Homann Designs TM20LV (BF20,G0704) conversion - Page 2


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Thread: Homann Designs TM20LV (BF20,G0704) conversion

  1. #13
    Registered phomann's Avatar
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    The Y-axis mount is located via a boss. There is no alignment adjustment in that method.

    I could get some alignment capability in where the nut mounts to the nut holder by using smaller mounting bolts or enlarging the mounting holes. Sounds like a hack though.

    Initially I'll just try to make an accurate mount and see how I go.

    The nut is mounted at the rear of the saddle. The screw is only fixed at the front of the machine so at the closest point the nut is some 6" from the screw mounting point. so a minuscule od misalignment may be tolerated.

    Cheers,

    Peter

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    Homann Designs - http://www.homanndesigns.com


  2. #14
    Registered phomann's Avatar
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    OK, I think I understand how they are doing the leadscrew alignment.

    Attached is an image of the base where Y-axis bearing mount attaches. As can be seen there are the 2 threaded holes for the mounting bolts. There are also 2 holes that alignment pins are mounted into. You can see that on the 2nd image.

    I believe that the bearing mounting plate is nudged around until the bearing block, leadscrew and nut are aligned. Then the bearing block is tightened and then the holes for the alignment pins are manually drilled and the pins inserted. If you look at the pins and holes, they are not symmetrical.

    I should be able to do the same, drilling new alignment pin holes. Or, maybe the pins aren't needed?

    Cheers,

    Peter.

    Attached Thumbnails Attached Thumbnails Homann Designs TM20LV (BF20,G0704) conversion-y-axis_base1-jpg   Homann Designs TM20LV (BF20,G0704) conversion-y-axis_alignment-pins1-jpg  
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    Homann Designs - http://www.homanndesigns.com


  3. #15
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    I'd personally skip the pins. You will have to realign every time you assemble though.



  4. #16
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    My plan for the conversion was to use belt drives, primarily so that I could tuck the motors away, rather than sticking out the ends. With the low profile saddle and the way the table ends can move right up to the saddle, there is too much work to ensure that there is clearance for the motors.

    So, I'm now looking to direct drive the axes. I'll see if the bdtools conversion kit can be used. If so, I'll use that. That said, I think there will be too many differences.

    I'm also not sure how important the alignment pins are. Obviously they are needed for mounting repeatability. They may also be need to stop misalignment if things are bumped, etc.

    For the Y-axis I can't reuse the alignment holes as I don't know the locations. I may need to drill new ones by having holes at known locations in the bearing support plate, then using them as guides for drilling into the base.

    Any advise welcome.

    Cheers,

    Peter

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    Homann Designs - http://www.homanndesigns.com


  5. #17
    Registered phomann's Avatar
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    Quote Originally Posted by 691175002 View Post
    I'd personally skip the pins. You will have to realign every time you assemble though.
    Yes, that's what I was thinking. Hopefully it wouldn't be too often.

    Cheers,

    Peter.

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    Homann Designs - http://www.homanndesigns.com


  6. #18
    Gold Member Bubba's Avatar
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    Peter,
    On my RF31, there are no alignment pins. Never has been and like you say, it has to be aligned each time. However in ten years or so, I haven't had to do that more than a couple of times. Also, the original lead screw nuts look exactly the same as my RF31 did. When I made my X axis one I kept having a problem with the two bolts not holding the nut mount tight enough and it would work loose causing backlash. For the nut mount, I used a couple of alignment pins and haven't had a problem since.

    Art
    Country Bubba (Older Than Dirt)


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    Quote Originally Posted by phomann View Post
    OK, I think I understand how they are doing the leadscrew alignment.

    Attached is an image of the base where Y-axis bearing mount attaches. As can be seen there are the 2 threaded holes for the mounting bolts. There are also 2 holes that alignment pins are mounted into. You can see that on the 2nd image.

    I believe that the bearing mounting plate is nudged around until the bearing block, leadscrew and nut are aligned. Then the bearing block is tightened and then the holes for the alignment pins are manually drilled and the pins inserted. If you look at the pins and holes, they are not symmetrical.

    I should be able to do the same, drilling new alignment pin holes. Or, maybe the pins aren't needed?

