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  1. #21
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    Default Re: How to Select a 4TH Axis

    Hi,
    the DYN2 drives require a DC power supply, so you buy a power supply to go from 110VAC or whatever your local supply is to 70VDC. Easy. Makes the most of the AC supply you've got
    and gets you full potential of your servos.The DYN4 have a direct off-line supply. If you applied your local line voltage,110VAC or whatever, the servo drive would only have half it voltage,
    so it would still work but in stead of driving the servo to 3000rpm it might run out at 1500rpm. Who wants that sort of rubbish? You didn't pay all that money only to have it get to only half speed

    Most direct off-line AC servo drives like the DYN4's and all of the Delta ones are 230VAC single phase, up until about 2kW then you'll want three phase. Anywhere between 200VAC up
    to about 250VAC should work. Certainly I would expect DYN4's to work in any Canadian state...after all it is a Canadian brand. You'll have to fit a 110VAC to 220VAC transformer if you can't
    get 220VAC into your shop.

    You most certainly have used open loop steppers before, just ordinary steppers. Closed loop steppers have an encoder mounted on the back of the motor and that encoder can
    inform the drive of 'where it is'. If the motor misses a step the encoder will not match its commanded position and the drive will insert a few extra steps to 'catch up'. Sounds
    great doesn't it!. The manufacturers of closed loop steppers will tell you 'never misses steps, goes faster, more power, more this that on the other thing, all BS.

    The problem is that when a stepper is marginally overloaded it will start missing steps, closed loop or open loop doesn't matter, when a stepper gets overloaded its in trouble. The driver of
    a closed loop stepper will insert some extra steps, but guess what; the extra steps are just as likely to be missed as any other. A closed loop stepper will try to catch up and even
    succeed sometimes. What it can do is recognise when its got too far behind and signal a fault where an open loop stepper would just carry on making an out of shape part.
    Closed loop steppers can interpolate between full steps and offer increased resolution over open loop steppers. All-in-all the advantages of closed loop steppers are pretty slim
    and in my estimation poor use of your money.

    True closed loop performance comes with servos such as the DMM's you've seen.

    The downside is that once you buy and use a good servo, it will put steppers, closed loop or otherwise, into the shade and you'll not want to buy another stepper ever again.
    Servo 'addiction' is an expensive habit. I find 'God grant me the serenity.......etc' helps, but the addiction is cunning baffling and powerful!

    Craig



  2. #22
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    Default Re: How to Select a 4TH Axis

    Quote Originally Posted by ardenum2 View Post
    it means it runs smoother, most modern motors are like this, expect frameless motors that you can buy relatively cheap on aliexpress which use permanent magnets still tend to be 'straight' but for pm's it doesn't matter that much because of their native synchronous nature. the motors in the picture look like 1990's tech, you'd probably be better off with a modern closed looped stepper than this.
    Thank you for your time

    Nicolas


  3. #23
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    Default Re: How to Select a 4TH Axis

    If I need 220VAC to run servos it means I can’t buy one! And neither I want to have a transformer!. I think we discussed this subject a while back, although I can run 220VAC from my control panel to my workshop to do so it means I have to brake ceiling/walls gyprock or run exposed conduits on top of the walls/ceiling which the wife hates. Had I know this 25 years ago when I bought my house and completely renovate it myself then it would have been a piece of cake but then I didn’t even know what a cnc means!

    I also understand and appreciate the value of a good servo but often times we must do what needs to be done. Like it’s wonderful to drive a Ferrari but a VW will do the same job but not as fast neither as comfy.

    Now back to reality it means I must stick to steppers and for my hobby projects RPM’s is not important as long as it “turns”.

    You amaze me Craig with the knowledge you have in this field and I thank you for your time and well written explanation. It’s true I used steppers before many times but I bought them as a kit from an outlet in USA which included everything to run a cnc (steppers, drivers, BOB, PSU etc.). Now I will try to buy the same kit from AliExpress or similar and they have the option of close loop steppers etc. and that’s why I asked the question.

