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1 Attachment(s)
What size stepper motor do I-need.
A Tutorial on motor torque calculations
A question oft asked on MYCNCUK is "how big a motor do I need?". There is no simple answer to this, and the options are usually:
a) follow someone elses build and copy theirs;
b) take a guess and try again if you are wrong; or
c) work it out, which is the subject of this tutorial.
When choosing a motor you need to know:
a) what power and torque output is required at a given speed
b) what electrical characteristics are appropriate to acheive that
What I have tried to do here is the engineering approach, by showing the calculations needed to get some idea of power, which then dictates motor size. I am concerning myself with a stepper motor directly driving a leadscrew to move the gantry, table, etc. Similar calculations can, however, be done for belt drive or geared up/down with timing pulleys.
DISCLAIMER: This tutorial is to give you an insight into how to approach the selection of a motor. I take no responsibility for any consequences of following this tutorial and you alone are responsible for your choice and purchase of motors etc.
So lets start with assessing what torque might be needed. The basic properties we need to be concerned with start with the moving element, be it table, gantry, milling head or whatever, and that is its mass. We need to know this, either by actually weighing it, or by estimation based on the volume of material and the density of the material or by adding up the weights of the component parts.
A gantry for a router would be the weight of the slides (from manufacturer data) plus the weight of the aluminium parts (calculated using 2750 as the density) and the weight of the steppers, router, etc. Typically on a small router this would be in the order of 20kg, which we will use as our worked example - yours will be different. If you work out the motor needed for the heaviest element, then this is the worst case and the same motor will work for everything else (although you may chose to do the calculations for each axis in turn to see if there are saving to be made).
So, we know what our moving part's mass is. The motor has to make this component move, first by accelerating it and then maintaining that velocity. To do so it must first overcome the initial friction (stiction) and then maintain the drive against the friction of the moving parts and against any cutting forces. Minimising that friction is therefore crucial. For linear or rolling bearings the friction can be calculated and the stiction is generally very small. For dovetails (as on a mill) it is not easy to calculate and is best measured with a spring balance, firstly to determine what pull is required to get the table moving and then to maintain that movement. This might be as much as 15kgf initially, dropping to 5kgf.
The second aspect to accelerating the moving item is to overcome its inertia (the tendency of something to remain at rest) - this is true even if friction were zero.
The motor turns the leadscrew to convert rotational motion into linear motion. There is friction here too, expressed as the efficiency of the leadscrew. This is typically 80% for ballscrews and as low as 30% for trapezoidal screws (bronze or delrin nuts on steel) and inertia, as the screw itself has inertia which is dependent on its mass and its length.
Now we have all the elements we need.
So, considering the frictional component of the torque, this is given by:
Torque = F * p/(2pi * e)
[1]
where F is the force to be overcome in Newtons, p is the screw pitch in metres and e is efficiency.
For this example I shall assume a TR12x3 trapzoidal screw 12mm dia, 3mm pitch.
The force to be overcome is, as said above, either the stiction or the kinetic friction plus the cutting forces. For the purposes of simplicity
assume the cutting forces range from 5N for wood to 20N for alloy using the sort of spindles/cutters found in hobby sized machines up to 75N for steel on a mill.
The frictional forces are calculated from the mass of the load and the friction coefficient:
F = M * g * Fc
[2]
where g is gravity, which can be taken as 10
Typical static friction coefficients for common sliding mechanisms are:
0.003 for a ball slide,
0.01 for low-end ball races on aluminum channel,
0.05 for teflon on steel,
0.16 for bronze on steel
1.10 for cast iron on cast iron.
For most of these the kinetic frictional coefficient can be taken as the
same, although it is around 0.2 for greased cast iron to cast iron.
Assuming a low cost router using ball races and our 20kg load the frictional force (from equation 2) is 20 * 10 * .01 = 2N. Add to this the cutting force for wood at 5N and the force to be overcome is 7N, therefore the torque (from equation 1) is:
T = 7 * .003/(2pi * .3) = 0.01Nm
This doesn't sound a lot when motors are rated at 1 - 3Nm, but we haven't finished yet.
