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#1
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Gathering Information for Build
Dear Gerald
Can i use this power supply with g203? this supply is available here in uae Please help to chose Model SCP-600 Model PSP-500 Model SP-500 Also other models are available Her http://www.manaautomation.com/html/dcT.html# Last edited by asif3244; Fri 03 December 2010 at 15:56.. |
#2
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You need to read on the forum about power supplies before posting a series of questions.
If you goto the forum home page you will see the sections of the forum are seperated by the areas that you are asking your questions. http://www.mechmate.com/forums/index.php You will also see a lot of "sticky" threads at the top that have most of the answers to your questions. As far as power supplies you will see that most systems use a PS like this one. http://www.antekinc.com/details.php?p=364 Also post the question without pointing it to one specific person. We can all chime in and give feedback . |
#3
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If you decide on the switching PS I think the best choice would be the 600W unit. It has the most amps on the 48V selection.
You will need to make sure you Motors are rated at 48 volts or less. Typically this would be 2.2 mH Inductance or less like this motor http://www.kelinginc.net/KL34H280-45-8A.pdf |
#4
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Mike,
Thanks for your help, i haven't decide about the motor yet, Please advice me the reasonable priced motor & drivers, by the way what about? kelinginc |
#5
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Good company as far as I know with lots of following.
Look around on the forum. There are others who may be better equipped to ship out to you. |
#6
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Asif,
It's easier to use a systematic approach when it comes to designing electronics for a machine. Breaking the process down into steps reduces the chance for error. 1. Decide on a motor. To do that, you need to know how much load the motor is expected to handle. Mechmate builders have three basic choices, direct drive, geared motor or belt-drive transmission. For those who select direct drive motors, many choose motors that produce 600-800 oz*in. Motors that produce 600-800 oz*in are easy to find without costing too much. For those who select geared motors, many choose to use the Oriental Motor PK296A2A-SG7.2 motors. For those who select belt-drive motors, I recommend a motor that produces at least 300 oz*in of holding torque but I prefer motors that produce 450 oz*in or higher torque. Whenever possible, select motors that have low inductance (2.5mH or lower is best, but Geckodrive G201x and G203v can handle motors that have as much as 6mH inductance with excellent results). 2. Select a stepper driver and decide on the wiring/connection method that you're going to use with your motors. I only recommend Geckodrive stepper drivers, either the G203v or the G201x. Other stepper drivers are available. Sometimes in some parts of the world, the Geckodrive products are either not available or too expensive; but, if they are available at a reasonable price, I would highly recommend them. Stepper motors, depending on the number of wires, can be wired three different ways when they're connected to a Geckodrive, bipolar series, half-coil and bipolar parallel. Four wire motors can only be connected bipolar series. Six wire motors can be wired bipolar series or half-coil. Eight wire motors can be wired bipolar series, half-coil and bipolar parallel. I connect my motors using half-coil wiring unless I have a really good reason to use another method. Half-coil wiring/connections give excellent speed and 70% of the torque of a motor wired either bipolar series or bipolar parallel. Half-coil wiring gives the same speed as bipolar parallel but produces much less heat. Half-coil gives much higher speed than bipolar series. 3. Select a power supply. There are two basic types of power supplies, switching and non-switching. The switching power supplies are normally used in applications where voltage regulation is important. Non-switching power supplies are normally used where tight voltage regulation is not important. Stepper motors don't need tight voltage regulation, but they do needs lots of current. (For years, I used 24VDC switching powers supplies to drive Oriental Motors PK268-02A motors that I used in a Kodak 5-S printer controller. The power supplies were reliable and inexpensive. The motors used Oriental Motor stepper drivers and were lightly driven, so everything worked. If I were to do that project over, I would use Geckodrive stepper drivers and a toroidal type power supply. Years ago, Gerald patiently explained the advantages of using a toroidal type power supply. He was right and I've used toroidal power supplies for all stepper motor applications since that time.) Before choosing a power supply, you need to run two equations. A stepper motor has two values that are used in the equations: Inductance and Rated Current. Use the inductance rating to determine the MAXIMUM voltage of the power supply: 32 X SQRT( Inductance ) = MAXIMUM voltage. Depending on the motor and the application, I typically us a 75% to 85% of the maximum voltage listed by that equation. Reducing the voltage costs a little speed, but it greatly reduces the heat produced by the motor. Speeds higher than the shoulder on the torque curve (the point where torque rapidly drops as the speed increases) have too little torque to be of much value in a CNC router application, so I don't worry about clipping the speed. The second value, Rated Current, determines the size of the filtering capacitor that you'll need to use. (Yes, you will need to add a filtering capacitor to the output of a switching power supply.) The formula is: (80,000 X Current) / Voltage = Capacitance. For instance, four motors that pull 4A each used with a 35VDC power supply would require (80,000 X 16A) / 35V = about 30,000 uF; however, because all motors on a CNC router are not normally running at full load, you can safely use 66% of the rated current load in your equation, which would equate to about 25,000 uF. Remember that capacitors can be connected in parallel to increase the capacitance. Also remember to use capacitors that have a voltage rating at least 1.5X greater than the AC output voltage rating of the toroidal transformer. Whenever possible, I select capacitors that have 2X the AC voltage rating of the transformer. By following those three steps, you will have motors that work well with your machine and electronics that work well with those motors. |
#7
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Mike your time spent explaining this is greatly appreciated. Thanks for your continued support with the forum. A true asset to the Mechmate community.
