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  1. #11
    Thanks,
    If i had the cash i would buy that 1250 table tomorrow! It is exactly where i want to be, has the full cut speed range I want, pity the pictures are not clearer ;)

    I see that have R&P drive but use V-Rails all round, Can't seem to find that stuff?

    I like the below-table idea too for the transport, places more stress on the gantry support but obviously works.

    The motors are not much above what i have - they use 4Nm and I have 3.1Nm, both hybrid so thats a good sign.

    Now, can i build that table with Linear rail or does anyone know where I can source the V-rails????

  2. #12
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 3 Hours Ago Has been a member for 9-10 years. Has a total post count of 1,834. Received thanks 192 times, giving thanks to others 5 times.
    Google has the answer - http://www.linearonline.co.uk/acatal..._Bearings.html

    (although it did take a few attempts to find it!)
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

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  4. #13
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 3 Hours Ago Has been a member for 9-10 years. Has a total post count of 1,834. Received thanks 192 times, giving thanks to others 5 times.
    Oh, and their youtube videos give a little bit more detail if you pause at the correct moment ;)
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

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  6. #14
    Thats the stuff, thanks

    Now i have even more options;)

    Trouble is, what way to proceed???

    Vee rails with R&P drive
    Linear rails with R&P
    Linear rails with ballscrews
    Flat plate & skates with R&P
    Other...

  7. Quote Originally Posted by Davek0974 View Post
    Thats the stuff, thanks

    Now i have even more options;)

    Trouble is, what way to proceed???

    Vee rails with R&P drive
    Linear rails with R&P
    Linear rails with ballscrews
    Flat plate & skates with R&P
    Other...
    sorry about this but what are the advantages and disadvantages of these different types??
    Gavin,

    F1 Transportation & Engineering Services
    f1transportationservices@gmail.com
    We Move, Repair & Fabricate.

    Facebook - https://www.facebook.com/f1transport
    LinkedIn - https://www.linkedin.com/pub/f1-tran...ces/61/783/a06

  8. #16
    Vee rails with R&P drive - seems to be pretty common, reasonably easy to build, precision depends on rail mounting, backlash in rack, adjustment of rollers
    Linear rails with R&P - very accurate transport, precision depends on backlash again
    Linear rails with ballscrews - highest precision, highest cost, hardest build
    Flat plate & skates with R&P - a very common method, precision depends on quality of plate used and how its mounted, easy to replace, lowest cost, needs to be kept clean from grit etc

  9. Quote Originally Posted by Davek0974 View Post
    Vee rails with R&P drive - seems to be pretty common, reasonably easy to build, precision depends on rail mounting, backlash in rack, adjustment of rollers
    Linear rails with R&P - very accurate transport, precision depends on backlash again
    Linear rails with ballscrews - highest precision, highest cost, hardest build
    Flat plate & skates with R&P - a very common method, precision depends on quality of plate used and how its mounted, easy to replace, lowest cost, needs to be kept clean from grit etc
    What is backlash?
    And when you say highest cost re ballscrews how much are we talking??
    Gavin,

    F1 Transportation & Engineering Services
    f1transportationservices@gmail.com
    We Move, Repair & Fabricate.

    Facebook - https://www.facebook.com/f1transport
    LinkedIn - https://www.linkedin.com/pub/f1-tran...ces/61/783/a06

  10. #18
    Backlash is the slop or lost motion you can get with rack and pinion drive, normally gears are run with a small clearance between the teeth, when used in motion control you take all the clearance out by spring-loading the pinion against the rack so there is no clearance at all, this works well until the pinion or rack wears and backlash comes back. This will cause steps in the cut finish where the direction changes or circles to come out not quite round etc, basically its a bad thing.

    Ballscrews can have anti-backlash nuts fitted which are two nuts with tension between them.

    Cost for a 1.4m 20mm screw with end bearings and nut in the UK is about 350-400, length is also limited.
    Last edited by Davek0974; 27-06-2015 at 01:04 PM.

  11. #19
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 3 Hours Ago Has been a member for 9-10 years. Has a total post count of 1,834. Received thanks 192 times, giving thanks to others 5 times.
    You do realise you can get anti-backlash gears?
    Essentailly two gears mounted together and spring loaded out of alignment. You could do something similar using two gears mounted apart with a spring loaded belt between them, however you have to remember high acceleration forces could overcome the anti-backlash spring and allow backlash to develop briefly until the forces reduce again.
    Then you don't get prefect motion with a straight cut rack, as you get a slight notchyness as each tooth engages/disengages with a resultant increase/ (there is a proper term for this, but it's essentially what makes straight cut gearboxes so noisy), but for a plasma cutter it's not really an issue. If you're really concerned, you could use a helical rack, but I wouldn't worry about it.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  12. #20
    Thanks, i have read of some innovative ideas re backlash removal.

    Without sounding rude to anyone here, I have just had a reply from a very well respected heavy-duty expert in plasma cutting process and machinery via email, his examples of work are what i would like to see and are well known.

    Due to my budget constraints, it is felt that I should be looking at V-Rails and rack and pinion, or, ground, flat plate and skates with rack and pinion for my build.

    This makes a lot of sense and is in line with 90% of the commercial production built machines available - no point in re-inventing the wheel.

    I will price up and sketch out a v-rail build.

    There is another option for drive - open-ended toothed belt with an omega loop drive - this is simply a length of timing belt stretched tightly from front to back with the motor on the gantry and the belt wrapped in a loop over the sprocket. It is supposed to be a very good system as long as steel corded belt is used and it's pulled tight.

    My existing build uses a belt but its looped which doubles the stretch possibility and its too small at only 10mm wide, also due to the poor design at the shafts, i cannot stretch it very tightly.

    Its too easy to forget things like a budget at times :(

    Need to get back on track now I think ;)

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