First Build 5 x 12 Steel Frame CNC router

[Boyan Silyavski]

BST automation is the usual choice for Chinese stuff and linear rails, so its a well known and recommended seller. Price wise, packing, support and warranty.

Do you have a cable chain? If not i highly recommend the Russian ARKO 22x80 R60 which is cheaper and better than the similar Chinese

[Ger21]

Leadshine has 10m cables available for their motors.
I would email BST and ask if he has them for his motors. Or, you can always make your own.

At those prices, I'll have to seriously consider going that route, if it saves $225/motor.

I have a "build log" at CNC Zone, that's about 7 years long, with almost no actual building, and another 2 year old thread when I started the design.
I've got a few thousand dollars in components, but life doesn't leave me any time to get to it.
I also spent the last 3 years of my spare time working on this: www.jointcam.com
(Actually 2 years, and a year of doing nothing)

[JAZZCNC]

BST will provide cables upto 7mtr long. This is Video I made showing there 1.8Kw set.

[AVF]

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!

[JAZZCNC]

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.!

[Scott Damman]

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!!!

[Scott Damman]

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

[mekanik]

Hi guys sorry to but in but could someone post a link for BST Automation.
Please
Regards
Mike

[AndyGuid]

BST Automation = http://www.aliexpress.com/store/314742

[Clive S]

Hi guys sorry to but in but could someone post a link for BST Automation.
Please
Regards
Mike

here you go http://www.aliexpress.com/store/314742 but you can email him direct bstlinear [[@ ]] gmail.com