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IndustryArena Forum > Mechanical Engineering > Mechanical Calculations/Engineering Design > Need help brainstorming a solution for this mill turn spindle
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  1. #81
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    Re: Need help brainstorming a solution for this mill turn spindle

    Quote Originally Posted by QuinnSjoblom View Post
    Saying that belts only stretch unless overloaded is incorrect. Same with tooth deflection. Any load at all will cause tooth deflection and belt stretch, it's just a question of how much. Everything in this universe deflects with any amount of pressure. If you place a grain of rice on the corner of a 12 inch thick chunk of granite, the granite bends. There is no such thing as "no deflection". Tooth deflection and belt stretch is proportional to belt width. The fact that you say things like "there will be no stretch" makes me think you don't understand these facts. There will always be stretch and tooth deflection. The goal is to reduce it as much as possible. There is no point where it's eliminated completely. It's the laws of physics

    And once again, the 50mm may very well be overkill and beyond what's going to give significant improvent, but I definitely dont believe there's no reason to go bigger than 16mm. The more deflection there is, the worse chatter will be during machining.
    If you place a grain of rice on the corner of a 12 inch thick chunk of granite, the granite bends that's just to funny to make a comment (nuts)

    It's all about Design once a Belt has been correctly Tensioned to the manufactures spec's it does not stretch anymore unless the load exceeds the spec's you obvious have not put/used any design spec's for your belt and just gone bigger is better

    First you need an understanding of physics before you make those quotes

    I'm sure what ever you end up with it will be perfect
    Mactec54

  2. #82
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    Quote Originally Posted by mactec54 View Post
    If you place a grain of rice on the corner of a 12 inch thick chunk of granite, the granite bends that's just to funny to make a comment (nuts)

    It's all about Design once a Belt has been correctly Tensioned to the manufactures spec's it does not stretch anymore unless the load exceeds the spec's you obvious have not put/used any design spec's for your belt and just gone bigger is better

    First you need an understanding of physics before you make those quotes

    I'm sure what ever you end up with it will be perfect
    So you're really trying to say once the belt is tensioned, there be ZERO stretch and tooth deflection until you exceed the specs? Sorry man, you're wrong. Yes I understand the physics of it and it doesn't work that way. Are you disagreeing with the comment about the grain of rice on the slab of granite? Because it's absolutely true. Yes, my belt might be overkill, but your idea of a zero deflection situation is a fantasy. Everything deflects. It can't be avoided. There is no magical material that doesn't stretch/compress when applying a load. We obviously have 2 different ideas of how the laws of physics work so there's no point arguing it anymore. I've already admitted my belt may be wider than what is significantly advantageous, and if it causes problems i will go down to 30mm, but your scenario of zero deflection under load just doesn't exist.

  3. #83
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    Re: Need help brainstorming a solution for this mill turn spindle

    Quote Originally Posted by QuinnSjoblom View Post
    So you're really trying to say once the belt is tensioned, there be ZERO stretch and tooth deflection until you exceed the specs? Sorry man, you're wrong. Yes I understand the physics of it and it doesn't work that way. Are you disagreeing with the comment about the grain of rice on the slab of granite? Because it's absolutely true. Yes, my belt might be overkill, but your idea of a zero deflection situation is a fantasy. Everything deflects. It can't be avoided. There is no magical material that doesn't stretch/compress when applying a load. We obviously have 2 different ideas of how the laws of physics work so there's no point arguing it anymore. I've already admitted my belt may be wider than what is significantly advantageous, and if it causes problems i will go down to 30mm, but your scenario of zero deflection under load just doesn't exist.
    We obviously have 2 different ideas of how the laws of physics work Yes it's called education

    As I said do the calculation's the spec's are out there, and many are doing this in commercial installations just as you want to do
    Mactec54

  4. #84
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    Quote Originally Posted by mactec54 View Post
    We obviously have 2 different ideas of how the laws of physics work Yes it's called education

    As I said do the calculation's the spec's are out there, and many are doing this in commercial installations just as you want to do
    "Yes it's called education"
    Which you must not have had if you believe there's anything in this universe that doesn't deflect under load. Why do you think gates has polychain carbon gt belts? One of the reasons is to reduce belt stretch. All belts have SOME stretch after being tensioned correctly and used within their specs.
    If you want to go with the education comment, why don't we start with basic punctuation in a sentence before moving on to physics.

  5. #85
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    Re: Need help brainstorming a solution for this mill turn spindle



    Calm down, fellas.

