3 Tenths


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Thread: 3 Tenths

  1. #1
    Gold Member Bob La Londe's Avatar
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    Default 3 Tenths

    I hand loaded a bunch of tools today in the 1100 using Tormach's Electronic Tool Height Setter. For the tools I figured I would use the most I swtiched to the ATC screen and clicked store curent tool. After the carousel was full I ran the operation to touch off all tools in the carousel. Every single tool measured .0003 longer. The tool height setter didn't move. The table didn't move. Th spindle flexs the tool forks slighly before it grabs the tool. Now I know 3 tenths is no big deal in the grand scheme of things, but it was interesting to note.

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    Default Re: 3 Tenths

    If it's that repeatable, you could probably compensate for it!
    Sometimes, I find repeatability is more important than the exacct number ...



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    Gold Member Bob La Londe's Avatar
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    Default Re: 3 Tenths

    I was thinking if I alway have the same ten tools in the carousel or I always touch off the tools in the crousel from the carousel it doesn't matter. Hand load and touched off tools stay hand loaded, and ATC loaded tools stay ATC loaded and touched off. Yes, it was consistent. I took a photo of the tool table from hand loading, and then ran the touch off all ATC tools routine. All ten showed .0003 longer. For most of what I do it really doesn't matter. As long as the tools load the same and the first operation is creating the reference surface of the part. It could matter I suppose if working from a preexisting reference surface, but like I said 3 tenths is not that big of a deal anyway.

    Bob La Londe
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    Default Re: 3 Tenths

    If you take a tool out by hand and put it back then remeasure it do you lose the 3 tenths again? Is it possible the ATC is side-loading the spindle a bit when it loads, causing some friction to not let the tool get pulled quite as far in?
    I'd try messing around hand-loading and try to duplicate what the ATC is doing. Like you said, it's only 3 tenths, but that would bug the hell out of me.



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    Gold Member Bob La Londe's Avatar
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    Default Re: 3 Tenths

    Quote Originally Posted by skrubol View Post
    If you take a tool out by hand and put it back then remeasure it do you lose the 3 tenths again? Is it possible the ATC is side-loading the spindle a bit when it loads, causing some friction to not let the tool get pulled quite as far in?
    I'd try messing around hand-loading and try to duplicate what the ATC is doing. Like you said, it's only 3 tenths, but that would bug the hell out of me.
    You could be right. It might pay for me to go through the ATC setup and alignment again. I didn't reverse check as you suggested, but it was consistent across ten tools. There is certainly something.

    Bob La Londe
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    Default Re: 3 Tenths

    Have you ever calibrated your tool height probe ?? The speed at which you probe effects the probed value of the probing function. You should always calibrate the probe to the Feedrate you plan to probe at. Then always do your finish probing at THAT feedrate.

    Just a thought, (;-) TP



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    Gold Member Bob La Londe's Avatar
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    Default Re: 3 Tenths

    Quote Originally Posted by vmax549 View Post
    Have you ever calibrated your tool height probe ?? The speed at which you probe effects the probed value of the probing function. You should always calibrate the probe to the Feedrate you plan to probe at. Then always do your finish probing at THAT feedrate.

    Just a thought, (;-) TP
    That's a good thought. Acceleration and speed are an issue. I'll have to do some checking there. I probed hand loads at 30ipm after jogging close. I believe the automatic routine probed at 50. However it seemed to me that it probed twice. Once at speed and a second time slower Now I suppose I'll have to double check that too. If that's the case I should be able to repeat the 3 tenths difference with the same tool just by changing the feed rate. I didn't even think of that. Certainly its worth a check, and it won't take more than a minute to do.

    Bob La Londe
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    Gold Member Steve Seebold's Avatar
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    Default Re: 3 Tenths

    If you need to hold 3 tenths on your machine, I’m guessing you probably bought the wrong machine.

    I can hold +/-.001 on my 7 year old PCNC 1100 all day long, but .0003, I don’t think so.

    You can buy GOOD PARTS or you can buy CHEAP PARTS, but you can't buy GOOD CHEAP PARTS.


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    Gold Member Bob La Londe's Avatar
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    Default Re: 3 Tenths

    Quote Originally Posted by Steve Seebold View Post
    If you need to hold 3 tenths on your machine, I’m guessing you probably bought the wrong machine.

    I can hold +/-.001 on my 7 year old PCNC 1100 all day long, but .0003, I don’t think so.
    … and I bet you never worry about cumulative error either. Geez!

    Bob La Londe
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    Default Re: 3 Tenths

    Quote Originally Posted by Steve Seebold View Post
    If you need to hold 3 tenths on your machine, I’m guessing you probably bought the wrong machine.
    The issue isn't 0.3 mils of variation, that would fall well into "expected". The issue is actually that all of his cutting tools are off by the same amount and in the same direction. The latter indicates a systematic error rather than random tolerance variations.



  11. #11
    Gold Member Bob La Londe's Avatar
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    Default Re: 3 Tenths

    If you read the thread Little Things 3 tenths are the least of my worries right now.

    Bob La Londe
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    Default Re: 3 Tenths

    Could also be temperature. Iron expands about 6 millionths per degree per inch. If the column is roughly 17", it doesn't take that much temperature difference to change that column length a couple of tenths.



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