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crossleymarko
10-04-2012, 06:35 PM
hi im trying to check my dir voltage on eg:-pin 2 for mach3, im just getting a constant 3.26 volts.
ive check settings in pin n ports.. is it my port..

Jonathan
10-04-2012, 06:56 PM
Are other pins the same? Is it a laptop?
Ideally you want 5V.

crossleymarko
10-04-2012, 07:04 PM
yes its a laptop... does that matter.. i get the 3.26v even before mach3 starts up. also, when i remove the port in device manager it goes to 5v...

Jonathan
10-04-2012, 07:16 PM
Laptops are well known for not running having substandard parallel ports and thus not running mach3 very well, if at all. Have you got a spare computer with a parallel port you could compare it to?

crossleymarko
10-04-2012, 07:20 PM
Laptops are well known for not running having substandard parallel ports and thus not running mach3 very well, if at all. Have you got a spare computer with a parallel port you could compare it to?

yes a compaq, never used lol. mrs brought it from work. that will be the machine i will probably be using when the work shop is built, ill give it a try...

russell
10-04-2012, 08:53 PM
It sounds as if you may have the port configured as inputs which gives a floating high impedance. Alternatively you may require a pull down reistor between the output and signal ground.

Russell

crossleymarko
10-04-2012, 09:55 PM
mach3 dosnt seem to be communicating with the port... as i said before im getting a constant voltage reading, of 3.267.
when i uninstalll lpt drivers in device manager i get a constant 5v,,,

crossleymarko
10-04-2012, 11:25 PM
when i press the curser keys to try and see voltage should i get a change in the on sceeen coordinates (are the called dro)
as i get nothing in mach 3.

crossleymarko
10-04-2012, 11:50 PM
ok read i should have port as ecp in bios...
and something weired...
i start my laptop (with meter still connected) i get a steady 4.77 volts. then i start up mach3 and still the same. as soon as i shut mach3 down i get 25mv.. i went bach into mach and nothing 25mv.

Jonathan
11-04-2012, 12:19 AM
when i press the curser keys to try and see voltage should i get a change in the on sceeen coordinates (are the called dro)
as i get nothing in mach 3.

Yes, when pressing the arrow keys, or pg up/down they should change. If not then it's probably in emergency stop mode. Have you (for now) disabled the emergency stop, or is it flashing? Go to config->ports and pins and look for e-stop, then change it from active high to active low (or vice versa, i.e. invert it). That should get it running...

crossleymarko
11-04-2012, 01:09 AM
its now in active low.ports n pins inputs...! pin is 0 still enabled. still no number changes, when pg up etc is pressed.. is this the root of my problem...

crossleymarko
11-04-2012, 01:16 AM
done driver test, system under mach controll

crossleymarko
11-04-2012, 09:30 AM
might i add i have nothing plugged in.. ie breakout board etc.. software dosnt do anything when cursers are pressed.. maybe thats part of the problem.. no cooordinate change at all.

Jonathan
11-04-2012, 11:34 PM
software dosnt do anything when cursers are pressed

That's a problem. Try going on to the MDI tab and in the white box type:

G0 X10

That should make it move to X=10 and you should see the numbers count up on the DRO. Send a screenshot if not...

crossleymarko
12-04-2012, 12:25 AM
No idea what's going on. Come home and drop working. Coursers PG up Dec. Still odd voltage reading. Messed about and now back to square 1.

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m_c
12-04-2012, 01:42 AM
Have you tried running the Mach driver test?

crossleymarko
12-04-2012, 01:50 AM
No idea what's going on. Come home and drop working. Coursers PG up Dec. Still odd voltage reading. Messed about and now back to square 1.