The second calculation is the inertia of the moving item, expressed in terms of the inertia seen by the motor. The symbol we use for this is J(load) and it is calculated thus:
J(load) = mass(load) * pitch^2/(2 * pi)^2
[3]
where mass in Kg, pitch in metres gives inertia in kg m^2
[note: ^2 means raise to the 2nd power, e.g. square it]
In our example we will use a trapezoidal TR12x3 single start screw to move this 20Kg gantry, so from equation 3, J(load) = 20 * 0.003^2/40 = 4.5 x 10E-06 kgm^2 (the 40 is a good approximation to 2pi squared). To this we add the inertia of the screw, which is given by:
J(screw) = 1/2 Mass * radius^2
[4]
where the mass is given by:
mass(screw) = pi * radius^2* length * density
[5]
In our worked example a 12mm screw 800mm long has a mass of 3.1416 * .006^2 * .8 * 7800 = 0.71kg and therefore an inertia of J(screw) = 1/2 * 0.71 * .006^2 = 1.28 x 10E-05, so the screw has a higher inertia than the load!
The total inertia to be overcome is the sum of J(load) and J(screw) = 1.72x10E-05 kgm^2. (Note the spreadsheet also adds in the rotor inertia of the motor)
Next we have to decide how fast we want the gantry to move under load. Typically for a wood router anything from 500 to 1000mm/min would be suitable, for cutting aluminium you might want to look at 1800mm/min or better when using small cutting tools. The maximum traverse speed is given by:
Smax = max motor rpm * screw pitch.
[6]
In many cases the speed will be determined by the available drivers and the motor. Few motors will give much torque above about 1000steps/sec on low voltages (24v being the typical supply used), so the maxium speed we could reasonably expect under load for a 200step motor is going to be 1000/200 * 60 * .003 = 0.9m/min or 900mm/min. At this speed the angular velocity of the screw will be:
w = 2 * pi * screw revs/sec
[7]
In our example this becomes 6.28 * 1000/200 = 31.4 rads/sec.
Note that the spreadsheet also shows whether the screw is likely to whip at the chosen speed depending on the type of fixing. For most basic systems fixed/free or supported/supported would be a typical configration, but this may need to be adjusted (or a bigger diameter screw chosen) for larger/faster designs.
Now we need to decide what acceleration we want. There is a correllation between the speed of movement and the ideal acceleration to avoid loosing steps but allow rapid direction changes for accuracy of cut. Obviously as the speed increases the acceleration needed to maintain cut accuracy is higher, however for rapids a lower acceleration can be tolerated. A typical router at around a 1000mm/min would need an acceleration on the order of 2300rads/sec^2. The torque required to achieve this acceleration against the inertial loads is
T = J * A
[8]
Which gives 1.72x10E-05 * 2300 = 0.04Nm. (the spreadsheet assumes rapids need ~1/3 the acceleration of that used for cutting).
Adding the two components of torque together we have a total torque requirement of 0.052Nm at the motor speed of 1000steps/sec (i.e. 5rps, 300rpm). The spreadsheet also adds in the detent torque (the torque needed to overcome the magnetic attraction between stator and rotor - this is what gives rise to the 'cogging' feel of a stepper motor when turned by hand.)
You can see that the torque required is very different to the 'torque rating' of the motor. It is important to note that the holding torque of a stepper motor is to some extent of little relevance. This is the physical torque required to overcome the electromagnetic forces holding the rotor stationary and is the torque the motor tends towards as speed drops to zero. In practice this torque is rarely available or used. While the size of a stepper motor generally dictates the low speed torque, the ability of the drive electronics to force current through the windings of the motor dictates the high speed torque. Remembering that a stepper motors torque ratings are based on sinusoidal drive current; running it on a square wave signal of a switched driver is at best an approximation at low revs and is progressively worse at higher revs unless there is sufficient voltage to force the current through the winding. A good rule of thumb, for best performance, is:
Vd = 32 * sqrt(L)
[9]
where Vd is operating voltage, and L is the motor inductance in mH. If your drivers are limited in voltage a low inductance motor is essential if you want any reasonable speeds.