    Nicolas


  4. #24
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    Default Re: How to Select a 4TH Axis

    Hi,
    firstly what so wrong with having a transformer? They aren't evil.

    Secondly, that's why I thought the DYN2 drivers would be appropriate for you. A 110VAC to 70VDC power supply and your servo and drives would be as happy as sand boys
    and go full speed. Just as a matter of interest there is likely to be a '....get ready for it....a bloody.. f'ing transformer in it.....evil things they are'

    Craig



  5. #25
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    Default Re: How to Select a 4TH Axis

    I know transformers aren’t evil Craig (BTW I think they aren’t called transformers when you go from 220VAC to 110VAC) but the problem is that I still have to drag a 220VAC cable to my garage to feed the transformer to get the 110VAC or if I leave the transformer close to the panel still have to drag a 110VAC to the garage (that’s where I have the space for the cnc).

    Thinking ahead I just realized that it will also be more difficult to sell a cnc which requires 220VAC because most houses do not have 220VAC available in a garage. All my previous machines were sold to people with a garage like mine except one went into an artisans shop where 220VAC was available.

    Nicolas


  6. #26
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    Default Re: How to Select a 4TH Axis

    Hi,
    I'm not sure what you're talking about. What voltage do you have in your workshop? If you need or want 220VAC (or 230VAC or 240VAC) to run specific device in your workshop then a transformer
    to take your available input supply to the required output voltage, say 220VAC is required. No big deal, they are moderately costly but thereafter do well for decades.
    The transformer can be in or on or near your machine, it does not need to be in the distribution panel.

    A transformer is a still a transformer whether the voltage is increasing or decreasing.

    I have said time and again that given that you don't have 220VAC (or 230VAC or 240VAC) in your shop direct then use the DYN2 drives. They require 70VDC, or thereabouts. So if you have
    110VAC (or 115VAC or 120VAC) in your shop you just hook a power supply to it and viola....you have 70VDC to run your servos. If you choose your power supply wisely then it will run on
    either 110VAC OR 220VAC, and that would make it compatible everywhere, a useful sales point. What's the bet if you equipped your machine with servos you'll not want to sell it!

    I presume you use a power supply for your steppers? That same power supply could be used for servos. Having said that IF you do buy servos then you would be very poor idea
    to give them anything less than the manufacturers recommends. As I've said before if you pay big money for servos don't throw any performance away by saving a few dollars on the power supply.

    This is the sort of thing I had in mind:

    https://www.antekinc.com/ps-15n70-15...-power-supply/

    This thing kicks arse! 70VDC rock steady day in day out, 200% overload for minutes at a time. It can be wired to run on 115VAC or 230VAC, and we are NOT going to get hung up on a few volts either way
    are we? With this power supply you could run four or five 200W or maybe even 400W servos and it wouldn't break a sweat.

    Craig

    Attached Thumbnails Attached Thumbnails How to Select a 4TH Axis-antekpowersupply-png  


  7. #27
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    Default Re: How to Select a 4TH Axis

    Sorry Craig, I misunderstood.

    That will work but now we come to the total cost of a 4TH axis with a servo.

    $230 for the transformer + Shipping from USA to Canada approx. 70 = 300
    Approx. cost for a servo 400 + Shipping = 470
    Approx. cost for a gear box 500 + Shipping which I don’t know the cost
    Total approx. USD$1280 = CAD$1721, say CAD$1800
    Duties and taxes for the above to enter Canada are not included in the above but I will estimate them to be close to CAD$150

    So we are talking to increase my cost by about 2000 – 2500 if we add the aluminum pcs I need to mount the 4TH axis, wiring and what not. That is a lot and it will be a hard sell. I’m not say no but will have to think about it.

    Nicolas


  8. #28
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    Default Re: How to Select a 4TH Axis

    Hi,
    the 1500W power supply I linked to would power four or five servos, not just one. If you had only one servo for a fourth axis then you could use a much smaller and cheaper
    power supply. None the less a servo driven fourth axis and a servo reducer much like that I have used is expensive....and you are right to question whether such
    a big investment is warranted.