    Cheers,

    Peter.


    Your exactly right about the order/proccess for installing new pins. Infact not being symetrical may even have some benifits in stability ( but maybe not, but its not important). One thing the none symetrical pattern of pins does do is help you to know which end plate goes in which possition. With a odd pattern there is no question as to where each piece goes.


    I would add the pins after making your alignment. Bolts work loose to easy and flex/slipping happens very easy. Thats not to say that with carefull alignment and tightening of the bolts it will not hold as needed, but if it did move just a tick and this was not enough movement so that it was noticed by the operator
    then the screws/parts would be getting used while out of alignment. Ofcourse this could accelerate wear, and even cause possible problems with the accuracy which may not get noticed until something is warn, or after a 1000 parts where made incorrectly.


    So in simple terms it is just much safer, plus anytime you tear the machine apart it will go back together much easier/faster. This is the way you want the machine, this way its an easy job to jump in and do inspections or ajustments. You will be more willing to do so if its easier. And anyway, its not hard to drill a couple of anywhere you want them holes for the pins. A tappered reamer for the pin size will be needed, but these are cheap. Plus once you get in the habit of using pins on assymblies they will hold up better (other parts/projects). I like the pins with a center hole drilled and tapped for using a screw/slide hammer to pull them back out when needed, another "it makes it easier" in the end kinda thing when it comes time to dissasemble the parts.


    Jess

    GOD Bless, and prayers for all.


  8. #20
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    I fail to see how the alignment pins save any significant amount of time on re-assembly. You simply leave the bolts loose, run the axis so the ballnut is as close as can get to the bearing support, then tighten up the bolts. It takes no time at all.

    Regards,
    Ray L.



  9. #21
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    Quote Originally Posted by Bubba View Post
    Peter,
    On my RF31, there are no alignment pins. Never has been and like you say, it has to be aligned each time. However in ten years or so, I haven't had to do that more than a couple of times. Also, the original lead screw nuts look exactly the same as my RF31 did. When I made my X axis one I kept having a problem with the two bolts not holding the nut mount tight enough and it would work loose causing backlash. For the nut mount, I used a couple of alignment pins and haven't had a problem since.
    Hi Art,

    I was thinking that there was not much "meat" on the mounting flanges and wondered whether it would be a problem.

    How did you align the nut onto the saddle since it can't be adjusted once the table in put on. Is it a matter of tightening it so that there is a little movement, fit the table, get it aligned then remove the table and fully tighten the nut?

    Then once it is all aligned, drill and insert the pins?

    I am also considering having clearance holes in the saddle for mounting and threading the nut holder. That way, I could tighten the bolts from underneath.
    The saddle would be mounted to the upside down table on a bench.



    Cheers,

    Peter

    -------------------------------------------------
    Homann Designs - http://www.homanndesigns.com


  10. #22
    Gold Member Bubba's Avatar
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    Peter,
    On the X axis, I followed some instructions that was on the old IH site. I made the nut mount and loosely bolted it to the saddle. Then using my highly calibrated :}) digital caliper, made the lead screw parallel to the dovetails as I could. At this point, I tightened down the bolts for the mount. Next, I drilled the holes for the roll pins that I used to anchor the mount in one place ( see picture on my old web site:
    My CNC Homepage ). Then the table was placed on the saddle, the gib strip put in and snugged down. At this point, the end plates were loosely mounted and using a socket wrench, we moved the table to one end of max movement and that end plate was tightened down. Then we moved the table to the opposite extreme and the procedure repeated.
    The Y axis was done in a similar manner except there are bearings on only one end.

    HTH

    Art
    Country Bubba (Older Than Dirt)


  11. #23
    Registered phomann's Avatar
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    Hi Art,

    Thanks for the link. It all makes sense and I think I may copy what you have done.

    Cheers,

    Peter.

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    Homann Designs - http://www.homanndesigns.com


  12. #24
    Gold Member Bubba's Avatar
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    Glad it helps

    Art
    Country Bubba (Older Than Dirt)


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Homann Designs TM20LV (BF20,G0704) conversion
Homann Designs TM20LV (BF20,G0704) conversion