The inductance of the windings and the drive voltage used dictates the corner speed of the motor. The calculations are too complex to describe here but the spreadsheet allows you to put in the motor parameters to get a go/no go view. In an ideal world you would want to run the motor just below its corner speed to get maximum power output and a torque that is essentially constant across a range of revs. Once you get past the corner speed the torque falls off rapidly. This is a consequence if you design for high power at cutting speeds (to minimise the likelhood of loosing steps) but then want fast rapids which take you over the corner speed - if the torque drops too low you will either lose steps or worse the motor will stall.
So, lets look at the motors available. Pick any website, such as Zapp Automation's, and look at the list of NEMA17 and NEMA23 motors. Here are the options:
Motor V A mH Nm Inertia
SY42STH47-1684B 2.80 1.6 2.8 0.44 68
SY57STH51-1008B 9.24 0.7 32.8 1.00 275
SY57STH51-3008B 3.10 2.1 3.6 1.00 275
SY57STH56-2008B 5.04 1.4 10.0 1.24 300
SY57STH56-3008B 3.15 2.1 4.4 1.24 300
SY57STH76-3008B 4.00 2.1 6.4 1.85 480
Plugging any of these into the spreadsheet gives similar results, so which to choose? Next calculate the ideal voltage for each (the spreadsheet shows this as the 'ideal voltage')
Motor V A mH Vd
SY42STH47-1684B 2.80 1.6 2.8 54
SY57STH51-1008B 9.24 0.7 32.8 183
SY57STH51-3008B 3.10 2.1 3.6 60
SY57STH56-2008B 5.04 1.4 10.0 101
SY57STH56-3008B 3.15 2.1 4.4 67
SY57STH76-3008B 4.00 2.1 6.4 81
Lets assume we want to use a low cost driver board, such as the System3 from DIYCNC which is OK to 2.5A but limited to 30v max, or the TBA6560 boards available on eBay. None of those are going to manage 60v, indeed 24v is the likely voltage, but the motors that are the lower ideal voltage will perform better with those drivers. So on this basis the SY42STH47-1684B or the SY57STH51-3008B would be contenders. I'd probably opt for the 1Nm NEMA23 motor over the 0.44Nm NEMA17 to give a bit more leeway and scope for upgrades. Anything bigger would be a waste of money and would perform no better (and usually worse - there is such a thing as too big a motor).
Below shows similar calculations repeated for a number of examples
25kg gantry 4' Rockcliffe oilite bronze on steel, TR12x3 1.2m long. 1000mm/min. Torque = 0.1Nm, power = 3W so a 1Nm - 1.5Nm motor.
35kg gantry 2m ballrace on channel, 16mm ballscrew 5mm pitch, 1.8m long, 2000mm/min. dense hardwood capable. Torque = 0.4Nm, power = 12W (typical 2Nm NEMA23 motor)
50kg dovetail table + 5kg workpiece + 5kg vice, 20mm ballscrew 5mm pitch, 900mm long, 1200mm/min, light alloy/steel cutting. Torque = 0.9Nm , power = 32W (8Nm NEMA34 motor)
50kg dovetail table + 10kg workpiece + 5kg vice, 25mm ballscrew 5mm pitch, 900mm long, 1800mm/min (with slightly reduced acceleration), heavy alloy/steel cutting. Torque = 1.1Nm , power = 64W (possible with 12Nm NEMA34 motor, but this is starting to get into servo motor territory to meet that speed/accel requirement)
The calculations are contained in a Excel spreadsheet in the attached zip file
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Re: What size stepper motor do I need...? A tutorial
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Re: What size stepper motor do I need...? A tutorial
irvine:clap:
i read many posts on forums concerning stepper size
when i was looking to buy motors .. but could not find much information as in in , this motor + this driver + this load = ?
very informative read , sure this will help many of us noobies
with motor selection
:beer:
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Re: What size stepper motor do I need...? A tutorial
Stunning Tutorial, I have been worried about just this problem. Many thanks indeed.
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Re: What size stepper motor do I need...? A tutorial
wow!:eek: thats a lot to take in, but very informative and usefull info for all us new builds out there keep up the great work:clap:i will need to dig out that old spring balance out the shed and get to work:beer:
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Re: What size stepper motor do I need...? A tutorial
Clicking the "thanks" button wasnt enuff for me, great post and top marks irving....you the man !