Sent from my HTC Desire HD using Tapatalk 2
just read this sorry.. any way

got home and all was working.. apart from voltage change on paralell port.
messed about reinstalling etc and i lost dro function. ive installed and uninstalled 20 times still no joy...

and then i came accross this post..http://www.machsupport.com/forum/index.php?topic=17552.0

so i deleted the mach3 driver and dro is working.. but still no communication to my port.. arrrggghhhhh

ive tried every bios setting.. no joy on the laptop.. i would of tested my desktop i have but im a couple of cables short..

ecat
12-04-2012, 02:14 AM
Silly question:
When LinuxCNC starts up it will disallow all control of the machine until the user clicks the magic EStop button - effectively saying they are in control of the machine and the environment. If I remember Mach works in much the same way, a big red stop button perhaps? Have you clicked it?

crossleymarko
12-04-2012, 02:24 AM
Yep about 40 times all ok.. it said

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ecat
12-04-2012, 02:30 AM
Any limit or home switches configured?

crossleymarko
12-04-2012, 02:34 AM
well its deffo the mach3 drivers. reinstalled them and hey pesto no dro movement, so i disabled my lpt1 port and tried that still no dro but had a constant 5v voltage on pin 2... whats going on at all.

crossleymarko
12-04-2012, 02:35 AM
no none.. estop is enabled, port 0 pin 0

crossleymarko
12-04-2012, 02:41 AM
Silly question:
When LinuxCNC starts up it will disallow all control of the machine until the user clicks the magic EStop button - effectively saying they are in control of the machine and the environment. If I remember Mach works in much the same way, a big red stop button perhaps? Have you clicked it?

not silly at all any input is welcome..

but yes the reset button is clicked on start up.

crossleymarko
12-04-2012, 02:55 PM
When the mach driver installed no dro. Also I have a constant 3.26v from boot up. When I close mach3 software down I get 0v. When mach3 driver is disabled dro changes and v from boot remains at 3.26. Even when I close mach3.

Think I'm gunna try another machine.

Sent from my HTC Desire HD using Tapatalk 2

crossleymarko
12-04-2012, 11:48 PM
ok so rebuilt this hp desktop, installed vista.. ( 3 of my xp disks) wont install.. scratched to buggery... so ive tried vista.

ok all works.. voltage up/down etc..... wehey!lol... BUT!!!!!

my voltage is only 3.3v.... aaarrrggghhh lol.

now on the disk i got with the software, there is a read me file that says to install memoryoveride reg file.. or itll crash on startup.. it hasnt though...

how do i get the 5v needed..

cheers all

crossleymarko
13-04-2012, 12:56 AM
ok got it breakout board supplies 5v... slowly getting there.. am i right...lol

so ive tested pin 2,3,4,5 al work x,y,z,a.. ive tested cable... all connected .. my next miff is the break out board..?

on the x-1 i have xn,xd,xs,xe. same for y-1 and z-1 i tested all terminals to check voltage.,on the x terminals i get voltage change on the xs terminal.. on the y i get change on the yd terminal and on the z no change just 5.11v.. is it a faulty board...

thanks

JAZZCNC
13-04-2012, 01:20 AM
First are you still on the laptop or desktop.?
If laptop then forget it they are just too unreliable due to heavy memory management and Mach's driver really doesn't work well with most Lappy's. To use a Laptop reliably you need an external motion controler like smooth stepper, this is how laptop runs machine I use.

If it's a desktop is it a PCI PP card or built into mother board.? If it's a modern-ish PC then chances are it's 3.3V PP if so thats it there's nothing you can do about it other than use a PCI PP card. Even then you have to be carefull because some use the USB bus to simulate a PP and again don't work with Mach. If you go to the Mach forum you will find more info regards this.

Check the bios to see what the Printerport is set to EPP/ECP etc
Are you actually hooking upto drives and motors like in a full working machine or just testing on the bench.?
Does it have an Estop wired up or the BOB have a charge pump.?
Does the bob need an external supply to activate it's opto's.? some do.!
Also what are you using for a PP cable.? are you 110% sure it's a straight thru cable standard printer cables are very often not straight thru, I've even had some that tested ok with multimeter but still had some trickery built into the plug that switched signals.!!! (Drove me F'~@ing nuts)

Have you done the Mach driver test.?
Also can you post the Mach XML file your using, it will be in the Mach folder under the same name as the profile you use to load Mach.
This will make it much easier to see if it's just a PP setting issue.? I'm curious because some where you mentioned port 0 pin 0 for estop this don't sound correct and it could be that your port address is wrong.?

