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- CAD-CAM-EDM-DRO
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Subject: Allegro Stepper Drivers
On 25 Feb, CAD_CAM_EDM_DRO@... wrote:
Subject: Allegro Stepper DriversTo be honest, I haven't .. nor will I. Good luck getting the current out AND keeping package dissipation within spec. Good luck getting the current in and out with leads that size without burning PCB traces. Mostly, though, it's too many chips. There's another chip required for step/dir -> phase logic and at least another for current chopping, probably two, still more for 1/2 & 1/4 step logic. Contact Dan Mauch - the 3776 IC + FETs is still the way to go. Alan -- Alan Rothenbush | The Spartans do not ask the number of the Academic Computing Services | enemy, only where they are. Simon Fraser University | Burnaby, B.C., Canada | Agix of Sparta |
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Re: is my software stable?
Ernst Aardal
Hi!
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I am running DeskNC on my step/dir servosystem from Dan Mauch. I am running at a speed of 4000mm/min that is 157ipm. I have been running files that takes up to 3 hours to finish and without errors. My machine is a 133mHz Compaq notebook. The resolution is 2000 pulses for 10mm (~3/8") or 200 steps /mm. Ernst ----- Opprinnelig melding ----- Fra: Tim Goldstein <timg@...> Til: <CAD_CAM_EDM_DRO@...> Sendt: 25. februar 2000 22:00 Emne: Re: [CAD_CAM_EDM_DRO] is my software stable? From: "Tim Goldstein" <timg@...> |
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WOW!! new EMC Build
I just downloaded the new 25-Feb-2000 build of EMC and you will not believe
what Fred has put in there for us stepper people. EMC now does closed loop steppers using the Kulaga/Mauch DRO card!! EMC now has MAX_VELOCITY settings on a per axis basis. Check out the .txt file for this new build. Guess I need to get busy and hook my encoders up to the machine and put that spare DRO card I got from Dan into the Linux box. Tim [Denver, CO] |
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Re: is my software stable?
I have run desknc G code files up to 2 hours. There should be no stability
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problems Dan -----Original Message-----
From: Joe Vicars <jvicars@...> To: CAD_CAM_EDM_DRO@... <CAD_CAM_EDM_DRO@...> Date: Friday, February 25, 2000 12:31 PM Subject: [CAD_CAM_EDM_DRO] is my software stable? From: Joe Vicars <jvicars@...>discussion of shop built systems in the above catagories. To Unsubscribe, read archives, change to or from digest. |
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Re: chopper drive - resonance problems - need ideas
That's like fighting a windmill. It sounds like stepper motor resonace
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except that you generally see resonance at a much lower speed. I's say 500 SPS is the range. But if you put a load on it and it goes thru the range then stop fighting the windmill. Hook it up to your machine. It should be fine. The real test for resonace comes with it connected to your machine and you run a G02 command say G02 X1y1J1 F15 If it goes thru the transitions from one axis to the other smoothly without losing steps you should be fine. I have found testing a motor on the work bench with no load is the worse case basis. Reducing the current and also going to half step should also help Dan -----Original Message-----
From: Joel Jacobs <jj@...> To: CAD_CAM_EDM_DRO@... <CAD_CAM_EDM_DRO@...> Date: Friday, February 25, 2000 9:57 AM Subject: [CAD_CAM_EDM_DRO] chopper drive - resonance problems - need ideas From: "Joel Jacobs" <jj@...>so severely that it looses steps with no load on the motor. Particularly baddiscussion of shop built systems in the above catagories. To Unsubscribe, read archives, change to or from digest. |
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Re: DRO
Ian Wright
Hi,
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I got some cable which is pretty ideal for small DROs if not for bigger ones. It is multistrand stainless steel core with a clear pvc? sheath and is about 1/32 - 1/16" dia. It is used here for keeping birds from settling on window ledges in important buildings (I used it at Sheffield Town Hall which is an historic building). It is stretched between stainless steel pins fixed into the stonework and projecting about 3" so that the birds don't find anything sound to land on. When the contractors finished the job they threw away hundreds of yards of the wire either on part used spools or in tangled lengths where they had got it in a mess and couldn't be bothered to sort it. I picked up an almost new 100 yard spool of the stuff 'just in case it might come in useful' ! Seems it now will! It is very strong and also very flexible - ideal for driving DROs and, at the price, just about right. I would have thought the stuff used on drawing boards was a bit too stiff - certainly when mine broke once, I was lucky it didn't take my eye out. Ian -- Ian W. Wright Sheffield UK ----- Original Message -----
From: A. G. Eckstein <axtein@...> To: <CAD_CAM_EDM_DRO@...> Sent: 24 February 2000 22:08 Subject: Re: [CAD_CAM_EDM_DRO] DRO From: "A. G. Eckstein" <axtein@...> |
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Re: Stepper Power
Jon Elson