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Re: What size stepper motor do I need...? A tutorial
Thanks Irving :yahoo:, just need to get my wizard hat out and start figure out what kinda motor's to get to my CNC conversion project :idea:
Thanks again
Mark
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Re: What size stepper motor do I need...? A tutorial
Tutorial updated with new easier to use spreadsheet that does critical speed calculations for the leadscrews as well as allowing you to plug in different motors to get a better view of the fit. Also does checks for performance at both 'cutting' and 'rapids' speeds.
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Re: What size stepper motor do I need...? A tutorial
Thanks for the great spreadsheet. So much key knowledge in one document!
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Re: What size stepper motor do I need...? A tutorial
Thanks a lot for the excelent advice,
I'm just concerned about the microstep selection, actually I've found the right balance in my cnc, I run 3 2M2280N coupled with 3 12NM nema 34 motors, I could run my cnc as fast as 10m/min in rapid and 2,5m/min while working (mach3, parallel port), but in a work of 4 hours it loosed the step and I had to trash the work out, so i reduced the microstep resolution to half step and it seem to work right, but the motors do a hell of a noise.
I've read different opinion on the web about microstep resolution, someone says that the more you set higher this value the lesser will be the torque, others says that in the modern drivers, microstep res. almost do not afflict the torque,
Who do I have to listen to?
Can you explain how this value can be taken in account?
Thanks a lot if you can reply.
M.
P.S. I'm wondering to move to servo with brushless motors,maybe this can be tha solution?
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Re: What size stepper motor do I need...? A tutorial
How long is the cable on the parallel port.
A TTL signal might get you a reliable 10 feet without handshaking at that speed, if you were lucky :smile:
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Re: What size stepper motor do I need...? A tutorial
I think its a fact that microstepping, where you are actually stopping at the microsteps (i.e. using them for resolution) definitely is less torque, simply because the motor cannot hold that position accurately against load. In a dynamic situation however, lots of factors come into play. For example, if the axis is in constant motion the only torque required is to overcome friction and cutting loads, there is little torque required to provide acceleration. Unless the motor is being operated close to its torque limit (at that speed/volt/current combo) then microstepping should have little impact. The general rule I have used is in the spreadsheet is that the motor should provide 3x required dynamic torque at the maximum speed.
Large motors have high inductance so the torque drops off very fast with speed - the corner speed of those motors is 240rpm. I don't know how big your axis are, but I'm guessing its going to be around 1 - 1.2m? With your 10mm pitch screws 2.5m/min = 250rpm, so that is close to optimal (and 1/8 stepping = 6664steps/sec) and it looks OK at cutting speeds, but its very marginal at 10m/min rapids and that is where you may have lost steps (=27000steps/sec). You need to reduce rapids to 7m/min but it should be OK at 1/4 or 1/8 stepping.
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Re: What size stepper motor do I need...? A tutorial
Thanks again, i will reduce the rapid to 5m/min and the working speed up to 2,2 m/min as top speed, setting the microsteps to 1/8.
M.
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Re: What size stepper motor do I-need.
I have a couple of questions about your motor calculation spread sheet. The motor inertia is input in gm-cm^2 (B32). The rotor inertia given in I27 must be Kg-m^2 since the total inertia is the sum of the screw inertia, load inertia and motor inertia, the others are in Kg-m^2. I27 = G35 which is a lookup to convert units of the motor inertia.
The problem is 1000 gm = 1 Kg and 100 cm = 1 m so gm-cm^2 should be divided by 1000*100^2 = 1*E7 not 1*E8 as in G35. The motor inertia in the sum is 10 times too small.
I cannot find the time used for the acceleration torque (I34). The equation is G32*I28. G32 is labeled as V but it is really the number of pulses/second of the stepper based upon a 200 pulse/revolution motor and the screw speed (which is the Max. linear speed divided by the screw pitch). From looking at the equations, the running torque is small compared to the acceleration torque unless there is a lot of friction in the system. I have not found any references as to what range of acceleration is needed for a CNC. Obviously, when a stepper system is tuned it will limit the acceleration so positioning steps are not dropped due to the loads. Too small motor torque will result in a very slow CNC due to acceleration limitations. At some point a larger motor torque results in small performance gains for the cost increases. Are there any guidelines for this? Thanks.
