Yet another BT30 Design and Build Adventure.
Hi Everyone, I own and run an engineering and fabrication company with a high-end Auto tool changing CNC Lathe. We also have a few smaller CNC Mills, I will get to the point.
We are working on designing a BT30 Spindle with a capacity of up to 15,000RPM for a custom Vertical CNC Mill, the work area is roughly 0.95m x 0.95m we are still defining the Z height but we believe we will have a tall height to allow for 4 or even 5 Axis modules.
Right now we are only planning on making the CNC 4 Axis compatible with a controller that has capabilities of up to 6 individual servo motor outputs. We have been doing a lot of research on Servo-style spindles and we believe that is what we want to go with because it will allow us to automatically make threaded holes and allow us to have a lot more tooling capabilities as far as threading goes, the CNC Lathe will be a structure in Steel using 1/4 inch tubing and some rebar which will then be filled in with epoxy to help reduce vibrations and increase structural integrity. With all of those details behind us, we are currently looking at designing a BT30 Spindle with auto tool changing capabilities and forced cooling with air or liquid, We have just begun designing the spindle if anyone has any links to share for designs of the tool holders that would help us. we have found a few but they are all a little bit different. Once we are done with the spindle design we will run physic simulations on the spindle and share the plans here. Good day!
Re: Yet another BT30 Design and Build Adventure.
Search for sk30 standard, its the same as bt when it comes to the taper, the only thing that's different is the inside contour and the drawbar gripper. You can get proper dwg drawings from acrow, they carry normal bt grippers and ott style. ott cost the same so I'd go with them, also because its a pain to get mas403 drawing standard, and ott makes sk30 readily available. if you want accurate toolholders just download the 3d models from sandvik coromant, if you make the taper angle correct in your cad you can add an assembly constrait that will mate the tapers perfectly together without an error.
On another note, I'd go without rigid tapping and instead do thread milling with multiple flutes. Rigid tapping has size limitations on top of torque and synchronous action. In my opinion not worth the trouble. With thread milling you can machine any thread size and if you use multiple flutes it can be as fast as rigid tapping.
Re: Yet another BT30 Design and Build Adventure.
Quote:
Originally Posted by
gloveless
Hi Everyone, I own and run an engineering and fabrication company with a high-end Auto tool changing CNC Lathe. We also have a few smaller CNC Mills, I will get to the point.
We are working on designing a BT30 Spindle with a capacity of up to 15,000RPM for a custom Vertical CNC Mill, the work area is roughly 0.95m x 0.95m we are still defining the Z height but we believe we will have a tall height to allow for 4 or even 5 Axis modules.
Right now we are only planning on making the CNC 4 Axis compatible with a controller that has capabilities of up to 6 individual servo motor outputs. We have been doing a lot of research on Servo-style spindles and we believe that is what we want to go with because it will allow us to automatically make threaded holes and allow us to have a lot more tooling capabilities as far as threading goes, the CNC Lathe will be a structure in Steel using 1/4 inch tubing and some rebar which will then be filled in with epoxy to help reduce vibrations and increase structural integrity. With all of those details behind us, we are currently looking at designing a BT30 Spindle with auto tool changing capabilities and forced cooling with air or liquid, We have just begun designing the spindle if anyone has any links to share for designs of the tool holders that would help us. we have found a few but they are all a little bit different. Once we are done with the spindle design we will run physic simulations on the spindle and share the plans here. Good day!
Be interested to see the servo motor that can run at 15,000RPM most top out at 12,000RPM
Re: Yet another BT30 Design and Build Adventure.
Quote:
Originally Posted by
ardenum
Search for sk30 standard, its the same as bt when it comes to the taper, the only thing that's different is the inside contour and the drawbar gripper. You can get proper dwg drawings from acrow, they carry normal bt grippers and ott style. ott cost the same so I'd go with them, also because its a pain to get mas403 drawing standard, and ott makes sk30 readily available. if you want accurate toolholders just download the 3d models from sandvik coromant, if you make the taper angle correct in your cad you can add an assembly constrait that will mate the tapers perfectly together without an error.
