Page 5 of 11 FirstFirst ... 34567 ... LastLast
  1. Quote Originally Posted by JAZZCNC View Post
    Boyan Your forgetting the Encoders are Quadrature so that's 2500 x 4 =10,000ppr.!

    I am always confused about that info. Why are they never more clear. When i bought my Samsung servos, it stated 2500ppr, then i thought like you say- that they are quadrature, but it went they really meant 2500 pulses per revolution. So i actually for my machine have them programmed in Mach3 at 2500/10=250x(30t:20t)=375steps

    Thats why i said he must check in servo manual and every time i think about servos ppr i check in manual.



    Scott,
    they are talking about controlling the resonance frequency, so if you are near it will be ok.

    The bst motor inertia could not be different than typical servo motor inertia. Just make sure you know the correct length of motor and shaft diameter and you could use data from comparable motor
    project 1 , 2, Dust Shoe ...

  2. #42
    Quote Originally Posted by JAZZCNC View Post
    The fact you even considered 5mm pitch screws and Steppers on such large machine shows you need to do much more research.
    Sometimes I forget about the speed of the screw also being an important factor. I put together a little table for resolution based on ballscrew, based on my calculations I need to go with a higher pitch or up the gear ratio to keep the speed ~80% max. Upping the ratio of course hurts resolution so Im looking for a 20 pitch screw. Higher pitch also helps keep the ballscrew speed down, but of course hurts resolution per mm.

    Click image for larger version. 

Name:	Ballscrew precision.JPG 
Views:	102 
Size:	74.8 KB 
ID:	17903

    Thoughts on this?

  3. #43
    From my table above I am looking at a 2525 screw for the long axis. If I do a 2:3 ratio I get 37.5 mm travel per one motor revolution. 37.5/10,000 pulses = 0.00375 mm per pulse. This would be the best resolution. Or 0.0001476 inch resolution. This seems plenty good to me but thought I would ask

    This reduces the speed of the screw considerably to reach the same machine speed and actually gives me some headroom on the motor max speed as well.

    At the moment I am planning on rotating the screw and putting in multiple ballscrew supports. Something like...


    If I choose to do rotating ballnut I will need to recalculate the inertia and just make sure everything still matches up. I am leaning the other way as my parts are coming back around $300 usd per side....

    Does this sound like a reasonable solution?

  4. #44
    Quote Originally Posted by Scott Damman View Post
    From my table above I am looking at a 2525 screw for the long axis. If I do a 2:3 ratio I get 37.5 mm travel per one motor revolution. 37.5/10,000 pulses = 0.00375 mm per pulse. This would be the best resolution. Or 0.0001476 inch resolution. This seems plenty good to me but thought I would ask

    This reduces the speed of the screw considerably to reach the same machine speed and actually gives me some headroom on the motor max speed as well.

    At the moment I am planning on rotating the screw and putting in multiple ballscrew supports. Something like...


    If I choose to do rotating ballnut I will need to recalculate the inertia and just make sure everything still matches up. I am leaning the other way as my parts are coming back around $300 usd per side....

    Does this sound like a reasonable solution?
    Got my gear ratio backward. I need to redo my calculations...

  5. #45
    Alright new table now that I got the gearing correct the ballscrew and motor speeds were correct but I took the ballnut travel per motor rev the wrong way.

    Click image for larger version. 

Name:	Ballscrew precision.JPG 
Views:	94 
Size:	69.3 KB 
ID:	17904

    So based on these numbers still looking at 25mm lead screw. With a ratio of 2:3

    Ballnut travel per motor rev 25*0.66 = 16.5mm
    Precision mm = 16.5/10,000 = 0.00165 (is this real? i.e. with a quadrature resolver will I truly get 10,000 counts per motor rev?)
    1600 rpm ballscrew speed to get to 40,000mm/min (~1500ipm)
    Motor speed of 2424rpm (67% of max motor speed)


    So am I looking good here? The precision seems great and the speeds would be very acceptable with some headroom on the motor speed.

    Thanks

  6. #46
    AVF's Avatar
    Lives in Aalsmeer, Netherlands. Last Activity: 25-12-2016 Has been a member for 1-2 years. Has a total post count of 1.
    Quote Originally Posted by JAZZCNC View Post
    BST will provide cables upto 7mtr long. This is Video I made showing there 1.8Kw set.

    Hi Jazz,
    I saw your video which made me curious: would it be possible to use this 1.8kW servo and controller for driving a spindle or could I hit trouble doing so?
    BTW: Nice thread - and sorry for my little hijack!

  7. #47
    Quote Originally Posted by AVF View Post
    Hi Jazz,
    I saw your video which made me curious: would it be possible to use this 1.8kW servo and controller for driving a spindle or could I hit trouble doing so?
    BTW: Nice thread - and sorry for my little hijack!
    Don't want to let this run on so please start another thread if you want to know more.!!. . . But yes large Servo's are often used for Lower RPM spindles. Better controllers like the Cslabs IP-A let you control the spindle using Servo. This means you can use the Encoder for spindle orientation for things like ATC or Ridged tapping etc and do things like this.!

    Last edited by JAZZCNC; 10-03-2016 at 10:51 PM.

  8. #48
    Got a little more done on the frame, havent had as much time as I would like in the last few days. My bed is 16 inch on center and I decided to brace in between each of the bed cross members only the first ones in so far.
    .