James |
#8
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Thanks mike for your time i appreciate the effort you do for us
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#9
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Dear Mike
i read your thread at shop-bot forums Quote:
Question is is this combination is suitable for mechmate? witch size & torque motor can be suitable other then "OM" because the price is to high for my pocket Sorry for poor english Regards: Asif Last edited by asif3244; Fri 10 December 2010 at 02:06.. |
#10
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The G540 will work for the MechMate. If you read in the forum you will find at least one build thread that used the G540. You do have to pay attention to your motor selection since the current and voltages for the G540 are particular. That has also been discussed in the forum.
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#11
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Mariss (owner of Geckodrive and designer of their drivers) made an observation on cnczone that should be memorized by everyone who uses stepper motors. He noted that when motors are run at their maximum voltage that many motors run at 3,000 RPM. Three-thousand RPM would require a pulse source of 100,000 steps per second. That's possible, but I've had trouble sustaining a pulse rate higher than 64,000 on my testbench (running a fast Windows XP machine through its parallel port). My G100 can easily hit 100,000 and I suppose that a SmoothStepper could also easily hit 100,000 steps per second.
The more important point is that mechanically, it would not be prudent to jog a CNC machine at 100,000 steps per second. Even geared down 7.2:1, three-thousand RPM = about 30 ips. Hitting a hard stop at 30 ips per second is not a pretty sight. (Don't ask how I know). A motor running at 1,000 RPM would have sufficient speed for CNC work. It would allow you to cut as fast as your desired chip load would permit and it would still give fast jogs (around 10 ips with a 7.2:1 gearbox and almost 20 ips with a 4:1 belt-drive). That speed is much more prudent on a big, heavy CNC machine. The good news is that there are a lot of motors that draw 3.5 amps or less (like the Oriental Motor PK299-02AA motor). That motor, and other similar motors, has a relatively high inductance rating (6 mH); however, when driven with a G540 with a 48VDC power supply, that motor gives all the performance that a CNC machine needs. It runs cool. It has lots of torque. It can hit speeds over 1,000 RPM. Granted, the math says that it shouldn't be used, but it is a near ideal match when used on a CNC router. That's the key. Sometimes we fixate on finding the perfect match between a motor and a stepper driver in our effort to get maximum performance and loose sight of what we're trying to accomplish. That motor has 620 oz*in of torque, so it is an ideal candidate for a 3:1 belt-drive. Even using a 1.25-inch pinion gear, that motor would be capable of jogging faster than you'd ever want to jog a CNC router. If we look at motors that have about 600 oz*in of torque (half-coil - use the unipolar rating) and then select a motor that has an Amp rating of 3.5A or less and then (finally) if we look for a unipolar Inductance rating of 8 mH or less, we'll be looking at a motor that can be driven with the G540 and a 50VDC power supply. High performance motors, like the PK299-F4.5 require too much current for the G540. I have run that motor with my G540 and it still performs well, but I have to limit its torque by limiting the current that that motor draws. I would much rather limit a motor's top speed than limit a motor's torque. |
#12
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Motors for G540
Hi Mike & All
Thanks for your quick reply, as for my understandings after reading posts about G540 requirement ( if connecting unipolar) of phase current (A) & inductance i start to search G540 compatible nema 34 size motor on the internet and found these motors and i need senior's opinion on these motors Last edited by asif3244; Sat 11 December 2010 at 16:06.. |
#13
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Hi Mike & All
I change my concern at this point, i started this thread by seeking power supply help, i think if my driver is G540 then i should look for the motor first, These are Chinese Nema 34 motors, i remove the company name & heading because it is against the forum rules, this catalog has more details then the previous one so it is easy to read all type of rating bipolar or unipolar, i hope there are some motors that can be mach with G540 if connecting unipolar, senior member's advice is impotent in this regard |
#14
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Who is the supplier of these motors?
