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  1. #61
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    Default Re: Large Epoxy granite VMC building

    Hi Azalin,
    I don't think that is quite what I had in mind. I think that setting modifies the behavior of the Space Vector Modulator which is the drive output mechanism.
    It sounds like it might get you a few more rpm but it also sounds a crude way to achieve it, I imagine the electrical noise of the drive would go from
    bad (normal for servo drives) to shocking!

    May I suggest searching Google for some videos put together by Texas Instruments about (and search by) Field Oriented Control. It a fascinating subject.
    The upshot is that to maximize torque of an AC servo the applied field current must be in phase-quadrature with the field of the rotor. The control algorithm
    results in controlling two parameters, Iq, the quadrature current and Is the in-phase current.

    For a permanent magnet rotor you don't need any in-phase current to maintain the rotor field, so consequently for AC servo the controller tries to maintain
    Is at zero. This ensures maximum torque for the least current but also ensures maximum Back EMF and therefore determines the highest
    possible speed with a given supply voltage.

    Where field weakening comes into play is when the controller tries to maintain Is at a negative value and therefore a fraction of the applied
    field current is OPPOSED to the permanent magnet thereby reducing (weakening) the net rotor field. This in turn allow a reduction in Back EMF and therefore allows
    a greater top speed with the same supply voltage.


    The application of field weakening is progressive and smooth and linear. It does not in any way degrade the performance of the servo or unduly pollute the
    power supply. Note that the application of field current to reduce the net rotor field is reversible, ie when the field weakening component of the current is
    discontinued the rotor field returns t normal.

    This is a very clever idea! I recommend to you those videos, it will give you a true appreciation of how AC servos work and why all electromotive control
    engineers are nervous, chain smoking wrecks....like me!

    Craig



  2. #62
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    Default Re: Large Epoxy granite VMC building

    well since we have an expert here, I want to monitor the load on the motors, for the axis 1kw servos I bought three 15A AC Amp meters the drivers are single phase sop it's easy, now for the spindle the driver is 3 phase how can I monitor the thing?

    best regards



  3. #63
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    Default Re: Large Epoxy granite VMC building

    Hi,
    You don't need any clamp meters or anything else.

    Each servo drive has current sensors built in. They are required for the control loop electronics. All servo drives I have come across allow you
    to monitor the current usually by an analogue voltage output back to your controller. Note most servo drives allow you to measure and monitor other
    servo parameters as well, power, temperature, torque, speed and terminal voltage among others. Thus if you have modern AC servos and drives
    you don't need to supply any clamp meters or other electronics......just program the drive to output an analogue voltage reflecting the power output.
    Easy!

    I would guess that your spindle motor, being essentially an AC servo with enhanced field weakening control, will also be able to monitor power and/or
    current etc.

    Do you actually have the servos and drives? Or more importantly do you have the drive manual.....I'm almost 100% you can monitor power/current
    just with a few keystrokes. Likewise do you have a manual for the spindle motor drive?

    Craig



  4. #64
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    Default

    Quote Originally Posted by joeavaerage View Post
    Hi,
    You don't need any clamp meters or anything else.

    Each servo drive has current sensors built in. They are required for the control loop electronics. All servo drives I have come across allow you
    to monitor the current usually by an analogue voltage output back to your controller. Note most servo drives allow you to measure and monitor other
    servo parameters as well, power, temperature, torque, speed and terminal voltage among others. Thus if you have modern AC servos and drives
    you don't need to supply any clamp meters or other electronics......just program the drive to output an analogue voltage reflecting the power output.
    Easy!

    I would guess that your spindle motor, being essentially an AC servo with enhanced field weakening control, will also be able to monitor power and/or
    current etc.

    Do you actually have the servos and drives? Or more importantly do you have the drive manual.....I'm almost 100% you can monitor power/current
    just with a few keystrokes. Likewise do you have a manual for the spindle motor drive?

