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  1. #1

    Chinese ATC Spindle Help

    Hi guys,

    I’m really new to the CNC world here. I recently bought a BT30 ATC spindle from aliexpress and I’m really struggling to understand how it works. The seller has been really hard to get help from, but did supply me with a picture of a machine using the spindle. I mainly just don’t understand how the drawbar/tool changing works. I know it is pneumatic, I know it needs ~100psi to operate, and I know the top of the spindle is not stationary when the machine is running so I can’t directly connect an air hose (if that’s even what I need…).

    Can someone help me understand what exactly I need to be able to change tooling? At this point I realize I’m in way over my head. I figured if I had it in my hands I’d be able to figure it out, but that is clearly not the case. Any help would be much appreciated.

    From the seller: “ This is a belt spindle with an external cylinder. The cylinder is pressed down, the claw stretches out and loosens, the air source pressure,
    500kpa-800kpa”

    Listing:
    https://www.aliexpress.com/item/1005...89676531%22%7D

    Picture from seller of pneumatic cylinder above the spindle?:
    https://ae02.alicdn.com/kf/Hc03de4f0...5066f5000k.png
    Attached Thumbnails Attached Thumbnails 2C6AB985-538D-4492-B150-6B0B8CD1C702.jpeg   CD774413-06D9-481A-AB1E-E25537C3D826.jpeg   4E0EB30C-6BFF-4160-9E91-0B06434D5588.jpeg  

  2. #2
    Registered
    Join Date
    Mar 2016
    Posts
    216

    Re: Chinese ATC Spindle Help

    Are U sure it has losening actuator built in? Maybe drawbar just needs to be pushed by something from outside.

  3. #3
    Quote Originally Posted by steryd View Post
    Are U sure it has losening actuator built in? Maybe drawbar just needs to be pushed by something from outside.
    I believe the pull stud clamp is held closed by a spring. From the seller: “ The cylinder is pressed down, the claw stretches out and loosens, the air source pressure, 500kpa-800kpa”

  4. #4
    Registered
    Join Date
    Jan 2018
    Posts
    1097

    Re: Chinese ATC Spindle Help

    If that's the image he sent then that shows you need a pressure cylinder above the spindle to push down on top of the drawbar to release it.
    The chinglish description likely means the drawbar in spindle itself is spring loaded pressure not air.
    Hence an extra cylinder part is needed.

    Example on a mill:
    https://www.youtube.com/watch?v=5HjaMnmtYbg
    Shown active in video between
    11:42 to 11:58

  5. #5
    Member
    Join Date
    Jan 2005
    Posts
    13253

    Re: Chinese ATC Spindle Help

    Quote Originally Posted by blakenev10 View Post
    Hi guys,

    I’m really new to the CNC world here. I recently bought a BT30 ATC spindle from aliexpress and I’m really struggling to understand how it works. The seller has been really hard to get help from, but did supply me with a picture of a machine using the spindle. I mainly just don’t understand how the drawbar/tool changing works. I know it is pneumatic, I know it needs ~100psi to operate, and I know the top of the spindle is not stationary when the machine is running so I can’t directly connect an air hose (if that’s even what I need…).

    Can someone help me understand what exactly I need to be able to change tooling? At this point I realize I’m in way over my head. I figured if I had it in my hands I’d be able to figure it out, but that is clearly not the case. Any help would be much appreciated.

    From the seller: “ This is a belt spindle with an external cylinder. The cylinder is pressed down, the claw stretches out and loosens, the air source pressure,
    500kpa-800kpa”

    Listing:
    https://www.aliexpress.com/item/1005...89676531%22%7D

    Picture from seller of pneumatic cylinder above the spindle?:
    https://ae02.alicdn.com/kf/Hc03de4f0...5066f5000k.png
    First you will have to build a Z axis head, for the spindle and drive motor, then you will need a double stack air cylinder or an air over oil cylinder that will push down on the center of the spindle Drive End draw bar, by the look of the design you will use a moving air cylinder design, which will use a fork that will be under the top nut on the spindle, so when the air cylinder is actuated the fork will move up under the nut as the piston pushes down on the center push rod, this method takes the load off the spindle bearings

    Yes, the photo of the air cylinder is a double stack cylinder, but they are not showing it as a moving cylinder, which would be the best design to use for this spindle.
    Mactec54

  6. #6
    Member
    Join Date
    Jan 2005
    Posts
    13253

    Re: Chinese ATC Spindle Help

    Quote Originally Posted by blakenev10 View Post
    Hi guys,

    I’m really new to the CNC world here. I recently bought a BT30 ATC spindle from aliexpress and I’m really struggling to understand how it works. The seller has been really hard to get help from, but did supply me with a picture of a machine using the spindle. I mainly just don’t understand how the drawbar/tool changing works. I know it is pneumatic, I know it needs ~100psi to operate, and I know the top of the spindle is not stationary when the machine is running so I can’t directly connect an air hose (if that’s even what I need…).

    Can someone help me understand what exactly I need to be able to change tooling? At this point I realize I’m in way over my head. I figured if I had it in my hands I’d be able to figure it out, but that is clearly not the case. Any help would be much appreciated.