crossleymarko
13-04-2012, 01:22 AM
i feel ppl are thinking "man this guy is demanding" hahaha.. sorry ppl just tryin to learn a new trend...

thanks all who have inputted.

crossleymarko
13-04-2012, 01:33 AM
i feel ppl are thinking "man this guy is demanding" hahaha.. sorry ppl just tryin to learn a new trend...

thanks all who have inputted.

hi thanks its a desktop pc now.. with onboard pp, i wasnt gonna use the lappy anyway.. but me being me had to play, and yes im just bench testing, (not even got motors yet) so testing what i can.. did a continuity test on the lead... mmmm trickery eh! well it came with the bob and 542 drivers. so who knows.. i think tomorrow ill test voltage through the lead would that help... how did you sort it...

yes the bob uses usb power...

so the 3.3v is converted by the bob.. to 5v is this right.

which terminal should i be getting my voltage change on the bob.. ie xs or xd...like i said xaxis is x-s and y is yd

think thats all

John S
13-04-2012, 01:44 AM
no none.. estop is enabled, port 0 pin 0

Port 0, pin 0 ?????????

should that be port 1, pin whatever ?

JAZZCNC
13-04-2012, 01:45 AM
so the 3.3v is converted by the bob.. to 5v is this right.

Ermm what bob is it.? you don't need 5v just a big enough difference between Hi and Low at 3.3v there's not a big enough differential and so unreliable signals.

Give me some details of what you have and I'll have a look.

crossleymarko
13-04-2012, 01:59 AM
Port 0, pin 0 ?????????

should that be port 1, pin whatever ?
i watched a setup vid on utube.. he had estop enabled, port 0 pin 0.. is this wrong, what would this settin do.

JAZZCNC
13-04-2012, 02:05 AM
i watched a setup vid on utube.. he had estop enabled, port 0 pin 0.. is this wrong, what would this settin do.

Yes it should be port 1 and then the pin you assign it to on your bob.

Like i said before post the XML file and I can load it into Mach here and check it for you. Often it's just a simple setting that like this that stops every thing working.?

crossleymarko
13-04-2012, 02:25 AM
http://www.ebay.co.uk/itm/CNC-Router-DIY-Kit-5-Axis-Breakout-Board-3x-M542-Stepper-Motor-Driver-1-0A-4-5A-/270951754294?pt=UK_BOI_Industrial_Automation_Contr ol_ET&hash=item3f15fbaa36#ht_7034wt_972

heres the kit. i dont have an estop so i thought the settings pin 0 port 0 still enabled was ok , sorrry,
ill send files now

crossleymarko
13-04-2012, 02:41 AM
http://dl.dropbox.com/u/19756368/Mach3Mill.xml?dl=1
http://dl.dropbox.com/u/19756368/Mill.xml?dl=1

these are the 2 mill shortcuts i have.. i use each one... as you can see on my desktop i have mach3mill.. and mill..

its a fresh install of vista..

JAZZCNC
13-04-2012, 02:57 AM
Do you have manuel for the Bob which gives the pin settings etc.?

Don't use the Mill xml it's all screwed up.

crossleymarko
13-04-2012, 03:05 AM
Do you have manuel for the Bob which gives the pin settings etc.?

Don't use the Mill xml it's all screwed up.

i dont (i think) ill delete it...
ill have a gander

whos manuel... lol are you on ya jollys jazz...hahaha

JAZZCNC
13-04-2012, 03:13 AM
No but i'm not working tomorrow that why the late one. . . See PM.

Manuel.!! . . The spanish waiter . . Ce Mr fawlty. . Lol

Bed time.!!

crossleymarko
13-04-2012, 10:06 AM
hey jazz, heres the pdfs sent with bob,,

http://dl.dropbox.com/u/19756368/User_Manual_5_axis_Breakout_board.pdf?dl=1

crossleymarko
13-04-2012, 10:07 AM
that 1 post took 2hrs....arrrgghhh. friggin laptop.. gonna sort it when i get a min.