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Re: What size stepper motor do I-need.
Hi,
I am building a gantry robot and for the Y-axis I am using a 1610 ballscrew (16mm diameter, 10 pitch, 1300mm long). I estimated that the mass is 36Kg and for the speed I planned to have 1800mm/min.
Using these calculations I concluded that the total torque is 0.23Nm. From the Excel the estimated torque resulted to 0.67Nm.
Now I have the following questions:
1) Can I use there calculations for a ball-screw system?
2) What is the calculation to determine the estimated torque (0.67Nm) from the total torque (0.23Nm)?
3) Is 0.67Nm enough for such mass? I did some research for similar projects and they use a much higher torque stepper motor.
All kind of help will be appreciated and sorry for my bad English.
Thanks in advance.
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Re: What size stepper motor do I-need.
I'm trying to use the spreadsheet to check some parameters of my planned new router. This has thrown up a few questions:
1. Acceleration seems to be the largest contribution to torque required, but I can't find where load acceleration is built in. It must be in one of the formulae somewhere but I can't manage to unpick the formulae in the hidden columns to find it.
2. The spreadsheet recommends a motor torque based on an assumed safety margin of 3; if the safety margin isn't high enough with my intended motor, I presume that I could restrict the machine to a lower acceleration? But given that I don't know what acceleration is assumed, it's difficult to see what's happening. I do see that the acceleration torque number is linked to cutting speed.
3. For a twin ballscrew X axis, I assume that I can use the spreadsheet using actual ballscrew dimensions (single ballscrew) to give critical speed, but then use a double-length ballscrew in the spreadsheet to do the torque, etc, calculation.
4. If I go to a twin-motor setup, can I simply double the nominal motor torque? Or is it easier to halve the gantry mass and do the sums for a single motor/ballscrew?
To put some reality into this exercise, what would be sensible numbers to use for cutting speeds and accelerations? Bit of a "how long's a piece of string?" question, but my current router is so far out of the norm I don't feel that I can extrapolate from what I'm doing at the moment, and I don't know what kinds of numbers are reasonable. For starters, I would assume profile cutting, say, 9mm ply with a 6mm cutter in a couple of passes. Currently, with speed limited by machine rigidity, I would cut that at maybe 600mm/min.
Many thanks for any help available!
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Re: What size stepper motor do I-need.
I'll save you a lot of headache and just say use 3Nm motors run at 65-70Vdc on 75-80vdc drives and you won't have any problems cutting anything.
Cutting speeds will depend on many factors like spindle power and tool material but 4500-5000mm/min wouldn't be out the way with 2.2Kw spindle using carbide tooling.
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Re: What size stepper motor do I-need.
Can you suggest a supplier of a kit of parts to do as you have described Jazz? for a 4 axis machine?
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Re: What size stepper motor do I-need.
I'm planning to re-use a set of Zapp SY60 3nm motors, 68V linear power supply and analogue drivers which should do for starters, then, and I'll see how it goes. Can always add another motor if needed.
This whole design process is interesting: we are urged to study, analyse, carefully consider. I used the spreadsheet to get better insight into motor sizing but the answer, in practice, comes down to "SY23 because SY17 are too small, SY34 are too high inductance, and you might as well go for 3nm as they cost barely any more than the lower power motors in that frame size." Power supply sizing is similar.
Ian - you could look at the Zapp web site for a kit. The price (at least when I bought) is the same as buying the individual parts but at least someone has identified a bunch of bits that play well together.
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Re: What size stepper motor do I-need.