    Ballscrew
    I need to finalize my plans for the X axis ballscrews so I can make mounts for them. Then motors mounts.
    So a couple questions -
    Do the numbers for the 2525 screw look good and make sense? On this long screw should I go with fixed:fixed mounts, I have read that this can stiffen things up a bit for a long screw.
    Like some of the big guys do, can I get away with intermediate supports along the ballscrew and drive the screw? Or go the rotating ballnut route?
    Do I even need the belt ratio on the X axis ballscrew? Would the motor speed be to slow without the gearing (~1600rpm at 1500ipm)? If I spin the screw, I could go direct drive with a 0 backlash coupling. Not that belting is all that difficult to implement it just takes some complexity out if I go direct coupled.

    Motors
    Ive run my inertia numbers multiple times with a few different numbers to try to account for some unknowns.
    What I ended up with is, 2 of the 1.8kw motors for the x, the inertia ratios in my calculations worked out between 1.75 ---> 3.4 depending on the numbers. And the torque worked out between 4.25 -->5 Nm per motor, these motors are 6Nm so I feel like this is a pretty good choice.

    Then for the Y I went with the 0.75kW motor 2.4Nm motor, inertia ratio calculations worked out between 2.25 --> 3.5 and the required torque was around 1.5Nm so a little headroom on torque.

    I also picked that same 0.75kW motor for the Z, my inertia ratios get closer to 1.5 here and if I find issues I could change the gear ratio

    If anyone has thoughts on these options for the motors Im all ears.

    One thing, that I cant yet confirm, but it looks like the drives from Fred show a limit on the inertia ratio of 5. This was based on data I found online from who I think is the supplier of the drives.

    Resonance
    I think I will cross this bridge if/when I need to. In my day job I am a noise and vibe engineer (although automotive and nothing to do with machine design) so I may be able to figure out the correct countermeasures. I will say, as the frame sits it rings when hit, so I may borrow some accelerometers and do some impact testing (frequency response...) on the machine and just see where things are if I get ambitious.

    Thanks for all the help this far!!!

  9. #49
    Click image for larger version. 

Name:	New Z Axis.JPG 
Views:	125 
Size:	23.3 KB 
ID:	17960Click image for larger version. 

Name:	New Z Axis3.JPG 
Views:	130 
Size:	24.9 KB 
ID:	17961Click image for larger version. 

Name:	New Z Axis.JPG 
Views:	118 
Size:	23.9 KB 
ID:	17962

    I think this will be my final Z axis design. 20 inches of travel with the ballscrew inside a 3inch x 5inch x1/4 wall box tubing. I have added supports to the internal of the box tubing to add strength and support the tubing when I cut the large slot on the backside for the ballnut.

    I think this will keep it pretty compact and also plenty strong. As always comments are appreciated.

    Thanks
    Scott

  10. #50
    I got a bit done on the Z axis over the weekend. When I was laying everything out for the Z I decided that 4.5 inches between linear rails was not wide enough. So I welded on some 3/8inch plate in order to widen it to 8 inches center to center on the rails.

    Starting the milled slot for the ballnut to travel
    Click image for larger version. 

Name:	20160319_171349.jpg 
Views:	149 
Size:	197.6 KB 
ID:	17975

    Slot cut through and now cleaning up the edges
    Click image for larger version. 

Name:	20160319_205921.jpg 
Views:	144 
Size:	95.7 KB 
ID:	17976
    Click image for larger version. 

Name:	20160319_205930.jpg 
Views:	133 
Size:	190.1 KB 
ID:	17977

    Internal view showing 2 internal supports. I figured these were needed to help keep movement to a minimum when I cut the large slot in the tube. They had to be driven in with a sledge as they were a little tight but I got them in. They are welded in place by drilling 3/8inch holes in the box tubing and then spot welding through those holes.
    Click image for larger version. 

Name:	20160319_205938.jpg 
Views:	131 
Size:	143.1 KB 
ID:	17978

    Begining the face milling process. I milled a linear reference for one of the rails. The curves are just the tool paths I had to take to make it all work as my mills travel isnt enough to do the whole thing in 1 pass.
    Click image for larger version. 

Name:	20160320_122648.jpg 
Views:	138 
Size:	165.7 KB 
ID:	17979 Click image for larger version. 

Name:	20160321_070717.jpg 
Views:	139 
Size:	77.6 KB 
ID:	17980

    Here you can see the milled linear reference for the rail
    Click image for larger version. 

Name:	20160321_070728.jpg 
Views:	125 
Size:	69.1 KB 
ID:	17981

    And a blurry picture of one of the rails test fitted
    Click image for larger version. 

Name:	20160321_070854.jpg 
Views:	135 
Size:	76.3 KB 
ID:	17982

Page 5 of 11 FirstFirst ... 34567 ... LastLast

Similar Threads

  1. BUILD LOG: First time build - Steel Frame CNC Router
    By examorph in forum DIY Router Build Logs
    Replies: 143
    Last Post: 30-01-2017, 11:37 AM
  2. BUILD LOG: New Build, Aluminium Frame Router/Mill
    By Davek0974 in forum DIY Router Build Logs
    Replies: 101
    Last Post: 31-08-2016, 04:28 PM
  3. BUILD LOG: Steel frame cnc router design/build
    By CraftyGeek in forum DIY Router Build Logs
    Replies: 110
    Last Post: 06-05-2015, 09:00 PM
  4. BUILD LOG: First steel diy CNC router build
    By ivars211 in forum DIY Router Build Logs
    Replies: 59
    Last Post: 28-07-2014, 07:29 PM
  5. BUILD LOG: 7' X 4' Steel frame build
    By Ricardoco in forum DIY Router Build Logs
    Replies: 6
    Last Post: 28-10-2012, 05:02 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
  •