Page 4 of 29 FirstFirst ... 2345614 ... LastLast
  1. #31
    Quote Originally Posted by fvfdrums View Post
    1 x nema 34 7.7nm running 2 x axis ball screws via a timing belt (as suggested by JAZZ) running 20/05 screw on a 2:1 ratio
    1 x nema 23 3.1nm running y axis on 16/10 screw
    1 x nema 23 3.1nm running y axis on 16/05 screw for better resolution
    Hold on think we may be at cross purpose's here or I've miss under stood you.? I wouldn't have recommended those screws and motors at this size.? Longer yes but not at 1200mm.

    16/10 and 3.1Nm 23's will be much better.

    Edit: The only exception is if you want to link the screws with timing belt.? Then you'll need the bigger motors but 16/10 could still be used.?
    Also don't use 80VPSU with 80V drive. You need a safety net for back EMF so use 75V psu with 80V drives.
    Last edited by JAZZCNC; 16-12-2012 at 11:32 AM.

  2. #32
    Quote Originally Posted by JAZZCNC View Post
    Hold on think we may be at cross purpose's here or I've miss under stood you.? I wouldn't have recommended those screws and motors at this size.? Longer yes but not at 1200mm.

    16/10 and 3.1Nm 23's will be much better.

    Edit: The only exception is if you want to link the screws with timing belt.? Then you'll need the bigger motors but 16/10 could still be used.?
    Also don't use 80VPSU with 80V drive. You need a safety net for back EMF so use 75V psu with 80V drives.
    My fault I am sure, the x axis will be joined with a timing belt in which case would this still negate the 34 or would the 23 be adequate. but if I can use the 16/10 then thats great!

    Noted on the drives voltage that makes sense must be a sunday thing on my part! As ever cheers for the response!

  3. #33
    Has sent FVF via email regarding others stuff has well as this but posted for benefit of others and to keep the thread complete without back door dealings so to speak. . .Lol


    Seeing your post got me wondering if i'd cocked up on advise but on reading this email again I feel vindicated and relief . .. Lol

    To be honest I didn't realise or missed the length was only 1200mm.
    Given this then it will be better to use 16/10 has it gives more options. If your wanting to still only use 1 motor linked with belts but nema 23 motor then there's still a possible option.? Thou i've never done it but can't see any problems if only cutting at lower feed rates needed for aluminium.!

    Like using the 34's gear it but in reverse so 2:1 (2x turns motor 1x screw) this has the affect of doubling the torque and increasing the resolution at the sacrifice of speed.

    To be honest with the price of digital drives dropping significantly and the fact they are soooo much better than Analogue drives in general but esp at handling stalling. Being able to stop all motors when one motor is detected Stalling has meant the racking issues when using twin slaved motors is greatly relieved and with minimal risk of damage if happening at high feed rates.

    That said your if your mainly going to cut aluminium then slaved motors is not so much a risk has again the feeds are low so available torque higher. Esp if geared 2:1

    Hope this helps
    Cheers
    Dean.

    PS: I will post this on the forum for others to see and critique.!!

  4. #34
    Agree with jazz about the X-screw - RM2005 wont help. The problem is the pitch is half what you get with RM1610, so you have to spin the screw twice as fast to get a given feedrate. Going from 16mm diameter to 20mm doesn't make the critical speed twice as much (only 25% more) so you actually end up worse.

    RM1610, critical speed - 1460rpm => 1460*10=14.6m/min
    RM2005, critical speed - 1825rpm => 1825*5=9.1m/min

    The feedrate with either screw is plenty, but since 20mm is more expensive and in addition to the above a 20mm screw requires significantly more torque than 16mm, so you only gain stiffness/lifetime which on a router like is completely negligible since the 16mm screw is strong enough and will last for many years.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  5. #35
    Jazz & Jonathan

    As ever thanks for the informative responses

    I follow on the 16 thread thats fine...... so I guess now really its a case of deciding between one motor driving two screws or having them slaved?

    Based on the spec what would you guys do if it were you? And will 1 x 23nema 3.1nm running both x axis screws be man enough?!? or is it better to just go down the twin motor route?