On another note, I'd go without rigid tapping and instead do thread milling with multiple flutes. Rigid tapping has size limitations on top of torque and synchronous action. In my opinion not worth the trouble. With thread milling you can machine any thread size and if you use multiple flutes it can be as fast as rigid tapping.
I will have to look into the thread milling with multiple flutes, it does sound better to me, I know the taps can be very weak too and I would hate breaking those due to programming not being 100% correct or a blip in the servo motors encoder. Could you imagine, that would be terrible.
Also I have made the 7/24 Taper, I will do exactly as you said and get the toolholders models from sandvik, I also have already purchased the SK30 but there is no 3D model, I got mine off ebay because the dutch website didn't respond. I actually bought two different ones, maybe they are the same who knows. But the models seem to be missing cooling components. I would love to be able to add water cooling to the outside body which of course would be easy for me to do myself, but designing an entire BT30 sounds like a good challenge and I really hate having a Solid Edge 3D Model without all the parts and by all the parts I mean in full detail :) I will send updates tomorrow as we proceed. Also I will see about a Servo that can accomplish 15,000 RPM I do agree that might be difficult to find haha.
Re: Yet another BT30 Design and Build Adventure.
sk30 is really easy to model, if you mail acrow they will send you the desired dwg that you can directly extrude/revolve a feature from. Just ask for the gripper drawing and the drawing will come together with the inside contour its compatible with.
By cooling components you mean in the spindle or through the gripper? In the gripper that's usually just a thin hole in the middle, for the spindle, only google images is left as there is no iso/din standard as far as I'm aware about cooling lines.
At this speed you're probably looking at synchronous ac motors like pmsm's. Although one could argue that you don't need it as synchronous because you don't need rigid tapping. Is yours a motorized spindle, or a cartridge that's belt/direct driven via an external motor?
Re: Yet another BT30 Design and Build Adventure.
Quote:
Originally Posted by
ardenum
sk30 is really easy to model, if you mail acrow they will send you the desired dwg that you can directly extrude/revolve a feature from. Just ask for the gripper drawing and the drawing will come together with the inside contour its compatible with.
By cooling components you mean in the spindle or through the gripper? In the gripper that's usually just a thin hole in the middle, for the spindle, only google images is left as there is no iso/din standard as far as I'm aware about cooling lines.
At this speed you're probably looking at synchronous ac motors like pmsm's. Although one could argue that you don't need it as synchronous because you don't need rigid tapping. Is yours a motorized spindle, or a cartridge that's belt/direct driven via an external motor?
We are looking at a belt-driven spindle, but if I could find a servo motor to put inline I would rather that, I was thinking about running a gearbox to obtain multiple speeds but I am thinking about the practicality of that. I won't be using Mach 3 that's for sure. I was thinking about running closed-loop servo motors but then I wouldn't have any feedback and if we had a crash or something bad which you should never have, but we all know does happen there would be no way to detect the crash with a closed-loop system, but if the servo motor driver had an output when the motor is not within the parameters of acceptance, meaning when the motor is supposed to spin 100 times but only spins 90 times around, I would like a fault. I'm not exactly sure this is something a closed-loop system could do, thoughts? We do not play too much with servo motors with encoders and drivers. Usually pistons, steppers, or non-encoder-driven servos, we have done servo systems also with PLC but not super complicated like this. do you have the email address for acrow? I think I will have to stick with belt-driven, no gearboxes, but we could have two pulleys on the motor to change speed, perhaps. For cooling yeah, I was looking at cooling the body, not the shaft. I don't think cooling the shaft is required.
Re: Yet another BT30 Design and Build Adventure.