    From the seller: “ This is a belt spindle with an external cylinder. The cylinder is pressed down, the claw stretches out and loosens, the air source pressure,
    500kpa-800kpa”

    Listing:
    https://www.aliexpress.com/item/1005...89676531%22%7D

    Picture from seller of pneumatic cylinder above the spindle?:
    https://ae02.alicdn.com/kf/Hc03de4f0...5066f5000k.png
    A good example would be to look at the Tormach Auto Draw Bar, they are using a floating type which I described in my first post, your spindle type is similar, and would benefit from this design
    Mactec54

  7. #7
    Member
    Join Date
    Nov 2020
    Posts
    237

    Re: Chinese ATC Spindle Help

    The BT30 you bought only has belleville washers inside, that act as a spring to hold the tool. There's nothing there besides that so you don't need to worry about it. Now what you need is a headstock that the BT30 mounts into, a pneumatic or hydraulic cylinder that goes on top of the headstock and a spindle motor to run it that also mounts on top of the headstock.

    https://www.haascnc.com/content/dam/...inal/image.png

    stef a member of this forum build a VMC using this type of spindle cartridge, you can view his total assembly here including the part you're interest in. It's a 3dmodel so you can see everything in detail.

    https://grabcad.com/library/epoxy-gr...cal-cnc-mill-1

  8. #8

    Re: Chinese ATC Spindle Help

    Any idea of how much force is required of the cylinder to release the draw bar? And how far it needs to actuate?

    I found a listing of another Chinese spindle that I'm willing to bet is the same thing - on that listing it states "pull stud travel: 4.5mm" and "force of loose holder: 280kgf" - are these the answers to my questions?

    Thank you for the help and the resources.

  9. #9
    Member
    Join Date
    Nov 2020
    Posts
    237

    Re: Chinese ATC Spindle Help

    If you take the bt30 apart you could theoretically approximate how much force you need based on the size of the belleville washer, but only an estimation would be possible because you can't really know what material they are made of, the the material can influence the force by as much as 30% or more. 4-4.5mm sounds about right. Acrow, that also makes the clamps state a min. travel of 4mm(hs value) is required to clamp the tool. Acrow Machinery Mfg. Co., Ltd.

    As for how much force you'd need that also depends on the material of the washers but you can also adjust it yourself to a certain degree by screwing the cap tighter or looser. Generally a holding force of 3000N is a good value when the tool is held, you can treat this as your base number. Once you measure the belleville dimensions you need to count the number of washers and also the arrangement.

    I suggest you download this tool (https://www.dssolver.com/) and get familiar with it, it has a number of free uses before purchase is needed.

    tldr:
    1. Measure belleville dimensions (OD, ID, sheet thickness and overall thickness)
    2. Figure out belleville arrangement
    3. Put values and arrangement into the solver above.
    4. set 3000N for deflection and see how much that squeezes the washers in mm.
    5. set the above value in mm. as deflection and add 4 or 4.5mm to it
    6. from the xxxxN you get, you substract 3000N and you end up with how much N your cylinder needs

    7.WARNING if total deflection in (5.) is more than 80% you will need to use less then 3000N to hold the tool otherwise you risk early washer failure. If you do want to hold the tool with more force you could just completely replace these washers with a brand name and a specific material and a different arrangement.

    Will you be using a central pneumatic system(compressed air) for the whole 'shop'? If not you could get away from all of this by using a hydraulic cylinder and a small dedicated oil pump. Hydraulic cylinders produce so much force it won't really matter what's inside the cartridge.

    Please note all the above is self taught and never tested in real life.

  10. #10

    Re: Chinese ATC Spindle Help

    Put it in the press with a load cell and measure how much force it requires to move the release.

  11. #11
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    Mar 2016
    Posts
    216

    Re: Chinese ATC Spindle Help

    Or simply large pneumatic actuator powered by system with presure reductor. While increasing pressure U will get value that opens clamp. Then just calculate force from F=P/S or proportion - nominal force / nominal pressure equals actual force / actual pressure.

  12. #12
    Member
    Join Date
    Jan 2005
    Posts
    13253

    Re: Chinese ATC Spindle Help

    Quote Originally Posted by blakenev10 View Post
    Hi guys,

    I’m really new to the CNC world here. I recently bought a BT30 ATC spindle from aliexpress and I’m really struggling to understand how it works. The seller has been really hard to get help from, but did supply me with a picture of a machine using the spindle. I mainly just don’t understand how the drawbar/tool changing works. I know it is pneumatic, I know it needs ~100psi to operate, and I know the top of the spindle is not stationary when the machine is running so I can’t directly connect an air hose (if that’s even what I need…).

    Can someone help me understand what exactly I need to be able to change tooling? At this point I realize I’m in way over my head. I figured if I had it in my hands I’d be able to figure it out, but that is clearly not the case. Any help would be much appreciated.

    From the seller: “ This is a belt spindle with an external cylinder. The cylinder is pressed down, the claw stretches out and loosens, the air source pressure,
    500kpa-800kpa”

    Listing:
    https://www.aliexpress.com/item/1005...89676531%22%7D

    Picture from seller of pneumatic cylinder above the spindle?:
    https://ae02.alicdn.com/kf/Hc03de4f0...5066f5000k.png
    There have been a lot of confusing posts; it is very simple, buy the Air cylinder the spindle manufacturer said you need, which by what you posted, it is a double stack 100mm bore x 15mm stroke, this will give you the load you need to acuate the draw bar, you will be needing around a 100PSI. air pressure to the air cylinder this will give you around 10830N with that cylinder
    Mactec54

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