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IndustryArena Forum > MetalWorking Machines > Uncategorised MetalWorking Machines > ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge
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  1. #1
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    ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    I thought i'd make a post on a spindle assembly endeavour I am about to embark on. I should first point out the CNC i'm planning on mounting this too is probably not stiff enough to take full advantage of the spindle assembly. My plan is to build the spindle assembly with the intention it may be mounted to a much more rigid setup in the future.

    Here is my previous CNC build thread of the machine I hope to mount this too

    The CAD of assembly looks like this:

    Attachment 434686

    My plan so far is:
    • Cast and then machine the spindle bracket in cast iron (approx. 18kg in weight - I've done a bit of work on this already)

    • Use a Chinese BT30 spindle cartridge (I have bought a 12,000RPM unit and it has arrived!)

    • Use a cheap 1.8kw servo motor as my spindle motor (I have bought this and this is all wired in)

    • Use a very big fan and a 3D printed shroud to cool that servo motor

    • Use a step up and down HTD pulley configuration to ensure I can have better slow speed torque or higher spindle speeds

    • Use a 100mm diameter pneumatic cylinder to provide the force to operate the ATC


    I also plan to document most of the build through the Youtube Channel:

    Here are some pics on the spindle bracket pattern:

    Attachment 434690
    Attachment 434692
    Attachment 434694
    Attachment 434696

  2. #2
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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    I'll be watching.

    I saw your router build log at the time - can you post the rest of the build?

    Looks like you are using a very long cutter for that MDF...
    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)

  3. #3
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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Quote Originally Posted by yezard View Post
    I thought i'd make a post on a spindle assembly endeavour I am about to embark on. I should first point out the CNC i'm planning on mounting this too is probably not stiff enough to take full advantage of the spindle assembly. My plan is to build the spindle assembly with the intention it may be mounted to a much more rigid setup in the future.

    Here is my previous CNC build thread of the machine I hope to mount this too

    The CAD of assembly looks like this:

    Attachment 434686

    My plan so far is:
    • Cast and then machine the spindle bracket in cast iron (approx. 18kg in weight - I've done a bit of work on this already)

    • Use a Chinese BT30 spindle cartridge (I have bought a 12,000RPM unit and it has arrived!)

    • Use a cheap 1.8kw servo motor as my spindle motor (I have bought this and this is all wired in)

    • Use a very big fan and a 3D printed shroud to cool that servo motor

    • Use a step up and down HTD pulley configuration to ensure I can have better slow speed torque or higher spindle speeds

    • Use a 100mm diameter pneumatic cylinder to provide the force to operate the ATC


    I also plan to document most of the build through the Youtube Channel:

    Here are some pics on the spindle bracket pattern:

    Attachment 434690
    Attachment 434692
    Attachment 434694
    Attachment 434696
    Should work well on your machine, the little Emco Mills have a nice 30 Taper spindle just like what you are going to build there is also a Taig one as well, these are expensive you can do it at a much better cost yourself

    These are just for reference

    eBay item number:
    233302223727

    264323872797
    Mactec54

  4. #4
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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Thanks for the replies,

    @pippin88 Unfortunately I didn't take much photos after that point on the build thread. I'm still using the table from my previous CNC so didn't have to build another. Most of the electrical work with the CNC can be found on Youtube with the first video in the series below:



    I'm yet to test the inaccuracies with the servo systems and I need to understand how well they are tuned from looking at the encoder feedback. First impressions running the machine seem really good though, In Mach 3 I have the X and Y stages set to accelerate at around 1G with rapids of 11M/Min and the servos seem to deal with this well but I was most impressed when doing some 3D milling the other day.

    Yeah long cutter right.......... unfortunately its all I had at the time and it left a fair bit of chatter marks on the MDF. I think I have some issues with the angular contact bearings on my X and Y stages, I didn't use matched pairs at the time and simply used a bearing shim to 'preload' the two non matched angular contact bearings in Face to Face configuration. I have since ordered some matched pair bearings so I am hoping this will alleviate some of my deflections as I suspect a fair amount is coming from these bearings. The bearings are from china and were fairly cheap so ill post my finding up here when I get them

    @mactec54 Thanks for the links, I haven't come across these.
    I have been doing some digging for some slower speed spindle setups and I have come across none that are in my price range or that seem suitable. Hence why I have opted to build my own. My impression form the first item number is the setup doesn't lend itself to being very stiff, do you know anyone that is using such a setup?