John S
13-04-2012, 10:30 AM
These boards have right weird pin outs.
X is pin 2 step pin 14 direction
Y is pin 16 step pin 3 direction
Z is pin 7 step pin 8 direction
Pin 1 is enabled.

crossleymarko
13-04-2012, 12:01 PM
Sorry john.. x pin..?. Were do I check voltage on each axis of the board

Sent from my HTC Desire HD using Tapatalk 2

JAZZCNC
13-04-2012, 12:09 PM
Hi Mark,

Ok Mark thats what I was after here's the XML altered so now you should get some sense.

I think you maybe haven't realised the importance of Mach setup.? If Mach is not setup to send signals down the correct output pins that your BOB use's then nothing will make sense or work.! Same applies to the inputs pins, like E-stop, limits, homes etc Basicly Mach is sending the signals to the wrong places so your not reading them there or it's not sending them at all because it thinks it's in E-stop mode.
The motor output pins where set wrong and the enables turned off. That's why you wouldn't get correct signals or voltage thou it's still possible you have a 3.3v PP. I very much doubt this cheap BOB will pull the pins upto 5V, it doesn't mention it anywhere but agian it's possible and we'll easliy know when you test the pins again.
I,ve also set the Estop to work of the correct pin, If you havent got an E-stop then just jump a wire from pin15 to it's ground pin, this will affectively lock E-stop on BUT ONLY do this for bench testing purpose's.

The only realy important bit in the BOB PDF is the short portion that gives you all the pin numbers for each Axis and I/O connection and also the Pic which shows the pin num for each connector. The rest is just padding really so it's not a 5 line manual.!!

The PDF shows specific connectors for X,Y,Z,A limits and E-stop you dont have to use these for that purpose, They are just inputs and can be assigned to any task you choose BUT Mach must be set to look at the pin number of the connector you choose.
IE: If you want to use connector next to 5V which now shows as E-stop has X axis limit then all you do is go into mach's inputs signals and tell it for X axis limit to look at pin 15.

Exactly the same applies with outputs, both motor and relays etc if you want X Axis motor to use the connector now showing Z axis just change the pins in Machs motor outputs to match which ever connector you choose.
Like wise if you want the relay to turn on or off the spindle or coolant even the lights in the workshop then just assign the correct connector pins to the relavant output in Mach output signals setup and when the relavant G-code appears IE M3, M4 the output will be triggered and the signal will be sent down that line and relay turned on or off.
Mach doesnt know or care whats attached to the Relay or any input or output all it does is turn them on or off or respond to signals and carry out some other action like when it see's an E-stop signal it will Stop the G-code and if setup as such turn any outputs, whether that be relays or motors or fruit machines on or off.

So as you can see if Mach set to send or recieve signals in one place and you measure in another nothing will make sense or work.

Now Mach's set to match the Bob you should see the voltages at the relavant pins.
Start with X axis first measure between pin 14 XD and XN when you push the X axis jog keys the voltage should show around 0V for one direction and upto 5V for the other if it shows around 0V and 3.3v then your buggerd because thats the PP voltage and it's too close to the threshold of the pin change state. It could work but you may get Odd things happen and missed steps etc.

Hope this helps.

PS I've changed the profile name to crossmill so it didn't clash with my standard Machmill profile.

crossleymarko
13-04-2012, 12:54 PM
Just a quick post.Thank you so much jazz.. ill have a look when I get home.... again thanks...

Sent from my HTC Desire HD using Tapatalk 2

crossleymarko
13-04-2012, 06:09 PM
home now done the estop jazz thanks,
voltage test on x pin 14 (4.3v), y pin 3 and z pin 8.(3.3v)

when i booted up the machine with the v meter on it was showing 5.1v untill windows logo.. so is it a 3.3v pp. next ill test bob...

JAZZCNC
13-04-2012, 06:19 PM
home now done the estop jazz thanks,
voltage test on x pin 14 (4.3v), y pin 3 and z pin 8.(3.3v)

when i booted up the machine with the v meter on it was showing 5.1v untill windows logo.. so is it a 3.3v pp. next ill test bob...