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#15
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Asif, you want motors with inductance less than 4 mH (or close to that), amperage less than 3.5A (or close to that), and 6 or 8 wires so that you can wire half-coil. Use the Unipolar data from above. So, the model labeled just "8A" in that table is a likely match, although I'm sure that's a misprint, so you'll have to figure out what the model number really is - I'd guess 34H260-30-8A. Other possibilities are 34H280-45-8A, 34H260-45-8A
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#16
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Mike, it looks like http://www.ms-motor.com/index.html
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#17
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Yeah I thought so. These also look to be the source for Keling motors.
One thing I was looking at today at the 540 and this is what the spec says. 50 VDC will damage the G540. 3.5 Amp Max Current So if your set on the G540 I think this is the way you remove motors that will not qualify for use with the G540. Someone please tell me if I get this all wrong. So taking those two items above and working the square root formula backwards you come up with the following. 50/32 = 1.5625 then multiply the total by itself 1.5625x1.5625 = 2.4414 . So the maximum inductance motors you need to choose from your list would be 2.44 so remove any motor that has an inductance higher than that. Then remove any motor that has the inductance of 2.44 or less but a current that is higher than 3.5. Then you will have a list of motors that should be matched to the g540's specs. (None actually) Doing that math the only motor I see that would be close is the 34H260-60-4a . But because it's current rating is higher than 3.5 it would be derated 3.5/6 to 58%of its rated power based on this from the G540 Spec http://www.geckodrive.com/upload/G54...4%20MANUAL.pdf From the manual "The motor’s rated phase current must be between 0 Amps and 3.5 Amps. Using a motor with a higher current rating will cause a proportional loss in torque, meaning a 5A motor will get 3.5/5 (70%) of its maximum torque." This derated motor may still have enough power with a belt drive setup to run the MechMate . That is a 465 oz in motor but derated it would be 465*.58=269.7 . But then multiply that by 4 if you are using 4:1 belt drive and you get 1078.8 oz. So all that said , I say search the forum for G540. I know we have at least one build using them but I do not know what drive he is using. I would not use this setup as a direct drive and actually I would not use the G540 at all and go to the proven G203v drives and a Break Out Board . Last edited by MetalHead; Sun 12 December 2010 at 10:18.. Reason: Adding information detail |
#18
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Looking at the build log
http://www.mechmate.com/forums/showthread.php?t=2575 The one thread I saw (MM - jehayes - Joe - SN 53) used the G540 but had the OM 7.2 Motors which meet all of the design specs for the G540 but have a higher price point than other motors (About 3 times higher actually). OM 7.2 specd out on other builds is running at 39V , 3.5amps , and 1.6mh Inductance. |
#19
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The 50VDC power supply limit would make us think that any motor with an inductance over 2.44mH would be ill suited for use with the G540. That only holds true if you need to run that motor at 3,000 RPM. That just doesn't happen on a CNC router.
