Milling Machine Design Request

[machine]

Try this http://www.youtube.com/watch?v=ELijl7mhOus   cnc mini mili machine, developed MIT.

[sputnik]

Hello. Try here:

Im sure some appreciate the plans, but Im not sure if your method of promoting your links is entirely acceptable. Maybe you should have posted the direct link to the file as opposed to another forum.

Not to mention the password file is heavily padded!! Cmon man, a 20Mb file for a rar pass


EDIT:  Here are the plans without padding and properly posted

http://rapidshare.com/files/347893768/cncplans.rar

pass: sonsivri

[lillbear]

Im sure some appreciate the plans, but Im not sure if your method of promoting your links is entirely acceptable. Maybe you should have posted the direct link to the file as opposed to another forum.

Not to mention the password file is heavily padded!! Cmon man, a 20Mb file for a rar pass


EDIT:  Here are the plans without padding and properly posted

http://rapidshare.com/files/347529398/ROCKCLIFF-CNC-PLANS.rar
pass: sonsivri

Gone.. snif anyone reload plz. sob im so slow..

yours

[sputnik]

re-upped

http://rapidshare.com/files/347893768/cncplans.rar

[babatundeawe]

hey check this site out http://rapidshare.com/files/31608929/CNC_Robotics.pdf

or do login to www.4shared.com and do a search on cnc, cnc plans etc.

[Ahmad_k]

My machine is almost done. Just a finishing design. I will upload the complete design soon.

But i have some problem with my stepper motor driver. I have made the design attached for a unipolar stepper motor 23H2100-30-8A. http://www.ms-motor.com/Stepper_motor/stepper_motor_nema23_18.html

I have contacted the supplier and they said that this motor can support up to 50vdc, a higher speed require higher voltage. the driver run very good on 5volts but there is no torque, and of course low speed.

When i apply 12v the current limiter in L297 works well but the motor is very very noisy when enabling the driver without stepping, and less noising when rotating. The noise is very annoying.

on 24volts, nothing happened than the motor is very hot and the Mosfets. I don't know how they told it can support 50vdc.

Anyway i have modified a little the schematic, i have swapped INH1 and INH2. there is no noise and the motor run very smoothly and the current is <1A when stepping. but when enabling the driver without rotating the motor the current limiter is not working (Because of swapping INH1 and INH2) and the current is over 5A on 12volts. Transistors become very hot, it can be used like a grill   . And i forgot, the MOSFET are mounted on a big heatsink.

So please guys, if anyone have used this motor with a driver that support current limiting, please help me. This design was found on the net. i have made some modification to meet motor requirement.

[Ichan]

Noisy layout, try:
- Add RC filter before Sense1 and Sense2 pin
- Make sure the sense resistor is not wire wound type, use low inductance resistor
- Separate power and driver section
- Use separate power supply for motor and driver
- Add 1000uF + 100n + clamping device at Vm near motor connector
- Redesign pcb layout, pay attention on the grounding
- Add more decoupling caps

-ichan

[Ahmad_k]

- Add RC filter before Sense1 and Sense2 pin : DONE it before and still noisy
- Separate power and driver section : it is separated, 12v for driver and 24v for motor
- Add more decoupling caps : i have added more than 5 100nF and still noisy
- Redesign pcb layout, pay attention on the grounding : Tested on two PCB, and still noisy
   

All these things are tested before but no luck


- Add 1000uF + 100n + clamping device at Vm near motor connector :  I will test this tomorrow. I hope it will be the problem
by the way, i'm using Switching mode power supply(24v 15A) for testing. and for the 5v and 12v tests, i have used a PC power supply.

[Ichan]

For testing, I would try to use transformer base linear regulator for the driver section.

-ichan

[Ahmad_k]

For testing, I would try to use transformer base linear regulator for the driver section.

-ichan

I remember that i made a test using 12v battery for the driver section, and the SMPS for the motors. Same noise.

Posted on: June 20, 2010, 07:05:49 19:05 - Automerged
For now with 5 volts power supply, the speed is only 60 IPM, which is too slow

[cncbasher]

to run the stepper motors you describe you will need at least a 24v dc supply with a current rating of say 6A
even though your running current will of course be less
stepper motors take full current at stop ( i.e all winding energised ) which show by the stepper becoming hot in the stall condition , but dont worry so long at the current drawn is lower than the motors rated you will be ok ( 8A )

i would look again at the driver and your current limiting resistors , and whatever software you are using to drive the controller board , will need to re-run motor tuning .

motor voltage = motor speed
motor current = motor hold (i.e stall )  / running applied torque

it is normal for stepper motors to run hot , it is supprising how hot they can get , but measure your current limiting
resistors and keep under the rated current and you will be ok

you can even go up to 36v on these motors , voltage is not so much of a problem , but current drawn is not to be exceeded .

[Ahmad_k]

thanks for your advice. do you know what is the maximum speed acheived by this motor?
Tomorrow is my last chance before buying a ready drivers for 70$ each   my driver cost me only 10$

[Ichan]

Would you show the pcb layout of this?

-ichan

[sgoum]

60 IPM is fast
If you want to make PCBs with your cnc don't expect to mill faster than 20IPM
I mill mine about 15IPM.
The router bits are to fragile for greater speeds.


There are a lot of variables that limit the cutting speed, such as material,spindle etc
I have 1 semiprofessional cnc and 2 DIY and never mill with speed higher than 50IPM with 1KWatt spindle 3mm bit and material wood or plastic.

Also for good PCB a floating head is a must. its is simple to make one.I just loose Z axis nut so when the depth limit attachment comes in contact
with the plate it pushes the Z axis up.

For driver i would suggest this http://www.easy-cnc.com/4axisdriver.html
That is what i use. I have also one cheap Chinese but i do have problems with it. 

[hosmis]

I am use..

Perfect driver
http://cgi.ebay.com/CNC-3-Axis-Stepper-motor-Driver-ROUTER-MILL-60V-5-0A-/110501503334?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item19ba672166

Good seller.
http://shop.ebay.com/jarod19810127/m.html?_trkparms=65%253A12%257C66%253A1%257C39%253A1%257C72%253A3018&_ipg=25&_trksid=p3911.c0.m14.l1513&_pgn=1

[Parmin]

Ahmad,
 when you say "NOISY" if you mean by actual noise as in what you hear by ear, you may have hit the motor's resonance frequency.
 To reduce this you can try either changing the micro stepping divisions or modify the PWM frequency to the motor.

Good power supply for a PWM drive would be between 20 to 25 times the voltage of the motor.
This is to ensure rapid power transfer to and from the coil, thus enabling the motor to be run faster and cooler.

60ipm is over 1500 mmpm!!
If your screw has a pitch of 1mm, your motor is rotating at 1500 RPM to keep up with the speed..
You may find that it might be better to use a smaller HOLDING torque motor to go up to that speed.
large holding torque motor are designed to go slow and strong (thus larger HOLDING torque) due to their core inertia.

Unless there is a more detailed data for the motor and screws, I cannot comment further than that

[Ahmad_k]

Ahmad,
 when you say "NOISY" if you mean by actual noise as in what you hear by ear, you may have hit the motor's resonance frequency.
 To reduce this you can try either changing the micro stepping divisions or modify the PWM frequency to the motor.

Good power supply for a PWM drive would be between 20 to 25 times the voltage of the motor.
This is to ensure rapid power transfer to and from the coil, thus enabling the motor to be run faster and cooler.

60ipm is over 1500 mmpm!!
If your screw has a pitch of 1mm, your motor is rotating at 1500 RPM to keep up with the speed..
You may find that it might be better to use a smaller HOLDING torque motor to go up to that speed.
large holding torque motor are designed to go slow and strong (thus larger HOLDING torque) due to their core inertia.

Unless there is a more detailed data for the motor and screws, I cannot comment further than that

Well i think you are right. First when enabling the motor only without any step. I hear a stable tone comming from the motor. When i start the rotation a new sound is heared but very noisy and not stable.

For the power supply, i have searched the net a lot, and i found that someone use these motor with 75v power supply. the rated voltage for the motor is 3.6. so 75v is suitable.  But i don't think if my driver can do the same as commercial drivers. Of course i have the change the MOSFET to support the higher voltage.

For the screw, i use a professional one from HIWIN with ballscrew and not a normal nut with 5mm pitch.

[TomJackson69]

Ahmad_k,

I may not completely understand your problem, but when I read your earlier post I think I can suggest you something.

It seem like you have problem with the CLOCK frequency. Try to reduce the frequency until the stepper motor runs without noise and without missing step.

You said: “I have contacted the supplier and they said that this motor can support up to 50vdc, a higher speed require higher voltage. the driver run very good on 5volts but there is no torque, and of course low speed.”

“a higher speed require higher voltage” may not true. For NEMA 23 with the rated coil voltage of 3.5 Volts, power supply of 24 to 30 Volts is just fine.

“the driver run very good on 5volts but there is no torque, and of course low speed” this is true for stepper motor because there is under current on each winding, the motor can rotate with slow speed.

To trouble shoot, I think you should start with lower Vref and then increase Vref until there is no MISSING STEP and NOISE. Also try to run with slow frequency and then increase it slowly. Power supply of 24 Volts is OK for testing.

I have questions:  
1- What method you are using to drive the clock? PWM with fixed frequency or variable frequency?
2- What is the frequency you are using?
3- What trajectory are you using?
3- When you said :
“When i apply 12v the current limiter in L297 works well but the motor is very very noisy when enabling the driver without stepping, and less noising when rotating. The noise is very annoying.

on 24volts, nothing happened than the motor is very hot and the Mosfets. I don't know how they told it can support 50vdc.”
This seem like the driver is supplying current to the winding but the motor is not moving and make a very loud noise. That cause by starting too fast, not enough RAM-UP. If you are lucky, the motor start to spins then less noise.

I will check back later with your answer. I don’t know I can help but I will try.

Tom

[cncbasher]

Hi i agree with Tom
his comments are valid , however you do not say what type of power supply you are using , or what you are driving the board with , i will presume Mach 3
i'd take a guess that the power supply may not be able to give the current needed , and or the settings in mach 3 for motor tuning need adjustment

you need to be able to supply 1.5A - 2A per winding , as a starting point from your power supply , so 5A minimum psu

also let us know how you have the stepper motor connected , it may be you have the windings incorrect , although i doubt that
their are so many variables to check .

also for driving stepper motors , my preferance is a simple linear transformer and bridge rectifier and smoothing cap .
this can be one application where switched mode power supplys are not the best deal .

[Ahmad_k]

I have made some test today and here my result. Test are made with separated motor and driver.

For the power supply, i'm using 24v 15A SMPS. For Lower voltage i'm using PC power supply. it can deliver 24A on 5V and 15A on 12V.
For the controler, of course i'm using MACH3 but when i found these problem, i made a small pulse generator that deliver 500Hz. i think this value is suitable for the stepper

For each voltage i made two test. Enabling only the driver and then applying the clock.

Test on 5V:
a - Current limiter < 3A : Enable Only. i start hearing the noise from the motor. When clock applied the motor spin and there is no noise at all and the motor run smoothly
b - Current limiter > 3A : Enable Only. No Noise at all but the motor start heating. Same as above when applying clock.

Test on 12V:
Enable only : Whatever i change the current limit, there is a noise from the motor. 10khz sawtooth signal on SENS pins
With Clock : The motor spins but i think with missing steps.
 
Test on 24V:
Enable only : Whatever i change the current limit, there is a noise from the motor. This time MOSFET start heating. 10khz sawtooth signal on SENS pins
With Clock : The motor spins but i think with missing steps and the motor is heating up.

From these test i think that with higher voltage i got more torque but the clock speed must be reduced.

[cncbasher]

you should be ok running under mach 3
but the motor tuning will need to be configured

set current to around 2.0A but no higher than  2.5A for setup and fine tune later this will get you going .
as untill the motors are tuned you will not reach optium running
hope your using a desktop pc for mach 3 and not a laptop !

24v 15a powersupply should work fine
make sure the ground 0v supply is also ground 0v pin on the pc

are you using only one winding on the stepper motor or put the windings in parralell

 

[Ahmad_k]

I am developing electronic project for more than 15 years and i should not make a mistake like grounding, of course they are the same. And i am using a desktop and connect an oscilloscope to inputs of the driver, and all signal are clear without any noises.

For the motors is you connect the windings in series or parallel you will get a Bipolar stepper motor. but i am using it as unipolar as the schematic of the driver show.

This noise made me insane.  

[Ichan]

Have you tried it with different motor, smaller one perhaps?

Are the mosfets from well known brand? Some imitation mosfet has very bad performance.

-ichan

[TomJackson69]

Ahmad_k,

"Test on 12V:
Enable only : Whatever i change the current limit, there is a noise from the motor. 10khz sawtooth signal on SENS pins
With Clock : The motor spins but i think with missing steps.
 
Test on 24V:
Enable only : Whatever i change the current limit, there is a noise from the motor. This time MOSFET start heating. 10khz sawtooth signal on SENS pins
With Clock : The motor spins but i think with missing steps and the motor is heating up."

10KHz pulse that is very fast (10000 / 200 = 50 complete turn, for FULL STEP) and your lead screw is about 5 turns per inch than your system moves 10 Inch/Second.

I never use MACH3 so I don’t know how to setup the motion profile. I think, there must have an option to setup the RAMPING (fast or slow, linear ram or S curve …). Anyways, stepper motor is not like DC motor, it needs STEP pulse to move a step. That is why I have said “a higher speed require higher voltage” may not true. Speed of stepper motor depends on CLOCK pulse, faster clock, motor turn faster. But, the stepper motor can not run fast at start up without RAMPING up. A simple explanation would be like you drive a 5 speeds car. The car start with 1st gear to slowly move the car and then shift to 2nd gear for little faster and so on until 5th gear with top speed.

I would test your system with this simple method:

1- Build simple PWM with a 555 timer which can vary frequency from very slow (zero if you can) to 10KHz (or higher if you wish).

2- Apply this clock pulse to your stepper motor driver.

3- Start with slow (motor should advance with each pulse).

4- Increase the frequency slowly until there is noise or missing step.

5- Your stepper motor can run up to the speed just before it skips step.

Here is a simple but popular RAMPING method that many peoples used:

Start RAMPING ---------------------------------------------------------- TOP SPEED                                   
__/’’’’’’’’’’\_______/’’’’’’’’\______/’’’’’’’\_____/’’’’’’\____/’’’’\___/’’’\__/’’\_..........

This is linear RAM up. Use it in reverse for RAM down.

You should start with FULL step first. If it works on full step, it will work on HALF step and so on (1/4, 1/8 …and more).

If the above testing method works then hook-up for MACH3 to see what is the problem. I think the CLOCK pulse frequency is the main problem.

Tom

[Ichan]

10KHz pulse that is very fast...

The 10KHz is not the step clock but half of the chopper frequency, determined by the 3.3nF Caps and 22K resistor.

-ichan