Were have you been measuring from because I don't understand the "Next I'll test bob" .?

crossleymarko
13-04-2012, 06:40 PM
the back of the pc... then the lead, just done the bob.. all good. i looked at the pdf, didnt know all the settings were there, im not sure but is there a mistake on it the y axis... i changed them round to suite the pdf... compare interface def with part 2 and part 3..

any way getting 5.1v on bob all axis xd yd zd pins... im made up fella,,, cheers again,

is there a way of testing drivers... with no motors.. be getting them next week...

oh, yeah estop kept popping on when i had bob connected... external estop requested, how do i stop it...

JAZZCNC
13-04-2012, 07:36 PM
is there a way of testing drivers... with no motors.. be getting them next week...

oh, yeah estop kept popping on when i had bob connected... external estop requested, how do i stop it...

E-stop easy go into inputs and toggle active low if it's cross change to tick or vise versa.

I wouldn't mess with drives it's very easy to let out the magic smoke just connect motors and chances are they will work and absolutley don't disconnect motors from drives with power on when you get them it WILL BLOW THE DRIVES.

crossleymarko
14-04-2012, 12:04 AM
E-stop easy go into inputs and toggle active low if it's cross change to tick or vise versa.

I wouldn't mess with drives it's very easy to let out the magic smoke just connect motors and chances are they will work and absolutley don't disconnect motors from drives with power on when you get them it WILL BLOW THE DRIVES.

i hear ya.. read that on different sites...

thinking of 3.1nm motors.. would they do the trick ,

Jonathan
14-04-2012, 12:38 AM
thinking of 3.1nm motors.. would they do the trick ,

For the vast majority of machines 3.1Nm motors are a good choice. If the machine is small enough to use smaller motors its hardly worth it as the cost saving is so small. Unless it's a big machine (towards 8x4 size) 3.1Nm nema24's are good. What size is the machine?

crossleymarko
14-04-2012, 12:52 AM
For the vast majority of machines 3.1Nm motors are a good choice. If the machine is small enough to use smaller motors its hardly worth it as the cost saving is so small. Unless it's a big machine (towards 8x4 size) 3.1Nm nema24's are good. What size is the machine?

not sur jonathon, think ive mentioned in earlier posts maybe 4 x4 to begin with... a starter... then progress... 4x6..what would be the limit ... could go 4.0nm but is that overkill.. mainly timber and mdf stock...


Can i just say this forum is awsome,,, so helpfull for us noobys so too speak not feeling like we are being talked down at by the people that know more than us... that has always been a pet hate of mine on some forums, infact when ive read some posts ive not even registered.. so thankyou all... especially jazz and jonathan..

Jonathan
14-04-2012, 12:54 AM
not sur jonathon, think ive mentioned in earlier posts maybe 4 x4 to begin with... a starter... then progress... 4x6..what would be the limit ... could go 4.0nm but is that overkill.. mainly timber and mdf stock...

3.1Nm will be perfect for a 4x4 or 4x6 machine.

crossleymarko
14-04-2012, 12:56 AM
sorry missread jonathon... so 3.1 is adequet.. for a 4x6 eventually.

crossleymarko
14-04-2012, 12:57 AM
lol... 3.1 it is then.... so future up grades up 8x4 maybe

JAZZCNC
14-04-2012, 12:58 AM
Can i just say this forum is awsome,,, ... especially jazz and jonathan..

Ye but Jonathan talks shite most the time. . .:whistle: . . Nah Luv him really.:couple_inlove:

crossleymarko
14-04-2012, 01:01 AM
uhoh.... here comes your typical forum fall out...lol

mtv forum death match... via tapatalk...hahahaha...