    Craig
    The axis servos yes I already have them, I need to check the manual but I'm almost sure that the driver don't have any analog voltage output, I know it allows me to display the amps on the onboard screen but I don't think it has an output that can output that. Tomorrow I'll take a look into it and share the manual just to make sure I'm seeing it right.
    As for the spindle servo I don't have it yet, so no idea if it has that output but I'm asking for the manual so I can take a look.

    Thanks for everything, best regards



  5. #65
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    Default Re: Large Epoxy granite VMC building

    Quote Originally Posted by vakeiros View Post
    well that looks right, I had no idea how this math was made and one thing I know, math never lie!
    thanks for the clarification!

    so according to your formulas, this motor torque @9kRPM is about 5.8Nm capable of 8Nm peak under 30min and @12KRPM about 4.4Nm capable of 6Nm peak under 30min

    even so look very nice for my needs, from FWizard my cuts generally are under 2Nm at those speeds so looks more than OK, thanks for sharing that math, really appreciate it!
    My guess is that the rated torque to 9000 RPM should be rated POWER to 9000 RPM. So the power may fall off a bit past 9k. I wouldn't expect it to drop by more than 25% or so though.

    As far as that DRIVEMODULATIONDEPTH, I think that's referring to non-sinusoidal commutation. To rectify DC into sinusoidal (what an AC motor wants) AC, you need a DC bus voltage of about 1.4x (sqrt(2)) the AC voltage you're looking for. Setting that parameter over 100% will start clipping the tops off of the sinusoid, bringing the AC voltage closer to the bus voltage, but at the cost of a ton of harmonic noise (electrical and possibly mechanical as well.)



  6. #66
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    Default Re: Large Epoxy granite VMC building

    Hi skrubol,
    Setting that parameter over 100% will start clipping the tops off of the sinusoid
    That is an excellent explanation....I couldn't quite imagine how such a setting would work but felt sure that its not genuine field weakening.
    By setting the modulation depth to over 100% you can increase the average voltage, at the cost of really bad harmonics. It becomes increasingly
    like trapezoidal modulation rather than sinusoidal. Its not a solution I would recommend to Azalin.

    Craig



  7. #67
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    Default Re: Large Epoxy granite VMC building

    well guys sorry for the delay but I've been out of town...

    anyway, I can't be sure if I'm checking this correctly but regarding the axis servo drivers I think it don't has any way to throw out the amps info.
    The spindle driver might have, I'm a complete noob at this thing, I'm sharing a folder with both drivers manuals if you don't mind to take a look... I see many info on the mBus outs, I'll explore this myself try to understand this thing...

    link: https://www.dropbox.com/sh/t29iibis9...IiLTgs71a?dl=0

    best regards and thanks for everything



  8. #68
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    Default Re: Large Epoxy granite VMC building

    Usually servo drivers or VFD's have an analog out for some representation of the current or load, but I don't see anything in those manuals either. Looks like no analog out. Is there a separate document on mBus?



  9. #69
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    Default Re: Large Epoxy granite VMC building

    Hi,
    I've come to the same conclusion as skrubol, I can't see any means of the drive monitoring power. There may yet be data inside the drive that could be
    accessed via serial comms.

    You have not posted or linked the drive manuals for your servos....I take it they are from a different manufacturer?

    Craig



  10. #70
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    Default Re: Large Epoxy granite VMC building

    Quote Originally Posted by joeavaerage View Post
    Hi,
    I've come to the same conclusion as skrubol, I can't see any means of the drive monitoring power. There may yet be data inside the drive that could be
    accessed via serial comms.

    You have not posted or linked the drive manuals for your servos....I take it they are from a different manufacturer?

    Craig
    Hi again guys, been out of tow for the last few days so I got delayed in replies...

    about the mBus extra documentation I haven't asked yet but I will... I think in mBus I'll have access to that kind of information (current, torque, and much more) how to access taht info that's an whole new problem but I'll ask about it.

