Brown & Sharpe Microval PFX 454 - "Hunting"
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  1. #1
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    Default Brown & Sharpe Microval PFX 454 - "Hunting"

    Hi all,

    I am going out on a limb and hoping someone here may have some insight to offer on this problem. I will preface by saying that I am a machinist and know very little about the mechanics of CMMs.

    My friend has a Brown & Sharpe MicroVal PFX 454 CMM. This is originally a manual machine, but has been retrofitted with CMM Manager software and a semi-automatic probe head (the type that is capable of automatic motion by manipulating the head position using a ball on the table). It was bought a year ago and has never been properly working. A few months ago, we had Hexagon come take a look at the machine. While here, they also replaced an encoder and the Y-axis glass scale. The main issue with the machine seems to be that it is "hunting" on the Y-axis, as well as not tracking. The Hexagon tech hooked up his diagnostic tools to the CMM, and while attempting to order the machine to move, we found that the Y-axis location readout was never changing on his software, even when the axis was moved by hand. When he tried to order the machine to move automatically via his software, the machine would find a position, but then begin "hunting" on the destination. My understanding of "hunting" is that it was not able to find the precise point to which it was told to go, so the axis begins driving back and forth over the point rapidly. This caused vibration throughout the machine.

    The Hexagon tech believes that the problem lies within the controller (I have to say that even given my limited experience with CMMs, the Hexagon tech did not seem knowledgeable or competent at all in his understanding of the technology). He referred to these types of controllers as "throwaway" controllers because everything is on one board. In order for them to even attempt to repair the board, the entire controller must be sent to B&S and they attempt repairs at the board level.

    Has anyone encountered issues like this before with the same or a similar machine? My friend is a good guy and while he probably could have done more research before he bought the machine, I hate to see him stuck with a CMM paperweight.

    Thanks!

  2. #2
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    Default

    I have never touched a CMM, so I can't list any common issues. This is based on my limited knowledge about automotive diagnostics as a hobbyist/enthusiast.

    I would start by hooking up an oscilloscope to the signal from the scale, and compare it to the signal from one that is working while moving the axis by hand. That should get you closer to an answer whether the problem is inside the controller or not.

    I have no knowledge about the electronics inside the controller, but sometimes one can get lucky and spot a bad solder joint or similar when opening such devices. It is often on the joints that connect the board to the external wires or connector. I have had some luck re-soldering connections in such cases, without knowing anything about the electronics on the board.

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  4. #3
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    Hi,
    maybe you've already found some help. If not, c below.

    First of all it would help to know which controller is used. You can identify this by having a look at the seperate standing black box, that's connected to the machine.

    If it's a Sharpe 32 controller, I can help with some things. you might PM me and we can exchange documents for this.

    But, might be far better, depending on where in MI you are, contact Kern smith from Triology Inc. in Hazel Park,MI. He's expert.

    Good luck,
    Tom

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    Quote Originally Posted by tom-m2 View Post
    Hi,
    maybe you've already found some help. If not, c below.

    First of all it would help to know which controller is used. You can identify this by having a look at the seperate standing black box, that's connected to the machine.

    If it's a Sharpe 32 controller, I can help with some things. you might PM me and we can exchange documents for this.

    But, might be far better, depending on where in MI you are, contact Kern smith from Triology Inc. in Hazel Park,MI. He's expert.

    Good luck,
    Tom
    Hi. I'm having issues with an encoder. I need to calibrate the encoder but the manual I have only shows the Sharpe 2 controller. Do you have the procedure for the Sharpe 32.

    Mike

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    Sorry, I can't upload this file. Yes, I have a servicemanual that shows this.
    PM

  7. #6
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    Quote Originally Posted by tom-m2 View Post
    Sorry, I can't upload this file. Yes, I have a servicemanual that shows this.
    PM
    Hi. For some reason I try to PM you but I can't see it in the sent items folder so I'm not sure it made it to you.

    Thanks!

    Mike


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