    For all the trouble and expense I have gone to building a fourth axis, does it get used? Well yes it does, but not that often. If you knew that you had plenty of work
    for a fourth axis then it would be money well spent, but if you have only a few project ideas then it's questionable if this is the best use of your resources.

    If you want to improve your machine then I would suggest you focus on the three main axes.....they after all do the lions share of the work. That is also where if you used servos
    you'll find your machine can fly. I suspect that servos on the linear axes would be of more value to potential purchasers down the line than a fourth axis. I could be mistaken of
    course.

    If I have a quick total up of all the money I have spent on a fourth axis and what I've already spent on a fifth axis and add what I expect to spend to get the trunnion table and fifth axis
    built and in service PLUS the $2000NZD I've spent for the CAM software the total comes to about $6500NZD (approx $4100USD) I have to ask myself ...'have I done the right thing?'
    I could well have had a new ATC spindle for that sort of money. Would that have been better?

    In some respects, I've backed myself into a corner. Some years ago I bought the first servo reducer. It sat around for a long time. I eventually decided I had to use it or admit that it was a waste
    of money. Of course to continue to build and use a fourth axis required even greater investment both in parts like the servo and materials PLUS the CAM software. In order to make the investment
    to date seem reasonable I need to have a fifth axis as well, which has in effect doubled the initial hardware cost. So I sort of feel that by making one decision that has set off a whole train of others
    which has resulted in me spending BIG DOLLARS for a result that may not get the use it deserves. Time will tell.

    CNC as a hobby has taught me some important lessons...and I'm thinking this episode may be in the same vein. To sum up 'be careful when undertaking an improvement that you cost out the full
    extent of not just the improvement itself, but then the other modifications and improvements that present themselves or are required in light of the initial improvement'. Geez, I hate second guessing myself!

    Craig



  9. #29
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    Default Re: How to Select a 4TH Axis

    Good to know Craig that I can use a smaller size transformer because logic says I shouldn’t use servos due to higher cost but since I would like to get my hands wet with them I may one day decide to go for it.

    As always you are right about the use of a fourth axis. Even if I get one I will use it once or twice and then it will never be used again and so $2K went to waste.

    Did you ever saw a DMM servo in AliExpress/eBay? During my search yesterday I couldn’t find any so I wonder. But perhaps it will be better if I decide to buy straight from them because the shipping cost will be much less since they ship from Canada.

    Nicolas


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    Default Re: How to Select a 4TH Axis

    Hey Craig

    The link shows a fourth axis drive which is quite inexpensive with free delivery. Its belt driven and with a ratio of 6:1 I calculated the chuck will turn at 83RPM. Am I correct?

    https://www.amazon.ca/gp/product/B08...M55UG43X&psc=1

    They don’t say the inductance of the motor but searching for a L76mm motor I found it is 5.4mH.

    Similar units at AliExpress with 80mm chuck have a delivery cost of CAD$177, quite expensive so I better find one at Amazon.ca which offer free delivery.

    I’m quite away from ordering one but searching for comparison purposes and the servo is not dead yet

    Nicolas


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    Default Re: How to Select a 4TH Axis

    Hi,
    now that you mention it I have not seen DMM advertised on Ebay or Amazon. I would guess that is a deliberate policy of DMM. They have a very good reputation
    for supporting their customers and keeping Ebay and Amazon out of the loop makes perfect sense if you are trying to cultivate that reputation.
    Unfortunately they are just too damned expensive for me....I don't quite know why it seems so much more expensive to ship from
    North America to New Zealand than it is from China to New Zealand....it's the same distance, any way I do not have any myself.

    I can promise you that once you start playing with servos it will put steppers, all steppers, in the shade.

    I have to agree having so much money invested in a fourth axis with a marginal use case is questionable. Worse is that the servo, quite a chunk of the cost,
    is going to end up with modest or occasional use.