I have the much reviled ebay 4 axis kit all on one board which i bought to get me going
having said all that its been absolutely fine and reliable but now i'm using it more I thought i would get a proper set up with individual drivers so in the event of problems i can switch a faulty one out
I was looking at cnc4you's site but his drivers are only up to 50v with a 36 v power supply
I'll have a look at zapps site
Ian
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Re: What size stepper motor do I-need.
looking at zapps site I cant see any kits of parts but if i put together
4 dm856 drivers 4 nema 23 3 nm motors and one plc6x BOB and a 68v 6amp power supply
its £632 ish
Cnc4you's kit of parts is 356 plus vat 427 ish thats this kit ...Nema23 Stepper Motor Kit 4Nm x 4 Axis
will I notice any major difference with either of those over my cheapy ebay special ?
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Re: What size stepper motor do I-need.
Quote:
Originally Posted by
IanParkin
I was looking at cnc4you's site but his drivers are only up to 50v with a 36 v power supply
Ian
Cnc4you is the best place to buy the steppers 3.1nm low inductance that I know of. But not the drivers Ebay is your friend for them like this one :- Leadshine AM882 Digital Stepper Motor Drive 80VDC 0 1A 8 2A Protect Function | eBay although I think there is a newer model you might find a better price as well. ..Clive
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Re: What size stepper motor do I-need.
Don't go with the kits has they tend to be under spec'd on the PSU or have lower spec drives etc. You don't really save anything buying kits anyway if you shop around and to be honest if you build your own PSU you'll save more money.
Ian Check your PM's.
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Re: What size stepper motor do I need...? A tutorial
Quote:
Originally Posted by
irving2008
The calculations are contained in a Excel spreadsheet in the attached zip file
Thank you very much for this! But I have question.
For example I have 2 screws for X axis and 2 motors as a result. How I should make calculations in this case? I just need to double "Holding Torque", "Detent Torque" and "Rotor Inertia"?
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Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
Thank you very much for a very informative explanation on motor selection.
I'm upgrading an older machine that had two motors driving X axis gantry. How do I calculate the motor size with two motors on the same axis? Is it a simple as dividing by 2?
Gecko recommends a 40% increase in motor size from base calculations, do you agree?
Thanks again
Mike
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
Quote:
Originally Posted by
CNC Visions
Thank you very much for a very informative explanation on motor selection.
I'm upgrading an older machine that had two motors driving X axis gantry. How do I calculate the motor size with two motors on the same axis? Is it a simple as dividing by 2?
Gecko recommends a 40% increase in motor size from base calculations, do you agree?
Thanks again
Mike
Not so simple. First you need to know the moving mass. Then the desired speed and acceleration. Then you decide the motors and the ratios. Then you check if your BOB can cope with that. Then you check what your resolution will be. Some back and forth between all that and a final decision. At least that's my logic.
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
Quote:
Then you check if your BOB can cope with that.
Do you mean the drivers?.
Mike But as Silyavaki has said there is more to it. How about posting some pics of the machine for a better answer. ..Clive
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
I did the calculation, 670 oz-in/4.6 NM is required to move the axis with one motor. I would normally add +30% for efficiency loss and use a motor in the 850/6 range. With all that, I have a pair of NEMA 34 frame motors that are 420/3. Will I be ok with these or should I go with something bigger? I'm sure that a frame size increase to 34 will slow down my Rapids.
My drives are Gecko 203V, I have several power supplies ranging from 36 to 70 volts available. I upgraded to a Ethernet Smooth Stepper with a high end BOB so I should be able to handle most anything.
Thanks again for your help.
Mike
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
Well are you using ball screws, pitch, size, direct drive, etc etc. Without full info nobody will be able to answer you. I take it you don't want to post any pics . Generally nema 23 are more than enough running at about 70V. ..Clive
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
Ball Screws, direct drive, .5"/rev, 48"X48" table, 2.2 KW water cooled spindle with 10" of travel. The machine is totally in pieces but I will post pictures as it goes back together. I'm replacing the rails and bearings so most of the machine is in tote boxes or stacked in a corner.
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
Quote:
Originally Posted by
CNC Visions
Ball Screws, direct drive, .5"/rev, 48"X48" table, 2.2 KW water cooled spindle with 10" of travel. The machine is totally in pieces but I will post pictures as it goes back together. I'm replacing the rails and bearings so most of the machine is in tote boxes or stacked in a corner.