  6. #36
    Updated spec after current discussions:

    1200x900 footprint area with approx 1000 x 800 cutting area
    80x40x4mm steel box section frame with adjustable bed
    Aluminium gantry made from a combination of 20mm/15mm plate either standard 6082 or ecocast for the bearing and guide plates
    20mm Profile rail on x,y,z
    **16/10 on x axis (running 2:1)**
    16/10 on y axis
    16/05 on z axis
    250mm cutting depth on z
    2.2kw chinese spindle

    electronics (just ideas at the moment)

    1 x nema 34 7.7nm running 2 x axis ball screws via a timing belt running dual 16/10 screws
    1 x nema 23 3.1nm running y axis on 16/10 screw
    1 x nema 23 3.1nm running y axis on 16/05 screw for better resolution

    80v Leadshine Drives

    75v PSU

    Mach 3

    How is this all sounding? are we on the right track :)

    Design wise the gantry design is very similar to the one Jazz has posted on here before with interlocking aluminium plates (copying someones idea is the best form of flattery right? or is that plagiarism :P) anyway it looks an extremely solid design and I tend to make things over engineered so figured this was a good place to start.

    With the y axis I was considering a direct drive using a coupler, all the other drives will use a belt to transmit motion, would it better to engineer it so the motors are all belt driven or would this make no odds?

  7. #37
    Quote Originally Posted by fvfdrums View Post
    **16/10 on x axis (running 2:1)**

    1 x nema 34 7.7nm running 2 x axis ball screws via a timing belt running dual 16/10 screws
    This contradicts the other.? If using 10mm pitch you won't need any ratio with 7.7Nm 34 and belt drive 1:1 will be fine.



    Quote Originally Posted by fvfdrums View Post
    With the y axis I was considering a direct drive using a coupler, all the other drives will use a belt to transmit motion, would it better to engineer it so the motors are all belt driven or would this make no odds?
    No don't direct drive keep the belts for resonance reasons even thou your planning using very good drives which handle resonance fantastic. If your copying the gantry I think then I've actually changed the design slightly and the Motor is now on the inside connected to screw with belt. It's very neat and compact. (code for F@#% tight fit.!!)

  8. #38
    copy and paste mistake yes I mean 1:1!!

    I was looking into that possibility and I think I must have guess the dims pretty close as I had exactly the same design issues but I think I can get it in!

  9. #39
    after a bit of redrawing last night I had a thought that the fk/ff bearings (which I have just stumbled across) may be a better option for the x axis that the bk/bf ones. I am trying to determine the exact length of the ballscrew I need and cannot tell if the bearings in these units are flush to the back of the mounting plates or they are set in? does anyone have or know a link to some accurate tech specs for these bearings? Because the design of the axis uses a plate either end of the frame to sandwich the x axis ballscrew between two bearing units and I need to know the length of ballscrew I need to order otherwise there will be play or it will be over sized!

    Alternatively if I were to machine up my own bearing blocks for the x axis, the floating end is straight forward, what does the fixed end comprise of? angluar contact bearings? sizes?

  10. #40
    D.C.'s Avatar
    Lives in Birmingham, United Kingdom. Last Activity: 05-01-2016 Has been a member for 4-5 years. Has a total post count of 326. Received thanks 30 times, giving thanks to others 24 times.
    Quote Originally Posted by fvfdrums View Post
    Price wise everything has been accounted for in our budget which is great managed to get some really good prices on steel and aluminium.
    I am going through the same design/collect materials phase that you are and I'm building a similar sized 2.2kw spindle, steel frame as you. In your budget did you account for all the 'little things'?

    Like:

    Control Cable
    E-Stop button
    Limit switches
    Nuts & bolts
    Water pump for the spindle
    Tubing for the water pump
    Connectors for the tubing
    Cable runs
    Welding supplies
    Paint
    Etc...

    Accounting for all these sorts of things is adding an easy 200-300 to my budget (even with making my own cable runs after the machine is built) and then of course before I cut a single thing I'll need a few different router bits so that is another 50.

Page 4 of 29 FirstFirst ... 2345614 ... LastLast

Similar Threads

  1. FOR SALE: Emco mill 50 cnc mill like Denford Triac
    By gavztheouch in forum Items For Sale
    Replies: 0
    Last Post: 18-05-2014, 10:19 AM
  2. Best all round mill/router? Vertical mill or gantry router?
    By Richard in forum Machine Discussion
    Replies: 2
    Last Post: 18-02-2014, 04:18 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •