Nema 23

[Paswest]

I have a dead Emco F1 milling, and I am trying to upgrade the electronic .
I bought a Chinese kit: 3drivers DM542A, 3stepper motor 280oz, 1 power supply and 1 interface board.
I never was able to run any stepper motor whit the original board.A friend lent me another Chinese board, with that one I can run the motor but max RPM is 220.
Are the stepper motor suppose to run faster ?

 

[dman]

I have a dead Emco F1 milling, and I am trying to upgrade the electronic .
I bought a Chinese kit: 3drivers DM542A, 3stepper motor 280oz, 1 power supply and 1 interface board.
I never was able to run any stepper motor whit the original board.A friend lent me another Chinese board, with that one I can run the motor but max RPM is 220.
Are the stepper motor suppose to run faster ?

depends on the step frequency and step angle. 220 rpm on a 200 step motor (1.8deg step angle) is about 733hz, sounds low but i don't know what the machine was origonally capable of. on a 2tpi lead screw it's 110 ipm. that's enough to do some pretty fast cutting but sounds slow for a rapid move.... that's about all i can tell you. if the leadscrews are 4 or 5 tpi like a manual mill it's not a very high performance machine... it being a table top machine it's all hard to say but the leadscrews may have even more tpi than a full size mill.

it could be that you stepper board is doing micro stepping at too small an increment, the old steppers may have had a bigger step angle or any number of other factors... what are you using for controls?

 

[Paswest]

I am using Mach3.

 

[dman]

well you have to setup mach to the positions per revolution of the motor and drive combo. a "borrowed chinese drive" doesn't tell me much. but i looked up the drive you bought and it can be configured for a lot of microsteps which will slow the rpm considerably, sounds like you need to get things figured out.

do you use a "smooth stepper?" or can mach step off the parallel port? i'm not familiar with mach personally.

what is the max step rate? you may need to read the help pages in mach to get this figured out.

if you are stepping from the computer at 25k you should be able to get 750 rpm with 1/10 microsteps but some of those chinese drives can do 1/256 microsteps or even finer for no good reason. if you want to use the drives you purchased the manual is on the internet and i may be able to help you get them configured. once they are configured you can setup mach for your steps per inch with the positions per rev and leadscrew pitch information. then you should see what rpm the motors will run.

 

[RonGinger]

Have you looked at teh Mach Installing and Configuring manual? That explains how to set up the system, including the pin connections on teh board and the steps per unit. The manual is on the machsupport.com web site.

Do you have the motors mounted on the mill, or are you just testing them on the bench? Motors often dont work well when just laying on a bench, unloaded.

 

[kf2qd]

Depending on your length of travel, 110 IPM isn't too bad. Many machines (full sized production machines) list some very high speeds, but they aren't able to accelerate fast enough for that number to do anything but look good on paper. I built some Plasma cutting gantry type machines. Or max speed was 600IPM. we could beat the big competitors machine in all but the longest moves because we could accelerate to 600 IPM in about 2 inches. his machine took considerably longer to accelerate so it never really got anywhere close to 1000IPM. On a 10 foot move his would go faster, but most rapids in production are less that 6 inches...

On a small machine a rapid feed rate of 100IPM will seem awfully fast. It will only take a few seconds to get from one end of the table to the other.

 

[Paswest]

Thank every one. Here is where I am now.
Nema23 382oz 3.0A stepper motor,
DM542A driver,
CNC4pc C1G breakout board,
48V 12A power supply.
The lead screw as a pitch of .100 and there is a 16 and 40 pulleys.
Everything is connect, the 3 motors are on the mill and move,
I don't think I have the dip switch correct (1-5 off 234678 on).
I put a dial indicator on the mill bed and move the X .100 with the jog on the keyboard ,on Mach3 the X dro move .202

 

[dman]

Thank every one. Here is where I am now.
Nema23 382oz 3.0A stepper motor,
DM542A driver,
CNC4pc C1G breakout board,
48V 12A power supply.
The lead screw as a pitch of .100 and there is a 16 and 40 pulleys.
Everything is connect, the 3 motors are on the mill and move,
I don't think I have the dip switch correct (1-5 off 234678 on).
I put a dial indicator on the mill bed and move the X .100 with the jog on the keyboard ,on Mach3 the X dro move .202

one more thing, what's your desired precision? .0001"? mach needs to be configured for where the dip switches are (in combination with the pitch and pulley ratio), not the other way around. so lets find where you'd like the dip switches. there will be several acceptable settings for that configuration since those drives will do microsteps in powers of 2 and on a log scale of 10, so there is some overlap.

what pulley is where? is it 40 on the motor or 16 on the motor?

 

[Paswest]

I will be happy whit a precision of .0005 .
16 on the motor and 40 on the lead screw.

 

[dman]

I will be happy whit a precision of .0005 .
16 on the motor and 40 on the lead screw.

the good news is full steps will get you .0002, you may as well go half steps for .0001 at that point for the basic fact that i think the motors will limit the top speed more than output frequency for this application. you can probably go 1/4 before speeds are too limited and it might help with motor resonance but it would be an unnecessary amount of precision.

good news is that you are configured for half steps on the drives already as the manual indicates on pages 4 and 5.

drive manual

you need mach to be set for 10,000 steps per inch (i assume you work in imperial). 16/40 simplifies to 4/10 and 400 positions per rev at half steps.

mach3 tutorial

if the motors stall on the bench it may be from resonance and may not happen in the machine. you may also try 1/4 steps and 20,000 steps per unit to fight resonance.

your current is set to about 1amp but the motor tolerate 3amps. i dont think you need all that but might want a little more than 1. if you turn the current up to 3amp (it's sw1,2 and 3 refer to the manual) then the mechanical advantage of your gear reduction and lead screw (efficiency aside) could give you more cutting pressure than my monster 1700oz/in steppers for my full size knee mill! but maybe or maybe not at speed, that depends on the torque curve of the motor.

sw4 is likely to keep the motors cool. it drops holding current and if you turn the current up to 3 i think you can use that. with the current at 1amp there is no need.

 

[Paswest]

Thanks Dman, I put : step 20,000 velo.25 acc.10 now the table move the same as the dro.
The table as a travel of 8in and move from one limit to the other in 20sec. I think its slow .
When I raise the velocity the motor stall , if I can go faster I live with it.

 

[dman]

Thanks Dman, I put : step 20,000 velo.25 acc.10 now the table move the same as the dro.
The table as a travel of 8in and move from one limit to the other in 20sec. I think its slow .
When I raise the velocity the motor stall , if I can go faster I live with it.

that's not to terrible for a bench top machine but I have to wonder what it'll do when you put a load on it.

there can be a couple things going on. the motors can be sucking up all the available voltage or you may need to up the current to meet increasing torque demands.. I have a feeling the inductance is a bit higher than that setup was designed for. it probably needs a low torque low inertia motor. a lot of the torque may be waisted on motor acceleration while it tries to change speed very rapidly. there also may be resonance. but let's see if the basic configuration will help things.

still unless it was sw6 that was actually off not sw5 I think something is wrong, like if there is a lathe configuration for the program settings or something. if sw5 is off you should be at half steps and unless I made an error in the math that should be 10,000 steps per unit. or did you change it over the 1/4steps?

if you can find the motor inductance a spreadsheet is available to find the motor torque at speeds. so you can predict stalls. it'll also get you the max voltage recommended for the motor (I still don't understand this myself, but the formula is on the gecko site as well. I need to read up on that, but more inductance means more voltage required as well as more is tolerated) if this says you reach a corner at 25 ipm and the motors accept more voltage then voltage will help as long as the drives tolerate it.

http://www.mycncuk.com/forums/faqs-problems-solutions/1524-what-size-stepper-motor-do-i-need.html

use the metric settings and if you have trouble with the conversions there is google. there seems to be an error in the imperial setting on the sheet, they give me different numbers and the leadscrew mass is all wrong. inductance is measured in "henries" and denoted with a capitol "H" that will account for most of the impedance at speed. if it's not on the side of the motor the spec sheets may be online if you have the motor part number.

 

[blighty]

i had a word with the Gecko guys the other day about this very thing.

they said the lose of steps is coursed by overloading the stepper or not supplying it with enough amps. sort of the same thing i know, but a stepper will come to the point where it just wont go any faster with the load its under.

also as dman said they may be better on the mill as steppers need a bit of a load on them (so i hear) so if that is true, you can get too powerful steppers for a certain application.

i have 960oz steppers on my x/y and even they start staling at a certain speed.

don't know if its been said, but play around with your acceleration. they might like to take off slowly rather then "dumping the clutch" as they say.

 

[Paswest]

Yes dman your are right sw6 is off, does it make a difference if it run at 20,000 steeps or 10,000.
The stepper motor are from automationtechnologiesinc.# KL23H2100-30-4B they are rate at 5.1V 3.0A and 495oz .On the site of CNC4PC they have the same stepper motor whith the same number but rate at 382oz ??
Since my steeps are right, last night I decide to play with the Current setting (8 choices).
The best I found pin 2 6 off, Steeps 20,000 , velo 35, acc 3
I have a RPM off 875 on the motor ,divide by the pulleys and the pitch = 35 IPM.

 

[dman]

Yes dman your are right sw6 is off, does it make a difference if it run at 20,000 steeps or 10,000.

ok that's the discrepancy. it should be ok at your IPM but if you want to get faster than about 70 or 80 (parallel port frequency limited arounf there somewhere) you would have to go down on steps per inch and change the dip settings. what you have is smoother and better for resonance so keep it for now..

The stepper motor are from automationtechnologiesinc.# KL23H2100-30-4B they are rate at 5.1V 3.0A and 495oz .On the site of CNC4PC they have the same stepper motor whith the same number but rate at 382oz ??
Since my steeps are right, last night I decide to play with the Current setting (8 choices).
The best I found pin 2 6 off, Steeps 20,000 , velo 35, acc 3
I have a RPM off 875 on the motor ,divide by the pulleys and the pitch = 35 IPM.

k, i looked up the spec sheet and the inductance is quite high for a nema 23. they have really good torque but not so much speed. what's happening is that the driving force like i said is more than i will see on my full size knee mill because of the gear reduction and fine leadscrew but in a dynamic situation the torque is lower and all that left is being waisted changing the motor speed as your rpm is 5 time mine at the motor and the torque at the motor is much less. the other thing is that in any electronic system there is a impedance in the form of resistance and in this situation there is inductive reactance. the high inductance creates curve of impedence that increases with frequency (motor rpm) at an exponential rate. the drive is current regulated so as impedance goes up voltage (on the drive output) goes up in proportion. when the voltage requirement to get the current setting increases beyond the input voltage the current falls below the setting and motor torque falls with it. they call that the corner speed. you are operating well above the corner speed. more voltage will help if the drives tolerate it. but there is a limit to what you can force through the motors.

you can keep the current setup but i wouldn't do any cutting above 15-20 ipm. i don't know what kind of torque surplus you'll have above that at your voltage. at 36 volts you might be able to get 25 ipm safely and above that, when you do the math you usually run out of spindle rpm on an open machine before you can actually cut more than 30-35 ipm and there is no reason to be that aggressive. any more ipm you could achieve would be for rapids only so you may be happy with it how it is.

2 things you can do for faster rapids are
1. keep the motors and get bigger pulleys for the motor side. you could go up to 20, 32, or 40 teeth and the numbers will still be nice to work with. your speed potential will go up but you'd need to change the dip switch settings and steps/inch in mach

2. you can ditch the motors and get some with a lower inductance and sacrifice torque.

what you don't want to do is run the machine at it's limits. that's how steps get lost and you make bad parts. you want to keep the speed lower to prevent a stall situation. lower acceleration helps too but then there are limits to how well it follows a curve at high speed without slowing down. not sure what the ideal acceleration numbers are. maybe turn it up till you get a stall and then cut that number in half.

 

[Paswest]

what you don't want to do is run the machine at it's limits. that's how steps get lost and you make bad parts. you want to keep the speed lower to prevent a stall situation. lower acceleration helps too but then there are limits to how well it follows a curve at high speed without slowing down. not sure what the ideal acceleration numbers are. maybe turn it up till you get a stall and then cut that number in half

I will try that.