    Joeavaerage, yes I posted both the spindle servo manual and the normal servos manual, they are both in the link I shared...

    anyway, been advancing a bit more the design part, I'm very close to a final design, just need to tweak some stuff in the enclosure and figure out some places for some missing sensors.
    I wasn't intending to make the ATC right now from the beginning but I might do... I had designed the ATC system already so I can check if everything fits and I'm glad I did it, I was able to find some problems that I wouldn't be able to fix...
    Here are some pics, it will be a 16 tool umbrella type, Geneva system with an AC motor driven it (I ordered a small motor 100RPM hope isn't too fast... it's cheap anyway... if I need a slower one)...
    this controller need a bunch of sensors to work with the ATC I'm really pleased with that (ATC slide in/out sensor, power draw bar up/down sensor, tool count sensor, tool slot in position sensor, Z safe height sensor)








    that's it for now... let me know what you think of me solution to attach the ATC to the machine, I was thinking to hanging it just to the column but I belt a bit unconfortable hanging it that way... from my calcs to should weight about 50KG fully load with tools and I got scared that it would move the column in any way so I grabed it to the base and column to share the load.



  11. #71

    Default Re: Large Epoxy granite VMC building

    Your mount looks more complicated than it needs to be. Most commercial machine tool builders basically bolt an angle plate to the column casting.



  12. #72
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    Quote Originally Posted by footpetaljones View Post
    Your mount looks more complicated than it needs to be. Most commercial machine tool builders basically bolt an angle plate to the column casting.
    Well I know that, I just don't feel confortable doing that it's not that much of a job doing if like I'm doing and think it's better... anyway if everyone agrees I should be doing a single angle to the column I guess I will do it but honestly I won't fell too good about it... I'm new to this kind of machines so I've no idea how strong is this column and if it takes this much weight without moving a bit...
    Thanks for your input tho!



  13. #73
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    Default Re: Large Epoxy granite VMC building

    Static weight on the column shouldn't matter much. Even if it makes the column tilt a thou or 2 (I doubt it'll even be that much,) that should be the same all the time you're locating and cutting so it shouldn't affect anything.



  14. #74
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    Default Re: Large Epoxy granite VMC building

    Hello guys, it's been a while since I posted anything here, so not any actual development in the build itself but I finally pulled the plug on the last expensive pieces of the puzzle. Ordered the spindle unit, BT40, 12KRPM with hydraulic clamp mechanism, about 2200USD total shipped DDP so no extra surprises in the customs and also ordered the 5.5KW 12kRPM spindle motor also ordered a 400w servo motor for the 4th axis, 400w should be more than enough to attach to a harmonic drive 100:1... also finally I found a "local" source for the sands I need, I was thinking of using Silimix but between they don't having it in stock and don't knowing when they were producing more as for the price (230€ sand plus 350€ shipping 1ton of it), I managed to get my hands on the spec sheet of that sand and my local source have all the sizes I need to produce an equivalent mix at a much lower price (should be able to order all the sand for less than 90€... quite a difference for the 230+350), so yesterday I bought 200kg of the required sands to try some mixes... I'll start aiming for 10% epoxy mix to start with... from what I've read, 8% would be the perfect ratio but I don't know if I'll be able to get that low...
    also I'll need to figure out a vibration table to vibrate the molds, I'm thinking of building a bench over some car springs so it won't go anywhere, attach a couple of cheap grinders under the top to provide the vibration... I think I can manage with that... we'll see.

    last big investment sould be the resin itself but first I need to test a few...

    anyway, just this quick update...

    I'll post some pictures of the new parts when I get them (should be here 20-25 april)
    meanwhile I sould be doing some epoxy mixes tests...

    best regards



  15. #75
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    Default Re: Large Epoxy granite VMC building

    If using just sands it usually requires a higher epoxy ratio around 14% but interested to see your experiments.