stratton@... wrote:
From: stratton@...First, not that for a 2-phase stepper motor, there are two windings, but the ratings are usually written for the voltage and current for EACH winding, so double these numbers for the total power. These sound like holding torque time RPM. Note that watts requires RPM times the instantaneous torque AT THAT SPEED! Multiplying the holding torque at ZERO speed times some RPM will VERY favorably overstate the power out. OK, I looked at the graphs. Using the curve for the 34M470, DR8010 and PWR7205, They are using half the coils at 8.3 A, 8.2 A ^2 * .42 Ohms = 28.9 W per winding, X 2 = 57.9 W input static. That apparently is from the same graph as your top number, with the 111 W output, if the conversion factor you used is correct. I'd like to see if you can get from MicroKinetics the current draw into the driver at this setting. Perhaps their driver draws more current when the motor is moving. Jon |
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Re: resonance and controllers
Joel,
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I think it is really much more complex that just interrupts. Matt Shaver and Fred Proctor can probably provide some good input on this subject as they have been working on a redesign of how EMC handles steppers and it has greatly reduced the resonance issue. In this case it is on a real time system so it is not an interrupt problem. From what I understand it has to do with the spacing between the pulses and how the changes from pulses at one frequency to another frequency are implemented. Tim [Denver, CO] ----- Original Message -----
From: Joel Jacobs <jj@...> To: <CAD_CAM_EDM_DRO@...> Sent: Friday, February 25, 2000 1:36 PM Subject: Re: [CAD_CAM_EDM_DRO] resonance and controllers From: "Joel Jacobs" <jj@...> |
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Re: is my software stable?
I don't want to fault the software, but the problem I was having did go away
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when I changed to EMC. When I was cutting a circle segment at a low speed I would frequently lose steps on the X axis. If I just made linear moves I was OK. It seems in the circular moves I was hitting and trying to stay at some speed that the combination of motor, machine and software just did not like. As I have said, once I moved to EMC with no other changes I was able to make the same cut without any loss of steps. As far as the question of whether you will have a problem or not, that is a good question and only time will tell. I can tell you that on my machine 18 ipm was about the best I could get reliably with DeskNC. On EMC with the frequency stepper driver I can get 72 ipm reliably and am running it at 60 ipm just to keep some cushion. Tim [Denver, CO] ----- Original Message -----
From: Joe Vicars <jvicars@...> To: <CAD_CAM_EDM_DRO@...> Sent: Friday, February 25, 2000 1:31 PM Subject: [CAD_CAM_EDM_DRO] is my software stable? From: Joe Vicars <jvicars@...>discussion of shop built systems in the above catagories. To Unsubscribe, read archives, change to or from digest. |
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Re: resonance and controllers
Joel Jacobs
Some poorly written software fails to use the hardware timer and trys to
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program the delays between steps with software loops. The problem is that they don't dis-able interrupts to do the software loops so the timing gets all whacked out when the processor goes off to refresh the memory or something. Joel ----- Original Message -----
From: "Joe Vicars" <jvicars@...> To: <CAD_CAM_EDM_DRO@...> Sent: Friday, February 25, 2000 1:59 PM Subject: [CAD_CAM_EDM_DRO] resonance and controllers From: Joe Vicars <jvicars@...>discussion of shop built systems in the above catagories. To Unsubscribe, read archives, change to or from digest. |
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Re: chopper drive - resonance problems - need ideas
Jon Elson
Joel Jacobs wrote:
From: "Joel Jacobs" <jj@...>This is not out of the ordinary, that's 67 steps/sec. The motor is not mounted so the case and the armature resonate - if I holdThis is an abnormal situation. The motor housing should always be tightly constrained, as it would be in a real application. If I apply slight drag by holding the pulley it stops resonating and runsYes. When the natural frequency of the rotor's rotational inertia and the springiness of the magnetic fields that drive it are near the frequency that the motor is being driven, resonant motion will build until steps are lost. You have two choices. One, don't go near these frequencies, or two, damp out those resonances. You can do it mechanically, and there are hydrodynamic dampers that have a hollow, disc-shaped chamber, with a heavy (like steel) disc floating inside, with a viscous fluid to couple the two. Or, you can do it electrically, with RC networks across the motor windngs, to absorb the resonant energy through the back-EMF generated by the motor. I would think you could start with 1 uF 100 Volt caps and a 10 - 22 Ohm resistor. I haven't done this, but I have heard of it working quite well. When the motor is stiffly connected to a load, like a leadscrew, it should perform much better. Jon |
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is my software stable?