    There's classical education (which acknowledges the 0.7 femtometre deflection of a block of granite yadda yadda yadda). Useful for scaling up into practical models that predict real things in the real world but, yeah, sometimes you can get lost in all those decimal places.

    Then there's the "school of hard knocks" which quite clearly states in lesson plan #17a of the unit "You young pricks don't know what the fvck you're talking about, back when I was your age I used to scrape the last three thousandsthtshts off an engine block with my foreskin" that "sixteen mm gates wraps will be right until they're not."

    Jeez, Quinn, have a little respect for your elders and be grateful for their wisdom you heathen.

    Surely there's got to be somewhere in the middle that works. Quinn - your 50m gut feels like a massive overkill unless your machine's gantry is a real bridge that crosses rivers and carries trucks or trains. That said, if you can afford the hardware and the money's not better shoved into other structure then fuggit, why not?!!

    Mactec: you've obviously reached that apogee in your life where feedback from mortals is of no value to you. Much as I'd like to help: I got nothing.

    But can't we all just get along?

    (hope not, just made popcorn)


  6. #86
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    Re: Need help brainstorming a solution for this mill turn spindle

    Well this conversation has spiraled down a rabbit hole more times than I could count while reading through the 7 pages

    Quinn, you are correct about the DMM drive limitation, I faced the same issue when setting up my servo spindle although I didn't run into a need for ultra fine positioning like you do. Totally agree with your concerns.Unfortunately, your only solution would be to select a drive/servo with a high encoder resolution AND a higher input frequency. I am using Allen Bradley Ultra 3000 drives with AB bulletin MPL motors. Something like 2 million counts per rev with a 4MHz input frequency.

    You are also correct about belt stretch. I would be willing to bet that your machining on a part held still by the belt and servo would have pretty poor rigidity even with the wide belt. The problem is that DMM servos (and most servos) don't respond well to high frequency loads like would be encountered during machining (tuning issues) and a belt will never be perfectly rigid. If you were to tension the belt high enough to get acceptable stiffness, you would likely run into problems with side loading of the shafts and issues at higher speeds. You might want to consider a disc brake for clamping the workpiece when indexing.

    Last comment on the belt (found through painful experience) is at higher speeds, timing belts suck air into the teeth of the pulley and make a loud pop when exiting. When this happens a few hundred times a second, the belt noise can get pretty crazy. I talked with engineers at SDP-SI and their recommendations were to use a belt with smaller teeth (I changed from a L series to a GT3 series pulley), select a curvilinear tooth profile (GT2, GT3, etc), select a fabric faced belt, and if wider belt widths are required for stiffness or load, use multiple thinner belts in tandem (allowing air to escape between the belts). This coupled with a low belt tension took my spindle from a painful 86dBA to a comfortable 68dBA. This was at 5000rpm.

    At the end of the day, tuning the servo to hold acceptable stiffness will most likely contribute 90% of the issue you have with deflection under load compared to the belt.

    Don't claim to be an expert on anything here, but my comments come from knowledge gained as an engineer at a major industrial automation company doing servo motor applications (and tuning ).

    Lets try to keep everything civil here, it is better for everyone who would want to learn from this conversation in the future.

  7. #87
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    Re: Need help brainstorming a solution for this mill turn spindle

    Yes, it has gotten quite out of hand. It's just hard for me to not respond in a harsh way when I'm basically told I must not have an education if I think there's going to be stretch and tooth deflection in a belt being used within it's limits. There's always stretch and deflection, no matter the size of the belt. Also didn't help that he was telling me the first half of this thread that im wrong about the resolution vs speed problem which I know for a fact is correct. You can't get 3k rpm with full encoder resolution using a 500khz drive being driven by step/dir. It's hard to let it go when someone continuously tells you you're wrong about something that you know you're not wrong about.
    As for my 50mm wide belt, yes it's probably overkill which I've said a few times and if it becomes a problem, I'll go down to smaller belt. I sourced pulleys and belts on ebay for pretty cheap so experimentation is not really that expensive. As for radial load from proper tension on the 50mm belt, I've used gates calculators and everything is well within limits. The servo shaft will only be at about one third of its max rated radial load when the belt is tensioned properly. As for the servo holding position well enough for machining, definitely possible it's not gonna cut it and I'm keeping it an option to add the brake later if needed. I'm hoping for the best. All i can do is try it out without the brake and see if it will work for me. If not I'll add the brake.
    The popping noise of the timing belt at speed is new to me. Hopefully it's not too terrible. I'm building a sheet metal enclosure around the pulleys/belts so hopefully that will help. My machine is also in a sound proof enclosure.
    Thanks for the advice guys. I'm hoping for good results, but I'm sure I will run into the need for possible changes. The spindle and servo were the big ticket items. Experimenting with a few versions of the rest of the components to see what works best won't be a huge deal. I got an awesome deal on a pile of 1 inch thick 7075 plate to use for this and a few other projects