A motor rated at 6mH will run at 1,000 RPM or faster if driven by a 50VDC power supply (at least the PK299-02AA motor that I have runs at 1,500 RPM when driven by a 48VDC power supply). Let's look at what 1,000 RPM buys you. If you use a 1.25-inch pinion gear and a 3.6:1 belt-drive, 1,000 RPM will move an axis at 18 inches per second. I set a maximum jog speed of 12 inches per minute when I started using belt-driven or geared motors on my PRT-Alpha. A 600 oz*in motor will produce 2,160 oz*in when geared down 3.6:1. That's 135 in*lbs, or 168% greater than the geared motors that Shopbot sells with its PRS-Alpha machines. In addition, using a 6mH motor with a 48VDC power supply will keep the motor's temperature down to around 45 - 50 degrees Centigrade. Other 'big' motors, like the PK299-F4.5 have to have their current limited to 3.5A maximum. That means that those motors (those rated over 3.5A) will produce less torque than expected. So, using a 3A to 3.5A motor that has a unipolar inductance rating of 6mh or even 8mh with a G540 will probably still give you all the speed that you can use for jogging and all the torque that you can use for cutting. |
#20
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Man I can see I still have some learnin to do with all this motor stuff..... clear as mud ... as always
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#21
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Quote:
Now that we are running 5 machines, with a variety of motors, I must disagree with you on lowering voltages. To get decent cutting speeds out of the machines (without loosing steps), and keep the motor heat tolerable, we find our voltages to be above the values given by the conservative Mariss formula. A reduction of voltage is a reduction of torque. |
#22
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I think the g540 can absorb maximum 68 to 70vdc but 50vdc is recommended
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#23
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The G540 has a 50VDC limit. It should not be exceeded.
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#24
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Be sure to read the specs on the given drives.
http://www.geckodrive.com/ You can also look here for combos since you are not in the states. http://www.driver-motor.com/Contact.aspx I think folks have bought from them with good success. |
#25
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the switching power suplies have efficience %? like some welding machines. 90% means have to rest 10% of the time. 10 minutes operation 1 minute rest. i didnt know that!
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#26
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Fernando, I don't think that is correct. Welders have a duty cycle limit. The efficiency percentage on a switching power supply is how much of the input power is converted to the output. So 90% means that 10% of the input power is wasted (usually as heat).
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#27
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Gerald,
(Sorry for the delay in responding. I've been spending too much time in the hospital.) Torque and high speed just don't go together very well with stepper motors. Mariss explained it in his stepper motor white paper that is available in the support section of www.geckodrive.com. If I remember correctly, he referred to the knee portion or shoulder portion of the torque curve as the point where increasing speed produced diminished torque. In my tests, exceeding the maximum voltage (obtained by Mariss's forumla of 32 X SQRT (Inductance)), increased motor heating above 80 degrees centigrade EXCEPT when using the PK296A2A-SGxx motors. Because those motors are listed as having maximum current draw of 3A, they can be safely run at higher voltages. Those motors are actually rated at 4.5A. If they are run at 4.5A and at 40VDC, under load, they will hit 80 degrees C. or higher. I've compared my PK296B2A-SG3.6 motors with a PK296-F4.5A motor. Both motors have the same electrical specifications except that the geared motor is rated at 3A and the non-geared motor is rated at 4.5A. My tests with the G540 have shown that I can get more torque using a PK299-02 motor wired half-coil than I can get using a PK299-F4.5 motor wired half-coil. The 02 motor is rated at 3A and the F4.5 motor is rated at 4.5A, so the 02 motor can be run at full amps but at reduced voltage while the F4.5 motor is run at reduced amps but at full voltage. When I restrict the F4.5 motor to 3A, it does not develop the same torque as the 02 motor. Of course, if I run those two motors with a G203v stepper driver and allow both to run at their maximum amps and at their maximum voltage, they are basically identical in performance and in heat build-up. I've found that heat build-up depends on speed and load. Running a motor with no load at maximum speed heats up a motor very quickly. Running a motor at moderate speed, at maximum voltage and with a maximum load also builds up heat quickly. So, what is the practical application of my testing? It seems that running a motor at high speed and low load (jogging) or running a motor at low speed and high load (cutting) will both cause the motor's temperature to rise. My cutting speeds were normally around 5-6 inches per second. My jogging speeds were normally around 12-15 inches per second. I've sold my Shopbot, so I can't run temperature tests, but I do remember how hot the geared motors got in production. The motors were too hot to touch after surfacing the spoil board (high speed 12-ips, low load 0.1-inch depth of cut) and the motors were also too hot to touch after cutting several MDF sheets in normal production (low speed 6-ips, high load 0.65-inch depth of cut). |
#28
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I just saw a post on the CNCZone that referenced a post that Mariss made two years ago. His post explains one way to compare motors. I also agree with his assessment of Oriental Motor stepper motors, but I realize that those motors are not easily available in some parts of the world and I know that in some countries they are too expensive to even consider; however, Oriental Motor has been my only choice since they started manufacturing their PK series.
Here's the address of Mariss's post: http://www.cnczone.com/forums/530370-post11.html |
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