JAZZCNC
14-04-2012, 01:04 AM
uhoh.... here comes your typical forum fall out...lol

No not at all he knows he has my utmost respect, I just like taking the piss at every opertunity. .:whistle:

crossleymarko
14-04-2012, 01:09 AM
you see,,, different forum completly dude,,, just doin a water change on the kids

JAZZCNC
14-04-2012, 01:25 AM
I'll mention this because Jonathan maybe didn't see you had 50V drives but these 3nm will be running slightly less than there ideal voltage.?

Because you have 50V Max drives then you'll need to run these motors with no more than absolute Max 48v and even thats on the high side. This is because the motors will produce current (back EMF) when de-accellerating which gets passed backdown thru the drives to the PSU, if the psu can't absorb this current then some can feed back at a much higher rate than 50v and damage the drives. sometimes esp with linear regulated type PSU's it can trip them out as they try to protect there circuits, thats why unregulated supplys are prefered.

So to be on the safeside you really need to be less than 48V or use a unregulated toroidal transformer supply which can handel the EMF much better.

Really if your looking to run 3nm and esp 4nm to there full potential they need much more voltage than 48V, 65/70v is much better for 3nm and 70/75V for 4nm so then you need drives that can handle 80V.

This is why I always say buy the drives/motors/psu after you have at least designed the machine. This way you can size them to suit.!

It's very common thou for eager new folks to rush out and buy drives/motors etc first it's also silly common for them to buy or be sold the wrong size PSU which doesn't match the drives or motors.!! I see far to meny 36V supplys bought with 50V drives and 3nm motors which want 60+ V to work to full potential. . :confusion:

crossleymarko
14-04-2012, 01:42 AM
correct me if im wrong surly its like audio speakers etc.. why drive something to its max?
so ie: 500w speakers would be comfortable at 200w.

so 50v drivers will be ok at 45v-48v.. i have read that 542 drivers are 50v max but:::: cappable of handleing 100v.. ill find the post,,,

crossleymarko
14-04-2012, 01:47 AM
and yes jonathon has talked me through toroidal psu's... not going the pre commercial route... deep end and both feet me...hahaha

crossleymarko
14-04-2012, 01:53 AM
at the end of the day, i was looking at the single driver tb6580.? i think... then i was pushed toward m542. (eyup budget change).lol i want a machine that i can learn from atthe min.) was even gonna go the route of threaded rod as the lead screw... thats changed.. now looking into sprockets, rack n pinion. ive got time no were to build it yet. or put it.. workshop is only just starting...

crossleymarko
14-04-2012, 02:03 AM
hey deebee you wanna say sumat.. you aint spoke since 2010.... lol. summat weired on ere...

JAZZCNC
14-04-2012, 03:49 AM
correct me if im wrong surly its like audio speakers etc.. why drive something to its max?
so ie: 500w speakers would be comfortable at 200w.

so 50v drivers will be ok at 45v-48v.. i have read that 542 drivers are 50v max but:::: cappable of handleing 100v.. ill find the post,,,

No it doesn't quite work like that with steppers but it's far too late for me to get into it too much now.
Steppers get there speed/torque from voltage/amps. So if your drives or PSU limit you below the motors ideal operating voltage/amps then you'll get far less speed/torque before the motors ideal corner speed is reached and torque drops away and stalls the motor.
So say at with 48V they will only reach approx 650-700rpm when motor stalls.
With 65v this changes to approx 1000-1100rpm. These figures are lose figures but you get the drift it could be 25-30% less performance than what the motors are capable of giving with correct size drives/psu.

Look around and some where on here Irving did a spread sheet that shows you the differences at different voltages.

All I'll say is your a braver man than me "Gunga Din" if you try to run these drives any were near them voltages. Give them 65V put the kettle on and see how long they last.? Bet you 10 the drives boil before the Kettle.!!

deebee
14-04-2012, 09:49 AM
hey deebee you wanna say sumat.. you aint spoke since 2010.... lol. summat weired on ere...