    Oh, I talked about the resolution problem earlier in one of my posts. It's going to work for me as long as my electrical gearing is a binary multiple. Here's a quote from earlier:


    After thinking about it, I decided this setup will live most of its life at the 1 to 1 mechanical ratio, 8 to 1 electrical, 3000rpm turning. Here's what i realized, 90 percent of the work I do will be turning, then 90 or 45 degree indexing with an irrelevant starting azimuth. As long as my mechanical ratio is a whole number (1-1,1-2,1-3, etc), and my electrical gearing is a binary multiple (1,2,4,8,16, etc), i will get precise indexing of 180deg, 90deg, 45deg, 22.5deg, etc., even though step res is .04 degree. Those indexing points will land exactly on full steps. A couple limitations to this, I can't load a part that already has a flat surface and dial it in to sweep perfectly flat, it would have to be dialed in to nearest .04 degree, or ease up on the drawbar and tap it into flat. This is not something I'll be doing though. All indexing happens at once starting with a round part. Other limitation is hex features. The binary gearing won't put full steps on 60 degree divisions. The workaround is easy, when I need a hex pattern, or dial in an existing flat feature, or anything else that needs higher res, I just drop the electrical gearing out and have .005deg step with 375rpm limit. Plenty of resolution for anything I would need to do including hobbing. If for some reason I want more, throw the 25t on the servo and get .0025deg step. As for holding torque with 1-1 mechanical, it's way more than enough after calculating machining forces at given radius with the work I do. I think the setup should work quite well, and since I work with almost exclusively aluminum, 3000rpm will definitely be an advantage over 1500rpm.

  8. #88
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    Re: Need help brainstorming a solution for this mill turn spindle

    Quote Originally Posted by mcardoso View Post
    Well this conversation has spiraled down a rabbit hole more times than I could count while reading through the 7 pages

    Quinn, you are correct about the DMM drive limitation, I faced the same issue when setting up my servo spindle although I didn't run into a need for ultra fine positioning like you do. Totally agree with your concerns.Unfortunately, your only solution would be to select a drive/servo with a high encoder resolution AND a higher input frequency. I am using Allen Bradley Ultra 3000 drives with AB bulletin MPL motors. Something like 2 million counts per rev with a 4MHz input frequency.

    You are also correct about belt stretch. I would be willing to bet that your machining on a part held still by the belt and servo would have pretty poor rigidity even with the wide belt. The problem is that DMM servos (and most servos) don't respond well to high frequency loads like would be encountered during machining (tuning issues) and a belt will never be perfectly rigid. If you were to tension the belt high enough to get acceptable stiffness, you would likely run into problems with side loading of the shafts and issues at higher speeds. You might want to consider a disc brake for clamping the workpiece when indexing.

    Last comment on the belt (found through painful experience) is at higher speeds, timing belts suck air into the teeth of the pulley and make a loud pop when exiting. When this happens a few hundred times a second, the belt noise can get pretty crazy. I talked with engineers at SDP-SI and their recommendations were to use a belt with smaller teeth (I changed from a L series to a GT3 series pulley), select a curvilinear tooth profile (GT2, GT3, etc), select a fabric faced belt, and if wider belt widths are required for stiffness or load, use multiple thinner belts in tandem (allowing air to escape between the belts). This coupled with a low belt tension took my spindle from a painful 86dBA to a comfortable 68dBA. This was at 5000rpm.

    At the end of the day, tuning the servo to hold acceptable stiffness will most likely contribute 90% of the issue you have with deflection under load compared to the belt.

    Don't claim to be an expert on anything here, but my comments come from knowledge gained as an engineer at a major industrial automation company doing servo motor applications (and tuning ).

