years ago broken washers were also involved. would run fine after a few hours.
    Alum jobs I never had a problem with but a 321 job gave me fits bit time on the drills. once I changed out the washers I never had another problem.


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