This site is one many forums I read, not much to contribute yet, maybe oneday I'll get to time to work on my own machine. Lots of useful info from all you guys though. Good luck with your build.
BTW I am also a Wiganer but living down in London, where in Wigan are you? My mum still lives near Atherton. Cheers.

crossleymarko
15-04-2012, 01:39 AM
No it doesn't quite work like that with steppers but it's far too late for me to get into it too much now.
Steppers get there speed/torque from voltage/amps. So if your drives or PSU limit you below the motors ideal operating voltage/amps then you'll get far less speed/torque before the motors ideal corner speed is reached and torque drops away and stalls the motor.
So say at with 48V they will only reach approx 650-700rpm when motor stalls.
With 65v this changes to approx 1000-1100rpm. These figures are lose figures but you get the drift it could be 25-30% less performance than what the motors are capable of giving with correct size drives/psu.

Look around and some where on here Irving did a spread sheet that shows you the differences at different voltages.

All I'll say is your a braver man than me "Gunga Din" if you try to run these drives any were near them voltages. Give them 65V put the kettle on and see how long they last.? Bet you 10 the drives boil before the Kettle.!!

i get it, motors will outperform the drivers,,, or drivers cant feed enough to the motors,, i was told these drivers would be adequet... what motor would you recomend..

so in my head i have it this motor would work as well as a motor running at the ful voltage .

Jonathan
15-04-2012, 12:47 PM
I'd bet more than 10 on that!


i get it, motors will outperform the drivers,,, or drivers cant feed enough to the motors,, i was told these drivers would be adequet... what motor would you recomend..

The drivers are adequate yet, but not ideal. Ideally the 3Nm motors should be run from at least 60V, which means you'd have to use m752 (which is what I use), or any 70-80V driver. The corner speed, which is the motor rpm at which the torque starts dropping off rapidly, is proportional to the supply voltage and inversely proportional to the inductance. Incidentally, this is why it's best to wire the motors in bipolar parallel since that's the lowest inductance and therefore highest torque configuration. Anyway, since the corner speed is proportional to the applied voltage running the motors from 48V instead of 70V will result in (approximately) 1-48/70=31% reduction in speed...as Jazz said.

For a fuller explanation see my post here:
http://www.mycncuk.com/forums/showthread.php/3861-MY-CNC-sessions-are-now-like-laundry-day?p=25191&viewfull=1#post25191

However you've got to consider that although you may find motors with a lower inductance, if their torque rating is much less you'll still have less torque at the corner speed.
Lets look at Zapp's offering:
http://www.zappautomation.co.uk/sy57sth763008b-nema-stepper-motor-p-38.html?cPath=9_159_42

The 1.85Nm motor inductance in Bipolar parallel is 1.6mH (compared with 3.2mH for the 3Nm). The corner speed can be approximated by 191*V/(IL), so on 48V that's 191*48/(4*1.6)=1432rpm and similarly 682rpm for the 3Nm motors.
Now we want to know which motor has the highest torque at the corner speed of the 1.85Nm motor, i.e. 1432rpm. This is a bit more difficult...

When operating at or below the corner speed the motor output torque is approximately the rated torque divided by square root of 2, so for the 1.85Nm motors it's 1.85/1.41=1.31Nm.
When operating above the corner speed the torque is calculated from the motor's rated power, which is calculated from; P=[torque at or below corner speed]*[corner speed]/9.55, so for the 3Nm motor the torque below corner speed is 3/1.41=2.12Nm. Substitute that into the formula for motor power and you get, P=2.12*682/9.55=151.5W. Now we can find the torque at 1432rpm, which is given by 9.55*P/rpm=9.55*151.5/1432=1.01Nm.

So at the corner speed for the 1.85Nm motor you will get about 30% more torque from the 1.85Nm motor than the 1Nm motor, however below 1100rpm the 3Nm motor will develop more toque than the 1.85Nm motor.

This demonstrates why it's a bad idea to just go and buy the biggest motor you can find, especially with Nema 34 motors, since the bigger motor may well actually be worse. But...

Thing to do now is do the calculation again, but this time take into account having pulleys to change the ratio since I'm confident you will find the 3Nm motors on 48V will perform better than the 1.85Nm on the same voltage if you gear them up - larger pulley on motor.

(This is essentially the same method of calculation as Irving's spreadsheet. I've just explained it step by step to hopefully make how the system interacts clearer.)