    Lets try to keep everything civil here, it is better for everyone who would want to learn from this conversation in the future.
    Fortunately the OP won't have to do much with servo tuning as Dmm have auto tuning and adaptive control, there are only 3 parameters to change so a very simple servo drive to setup

    I agree with that the his biggest problem will be making everything rigid enough especially the mechanics for the belt tensioning

    Guys you all need to rethink this and what he is doing, Quinn stated he is only going to be machining up to 1" diameter 25mm material, all the tech information is available from Gates, Education on Belt sizing, the belt he has selected a plus 100 Hp belt that will be driven by a 1.8KW motor or 2.4Hp, you can figure this out for yourselves

    Yes there is always some stretch and deflection but is all controllable if you design it correctly, correctly tensioned will be the first step all these belts have a cord modulus that you have to work with, and if you know what you are doing you can eliminate most of any stretch problems, the belt drive I posted a photo of has a 1micron resolution
    Mactec54

  9. #89
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    Quote Originally Posted by mactec54 View Post
    Fortunately the OP won't have to do much with servo tuning as Dmm have auto tuning and adaptive control, there are only 3 parameters to change so a very simple servo drive to setup

    I agree with that the his biggest problem will be making everything rigid enough especially the mechanics for the belt tensioning

    Guys you all need to rethink this and what he is doing, Quinn stated he is only going to be machining up to 1" diameter 25mm material, all the tech information is available from Gates, Education on Belt sizing, the belt he has selected a plus 100 Hp belt that will be driven by a 1.8KW motor or 2.4Hp, you can figure this out for yourselves

    Yes there is always some stretch and deflection but is all controllable if you design it correctly, correctly tensioned will be the first step all these belts have a cord modulus that you have to work with, and if you know what you are doing you can eliminate most of any stretch problems, the belt drive I posted a photo of has a 1micron resolution
    Look at my first post. I said MOSTLY up to 2 inch diameter, not one inch, with enough torque capability and rigidity for machining out at a radius of 2.5 inches on a horizontal mini tombstone. It's all laid out in my original post. Yes, a large amount of my parts will be 1 inch, but not limited to that. My 5c spindle has a hardinge 4 degree taper nose so I have the capability to run large step chucks with closing rings. If I was truly limited to 1 inch, then yes it could be a tiny belt but that's not the case.

  10. #90
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    Re: Need help brainstorming a solution for this mill turn spindle

    Quote Originally Posted by QuinnSjoblom View Post
    Look at my first post. I said MOSTLY up to 2 inch diameter, not one inch, with enough torque capability and rigidity for machining out at a radius of 2.5 inches on a horizontal mini tombstone. It's all laid out in my original post. Yes, a large amount of my parts will be 1 inch, but not limited to that. My 5c spindle has a hardinge 4 degree taper nose so I have the capability to run large step chucks with closing rings. If I was truly limited to 1 inch, then yes it could be a tiny belt but that's not the case.
    Well you are going to need more Hp then, you can always take light cuts though, for a comparison the small PC Emco lathes that have your spindle size start at 5Hp
    Mactec54

  11. #91
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    Quote Originally Posted by mactec54 View Post
    Well you are going to need more Hp then, you can always take light cuts though, for a comparison the small PC Emco lathes that have your spindle size start at 5Hp
    For turning operations I won't be going much larger than 1.5 inches. The bigger stuff like the mini tombstone will just be index milling. The servo is rated at 1.8kw continuous but can handle a peak torque of about 22 foot pounds. I talked to dmm and they said I could figure the peak torque as my max holding torque For index milling. At a radius of 2.5 inches on the tombstone, this allows me up to 105lb of tool pressure before the servo will fault. I should be well within those limits. It's just gonna come down to how well the servo responds to oscillating pressure like an endmill would apply. I think dmms auto tuning is more to do with the inertia of the axis. It will run through its auto tune cycle and come up with some gains based on the mass of the rotating assemblies but I'm not sure it does much auto tuning to help deal with oscillating forces. With a 1 to 1 ratio, I'm sure it's much harder for the servo to deal with. I can also choose tooling to give more consistent forces rather than oscillating, like higher helix, and always try to maintain full helix engagement as much as possible rather than jumping from one flute to the next during cutting. Should be easier for the servo to deal with holding position. So anyway, I have some things to try and if I don't get satisfactory results, I'll have to add a brake. If I start seeing less than acceptable surface finish, it will be easy to narrow down where the weak point is. I can try locking the servo shaft and if it gets better, it means the servo is having a hard time managing the forces, if there's no improvememt when locking servo shaft, it means the belt is the weak point. I can rule out other workholding rigidity problems by locking the spindle.