    I'm done filming the pattern build for the spindle bracket, hoping to find some time to edit the videos and post them early next week.

  5. #5
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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Quote Originally Posted by yezard View Post
    Thanks for the replies,

    @pippin88 Unfortunately I didn't take much photos after that point on the build thread. I'm still using the table from my previous CNC so didn't have to build another. Most of the electrical work with the CNC can be found on Youtube with the first video in the series below:



    I'm yet to test the inaccuracies with the servo systems and I need to understand how well they are tuned from looking at the encoder feedback. First impressions running the machine seem really good though, In Mach 3 I have the X and Y stages set to accelerate at around 1G with rapids of 11M/Min and the servos seem to deal with this well but I was most impressed when doing some 3D milling the other day.

    Yeah long cutter right.......... unfortunately its all I had at the time and it left a fair bit of chatter marks on the MDF. I think I have some issues with the angular contact bearings on my X and Y stages, I didn't use matched pairs at the time and simply used a bearing shim to 'preload' the two non matched angular contact bearings in Face to Face configuration. I have since ordered some matched pair bearings so I am hoping this will alleviate some of my deflections as I suspect a fair amount is coming from these bearings. The bearings are from china and were fairly cheap so ill post my finding up here when I get them

    @mactec54 Thanks for the links, I haven't come across these.
    I have been doing some digging for some slower speed spindle setups and I have come across none that are in my price range or that seem suitable. Hence why I have opted to build my own. My impression form the first item number is the setup doesn't lend itself to being very stiff, do you know anyone that is using such a setup?

    I'm done filming the pattern build for the spindle bracket, hoping to find some time to edit the videos and post them early next week.
    I have used the Emco Head as a 4th axis and as a milling head and it works very well, I normally build my own spindles though, the Emco head I used was from a parts machine I had so is still in use for many different machining operations

    When installing AC Bearings for best loading they want to be mounted Back to Back, when using standard AC Bearings then Grinding them to have zero clearance with Preload is also an option much better than using shims, you need a good surface Grinder to do this

    Building your own Spindles is more satisfying than buying one and can be a lot cheaper
    Mactec54

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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    I would love to build my own spindle one day but I certainly don't have the right tools atm. One day maybe

    I have ordered 60 degree angle Back to Back (DB) matched bearings. They are ground for a normal pre-load so hopefully no grinding or shimming required from me which is certainly beyond my capabilities.

    Have you got any build threads of the spindles you have made? I can imagine a huge amount of work and knowledge goes into making one

  7. #7
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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Face to face is what you want on a ball screw actually. It allows some forgiveness in alignment. back to back needs to be "perfect".
    Most machine tool ball screw specific bearings are 40 degrees, with rather oversize housings (NSK 15TAC for example). The ones you get in the little bk blocks are just 700X bearings with 30 degree angles. They are meant for light duty (your machine would qualify as light duty of course). Generally they use P5 grade, anything higher doesn't really offer any benefit (the screw itself will be considerable worse for runout than any grade bearing.

    On the topic of the spindle, I see them now for $500 for the 6krpm version. This is the one skyfire used a few years back. I know several people here bought that spindle, I've never seen any actual results with them though, outside skyfire demo videos. They are quite tempting, but my little machine is too small for it (and my big one already has an iso30 24krpm spindle).

    Make sure you post the results, I'm very interested to see how it performs on a small-is machine like yours (as opposed to a VMC).
    wotzBotz

  8. #8
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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Quote Originally Posted by ihavenofish View Post
    Face to face is what you want on a ball screw actually. It allows some forgiveness in alignment. back to back needs to be "perfect".
    Face to Face and Back to Back AC Bearing mounting need the same precession for mounting, there is no alignment forgiveness not sure how you would come up with this Bs

    Back to Back DB is a superior mounting over Face to Face
    Mactec54

  9. #9
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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Quote Originally Posted by yezard View Post
    I would love to build my own spindle one day but I certainly don't have the right tools atm. One day maybe

    I have ordered 60 degree angle Back to Back (DB) matched bearings. They are ground for a normal pre-load so hopefully no grinding or shimming required from me which is certainly beyond my capabilities.

    Have you got any build threads of the spindles you have made? I can imagine a huge amount of work and knowledge goes into making one
    This is a ER16 build I did for a Zone member some years ago, but the ER16 part was only modified I did not make that part, but do make complete Spindles if I need to, as well as special Bearings when needed

    https://www.cnczone.com/forums/cnc-w...dle-build.html
    Mactec54

  10. #10
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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Quote Originally Posted by mactec54 View Post
    Face to Face and Back to Back AC Bearing mounting need the same precession for mounting, there is no alignment forgiveness not sure how you would come up with this Bs

    Back to Back DB is a superior mounting over Face to Face
    NSK TAC series bearings - the ones they designed ONLY for ball screws - come in face to face and tandem orientations... they don't provide back to back.
    All THK BK series blocks are face to face.

    But yeah, I'm sure you know more abut it than them.
    wotzBotz

  11. #11
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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Quote Originally Posted by ihavenofish View Post
    NSK TAC series bearings - the ones they designed ONLY for ball screws - come in face to face and tandem orientations... they don't provide back to back.
    All THK BK series blocks are face to face.

    But yeah, I'm sure you know more abut it than them.
    The NSK Tac series Bearings come in DB/DF/DT and can be installed in any orientation you want, including Back to Back if you are smart you buy universal, it all depends on design and how you want the thrust to be handled, Back to Back will always have the best results as you have a better Thrust loading spread this is much better, Face to Face you have a small local area of concentrated thrust not so good unless you have more than 2 Bearings packs of 3 or more

    The post was about inexpensive AC bearing being used not mega dollar NSK Tac series Bearings
    Mactec54

  12. #12
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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    My NSK paper only showed the df/dt only, as that's what's used in my MAHO and brother machines. I guess they will make them any way anyone wants...

    From SKF:
    "If misalignment cannot be avoided between the bearing positions, face-to-face bearing arrangements are recommended. They are less sensitive to misalignment than back-to-back bearing arrangements"
    https://www.skf.com/ca/en/products/b...nts/index.html

    THK BKxx, the most common low cost support style for the type of machines built on this forum:

    Click image for larger version. 

Name:	thk.jpg 
Views:	0 
Size:	144.8 KB 
ID:	434976

    My Brother tapping centres use face to face (NSK 20TAC47BDF) bearings

    The MAHO bearings are nsk TAC25 and TAC30 face to face

    Here's the face to face / tandem setup in a mori lathe:

    Attachment 434974

    There are a handful of examples of back to back in machines I've found in a quick search, but almost everything is face to face, especially when just using 2 bearings (you would lose some of the alignment benefits with more than 2 bearings or when spacing out the bearings).

    On the very bottom end of cheap I should add that sieg uses 2 thrust bearings with a double lock nut and Belleville spring, on a 12mm c5 ground screw, and honestly, it worked better than the angular contact bearings in some other machines I've had because you can adjust the preload precisely.



    So, to the OP... look at what other machine makers do, and what the bearing manufacturers say, and don't blindly listen to what someone on a forum tells you - they *might* not have a clue what they are talking about it turns out.
    wotzBotz

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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Quote Originally Posted by ihavenofish View Post
    My NSK paper only showed the df/dt only, as that's what's used in my MAHO and brother machines. I guess they will make them any way anyone wants...

    From SKF:
    "If misalignment cannot be avoided between the bearing positions, face-to-face bearing arrangements are recommended. They are less sensitive to misalignment than back-to-back bearing arrangements"
    https://www.skf.com/ca/en/products/b...nts/index.html

    THK BKxx, the most common low cost support style for the type of machines built on this forum:

    Click image for larger version. 

Name:	thk.jpg 
Views:	0 
Size:	144.8 KB 
ID:	434976

    My Brother tapping centres use face to face (NSK 20TAC47BDF) bearings

    The MAHO bearings are nsk TAC25 and TAC30 face to face

    Here's the face to face / tandem setup in a mori lathe:

    Attachment 434974

    There are a handful of examples of back to back in machines I've found in a quick search, but almost everything is face to face, especially when just using 2 bearings (you would lose some of the alignment benefits with more than 2 bearings or when spacing out the bearings).

    On the very bottom end of cheap I should add that sieg uses 2 thrust bearings with a double lock nut and Belleville spring, on a 12mm c5 ground screw, and honestly, it worked better than the angular contact bearings in some other machines I've had because you can adjust the preload precisely.



    So, to the OP... look at what other machine makers do, and what the bearing manufacturers say, and don't blindly listen to what someone on a forum tells you - they *might* not have a clue what they are talking about it turns out.
    I did not say you could not use them Face to Face it is your choice and your uneducated knowledge with Bearings that you would use this configuration, most machining centers today use Bearings like the snip below and are all Back to Back

    You still talking or dreaming about your MAHO do you have it running now, would love to see that pile of scrap metal running, as I have worked on those old MAHO's Post a Video of it running
    Mactec54

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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Thanks for the replies. I chose my configuration mainly based upon the reading in the SKF bearing book and speaking to colleagues however since they are budget bearings from china I am bit dubious about how they will perform.

    In other news I took a few pics of the spindle. Heres the link to the one I bought and the seller if anyone is interested:

    Attachment 435094
    Attachment 435096
    Attachment 435098
    Attachment 435100

    I did a quick un-boxing video too and will post it when I get a chance to edit it.

  15. #15
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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Nice cnc machine and spindle project.
    Can I ask. What is rated and max speed of your servo and what size pulleys do you plan to use?

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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Hi,

    The spindle is rated for 12,000 rpm but the servo motor is rated to 3000 rpm (1.8Kw, 6N.m and 18N.m peak). I plan to gear the spindle with 3 options 22:56 , 56:20 , and 40:40 (Spindle:Servo) They are 8M HTD pulleys

    So the maximum spindle speed I can obtain is 7636 rpm. When I designed the system I planned to use the 8000 rpm variant of the spindle however the seller offered a very reasonable price for the much more expensive 12,000 rpm unit so I decided to go for it. Unfortunately I cannot find a pulley ratio that fits in the space that is able to make use of the 12,000 rpm the spindle can offer (either they cannot take the torque or they need more space than I have available). In the future I may use a gear box on the servo, there are some available that bolt onto and are compatible with my assemble with no modifications. However I suspect vibrations at a higher speed may become a problem.

    Here is the link to the youtube video of the pattern build:



    I have cast the bracket but unfortunately I may need to re-cast this as I made some mistakes when making the mould. Its been 2 years since I last cast some metal and I have forgotten a few tricks. The biggest problem is I didn't include a riser to feed part of the cope. As the metal cooled it contracted in this area and has lead to large shrinkage cavities on that surface of the bracket. I'm going to try and cast the bracket again and include a riser and fix a few other nags with the mould. Ill post the video of the failed casting on here when I have edited the footage and you guys will see what I mean.

  17. #17
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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    56T 8m is a big pulley

    Is the servo max speed 3000 also or can it run faster than rated speed?

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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Sorry for the delayed reply.

    Its one of those cheap Chinese servo motors and its rated to 3000rpm. I would have thought with a different drive i could probably run it higher but i am unsure how long the motor will last. The current drive does not have the option to operate the servo faster than 3000rpm

    I have uploaded the first attempt of the bracket casting. I have actually cast a second more 'successful' bracket and will upload the photos of this when i get a chance.


  19. #19
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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Quote Originally Posted by yezard View Post
    Sorry for the delayed reply.

    Its one of those cheap Chinese servo motors and its rated to 3000rpm. I would have thought with a different drive i could probably run it higher but i am unsure how long the motor will last. The current drive does not have the option to operate the servo faster than 3000rpm

    I have uploaded the first attempt of the bracket casting. I have actually cast a second more 'successful' bracket and will upload the photos of this when i get a chance.

    Very good example of what can be done
    Mactec54

  20. #20

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    Re: ATC Spindle Assembly using a Chinese BT30 Spindle Cartridge

    Hi yezard,

    I am looking at upgrading my scratch built CNC with a BT30 spindle. Just wondering if you could share the buyer you got your spindle from? Are you happy with the unit or is it too early to tell?
    Cheers.

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