NEMA 23, weird velocity results.. need help

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21 Nov 2013 05:46 - 21 Nov 2013 05:51 #41061 by PCW

So, will running the average 2.37A on my driver DIP be able to help me go faster?


sure, and setting the current to 0.50A will be even faster since it takes less time time to get to there
but it will not affect your speed vs torque curve (other than limiting the maximum torque),
only the motor inductance and supply voltage affect that
Last edit: 21 Nov 2013 05:51 by PCW. Reason: ommission

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21 Nov 2013 06:08 #41062 by fannlow
Well, to be honest...
Without any load, 1A works fine to a certain speed... maybe around 2~3mm/s...
However w load, I have to reduce further!

So I decided to stick w 4.2A for the load and cutting, speed to 13mm/s.
Acceleration to 200mm/s2.

Will get a 10tpi, 5 start lead to help my performance. ..
This can be done by spending USD70, 2x nut and 2x screw.. and 1wk
Which will help me more than spending USD250 for 3x nema23 4.2A, 3.8mH motors & 1x power supply as my psuis only outputting 10A max, 36V and 360watt...

Quite costly and insufficient for my scenario...

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21 Nov 2013 06:13 #41063 by fannlow
I wanna say a BIG thank you to moderators taking time to teach me and educate me on this awesome software.

I am now a better and smarter DIY cnc builder.

However, I really need to know how to choose a motor..
I read through the wiki, but I wanted to know if I wanna hit like 800 ipm or 1000ipm or even higher on my seemingly larger machine, which I have but no motors yet (10ft x 5ft x 4ft H)... pulling aluminum gantry sitting ontop a linear rail, max without load at about 60kg, with cutting force added to around 70kg (polyfoam cutting ~ high speed)

I should be aiming at nema42 ya?
High Amp, low induction?

Let me know if im in right direction or need reading?

BIG thank you!! :)

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21 Nov 2013 06:21 #41065 by andypugh

However, I really need to know how to choose a motor..
I read through the wiki, but I wanted to know if I wanna hit like 800 ipm or 1000ipm or even higher on my seemingly larger machine, which I have but no motors yet (10ft x 5ft x 4ft H)... pulling aluminum gantry sitting ontop a linear rail, max without load at about 60kg, with cutting force added to around 70kg (polyfoam cutting ~ high speed)
I should be aiming at nema42 ya?


No, for that you probably want servo motors.

They don't actually make as much torque as steppers (size for size) and they are more expensive, and the drives are more expensive, but a 1Nm servo will make 1Nm at 0 rpm and at 3000rpm, while your 4Nm stepper is down to 0Nm at 800rpm.

One potential source is this ebay shop of second-hand servo drive sets: stores.ebay.co.uk/FA-PARTS/SERVO-DRIVE-A..._trksid=p4634.c0.m14
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21 Nov 2013 06:27 #41066 by fannlow
Yup!
I did run a check on the nema43 in comparison. ..

Awfully slow but with so much torque around4.2k ozin...
Slower than my current nema23...

Haha, you guys have to show me the linuxCnC for servo settings nxt month...

By the way, if I run a 5axis, that is the spidle part for extra 2axis, will linuxCnC take 2 nema23 stepper motor for that, while running 3 servo motors for x, y, z?
Thanks

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21 Nov 2013 06:30 #41067 by andypugh

By the way, if I run a 5axis, that is the spidle part for extra 2axis, will linuxCnC take 2 nema23 stepper motor for that, while running 3 servo motors for x, y, z?
Thanks


You can control 9 axes (from G-code) with LinuxCNC.

(You can control more outside G-code)

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21 Nov 2013 06:56 #41068 by fannlow
Andy:
I mean running stepper along side with servo?
that is doable in LinuxCnC ya?

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21 Nov 2013 07:13 #41070 by andypugh

I mean running stepper along side with servo?
that is doable in LinuxCnC ya?


Yes, but don't expect Stepconf to be much help :-)
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22 Nov 2013 06:00 #41091 by fannlow
I have decided to do some understanding on how the PC works in relative to the steppers and perhaps servo as I need to get them next month.

here is the link, i found from wiki:
wiki.linuxcnc.org/cgi-bin/wiki.pl?Tweaki...ftwareStepGeneration

however, i do not quite understand how I am suppose to know which is sufficient as in the wiki says.
example: it will say the Xylotex has a sufficient max step/sec, but not the Gecko, and improving the Gecko's Dir hold from 1 to 2 or so, will actually improve this?

so, I am thinking, I set up my drive to:

StepLen : 3500
StepHold: 0
DirHold: 35000
DirSetup: 35000

I have a BASE_THREAD of 27600 (worst case senario)
my motor manufacturer gave me this image to help me figure out the time needed. (attached)

note: > = (larger or equal), < = (lesser or equal)

Width pulse A > = 1.0uS
Width pulse B > = 1.0uS
Pulse Freq < = 500KHz
Time Change Dir > = 2uS
Input Signal Vi 3.6V < = H Level < = 5.5V
-5.5V < = L Level < = 0.3V

in this case, is my time Dir setup = 2C in the diagram or (1.0uS + 1.0uS)?
adding that to the BASE_THREAD of 27600, my settings for BASE_PERIOD should be around 29000?

also, should I use this attached information to setup my
StepLen
StepHold
Dir Hold
Dir Setup

if so, following the guide
wiki.linuxcnc.org/cgi-bin/wiki.pl?Tweaki...ftwareStepGeneration

what should these numbers be, and perhaps how do i interpret them should be, so I can do these math for my other machines :)

thanks for helping me solve the math vs. understanding issues..
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22 Nov 2013 06:04 #41092 by andypugh
If the step pulses make the driver make a step, then that is all that matters, and you won't get any more speed or performance from changing the values.

Your low speed is due to high inductance motors and not-very-high voltage.

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