I am running desknc from a 486 DOS only machine. So far everything
works great, but the longest program I have run is less than 30 seconds total. Eventually I want to run more complicated paths, and much longer execute times. Am I going to run into stability problems from the software? |
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Re: DRO/cable source
Bertho Boman
This business with coatings on the cable bothers me. For absolute best accuracy we should have a wire that has a known and
uniform size. Since the plastic coating will compress around the shaft, it will look like a change in effective diameter. If that is exactly repeatable it would be OK. The problem I worry about is that the compressability of plastic varies with temperature and for some materials it vary with the rate of change. We could get some interesting errors to hunt for if the calibration factor varies with table speed. Bertho Boman |
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need help finding web page
Clint Bach
Hi,
I remember visiting a web page last fall which had a stepper driver circuit using the ??297, ??298 chip set. It looked good to me. I lost all my bookmarks and messages from that time so I can't find it now. It was from someone who joined this list about that time. Perhaps Hans W.???? Does anybody remember this? If so could you please send me the url? It wasn't dancam... Is there an archive for this list? If so where can I find it. Thanks, Clint Bach |
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resonance and controllers
I don't understand how the software control contributed to the
resonance problem that Tim described. The software controller just outputs a square wave of varying frequency. If you have control over your instantaneous start, accel and decel, then you should be able to find an operating range that works. What am I missing? |
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Re: chopper drive - resonance problems - need ideas
Joel,
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Resonance is a well recognized phenomena in steppers. One of the normal first cures is to use 1/2 steps instead of whole steps. This often eliminates the problem. It also seems you need to be concerned about it in the actual application, not with the motors free standing as the additional drag, inertia, etc. of the application will change the resonance as you have seen. Another way to reduce or eliminate it is to use micro steps instead of 1/2 steps. Finally, the software you use has a large bearing upon this issue. I was using DeskNC and while it is inexpensive, easy to setup and use I had a big resonance problem with it. I switched to EMC and the resonance was much reduced. I played with the acceleration and it got better. I switched to the new frequency based EMC stepper module and everything is running great. The point of all this is don't just look at the controller, resonance is a much more inclusive issue to deal with. Tim [Denver, CO] ----- Original Message -----
From: Joel Jacobs <jj@...> To: <CAD_CAM_EDM_DRO@...> Sent: Friday, February 25, 2000 11:08 AM Subject: [CAD_CAM_EDM_DRO] chopper drive - resonance problems - need ideas From: "Joel Jacobs" <jj@...>in only the one winding whose low side switch is on but when it's off (90% ofswitches share a current sense resistor as they are never both on at the same time.so severely that it looses steps with no load on the motor. Particularly bad1/2 current then go to full current. |
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Re: DRO/cable source
Darrell
Vinyl would be softer than nylon and should not slip as much as nylon.
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Darrell ----- Original Message -----
From: <wanliker@...> To: <CAD_CAM_EDM_DRO@...> Sent: Thursday, February 24, 2000 11:39 PM Subject: Re: [CAD_CAM_EDM_DRO] RE: DRO/cable source From: wanliker@...aircraft cable as follows:pounds. 7x7 strand 3/32 coated nylon or clear vinyl, breaking strength 480pounds. discussion of shop built systems in the above catagories. To Unsubscribe, read archives, change to or from digest. |
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Re: chopper drive - resonance problems - need ideas
Darrell
Stepper motors with no load will stall due to resonance. Put a flywheel of
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some sort or a load on the motor. What you are seeing is normal and will even happen with an R/L drive. It has nothing to do with the chopper. Darrell ----- Original Message -----
From: Joel Jacobs <jj@...> To: <CAD_CAM_EDM_DRO@...> Sent: Friday, February 25, 2000 10:08 AM Subject: [CAD_CAM_EDM_DRO] chopper drive - resonance problems - need ideas From: "Joel Jacobs" <jj@...>in only the one winding whose low side switch is on but when it's off (90% ofswitches share a current sense resistor as they are never both on at the same time.so severely that it looses steps with no load on the motor. Particularly bad1/2 current then go to full current.discussion of shop built systems in the above catagories. To Unsubscribe, read archives, change to or from digest. |
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Re: Reloading Ballscrew?
Darrell
First step, check the balls to see if they are all one size or do they
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alternate full size/under size. If they alternate, separate the balls into two piles. Do the recirculating tubes come off? Some are attached with screws and some are pressed into their holes in the nut. You will need a dowel the size of the minor diameter of the screw and a sleeve over the dowel that will hold the dowel centered in the nut to get you started. Start feeding the balls (big one, little one, big one) into the recirculating tube hole while turning the dowel just enough to move the balls into the nut. Keep sliding the sleeve out of the way as the balls take up the space. When the nut is full, put the rest of the balls in the recirculating tubes (you might need to use a little grease to keep the balls in the tube) once it is all together, screw the ball screw in letting it push the dowel out. Darrell ----- Original Message -----
From: <stratton@...> To: <cad_cam_Edm_dro@...> Sent: Friday, February 25, 2000 9:11 AM Subject: [CAD_CAM_EDM_DRO] Reloading Ballscrew? From: stratton@...discussion of shop built systems in the above catagories. To Unsubscribe, read archives, change to or from digest. |
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