Ok then I take it you have read this earlier in this post from Jazzcnc
Quote:
I'll save you a lot of headache and just say use 3Nm motors run at 65-70Vdc on 75-80vdc drives and you won't have any problems cutting anything.
Cutting speeds will depend on many factors like spindle power and tool material but 4500-5000mm/min wouldn't be out the way with 2.2Kw spindle using carbide tooling.
It might be better to keep away from direct drive and use belts and pulleys with a 2:1 reduction (that's what we tend to do this side of the pond) ..Clive
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
I apologize for not reading everything, Jazzcnc's post would have answered my question.
I'm looking into your advice about getting away from direct drive. It would be much easier to optimize stepper motor performance with the ability to change the drive ratio. I'm not sure why this side of the pond prefers direct drive and drives on the wrong side of the road.
One of the reasons I joined this group was to look into different ways to do things.
Thanks to all for your help
Mike
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
Quote:
Originally Posted by
TheGoodGuy
Well out of the two the Zapp motors are the better motors with slightly lower inductance and I know Gary's motors are good quality.!. . BUT whether or not these are the correct motors you should use depends on what your connecting them too.?
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
I am going to use PoStep60-256 drivers and 48V PSU.
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
Quote:
Originally Posted by
TheGoodGuy
I am going to use PoStep60-256 drivers and 48V PSU.
the motors that they sell at the same place http://www.poscope.com/nema23 are the same motors that zappautomation or cnc4pc sells. That are the motors that most people drive at 70V with Leadshine drives.
I also am looking at that drive you say, plus they have new 8axis ethernet board. Just today wrote them a big letter asking them many things about the board and the drives.
What i am saying is that when looking at the pdf of the motors StepperMotorDimensionsNema23.pdf the torque curve driven at 60V or 40V is very same till 3000rpm, hence 4 motors can be driven by 2x35VAC toroid 500w, which rectified will give ~49VDC, which is very near the drive capability /50VDC 6A/ . One of the questions i asked is if really this drive could drive the motor with this setup, i expect they will answer me tomorrow.
What i say is that will be better than the motor you say.
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
Quote:
Originally Posted by
silyavski
I also am looking at that drive you say, plus they have new 8axis ethernet board. Just today wrote them a big letter asking them many things about the board and the drives.
I've just received one of these boards for testing so I'll let you know.! . . . . Board looks Ok but dissapointing that it doesn't come with any connectors of any kind. This makes connecting more difficult than other boards as it needs IDC connectors to connect to board and then Terminal blocks for wires.
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
Quote:
Originally Posted by
JAZZCNC
I've just received one of these boards for testing so I'll let you know.! . . . . Board looks Ok but dissapointing that it doesn't come with any connectors of any kind. This makes connecting more difficult than other boards as it needs IDC connectors to connect to board and then Terminal blocks for wires.
Great! given the price and the added capabilities like IO for custom panels i hope that works good. 125khz is also a good thing.
I agree for the IDC, but on the other hand i like that option , if their drives are good i mean, cause i could connect drives and BOB with cables. This drives should be DSP, yes? Its not mentioned at any place.
Honestly i realy have great hopes for that combo, cause i prefer EU made stuff than Leadshine for example in my machines. Especially given the size of the drives.
I was almost ready to buy a 4 motor drive and bob today. how good that you have it already.
My biggest questions are:
-any major drawbacks like definite inability to do something in mach3?
-4rth axis, gantry squaring and so on...
I will wait then to see what you say. I hope at the end somebody managed to make decent cheap Ethernet board with more than 4 axis.
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Re: Motor size selection on a slaved 2 motor axis, is it a simple divide by 2?
Quote:
Originally Posted by
JAZZCNC
I've just received one of these boards for testing so I'll let you know.! . . . . Board looks Ok but dissapointing that it doesn't come with any connectors of any kind. This makes connecting more difficult than other boards as it needs IDC connectors to connect to board and then Terminal blocks for wires.
Would be interesting to read your opinion on these boards...
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Re: What size stepper motor do I need...? A tutorial
How can i calculate what motor size i need for my gantry if i use rack and gear on both sides. This example is for ballscrews. Looking forward for your answer.