Newbie Bridgeport ballscrew retrofit, design the yoke - Page 3


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Thread: Bridgeport ballscrew retrofit, design the yoke

  1. #25
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    Default Re: Bridgeport ballscrew retrofit, design the yoke

    William, can you explain to me why and how the 25mm screws didn't work as good as the Hiwin retrofit. I understand that the 25 mm screws are smaller compare to the Hiwin retrofit but if both systems have the same backlash on the same BP, the precision should be the same. At least this is what I understood. I really want to convert my BP into CNC at the lower possible cost (I'm cheap). I'm new to this milling machine world, I started last year when I got my manual BP. I like this tool, it makes me happy. If I have to spend more money to get a Hiwin retrofit, maybe I will, but before I order any parts, I need to better understand what I don't understand. Thanks for your help.



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    Hi Bill,

    Really good post but +1 on wanting more information on this. Do you recall any figures on the lack of precision that concerned you? Others on this forum (myself!!) may not have as critical a need for accuracy as yourself it would be useful to put it into context. I can live with 0.5 to 1 thou whereas other chaps need tenths

    Was it the linear precision that bothered you as I understood this was solvable via software, was it the lack of repeatability perhaps due to the yoke or ballscrew flexing, was it the backlash or something else?

    Your posts are much appreciated

    Cheers!
    David



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    Default Re: Bridgeport ballscrew retrofit, design the yoke

    Hello guys ,
    My bridgeport is now running 3 axis cnc with mach 3 free demo software, and i am pretty happy with it, since it is a hobby for me.
    x and y axis ballscrew are cheap aliexpress custom made double nut ballscrew 25 mm diam 5 mm lead just like this one https://www.aliexpress.com/item/1pcs...ddresstype=600

    The chinese supplier did a very nice job on the shaft tolerances , he reached the dimension to 0.0003in from my drawing dimension. I got both ballscrew completely machined to fit the bridgeport for about 350 $CAD shipping included !!

    I made a yoke to fit the chinese nut bolt pattern using the hiwin yoke 2d drawing ( see down the post) I machined a complete solid yoke made of aluminum 6061 t6( enough stiff for what i do with the machine ) The crucial dimension of the yoke is the distance from the two axis to the yoke fixation surface, and the perpendicularity of those axis / surface. I measured my old yoke and added about 0.003 in to the distance in order to compensate for wear( since it is a 1975 BP, and the ways have a little wear on the dovetail).

    The third axis is the 6 inches quill, which is not so accurate because of the rack and pinion configuration. It does the job when i have tons of holes to drill. I set Mach3 with backlash compensation , and it is handling it pretty well. I now plan to take the quill motor out and install it using a planetary gear ( ali express chinese nema 34 size!!! ) unit on the knee power screw for better accuracy.

    I will try to put down some picture soon.

    So for V8kid and jfroux_1 , if you guys have little money to spend on that project i suggest you start with chinese ballscrews. And btw, if you use those dfu2505 ballscrews , the nut flange dont need to be machined since it clears inside the knee.

    I hope it helps you



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    Default Re: Bridgeport ballscrew retrofit, design the yoke

    Here is my Yoke for BP, and some other pic from that project









    Attached Thumbnails Attached Thumbnails Bridgeport ballscrew retrofit, design the yoke-c6a26fb3-de1d-4a8c-824c-a32a7601d37a-jpg   Bridgeport ballscrew retrofit, design the yoke-4f93d327-ac9e-477b-b485-1a1f7eb1c88d-jpg  


  5. #29
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    Default Re: Bridgeport ballscrew retrofit, design the yoke

    Quote Originally Posted by daroc30 View Post
    Hello guys ,
    My bridgeport is now running 3 axis cnc with mach 3 free demo software, and i am pretty happy with it, since it is a hobby for me.
    x and y axis ballscrew are cheap aliexpress custom made double nut ballscrew 25 mm diam 5 mm lead just like this one https://www.aliexpress.com/item/1pcs...ddresstype=600

    The chinese supplier did a very nice job on the shaft tolerances , he reached the dimension to 0.0003in from my drawing dimension. I got both ballscrew completely machined to fit the bridgeport for about 350 $CAD shipping included !!

    I made a yoke to fit the chinese nut bolt pattern using the hiwin yoke 2d drawing ( see down the post) I machined a complete solid yoke made of aluminum 6061 t6( enough stiff for what i do with the machine ) The crucial dimension of the yoke is the distance from the two axis to the yoke fixation surface, and the perpendicularity of those axis / surface. I measured my old yoke and added about 0.003 in to the distance in order to compensate for wear( since it is a 1975 BP, and the ways have a little wear on the dovetail).

    The third axis is the 6 inches quill, which is not so accurate because of the rack and pinion configuration. It does the job when i have tons of holes to drill. I set Mach3 with backlash compensation , and it is handling it pretty well. I now plan to take the quill motor out and install it using a planetary gear ( ali express chinese nema 34 size!!! ) unit on the knee power screw for better accuracy.

    I will try to put down some picture soon.

    So for V8kid and jfroux_1 , if you guys have little money to spend on that project i suggest you start with chinese ballscrews. And btw, if you use those dfu2505 ballscrews , the nut flange dont need to be machined since it clears inside the knee.

    I hope it helps you
    350 $CAD shipping included !! ??
    I’m just a hobbyist, and to tell you the true my Bridgeport is a new tool to me. I really want to convert my BP into a CNC at the lowest cost possible and get a good reliable machine that I’ll use less than 150 hours per year.
    Why did you have to build a new yoke? I thought we can just dump the old ACME screw guts out of it and a ballnut for a 25mm screw fit perfectly. I’d like to get the ballnut flange hole drill by the supplier when I’ll order the ballnut flange. I can’t find the pattern needed on the ballnut flange. Do you know where I can find a draw with the pattern needed? I prepared a draw that I want to send to different ballscrew suppliers and I need to add this pattern.
    When you use your BP CNC with Mach 3 backlash compensation how happy are you with the results?



  6. #30
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    Default Re: Bridgeport ballscrew retrofit, design the yoke

    Jfroux_1 Exactly, both screws machined in china using my drawings and shipped for 350$ CAD.
    I build a new yoke in order to the save the original parts intact.
    You will find the bolt pattern in the supplier drawing infos from who you will buy the screws. The orignal yoke has no threaded holes for a ball screw nut.
    Mach3 Back lash compensation is working very well for me. Even with the rack and pinion setup on the quill.



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Bridgeport ballscrew retrofit, design the yoke

Bridgeport ballscrew retrofit, design the yoke