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  #301  
Old Mon 18 March 2013, 21:30
KenC
Just call me: Ken
 
Klang
Malaysia
Ross is absolutely right. & I overlooked the fact that Pete actually using Nema24 motors... that explains all his problems... expecting a stock scooter motor to power a NASCAR & win.... hmmm.....
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  #302  
Old Tue 19 March 2013, 05:09
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
I do like how this was happening before and now since I changed the XY config it is the belt drive. Someone must have missed this post. Now that is funny.
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  #303  
Old Tue 19 March 2013, 05:23
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
I did see that Mach likes the acceleration to be withing the 8 to 10 % range of the velocity or it might cause problems. This was on a systems builder website. Why is that? That is were I got the idea to change from 25 to 40 and it went away. It has run almost 12 hours straight know without problem. I would think the higher acceration would cause it to happen even more because it increases the Gs. I agree it the build design is limited but if I wanted more then why not servos. Back to my original question. Why would lowering the V and increasing the A work. Especially when the calculated Gs increased from .06 to .1 ? I do not know that is why I am asking.
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  #304  
Old Tue 19 March 2013, 05:51
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
Ken,
I thought NEMA was designated by flange size? This is a hard one to find information on. All the motors are 3.54 and one is 3.35. Would they not be a Nema 34 not a 24. Nema 23 if I am correct is about 2.4 inches round?
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  #305  
Old Tue 19 March 2013, 06:04
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
I did find this on Oriental's site and it took some digging. Good reference for anyone who needs it. The pdf link is at the second post.
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  #306  
Old Tue 19 March 2013, 06:52
Surfcnc
Just call me: Ross #74
 
Queensland
Australia
I was assuming NEMA 34, it was the motor length and by inference the magnet pack size that I was referring to.

Pete it is possible to increase the G's as long as it remains within the available torque. At the start lots of torque is available so as long as demand is not exceeded all is ok. Getting to the travel speed slowly or quickly will make no difference if it is the lack of torque at the travel speed itself that is at the heart of the problem.

The 8 to 10% estimate only holds for high travel speeds. Mach is totally happy to accelerate at 50% of a slow velocity. So the rule is just a generalisation not a commandment.

I checked the torque curve and it rapidly disappears after 200 RPM.
Suggest thinking in terms of containing and calculating your RPM rather than acceleration and velocity. Note that the curve is for the motor with the gear box in place. Changing to the 7:1 increases the torque but pushes RPM along into the lower part of the curve so their are trade offs. The curve is also not linear so rough estimations may not prove accurate.

I love your work, your workmanship and the fact you have chosen to experiment beyond the standard configuration. You should be rewarded with beautiful resolution but the only down side I can see is the trade off for some speed. To me this is a small price.

I hope this discussion adds to the mix rather than detracts in any way.
My intention is simply to understand.

Regards
Ross
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  #307  
Old Tue 19 March 2013, 07:08
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
Pete,
are you loosing steps on both x and Y?
or just on one?
are you loosing steps on the slaved access and the X at the same time?
or just on one of them?
the reason I say this is I have had this happen before, after running my machine for a bit after it was built I had to go back and check all the connections for the motor wires, I had a few loosen up where they attach to the motor drives.
do you use quick connectors between the motors and the machine?
I had xl connectors on my machine and removed them, ( motors are wired directly to drives ) once I checked the wires and removed the connectors all was well and I have not had an issue since. things loosen up and move especially on a new machine, also check your computer to see that all programs except mach are removed from the computer, if something stats up in the background like anti virus you will have similar issues
I would think one of these would be a more likely issue since you were having the issue before you switched to your new design. also check you kernel speed maybe you need to raise it ( data not fast enough ?) also raise the debounce.
this could also be a bad proxi if you are running them.

//chopper
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  #308  
Old Tue 19 March 2013, 07:17
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
Ross, that makes a little more sense. Nice explanation.
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  #309  
Old Tue 19 March 2013, 07:27
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
Chopper,
The action would be better for me to video than try to explain. More times than not, it will start with the Y then immediately the X will stall. There is a very distinct low hum that happens then the Z will stall. That is with the one program. With it, the movements never continue and mach will not index to the next line of code.

On the other programs, it depends on which linear direction it is moving the farthest. If X is longer than it is X, if Y is longer then Y. With those programs it will make the same low hum then resume. The only good thing if there is one is that it will affect the Z height by losing the position as it is lowering. At least this way the machine is not breaking the tooling. When the action is occuring it will lock one of the axes and the other one can travel for a long ways. I have seen anywhere for inches to feet. This has happened with both the SG7.2 gearbox and the 7.2 belt reduction.

The benefit to the belt reduction is the lack of backlash.
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  #310  
Old Tue 19 March 2013, 07:47
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
Ross,
I don't worry so much about speed. I spoke with a gentleman from Texas a while back. As he said, "You are not in a race with the guy down the road, it is the quality and care put into the part you make that will make the difference not that you were done cutting 30 minutes faster." This statement rang the Bell of Truth to me. I also agreed with him that when you start giving a little on accuracy, both accuracy and precision drop. For anyone reading this, here is wikipedia's explanation of them. Once you go down the path of giving up something, it will increase at an exponential rate and your end result will ultimately be affected. I try to strive for perfection but realize it is a goal few if any ever achieve.
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  #311  
Old Tue 19 March 2013, 10:24
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Two thoughts: with greater Accel, you may be passing through a portion of the torque curve that has problems more quickly. Also, you might try metering your power supply to see if there is a dip that correlates with your stalls. I'm poking at insufficient capacitance on that one.
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  #312  
Old Tue 19 March 2013, 10:39
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
Thanks, Brad. I will check that as soon as I finish this last sign. It may be a couple days but I will post what I find.
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  #313  
Old Thu 21 March 2013, 03:12
KenC
Just call me: Ken
 
Klang
Malaysia
Pete,
Ross & Brad answers most part of your questions. & I agree with the the Texas gentleman Chopper spoke to.
but again, on general terms,
Power = Angular speed x Torque, you can only go so fast with the available motor torque & power.
the tricky part with stepper motor is its torque Vs rpm characteristics, its not linear & you gotta work within the motors' capacity.
Other than the torque, power, speed, voltage, impedance & current rating. The rotor inertia is also important factor in motor selection. General speaking, when the rotor inertial is too large, it can not stop fast enough (Muscle car), when the inertial is too small it can not rev up fast enough (drifter)...
With your lighter motor, I don't see why it can not work, as long as you play with the speed+Voltage combo which the motor is happy with.
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  #314  
Old Thu 21 March 2013, 03:36
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
In general, if the motor runs cool, push the voltage up (limited by what the drive will handle). Yes, that does need a different transformer, but it is well worth it to get the higher performance.
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  #315  
Old Thu 21 March 2013, 13:49
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
Gerald,
My motors do run cool. The room they are in never get above 60°F so that adds to the lesser heat of the motors. I may have to move up in the size of the power supply
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  #316  
Old Thu 21 March 2013, 14:28
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
What voltage are you running on your motors Pete
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  #317  
Old Thu 21 March 2013, 14:32
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
35vdc
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  #318  
Old Thu 21 March 2013, 17:08
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Pete

That seems small. I have a 56 VDC.
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  #319  
Old Thu 21 March 2013, 17:28
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
Nils,
I often wondered but it ran fine until I changed the settings from being the same. I was debating about a 35 to 42 in the beginning but opted for the 35. I spent time reading the pros and cons about voltage and really enjoyed reading the debates between Richards (Mike) and Gerald about the reason why one and why not the other. I opted for the lower based on conversations with Mike. I cannot complain. I am sort of tied up with finishing a sign but I am hoping Saturday to try and isolate it.

According to calculations I am pushing harder than the calculated maximum rpm but I had done that before with many different size steppers at work. But they have had a distinct purpose, this position to that. But I have also seen running maximum voltage on a stepper cause some of our 42's to be so hot it seems you can fry an egg on them and most definitely burn your hand.

It may be a bug with Mach and it may not. Bugs are like recalls to me, affects some people but not all. And some never take in for the recall and never have a problem. It is definitely interesting but it is working now at the current settings. I would like to change the settings back to 500 and 50 this weekend and dry run the problem programs and see if the problem still exists. If it does not, I will upgrade to Mach 57 and try again. If it still does not happen, I will lower the Z setting and see if it rears again.

In the end I may need to upgrade the power supply, only time, testing and further investigation will prove this out.
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  #320  
Old Thu 21 March 2013, 20:28
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Pete,

I have a background in software. We had to test stuff all the time to find the solution. That is my current state. I have finally gotten close to fixing a noise problem with my spindle. Then today, I cut a piece of 0.5" Acrylic with lots of pocketing. None of it turned out right. Pockets had high points and low points and it was a mess. Fortunately the customer could use what I gave him but it will cost me.

Later today, I created a cut file with some pocketed circles. I used a scrap piece of plywood, I cut the file in four different places. Each one of the pockets came out correctly. I was thinking that my new Z was not square to the table but after cutting the circles, I don't think that is the problem.

Tomorrow, I will cut part of the customer job out of plywood and see what kind of results I end up with. For me it is the only way to begin to understand why things don't cut right.

Good luck with you problem.
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  #321  
Old Fri 22 March 2013, 04:20
Surfcnc
Just call me: Ross #74
 
Queensland
Australia
Quote - "It may be a bug with Mach and it may not. Bugs are like recalls to me, affects some people but not all."

Pete until you have some stronger proof it is not fair on the developer to continue to cast doubt on his software.
You have already been presented with a series of potential causes, my suggestion is to use Occam's Razor and attack the most probable causes first and leave supposition to the absolute last.

Apologies for this outburst in advance but I just cringed when you got this one out again. Maybe I am just getting tired of the Mechmate forum.

Ross
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  #322  
Old Fri 22 March 2013, 04:38
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
Ross,
I was only inferring that just because it in not affecting you does not mean it is not there. No one is perfect, including me. I have programed plcs, robots with vb and mess with vba for rdms. It is easy to have one person affected and not a group. That being said I do not know what it is but for me not to include the software in the troubleshooting spectrum would be flawed approach to troubleshooting. When something is not working, everything is suspect. That is like saying my kids are perfect which they are far from it however every parent likes to think so.
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  #323  
Old Fri 22 March 2013, 14:07
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
Basic troubleshooting tools for the weekend.

Clamp meter
Voltmeters
FLIR

Based on what I know, the absolute maximum RPM is the following. I might be mistaken so please check my formula.

Freq steps per second 45000
Gecko steps per revolution 2000
Minute 60 seconds
Pinion diameter 1.5

Calculation revolutions per second 45000/2000=22.5 rev/sec
Revolutions per minute 22.5x60=1350 rev/min
Add in gear reduction 1350/7.22221=186.92339 rev/min
Calculate distance traveled per one revolution of the pinion 1.5x3.14159=4.712389 in/rev
Maximum distance per minute 186.92339 x 4.712389 = 880.8557 in/min

All in a perfect world at. Now to figure for the unknown.
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  #324  
Old Fri 22 March 2013, 17:03
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
One hour into testing, running only trouble programs.

First half hour was run at all axes settings of 400 and 40
Lowest power supply reading was 33.4VDC and highest amp reading was 5.1. Temperature reading was 75°F on the motors and 84°F on the bridge rectifier. Transformer is 65°F. Everything ran normal

Next changed all axes to 500 and 50. Have ran two problem programs so far. Overriding feed by 70% to try to induce problem. Lowest power supply reading was 33.1VDC and highest amp reading was 5.5. Temperature reading was 80.4°F on the motors and 85°F on the bridge rectifier. Transformer is still 65°F. Everything still running normal.

Average amp draw when running is 2.2A
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  #325  
Old Fri 22 March 2013, 18:14
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
Video of FLIR. IF you have never used one, they are great for finding hot spots, bad bearings, etc. Sorry about the focus, is hard to video with one hand and make the other hand work the tool as well as make sure I land on the objects I wish to capture

Hope you enjoy.

http://youtu.be/caNNt4C2Ksw
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  #326  
Old Fri 22 March 2013, 18:41
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
Steppers up to 103°F, toroidal 87°F, voltage and amperage are same as before. All trouble programs have run without problems. Next to lower Z Velocity and Acceleration
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  #327  
Old Fri 22 March 2013, 19:55
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Pete,

Did you use some software off of a web site to determine the timing pulleys and idler gear calculator and where to place them?

Thanks

Last edited by sailfl; Fri 22 March 2013 at 20:07..
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  #328  
Old Fri 22 March 2013, 20:29
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
Drew up the design of the timing pulleys, verified it through the company I had make them by asking for the ODs of the pulley and my axis calibration was exact as my calculations for the steps for mach. The size of the pulley can be calculated because it is relative. You can get the size of a pulley from SDP-SI data sheets and the formula would be (known # of teeth)/(desired # of teeth)=(known diameter of pulley)/x(unknown size of desired pulley). The placement of the idlers was determined from my cad drawings. You want an even approach to and from the idler in order to try to have an even tension and stretch on the belt. I like to limit the length of belt but have maximum contact on the both pulley teeth. But all of this has to work around your mounting bolts, posts, motor bolts, etc...
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  #329  
Old Sat 23 March 2013, 12:11
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
Update
Have been testing at 500 and 50 all axes now for 2 hours. Stopped and changed only Z to 250 and 30. Reran problem programs starting with the one that always stalled at the beginning. Machine stalled right away. Reset back to 500 and 50 all axes. Now stalls every move. Restarted the computer and is working again.
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  #330  
Old Sat 23 March 2013, 17:30
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
This is most likely a relationship with the torque as Ken, Brad and Ross have suggested. Have not yet tried an upgrade but based on the last couple hours I have found that only if the velocities are the same the acceleration setting are the same is iteliminating the stall. I have tried 500, 400 and 300. I do not think an upgrade would change anything. However I have not found the magic lower number for the Z velocity and acceleration that will allow it to run without stalling. I do find this odd. I would not think that the lower number on the one axis would start the stall. What is even more odd is it is only with the same programs that this occurs. And furthermore why is it the start of the one program when it goes into tool change but in another it is when it returns from tool change to the previous position and rapids to the next start point then stalls. On the one that it starts from the beginning, on occasion when it loads I receive an Alarm Watchdog Timer Triggered. Have disabled it in config for now.
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