new build and my heat bed is heavy, thin nema 17 looses track of where it is on fast moves, are there any alternatives like the longer nema 17's? running ramps 1.4 with standard pololu modules max 1.25v each. Suggestions welcome!

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You can try playing with the acceleration and jerk settings, but you may have to slow things down quite a bit to get it to print reliably. I use NEMA-23 motors in all axes. A massive bed running at "normal" speeds/accelerations requires a lot more torque than you can get from most NEMA-17 motors. You can run a lot of NEMA-23 motors using the RAMPS board- I was using it that way for 2 years without problems (except for vibration).

You should be able to estimate the torque required and then purchase a motor that meets that spec by using the motor sizing tools at [www.orientalmotor.com] You'll have to make some estimates for some of the inputs but guesstimates are fine and you'll arrive at a close-enough solution, then you buy a motor with a little more torque than it says you need. You might want to look into a wider belt for the Y axis if you're using the standard 6mm stuff. With a big mass moving back and forth a narrow belt is liable to act like a spring.

I went to DSP drivers and 32V power supplies for both X and Y axes in my printer, but it is certainly overkill in the X axis. NEMA-23 motors vibrate more than NEMA-17 motors so a DSP driver allows finer microstepping that helps eliminate some of the vibration.

Edited 1 time(s). Last edit at 04/27/2015 02:36PM by the_digital_dentist.

My bed plate is 3.5 lbs as it is aluminum 6061 12x12x.25 inches, I am wondering if I should try and hog it out but I do not want to loose flatness. The belt is not slipping but the nema 17 is losing position in y axis at anything over 40mm/sec but I believe as you mentioned the "normal" speeds/accelerations are what are actually going too fast and by lowering them to the print speed I should be able to see how far I can push it, I will settle for 100mm/sec with the current configuration but do not expect to reach it and if I do not get that fast whatever upgrade I do I would like to be able to reach over 220mm/sec. I will post the results I get once I change the settings tonight after work, thank you for your input it is appreciated!!!

Increasing the mass of the bed should not affect the speed you can attain unless there is a lot of friction in the bed mechanism; but it will reduce the available acceleration. So try reducing the acceleration. Of course, with reduced acceleration, it will take more distance to achieve a given speed.

As a rough guide, a long nema 17 motor can produce around twice the torque of a short nema 17. So a longer motor might help a lot. It also depends on how well the motor is matched to the driver. What is the specification of the motor you are using at the moment?

Another possibility might be dual Y motors, connected in series.

Edited 1 time(s). Last edit at 04/27/2015 03:47PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I am not sure, it is the shortest they come at around 1.5 inches thick, the rexroth bearing block has 2% preload as well. What is the largest nema 17 (longest) available off the shelf? Can my ramps 1.4 and poololu board push it?

Does your motor have a part number label on it? If so, the specifications can probably be looked up on the web.

Your RAMPS and pololu drivers can drive a longer motor provided that its current rating is well-matched to the driver. One of the more powerful NEMA 17 motors I use is the 17HS19-1684S, which is 46mm long. But I can't say whether it would be an improvement on your existing motor, without knowing that motor's specifications.

There are different versions of the pololu drivers, and some can drive the motors at higher current than others. It sounds like you are using the standard one with 1 ohm sense resistors and 1.25A max current. There are other versions, such as the Pololu black edition, and the Think3DPrint3D Ice Blue edition, that can provide more current. If the stepper motor is running cool then upgrading the driver may help.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

ok I have 3 ice blue's on the way, going to look at my model number on the nema 17 when I get home, chinese origin so not expecting much, whatever the best powered nema 17 is for the ice blue 2a output let me know and I will buy a couple immediately. The stepper is driving cool at 1.25v

Edited 1 time(s). Last edit at 04/27/2015 07:45PM by lunarkingdom.

here is the info from the side of the stepper motor:

17H53413L19P1-X
1.8 deg 1.3A
1409290805

If you want to print at 100 mm/sec I suspect you'll need something larger than a NEMA-17 motor. Preload on the linear guide, while great for precision, looks like friction to the motor and is going to require extra torque just to move the bed at ANY speed.