Quote:
Originally Posted by
gloveless
I was thinking about running closed-loop servo motors but then I wouldn't have any feedback and if we had a crash or something bad which you should never have, but we all know does happen there would be no way to detect the crash with a closed-loop system, but if the servo motor driver had an output when the motor is not within the parameters of acceptance, meaning when the motor is supposed to spin 100 times but only spins 90 times around, I would like a fault. I'm not exactly sure this is something a closed-loop system could do, thoughts?
By definition all servos are closed loop, the loop can be closed at the drive or the controller.
Every servo drive I have seen has an error (fault) output. Most have a settable encoder error limit parameter, where if the following error becomes too great or the servo is greatly overloaded, then the servo drive will shut down and trigger the fault output.
Rigid tapping does not require a servo motor, all that is required is an encoder on the spindle and the proper software to electronically gear the spindle to the Z axis.
Re: Yet another BT30 Design and Build Adventure.
Quote:
Originally Posted by
gloveless
We are looking at a belt-driven spindle, but if I could find a servo motor to put inline I would rather that, I was thinking about running a gearbox to obtain multiple speeds but I am thinking about the practicality of that. I won't be using Mach 3 that's for sure. I was thinking about running closed-loop servo motors but then I wouldn't have any feedback and if we had a crash or something bad which you should never have, but we all know does happen there would be no way to detect the crash with a closed-loop system, but if the servo motor driver had an output when the motor is not within the parameters of acceptance, meaning when the motor is supposed to spin 100 times but only spins 90 times around, I would like a fault. I'm not exactly sure this is something a closed-loop system could do, thoughts? We do not play too much with servo motors with encoders and drivers. Usually pistons, steppers, or non-encoder-driven servos, we have done servo systems also with PLC but not super complicated like this. do you have the email address for acrow? I think I will have to stick with belt-driven, no gearboxes, but we could have two pulleys on the motor to change speed, perhaps. For cooling yeah, I was looking at cooling the body, not the shaft. I don't think cooling the shaft is required.
This is not complicated at all it is even simpler than what you did in the past, most modern AC Servos Drives close the loop and can have feedback to a control if needed, they have a fault output which can be add to any safety circuit, so if a Servo Drive was to fault then everything would shut down
Depending on the motor you use you can have any speed you want with a servo motor, or if a AC 3Ph motor you would be using a VFD Drive which again you can vari the speed of the motor within the limits of the motor and the torque you need.
If it is a real Servo motor it needs an Encoder, it won't run very well without it. you will see people call there motor a Servo Motor but they are not using a servo motor, they may have a PM motors which are quite common and have a Drive that suits for a PM motor
The PLC is the control nothing more, this feeds the programed signal to the Servo Drive
Re: Yet another BT30 Design and Build Adventure.
Quote:
Originally Posted by
gloveless
We are looking at a belt-driven spindle, but if I could find a servo motor to put inline I would rather that, I was thinking about running a gearbox to obtain multiple speeds but I am thinking about the practicality of that. I won't be using Mach 3 that's for sure. I was thinking about running closed-loop servo motors but then I wouldn't have any feedback and if we had a crash or something bad which you should never have, but we all know does happen there would be no way to detect the crash with a closed-loop system, but if the servo motor driver had an output when the motor is not within the parameters of acceptance, meaning when the motor is supposed to spin 100 times but only spins 90 times around, I would like a fault. I'm not exactly sure this is something a closed-loop system could do, thoughts? We do not play too much with servo motors with encoders and drivers. Usually pistons, steppers, or non-encoder-driven servos, we have done servo systems also with PLC but not super complicated like this. do you have the email address for acrow? I think I will have to stick with belt-driven, no gearboxes, but we could have two pulleys on the motor to change speed, perhaps. For cooling yeah, I was looking at cooling the body, not the shaft. I don't think cooling the shaft is required.
[email protected]
Gearboxes for spindles are quite complicated and custom, don't think that's where you'd wanna go.
Re: Yet another BT30 Design and Build Adventure.
Quote:
Originally Posted by
Jim Dawson
By definition all servos are closed loop, the loop can be closed at the drive or the controller.