    If you are going to get servos then you should probably equip at least your X and Y axes with them, and ideally the Z as well. That would of course mean three or maybe four servos but
    at least you'd get the satisfaction of long hours of use. I suspect also that prospective buyers would be mightily impressed with servos on the linear axes rather than a fourth axis alone.

    About four years ago I bought a 400W Delta B2 series servo kit. My intention was to experiment with it to see if they were any good, and also to try out the new supplier Fast-to-Buy.
    Both the servo and the company exceeded my expectations by quite a margin and I've been buying Delta servos from them ever since. That servo I ended up selling to my boss and
    we built it into our speedometer calibrator and has been used daily ever since. Some days I wish I could steal it back!

    Craig



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    Default Re: How to Select a 4TH Axis

    Hi,
    that fourth axis looks better and worse at the same time.

    It has a 6:1 belt reduction only so it will run much faster than a harmonic drive but with commensurately less torque.
    Remember you entertained the possibility of a servo to overcome the slow speed of a harmonic drive, and so not only did the harmonic drive
    cost extra but you need to spend even more on a motor that runs it fast enough to be useful.

    That sort of make this one much MUCH cheaper.

    It looks like a four-jaw chuck, which is probably not self-centering? Is that what you want?

    Keep searching, I think you'll find something cheap enough to try and not commit huge sums of money to a device of potentially limited use.
    If it later turns out you do use it a lot....then that changes the calculation, maybe then you get the 'you beauty' fourth axis.

    Craig



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    Default Re: How to Select a 4TH Axis

    If I use servos on the X Y Z axis I will never be able to sell, LOL. An average homeowner doesn’t have this kind of money.

    I thought the 4 jaw chuck is self-centering because that’s what I want.

    I just sent an email to DMM asking for a quote, told them that’s for a hobby use and select a complete kit. When I get the reply, most likely on Monday I will let you know

    Nicolas


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    Default Re: How to Select a 4TH Axis

    Hi,
    all four jaw lathe chucks I've encountered are independent jaws, ie not self centering.I have seen self centering four jaw chucks advertised but never actually seen one.

    Servos are not cheap, at a guess $400 each, so for a three axis machine with a slave on the gantry that's $1600. What are your stepper kits costing?
    As always it price verses performance.

    Craig



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    Default Re: How to Select a 4TH Axis

    The $400 you say for a servo, does it include everything?

    Last March I bought this kit from USA for my current cnc:

    4 Stepper digital drivers, 4 NEMA23 270oz-in stepper motors, 1 48VDC 12.5A PSU, 1 C11G BOB with relay spindle control, 1 Ethernet SmoothStepper motion control board for Mach3, 1 5VDC 3A PSU, FedEx shipping US$(88.00). Total cost US$715.00 + CAD$45.00 for duties/taxes at the border.

    I think you are right about the 4 jaws chuck perhaps I should go with a 3 jaws. Do you see any disadvantage?

    Nicolas


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    Default Re: How to Select a 4TH Axis

    Here is the reply from DMM:

    “The 4th axis is a rotary axis, correct? Do you know what size motor you need? You can also send me the reduction ratio and rotary chuck/workpiece mass and dimension and I can calculate the motor size needed.

    We have a NEMA23 motor with 540oz-in torque, this is our 400W motor with attached dimensions (57N-DHT). We also have a 200W motor with 270oz-in torque but the dimension is not exactly NEMA23, its close, also attached is dimension for this 200W motor (620-DST).

    So depends on your preference which motor is best to use.

    The servo drive you can use our DYN2 servo drive and power with 48VDC power supply.

    The C11G is no problem. I will send you step by step setup instructions for everything needed to do.

    Let me know what you think,”

    What do you think Craig?

    Nicolas


  17. #37
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    Default Re: How to Select a 4TH Axis

    Hi,
    the 400W Delta B2's are $398USD a kit, which includes the servo, the drive, the cables and the plugs necessary to make your own input cable. Of course that is in Hong Kong
    so shipping on top of that.

    https://www.fasttobuy.com/220v-127nm...ol_p28069.html

    You may notice that the 750W Delta B2's are $438USD....so an extra $40 dollar gets you nearly double the power....so that's why I get them. Still shipping to pay.

    https://www.fasttobuy.com/flange-80m...er_p28084.html

    Depending on what DMM come back with you might find servos cost about double what your steppers are. I guess you need to figure in the big DC power supply to, maybe $230USD for
    a 1500W version, or maybe a bit less for a 1000W version. Either way you are paying a premium for servos, but about double is not that out of the way, and the performance benefit is tenfold.

    Three jaw chucks are easy to use and centralise to within a few thousandth on an inch...so OK for most things. If you must get absolute best accuracy then independent four jaw is the next step up.
    Also with a four jaw you can hold different or odd shaped parts. For 95% though, a three jaw self centering is the norm. Even if you bought a four jaw later on you can get perfectly usable Taiwanese
    four jaw chucks (Vertex) for $150 or so and less, maybe a lot less, second hand.


    Craig



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    Default Re: How to Select a 4TH Axis

    Hi,
    typically the price for a 400W servo is damn near the same for a 200W one....so I would go for 400W. I'm no Yank, but if I can get twice the power for free, or nearly free, I'm taking it!
    For a fourth axis you'd most likely need no more than 200W, but if you can have more torque authority take it.

    The thing you want to be aware of is that you'l probably want the DYN2 drives, so whatever servo you select has to match the DYN2. If memory serves they are a little cheaper than the DHT servos
    anyway. The DHT servos are matched to the 220VAC input drives.

    Craig



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    Default Re: How to Select a 4TH Axis

    Craig here is my reply to DMM:

    “ You are right, the 4th axis is a rotary axis.

    I would say the 270oz-in sound good for my needs but I don’t understand about “dimensions is not exactly NEMA23”. I don’t see any problem with the dimensions as long as it will fit to the servo drive. What I don’t understand, please excuse my ignorance, why I get a NEMA23 motor. I thought a servo motor it’s a special motor itself and I don’t need a NEMA motor, please explain.

    I don’t know the reduction rate as long as the working peace turns at reasonable RPM. Can you provide a 3 or 4 jaws chuck or something similar? ”

    Now I’m confused Craig because I don’t understand the need for the Nema motor, can you please explain?

    And what do you think about the dimensions on Nema23 which he says are a bit different. Does it matter to me?

    Nicolas


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    Default Re: How to Select a 4TH Axis

    Hi,
    NEMA23 is an American standard and actually means 2.3 inches across the flats of a motor. If you convert that to metric that is 58.42mm. A less precise conversion (1"=25mm) is 57.5mm.
    You may well note that many steppers, even those of Chinese or Japanese origin, both metricized nations, have a 57 in their part number. This is a fair indication that the manufacturer has
    used the genuine NEMA23 size to make his motors and thereby have a market for them in the US.

    A lot of manufacturers' have chosen to ignore the quirky US size and adopted 60mm across the flats. For instance, the 400W Delta B2's I've linked to are of that size. They are just different enough
    that they will not fit in a machine which is genuine NEMA23. To make matters more confusing some people call these motors NEMA24. There is no official NEMA24 size in any NEMA literature,
    but using logic would dictate that NEMA24 is 2.4 x 25.4=60.96mm. which actually is a slight overestimate of the true 60mm that various metricized manufacturers use.

    The problem with Canada is that your too bloody close to the Yanks....go mad and emigrate now, beat the rush!

    I think you'll just have to get the DMM servos in whatever size they come in, and then adapt your machine to suit. A PITA.

    All my Delta servos are true metric sizes and therefore there is less confusion, but it does not go away. For instance the 750W Delta B2's I buy are 80mm across the flats,
    meant to mimic NEMA34. But NEMA34 is actually 86mm across the flats. Confusingly Delta also make a 90mm servo. The next size up in the Delta line up is 100mm.
    In my case as I am building the machine I can make it to match the equipment I can get, and in tis case its 80mm of 750W Delta B2's.

    Craig



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How to Select a 4TH Axis