  12. #92
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    Re: Need help brainstorming a solution for this mill turn spindle

    Quote Originally Posted by QuinnSjoblom View Post
    For turning operations I won't be going much larger than 1.5 inches. The bigger stuff like the mini tombstone will just be index milling. The servo is rated at 1.8kw continuous but can handle a peak torque of about 22 foot pounds. I talked to dmm and they said I could figure the peak torque as my max holding torque For index milling. At a radius of 2.5 inches on the tombstone, this allows me up to 105lb of tool pressure before the servo will fault. I should be well within those limits. It's just gonna come down to how well the servo responds to oscillating pressure like an endmill would apply. I think dmms auto tuning is more to do with the inertia of the axis. It will run through its auto tune cycle and come up with some gains based on the mass of the rotating assemblies but I'm not sure it does much auto tuning to help deal with oscillating forces. With a 1 to 1 ratio, I'm sure it's much harder for the servo to deal with. I can also choose tooling to give more consistent forces rather than oscillating, like higher helix, and always try to maintain full helix engagement as much as possible rather than jumping from one flute to the next during cutting. Should be easier for the servo to deal with holding position. So anyway, I have some things to try and if I don't get satisfactory results, I'll have to add a brake. If I start seeing less than acceptable surface finish, it will be easy to narrow down where the weak point is. I can try locking the servo shaft and if it gets better, it means the servo is having a hard time managing the forces, if there's no improvememt when locking servo shaft, it means the belt is the weak point. I can rule out other workholding rigidity problems by locking the spindle.
    Your servo is on the end of your belt I doubt that it will see much in the way of milling oscillations, the belt will absorb a lot of the milling action, if the servo drive is set correct the milling should have very little affect on the servo motor a Brake is the normal thing that most have for a build like this

    What you do for tuning you set what you think you want then auto tune, auto tune will only correct if you are way off with your settings, so can't really go wrong with there system

    If you have any servo motor oscillation problems you only have 3 parameters to play with, a servo motor like this you should never have an oscillation of any kind

    I have never used there auto tuning, but must give it a try sometime to see if it make any improvement over how I set them up, I know others have had good results from using it

    Warning you can not mechanically lock the servo motor shaft with the power ON
    Mactec54

  13. #93
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    Re: Need help brainstorming a solution for this mill turn spindle

    "Warning you can not mechanically lock the servo motor shaft with the power ON"

    I was thinking that might be the case. If it locks in a position that's a fraction of a degree off where it wants to be, I assume it over loads and faults.

    I'll start with at least a simple locking mechanism for the spindle so I can see the difference in surface finish with it locked vs unlocked and decide from there if I want to add an automated brake. Main reason I want to avoid the brake if possible is because of how code needs to be done. Easy enough to manually add in to gcode before and after all A moves, but I want to streamline the process as much as possible from cam to machining. Might be able to have a post processor edited to add in the enable and disable before and after A axis moves. If I end up adding the brake, I'll downsize the belts to 25mm wide 5mgt profile. 5mgt has slightly less backlash than 8mgt, and also probably quieter so that would be another added benefit.

  14. #94
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    Re: Need help brainstorming a solution for this mill turn spindle

    Quote Originally Posted by QuinnSjoblom View Post
    "Warning you can not mechanically lock the servo motor shaft with the power ON"

    I was thinking that might be the case. If it locks in a position that's a fraction of a degree off where it wants to be, I assume it over loads and faults.

    I'll start with at least a simple locking mechanism for the spindle so I can see the difference in surface finish with it locked vs unlocked and decide from there if I want to add an automated brake. Main reason I want to avoid the brake if possible is because of how code needs to be done. Easy enough to manually add in to gcode before and after all A moves, but I want to streamline the process as much as possible from cam to machining. Might be able to have a post processor edited to add in the enable and disable before and after A axis moves. If I end up adding the brake, I'll downsize the belts to 25mm wide 5mgt profile. 5mgt has slightly less backlash than 8mgt, and also probably quieter so that would be another added benefit.
    Correct, a post processor just for that type of operations is not much to add just a M code that may be used for Tool clamp M25 Unclamp M26 these are standard codes
    Mactec54

  15. #95
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    Quote Originally Posted by mactec54 View Post
    Correct, a post processor just for that type of operations is not much to add just a M code that may be used for Tool clamp M25 Unclamp M26 these are standard codes
    Problem is, it gets a bit messy in my case. If it was just a 4th axis, the post would just need to be set up so the m25/m26 happens before and after A axis moves. Since its a mill turn, I'll have a swap axis macro for switching it back and forth from A axis to spindle for turning operations. This means the brake will also need to deactivate for an sxxx m3 command, but only when the swap axis is active. I suppose it could be setup in a way so that if the swap axis is active, the brake is deactivated in that same macro until the reset swap axis runs at which time the brake becomes reactivated, and then the post processor can just be setup to deactivate brake before A axis move, active after A axis move. Kind of a headache. That's why I was really hoping to just eliminate the whole brake mess with a rigid enough belt setup.

  16. #96
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    Re: Need help brainstorming a solution for this mill turn spindle

    Quote Originally Posted by QuinnSjoblom View Post
    Problem is, it gets a bit messy in my case. If it was just a 4th axis, the post would just need to be set up so the m25/m26 happens before and after A axis moves. Since its a mill turn, I'll have a swap axis macro for switching it back and forth from A axis to spindle for turning operations. This means the brake will also need to deactivate for an sxxx m3 command, but only when the swap axis is active. I suppose it could be setup in a way so that if the swap axis is active, the brake is deactivated in that same macro until the reset swap axis runs at which time the brake becomes reactivated, and then the post processor can just be setup to deactivate brake before A axis move, active after A axis move. Kind of a headache. That's why I was really hoping to just eliminate the whole brake mess with a rigid enough belt setup.
    I would write the 2 programs separate and cut/paste them as needed for each operation, unless you have very expensive software like Gibbs Cam that does Mill Turn operations I don't see any other simple way you can do it, even with a custom postprocessor it is still going to be a task, macro's should work, but not always needed when you do separate programs each operation could still be continuous, unless you wanted to use a cycle start for each operation
    Mactec54

  17. #97
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    Quote Originally Posted by mactec54 View Post
    I would write the 2 programs separate and cut/paste them as needed for each operation, unless you have very expensive software like Gibbs Cam that does Mill Turn operations I don't see any other simple way you can do it, even with a custom postprocessor it is still going to be a task, macro's should work, but not always needed when you do separate programs each operation could still be continuous, unless you wanted to use a cycle start for each operation
    Yeah, I am gonna have to post turning and milling separately, then paste together. Mach3 wants Fanuc turning post from fusion 360 for turning and mach3 post for milling. Fusion cam will let me post milling ops and turning ops together, but I would need some post work for both to work. When trying to post the turning code with mach3 post, it just fails.
    A lot of the turning I need to do is pretty basic, so in some cases I'll just cam the 4 axis milling from fusion and hand write the few turning moves it needs to do before the milling. I can actually hand write these into manual nc in fusion and it will post it all together that way. I'll try a few different ways and see what work flow is easiest. It's really not a huge deal to put some extra work in the code. The goal with my mill turn is to produce batches of 50 parts or so at a time. About 8 different parts on my airframe design that are gonna be really quick on the mill turn. Before they needed many setups to get one part done. Now it will be 1, or 2 at the most. Once I add an air closer and bar puller, I could really be pumping some parts out.

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    Duplicate

  19. #99
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    Quote Originally Posted by QuinnSjoblom View Post
    Duplicate
    Couple pics attached below

    Almost ready to test the first version. Had to get a bit tricky with the servo mounting to get the clearance i want in the front end. Servo is mounted with the backside of the flange. Otherwise it would have stuck out past the spindle nose, which could have worked but would have limited turning tool mounting options. It's still quite stout as it is. All 7075 aluminum. Base plate and main vertical plate is 7/8 thick and 5/8 thick corner supports. I designed a simple brake assembly that tightens with a bolt but it's not assembled yet. It's purpose is just to compare surface finish with spindke locked vs unlocked. If the finish is significantly better with the spindle locked, I will probably redesign with narrower belt and actuated disk brake. This design is currently using the huge 50mm wide belt. The spindle headstock is mounted into a matching pocket that allows 15mm of lateral movement while keeping it coplanar with servo for tensioning the belt. There is a single bolt that is turned to pull the spindle over to set tension, then tighten the 4 bolts to secure it. Haven't powered up the servo yet, but I did get the tension set and turned it at about 2k rpm using a drill. Not hearing the loud popping noise that was mentioned earlier. It's very smooth and quiet. I don't think the large belt is gonna cause any issues. Should have it fired up this weekend, just waiting for line reactor, filter, and contactor to show up. This things is quite the chunk. About 80 pounds total. Not easy to pick up.

  20. #100
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    Re: Need help brainstorming a solution for this mill turn spindle

    Hi Quinn - I'm interested why you have used 7075. My experience of the stuff is that it will slowly turn to white powder unless you anodise it? Peter

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