Oh and if you want to know the recommended minimum voltage for a stepper motor it's 32*L^0.5, where L is the inductance. So for the 3Nm it's 32*3.2*2^0.5=57V, and similarly 40V for the 1.85Nm motors.

If I were you I'd wait until you've got much further with the design and know what ballscrews (silly to use anything other that ballscrews since most of the motor power is lost via friction with single start leadscrews or threaded rod) you'll be using and the mass of the gantry etc.

John S
15-04-2012, 02:19 PM
Hard facts of life here, no calculations but based on building over 120 cnc machines or conversions. The X3 cnc kit sold by ARC sold 58 units for a start and I'm not counting any of the Sieg CNC machines that are made by Sieg.

Hard fact is on any decent CNC stepper build the weak point is always the stepper drive, motors hardly ever go wrong unless you do something seriously bad to them.

Speed is voltage and the average stepper motor needs to run at 20 to 25 times it's nameplate voltage, as most are between 3 and 6 volts that's 75 to 150 volts. As most available stepper driver max out at 80 volts that normally determines the max. However the popular 80 volt Leadshine drivers also max out at 7.2 to 8 amps [ beware the 9.2's released , they were not reliable ]

When people read these specs they look well over spec'd for a 3.1Nm motor, which they are but as I said earlier the drivers are ALWAYS the weak link. now if you spend on these more expensive drivers and down rate you get various advantages, one is longer life because they are never stressed and always operation well with limits, never get hot, again for the same reason and you always have the correct driver for if you ever upgrade.

Do the sums, 3 expensive drivers that are the best part of bomb proof or buying cheaper ones and replacing then 2 and even three times ?

Out of those 58 X3 kits which drove 2.1Nm triple stack motors, we had 3 bad drivers and this one was from a guy who lives right next door to a power station and regularly has to replace televisions, computers etc because of spikes, as do his neighbours.
So discount this and it's a 100% success rate on machine used by users with different skill and experience levels.

Compare this to say a Route-out machine, I have often seen posts on here wanting new boards.

End of the day you get what you pay for.

JAZZCNC
15-04-2012, 10:04 PM
Compare this to say a Route-out machine, I have often seen posts on here wanting new boards.

End of the day you get what you pay for.

LMFAO . . If I'd have put that would have got banned. . Again!! . . John gets thanked. . :yahoo::joker:

Jonathan
15-04-2012, 10:16 PM
LMFAO . . If I'd have put that would have got banned. . Again!! . . John gets thanked. . :yahoo::joker:

:) Yeah the Routout drives are pretty useless. In the interest of balance, perhaps they beat the TB6560 on eBay!

JAZZCNC
15-04-2012, 10:40 PM
If your looking to build a larger machine, like you seem to be then Personally I'd sell them and start again.!!

You will lose very little money as they are brand new and they will be perfect for a smaller machine. Where has if you continue and use them you will only lose money.!

To use them now means you buy or build a 44-48V supply so this will be no use so wasted money at a later date when you WILL need new drives either because like John says they Die from the strain or you want higher speeds or torque.
Jonathan's suggestion to gear them is OK and a good work around but it is just that a work around and less than ideal and does come with cost's.?
Lower resoultion and lower torque plus more expense of belts and pulleys (Thou I'd still use them anyway but for different reasons!!)

Sorry to say this but I suspect these drives are cheap versions of real Leadshine 542's so the chances of them giving up the ghost under strain is quite high and this is why I say cut and run now before you waste money and get frustrated with the compromises.

The drives and PSU plus good quality control box build practice is one of the most important areas for a hassle free machine skimp here and you will regret it.!!

John S
15-04-2012, 10:55 PM
:) Yeah the Routout drives are pretty useless. In the interest of balance, perhaps they beat the TB6560 on eBay!

No way. They made 3,784,284 of the TB6560's, only 2,734,169 blew up.
Routout made 267 and 234 blew up. Notice he doesn't sell any boards now but the Leadshine drives so must be some truth in my statement. :encouragement: