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Author Topic: Need HELP Steppers Stalling on Shallow Moves  (Read 11262 times)

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Offline RICH

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Re: Need HELP Steppers Stalling on Shallow Moves
« Reply #20 on: September 29, 2009, 08:48:41 PM »
Cartiersium,
Unless someone has experience with equivalent steppers and in that voltage and amp setting  range you can't know what the 1810 or 2830 in oz  would do in terms of power. You need to take a look at the motor curves to get a flavor. Problem is you may not get a curve at that voltage ( which is usualy the case ). So you have an idea but nothing tested.  You can always ask the vendor.

If you are finding the problem at a particular feed rate, then maybe it's a motor resonance problem  at that rpm. Take a look at the Gecko site for info on it. Just a guess on my part as i have never experienced the resonance stuff.
Sorry i couldn't be of more help,
RICH
Re: Need HELP Steppers Stalling on Shallow Moves
« Reply #21 on: September 29, 2009, 09:52:17 PM »
Cartiersium,
Unless someone has experience with equivalent steppers and in that voltage and amp setting  range you can't know what the 1810 or 2830 in oz  would do in terms of power. You need to take a look at the motor curves to get a flavor. Problem is you may not get a curve at that voltage ( which is usualy the case ). So you have an idea but nothing tested.  You can always ask the vendor.

If you are finding the problem at a particular feed rate, then maybe it's a motor resonance problem  at that rpm. Take a look at the Gecko site for info on it. Just a guess on my part as i have never experienced the resonance stuff.
Sorry i couldn't be of more help,
RICH

Rich,

Actually, voltage has nothing to do with torque.  Torque is determined by current.  The high voltage is used simply to allow the drive to "overcome" the motor inductance and ramp the current up much faster.  The peak torque rating of a stepper gives you the low-speed torque capability, so he should be seeing pretty close to that peak torque at his 30IPM feedrate.

Regards,
Ray L.
Regards,
Ray L.
Re: Need HELP Steppers Stalling on Shallow Moves
« Reply #22 on: September 29, 2009, 09:54:48 PM »
What kind of power supply are you using here?  Linear regulated, linear unregulated, switcher?  Make/model?

Based on the somewhat flaky behavior, I'd bet you've got either a noise or ground problem, and not a motor/drive problem.  What BOB are you using?  How do you have things wired?  Some pictures of your electronics might help a lot.

Regards,
Ray L.
Regards,
Ray L.
Re: Need HELP Steppers Stalling on Shallow Moves
« Reply #23 on: September 29, 2009, 11:23:41 PM »
I'm using a Keling Power Supply KL- 7220, Unregulated Power Supply 1440W, 72VDC/20A, I'm using it with 120VAC. It's on this page http://www.kelinginc.net/SwitchingPowerSupply.html. I'm using a CNC4PC BOB C10 http://www.cnc4pc.com/Store/osc/product_info.php?cPath=33&products_id=45. I'm using all shielded wire. I don't have the shield part terminated anywhere, but I don't get any noise problem otherwise. The Problem is not flaky it's pretty much static, if I run it too fast X and Y at the same time where the one of the axis is shallow and no load I get the problem at about 65 IPM, if I'm hogging out material then 30 IPM. Seems pretty consistent to me.

Himy I don't have a scope, but I might be able to borrow one, if I use a multimeter what would I be looking for and what would I run on my machine to test it?
Re: Need HELP Steppers Stalling on Shallow Moves
« Reply #24 on: September 29, 2009, 11:36:41 PM »
Here are some pics. I use CPC Circular Plastic Connectors to hook up the Steppers to the electronics as I use the electronics for more than one CNC machine. I rewired it a few months ago and I had the problem before and after the rewire and all the other machines work fine.

Offline RICH

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Re: Need HELP Steppers Stalling on Shallow Moves
« Reply #25 on: September 30, 2009, 12:41:41 AM »
Ray,
Agree, but it does affect the motor curve. And what your after is power and that is where my thought was.
Off thread and nothing to add, so off i go,
LOL Cartiersum, your in good hands,
RICH
Re: Need HELP Steppers Stalling on Shallow Moves
« Reply #26 on: September 30, 2009, 12:37:17 PM »
I can see several things that are less than ideal in your wiring.  First, you really MUST have a very solid single-point ground.  Normally, this would be a metal plate, to which everything is mounted.  At a minimum, it should be a solid buss-bar to which ALL grounds are connected.  Never daisy-chain grounds - they should ALL connect directly to a single point.  It appears your power supply has two separate output?  If so, the grounds on those MUST be tied solidly together.  Never, ever connect a signal ground point to a power ground point (e.g. - connect an encoder power- signal directly to motor power- on the drive, to save a wire).  Run two separate wires all the way back to the single ground point.

What you're seeing "smells" like a bad ground, since it gets worse under load - that suggests that different parts of the system "see" different grounds at different times, which can cause an active input to be "seen" as inactive, or vice-versa.  Basically, the idea is to make sure that for each signal, there is one, and only one, path back to ground, and that path must NOT include shields.  Otherwise, the return current will be split among the available return paths, and things may not behave as expected.  In your case, I would add a buss bar alongside your power supply, tie BOTH power supply grounds to that, along with the power line ground, and make ALL ground connections directly to that buss bar.  My guess is this alone will go a long way towards resolving your problem.

Next, the shielded cables - If you don't have the shields connected, then they're effectively unshielded cables.  The shields should be connected to ground at the SOURCE end only.  This means the signal cables (STEP, DIR, etc.) should have their shields connected ONLY at the BOB end.

There is no reason for this stuff to be particularly sensitive, if wired up properly.  As an example, my E-box has the PC, power supply, two BOBs, SmoothStepper, home/limit/relay I/F board, spindle speed I/F, VFD, Geckos, Modbus board, etc. all in a single enclosure, and works flawlessly.  The mounting plates and the enclosure itself are all securely tied to ground.  You can barely see in the pictures that the grounds of both power supply filters are tied directly to the mounting plate, and all ground connections branch off from there.

Regards,
Ray L.
Regards,
Ray L.
Re: Need HELP Steppers Stalling on Shallow Moves
« Reply #27 on: September 30, 2009, 01:17:23 PM »
Thanks Himy, I appreciate all the help. I understand what you're saying but might have a few questions, but right now I'm running the machine and actually making some money for once, but later today I'll study what you said.
Re: Need HELP Steppers Stalling on Shallow Moves
« Reply #28 on: October 01, 2009, 10:58:22 PM »
Ok Himy, I understand what you're saying but help me clarify some things. I want the shield on each cable going to one lug on the metal body of the control box I have everything in. Now can I slide a copper wire up into the shielded cable as most of the shields are a foil, I think, then zip tie it so it has contact? If they have a drain wire for the shield then I'll just run off of those off course.

Now for the grounding of the power. Here are all my devices what wire should go to a ground location.

Main Power Supply -- It's a transformer so there are a ton of wires. Do I want to ground the actual ground coming off of the plug coming out of the wall? Then you mention bridging the grounds on the power supply, but there is only one 120V ground, or do you mean I should run the NEGATIVE from the DC side to a ground point on the metal cabinet?

Next I have 4 Stepper Drivers what wire do I use on those to ground? And which on the VFD Speed Control and BOB? And I have a 5VDC power supply coming in for the power on the BOB and for the Steppers, nothing is daisy chained. And I have a 12VDC Power Supply for the VFD Speed Control.

Thanks. Oh you said have all electrical grounds together, do you mean the NEGATIVE side of the DC goes to the same spot on the metal cabinet as the 120V GROUND?

Re: Need HELP Steppers Stalling on Shallow Moves
« Reply #29 on: October 02, 2009, 11:04:58 AM »
See below in []:

Ok Himy, I understand what you're saying but help me clarify some things. I want the shield on each cable going to one lug on the metal body of the control box I have everything in. Now can I slide a copper wire up into the shielded cable as most of the shields are a foil, I think, then zip tie it so it has contact? If they have a drain wire for the shield then I'll just run off of those off course.

[That should work OK.  The important thing is that the shield be connected only at the source end.]

Now for the grounding of the power. Here are all my devices what wire should go to a ground location.

Main Power Supply -- It's a transformer so there are a ton of wires. Do I want to ground the actual ground coming off of the plug coming out of the wall? Then you mention bridging the grounds on the power supply, but there is only one 120V ground, or do you mean I should run the NEGATIVE from the DC side to a ground point on the metal cabinet?

[Yes, the AC ground should absolutely be tied solidly to the machine itself, and to your E-box.  The wire used for making these connections should be as large as the largest wire used in the system.  This is for safety as much as anything else.  The - ouput(s) of your power supplies also should be tied to the metal case of your E-box, and to a buss-bar for making all the ground connections to the devices.]

Next I have 4 Stepper Drivers what wire do I use on those to ground? And which on the VFD Speed Control and BOB? And I have a 5VDC power supply coming in for the power on the BOB and for the Steppers, nothing is daisy chained. And I have a 12VDC Power Supply for the VFD Speed Control.

Each stepper driver should have a motor power - connection.  This should be tied directly back to the main ground buss bar from each driver.  If there's a logic ground as well (e.g. - for the step/dir signals), that should be a separate wire, even though it goes to the same place.  The VFD will also have a ground connection, that needs to tie back to the ground buss bar.  The control signals for the VFD should be run through a shielded cable.  If your input is single-phase AC, twist the two wires together with a couple of turns per inch - shielding should not be necessary.  If that 12V power supply for the speed control is powering the computer-side of the circuit, then it's - output should also be grounded.  If it's powering the VFD side of the circuit, then its - output should be connected to the - connection on the VFD analog input terminals.]

Thanks. Oh you said have all electrical grounds together, do you mean the NEGATIVE side of the DC goes to the same spot on the metal cabinet as the 120V GROUND?

[Yes.]


Regards,
Ray L.
Regards,
Ray L.