    Sent from my MI 8 using Tapatalk

    www.cncmachineplans.com


  16. #76
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    Default Re: Large Epoxy granite VMC building

    Quote Originally Posted by CNCMachineplans View Post
    If using just sands it usually requires a higher epoxy ratio around 14% but interested to see your experiments.

    Sent from my MI 8 using Tapatalk
    well, in fact, I ended up making a small test today just to see if I made my math right in the sand sizes to get the equivalent mix as the Silimix 261 and I mixed 2kg of the mix at 10% (1.8kg sand + 0.2kg resin), just a crude test in a plastic box and I must say it looks really really well... it's still curing but man, I was amazed... the resin I tried is very low viscosity, it's almost water, ok not water but like olive oil (I messed up the mix ratio of resin and hardener but nothing too serious but I'll repeat the test tomorrow just for piece of mind) it was all hand mixed with a stick but I must say first impressions are very pleasant. The resin was supposed to be mixed at 100:30 resin:hardener by weight and me, stupid as a door, mixed it at 30% by weight so for 200grams of mix I mixed 140g resin and 60g hardener while it should have been 154g resin and 46 hardener... but it mixed and poured very very well... I havent even vibrated the mould, just poured it and hammered at the top with a piece of wood... anyway I'm repeating the test tomorrow. I'm using 4 grades of sand, larger being 4-5.6mm and the smaller is like flower <0.1mm (at least 20% of this flower being <0.063mm) so it soaked really well with the epoxy...
    As in final molding I'll be mixing it with a machine and vibrating the molds I suspect it will run smoothly... witha 210min pot life I should be able to pour the whole part with all the mix still workable... I estimate the base taking about 300kg of this stuff and I'll be trying to make 30kg batches so when I pour the last batch the first one should still be in the pot life time so everything should settle fine... at least I hope lol



  17. #77
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    Default Re: Large Epoxy granite VMC building

    Ah k. So it's not all sand there is a percentage of gravel, having bigger sizes around the 4-6mm means you can use a lower percentage . Look forward to seeing the results.

    Sent from my MI 8 using Tapatalk

    www.cncmachineplans.com


  18. #78
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    Default Re: Large Epoxy granite VMC building

    Quote Originally Posted by CNCMachineplans View Post
    Ah k. So it's not all sand there is a percentage of gravel, having bigger sizes around the 4-6mm means you can use a lower percentage . Look forward to seeing the results.

    Sent from my MI 8 using Tapatalk
    ahh ok, sorry I also consider that sand XD my bad... if it works well I'll share my receipt, mainly I got my hands in the Silimix 261 datasheet and I tried to replicate the aggregate with available sand sizes of my supplier... I'm very happy with this supplier since they sell the sand in 25kg bags and it comes very clean and specially it's all DRY... it's just a matter of mixing it, if I needed more quantity (like 5 tons) they would even sell it to me all mixed to my request... but I'm very happy this way... Way cheaper than the german silimix and same quality... also it's >98% quartz. very happy, now I just need to order the resin... and that is not cheap... need to figure out how much I'll need first and get the funds for it... after spending about 4200eur in the BT40 spindle+hydraulic draw bar+spindle servo motor+driver+shipping I'm a bit on the low funds side... anyway the big expenses are almost over then it's all the small local stuff but they are many.... anyway... we must stay strong XD



  19. #79
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    Default Re: Large Epoxy granite VMC building

    Really looking forward to seeing the results, keep up the good work. The company that makes the silimax stuff especially designed for EG casting?

    Sent from my MI 8 using Tapatalk

    www.cncmachineplans.com


  20. #80
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    Default Re: Large Epoxy granite VMC building

    Quote Originally Posted by CNCMachineplans View Post
    Really looking forward to seeing the results, keep up the good work. The company that makes the silimax stuff especially designed for EG casting?

    Sent from my MI 8 using Tapatalk
    yes, they make these special aggregates for resin compounds. they have several aggregates sizes available according to the needs:
    https://www.euroquarz.com/products/t...artz-mixtures/



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