My print bed is the same size as yours and rides on preloaded linear guides. I use a ball screw to drive it and calculated it would require 380 oz-in torque to drive it to 50 mm/sec with 1000 mm/sec^2 acceleration and stopping within 0.1 mm. I use a 425 oz-in motor and it seems to behave pretty much as expected. The screw drive adds to the required torque, so you won't have that to deal with, but printing at 100 or 200 mm/sec will definitely add to the required torque. You'll have a hard time finding NEMA-17 motors that can produce more than about 100 oz-in torque.

It's really not difficult to use the motor sizing tool to figure out what you actually need to save the time and money wasted on under-sized motors. Once you know the torque required, start shopping for a motor that can deliver it.

You may want to consider an external, higher current/performance driver module. $40 will get you a pretty good DSP module that will let you drive the motor with higher voltage and current and finer microstepping (if your controller can handle it) than the little stepper modules.

I want to pull the trigger on some 60mm nema 17 motors but I need some feedback first, the ice blue pololu modules can run up to 2 amps so do I need to get some 60mm nema 17's that run at or below 2 amps? Looking at these now they are 1.8 amps:

[www.ebay.com]

yeah I would agree except I am having zero trouble on the x axis on the same preload setup, it is just 2 pounds lighter is all. I just might be satisfied at 70-90mm/sec as I am running out of real estate on this build. I want to keep it simple at this point I already got crazy to power the bed with a separate power supply. I just need a little more input on the 60mm nema 17's and however fast I can tune it I will have to settle for. I really appreciate you sharing your knowlege on the subject digital dentist thank you very much!

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lunarkingdom
here is the info from the side of the stepper motor:

17H53413L19P1-X
1.8 deg 1.3A
1409290805

I think you probably mean 17HS3413. Here is the data for that motor, from [www.longs-motor.com]:

17HS3413
Step angle 1.8
Length 34mm
Phase current 1.3A
Phase resistance 2.4 ohms
Phase inductance 2.8mH
Holding torque 28Ncm
Detent torque 1.6Ncm
Rotor torque 34Ncm

The 17HS19-1684S is a popular nema 17 stepper motor for 3D printers, but is 48mm long, max current 1.68A, holding torque 45Ncm. Phase resistance and inductance are similar. So with suitable drivers, it will provide nearly twice as much torque as your present motors would at their max current, so about twice the acceleration assuming you are not voltage-limited (which I think is unlikely). You probably can't get much more of an improvement than that without going to nema 23 motors as digital dentist suggests.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

thanks dc42, just pulled the trigger on 5 of the 17HS19-1684S (I like spares) thanks for the advice!!

Quote
lunarkingdom
thanks dc42, just pulled the trigger on 5 of the 17HS19-1684S (I like spares) thanks for the advice!!

Did you really need 5, if it is only the Y axis that is giving the problem? You could change just that motor.

btw when you get your new drivers, be aware that a given voltage on the pot wiper will give you more current with the ice blue stepsticks than with your old ones - twice as much I believe.

Edited 2 time(s). Last edit at 04/28/2015 09:29AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

For those who are interested, torque and sizing equations can be found on pages 102-115 in this document: [irtfweb.ifa.hawaii.edu]

Quote
dc42

Quote
lunarkingdom
thanks dc42, just pulled the trigger on 5 of the 17HS19-1684S (I like spares) thanks for the advice!!

Did you really need 5, if it is only the Y axis that is giving the problem? You could change just that motor.

btw when you get your new drivers, be aware that a given voltage on the pot wiper will give you more current with the ice blue stepsticks than with your old ones - twice as much I believe.

I built htis one because my old printer was falling apart because of the lexan it is made out of, I am going to rebuild that one as well so that is 2 motors per printer, why upgrade x and not y? what happens when I turn up the speed then y fails too? x and y times 2 machines and one spare is reasonable ;-)

Quote
the_digital_dentist
You can try playing with the acceleration and jerk settings, but you may have to slow things down quite a bit to get it to print reliably. I use NEMA-23 motors in all axes. A massive bed running at "normal" speeds/accelerations requires a lot more torque than you can get from most NEMA-17 motors. You can run a lot of NEMA-23 motors using the RAMPS board- I was using it that way for 2 years without problems (except for vibration).

Where do I change the acceleration and jerk settings in slic3r or in the firmware?

If you're using Marlin, I don't recall if you can set those from the LCD, but the variables are located in the config.h or configadv.h file. You'll have to edit the file and recompile the firmware to make the changes permanent.