Every servo drive I have seen has an error (fault) output. Most have a settable encoder error limit parameter, where if the following error becomes too great or the servo is greatly overloaded, then the servo drive will shut down and trigger the fault output.
Rigid tapping does not require a servo motor, all that is required is an encoder on the spindle and the proper software to electronically gear the spindle to the Z axis.
I understand that, I read that Linux CNC can close the loop, to you is there a huge improvement vs closing the loop at the brain or the drive controller?
I'm not sure myself what the big difference would be and I have seen a lot of people bicker back and forth about which one is better but in the end, it seemed no one that I read really had a winning argument over real-life scenarios where someone would close the loop on the motor vs the controller. Would you have any insight on this, if it really makes a difference and if it's even worth it?
Re: Yet another BT30 Design and Build Adventure.
Quote:
Originally Posted by
gloveless
I understand that, I read that Linux CNC can close the loop, to you is there a huge improvement vs closing the loop at the brain or the drive controller?
I'm not sure myself what the big difference would be and I have seen a lot of people bicker back and forth about which one is better but in the end, it seemed no one that I read really had a winning argument over real-life scenarios where someone would close the loop on the motor vs the controller. Would you have any insight on this, if it really makes a difference and if it's even worth it?
It really depends on your control system (''brain''). Today I don't think it makes a lot of difference if you close the loop at the controller (''brain'') or the drive. The old way of doing it was to close the loop at the controller because the drives had no ability to accept position commands and they could only be controlled by an analog signal. Today most drives can close the loop at the drive or controller and accept analog, step & direction, or Ethernet/Modbus control.
Personally I prefer to close the loop at the controller because I'm old and still do things the old way. I prefer Galil Motion Controllers because they can output either step & direction or analog. The simplest system is to close the loop at the drive using step & direction commands for positioning.
Re: Yet another BT30 Design and Build Adventure.
Quote:
Originally Posted by
ardenum
[email protected]
Gearboxes for spindles are quite complicated and custom, don't think that's where you'd wanna go.
Yeah, I thought about it last night and no, I don't want to do that.
Re: Yet another BT30 Design and Build Adventure.
What do you think about OTT Pull Style claws with a female thread, vs the normal ones with a male thread? I really like this type of design, thoughts?
https://chuck-tools.chumpower.com/en...cts_i_OTT.html
Re: Yet another BT30 Design and Build Adventure.
Quote:
Originally Posted by
gloveless
yes that's the standard ott design, but that's overpriced, hsk grippers cost that much not bt.
Re: Yet another BT30 Design and Build Adventure.
Quote:
Originally Posted by
ardenum
yes that's the standard ott design, but that's overpriced, hsk grippers cost that much not bt.
Okay, gotcha, where do you normally get your grippers?
Re: Yet another BT30 Design and Build Adventure.
Quote:
Originally Posted by
gloveless
Okay, gotcha, where do you normally get your grippers?
from acrow. If I recall the bt30 ott style was about $160 for a sample. I got one from aliexpress though, didn't wanna deal with the B2B shenanigans just for one piece. After looking at it physically I think I'll be making my own from now on. That's because I'll also be repurposing their drawing for a pallet clamping system. Did you get that drawing from them?
Re: Yet another BT30 Design and Build Adventure.
Quote:
Originally Posted by
ardenum
from acrow. If I recall the bt30 ott style was about $160 for a sample. I got one from aliexpress though, didn't wanna deal with the B2B shenanigans just for one piece. After looking at it physically I think I'll be making my own from now on. That's because I'll also be repurposing their drawing for a pallet clamping system. Did you get that drawing from them?
I haven't done it yet, we just had our newborn so I've been busy and tired and not tired all at the same time haha :)
But I hope to revisit this or next week and get those drawings sorted out. I did finally figure out how everything should be correct as far as the 7:24 ratio goes, I got the taper finished and everything the only other thing I'm figuring out is those clamps, trying to make sure we have enough tolerance to fit the clamps, I have been looking and it seems the sizes do vary so its a bit misleading right.
