MakerFarm Prusa i3 and i3v 66 oz. in. Stepper Motor Specifications

I finally tracked down specifications for the 66 oz. in. motors that Colin sells and includes in the MakerFarm i3 and i3v kits. It looks like they're not actually the same motors that Circuit Specialists sells (as I have suggested in other threads) but their characteristics are similar: around 18 ohms DC resistance and 35mH inductance.

Specifications from Colin:
Attachment 2024

And direct measurement:
Attachment 2025

The 35mH inductance is accurate, but you can ignore the series resistance value. This meter is attempting to estimate DC resistance from phase angle measurements, and it's out in the corners where it isn't very accurate. The 18.5 ohms I measured with a DC multimeter is more accurate and matches the spec sheet.

As you can see, the resistance and inductance of these motors is tremendous. I think this is why many of us have had trouble getting the extruder motor to retract properly at high retract rates (25-30mm/s).

If you're struggling with blobbing or stringing on your MakerFarm printer, try reducing your retract rate to 10mm/s. The extruder motor can usually keep up at this rate.

So how much should the amps be on the ramps board realy?

I thought i rememberd that Colin told me it was 0.38.
But i do get some skipping sometimes when doing around 60-80mm/s, so i kinda just wanted to ask if it would have been that.

Quote:

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Originally Posted by DrLuigi

So how much should the amps be on the ramps board realy?

I thought i rememberd that Colin told me it was 0.38.
But i do get some skipping sometimes when doing around 60-80mm/s, so i kinda just wanted to ask if it would have been that.

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Colin specifies .39v in his build document for the 8" i3v. This translates to a 2.5x.39=.98A current limit. In practice, the motor never reaches this current because its DC resistance of 18.2 ohms limits the current to .66A, which isn't too much higher than the actual rated motor limit of .5A. When the motor starts moving, the inductance reduces this current even further, depending on how fast you step.

The extra current doesn't hurt the motors, but it does make them get hot. The heat is only really a problem with the extruder motor, which is mounted to a plastic part. You can either turn down the current on the extruder motor, or you can add a fan with an appropriate shroud. My shroud is here: http://www.thingiverse.com/thing:343026

Or you can ditch the Greg's extruder altogether and use something else. Here's what I'm currently using: http://www.thingiverse.com/thing:389105

Technically speaking, the voltage on the drivers should be set to .5/2.5=.2V. Since the motors are running right near their current/torque limits at 100mm/s, this may or may not cause more skipping. I'm running with the .39v default, and I'm printing at 100mm/s and bridging at 120mm/s.

Edit: fixed broken link

Quote:

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Originally Posted by clough42

The extra current doesn't hurt the motors, but it does make them get hot. The heat is only really a problem with the extruder motor, which is mounted to a plastic part. You can either turn down the current on the extruder motor, or you can add a fan with an appropriate shroud. My shroud is here: http://www.thingiverse.com/thing:34302

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Looks like the wrong link, or I don't understand how that thing is used with motors :)

Quote:

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Originally Posted by clough42

Or you can ditch the Greg's extruder altogether and use something else. Here's what I'm currently using: http://www.thingiverse.com/thing:389105

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How is that extruder really different from Greg's? Except for the belt general construction looks very close, motor is still mounted directly to plastic. I have a great heat problem with extruder, it melted original small gear that came with the kit, and now it melted mount I printed with PLA. I gets so hot I can't really touch it, and it's set to 0.37v.

Quote:

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Originally Posted by DanSilov

Looks like the wrong link, or I don't understand how that thing is used with motors :)


How is that extruder really different from Greg's? Except for the belt general construction looks very close, motor is stinductanceed directly to plastic. I have a great heat problem with extruder, it melted original small gear that came with the kit, and now it melted mount I printed with PLA. I gets so hot I can't really touch it, and it's set to 0.37v.

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Sorry. The link was missing a character. I fixed it.

You can, of course, use any extruder you like. The heat problem you're experiencing is because of the motor that Colin chose and the current he recommends. You can turn down the current or use a fan to avoid the heat, but that won't solve the inductance problem, so your retract speed will still be limited. Replacing the motor will fix both.

If you choose to replace the motor, you may wish to buy a NEMA 14 instead and try the Itty Bitty Belted Extruder. It has a number of features I like, but not everyone may agree. It's about half the weight of the one that comes with the kit because of the smaller motor. This reduces the torque needed to move the X axis and may help with skipping or allow higher speeds. The belt drive doesn't make clicking noises and has no backlash. It does require more vitamins, though, so that's something to consider.

The motor being mounted directly to the plastic isn't a problem if it doesn't get hot. The NEMA 14 motor (and current setting) I list with the extruder reaches about 45C when printing, which doesn't threaten the ABS.

Oh...I see you're using PLA. I don't think 45C would hurt PLA, but I don't know for sure.

Quote:

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Originally Posted by clough42

If you choose to replace the motor, you may wish to buy a NEMA 14 instead and try the Itty Bitty Belted Extruder.

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Is it possible to use NEMA 14 with Greg's extruder? There's quite a lot of vitamins for the Itty Bitty Belted Extruder which I can't get ahold of easily, so I think I have to stick with Greg's for now. But it would be good to replace the motor, it's really scarily hot during printing.

I have not seen a NEMA 14 variant, but it may be out there.

The belt and pulley can be had on eBay for $5 total, including shipping. The rest of the vitamins, save the motor, are the same as the Greg's.

Quote:

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Originally Posted by DanSilov

...it would be good to replace the motor, it's really scarily hot during printing.

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Although you could do it, replacing the motor or going with a different extruder should not be a prerequisite for you to get your i3v up and running. Continue the dialogue in your print problems thread so we can help figure out what is going on in your case. Does the extruder motor get hot? Yes, as they all do with the driver setup suggested by MakerFarm. So hot that you can't keep fingers on it or hot enough to melt/soften the small gear? IMO, they shouldn't be getting that hot unless something is wrong. Make sure your power supply is set for 12V and not something else common like 13.8V. Lower the driver some. Unnecessary load on the motor will also cause it to get hotter than it should. Too low of a nozzle temp, motor and small gear pushed into large gear too tight, poor lateral alignment between small gear and large gear, dragging at the guidler bearing, large gear cranked onto hobbed bolt too far, and bolts rubbing on the large gear come to mind as some things that would put undue load on the extruder motor. I've since adopted Clough42's extruder motor shroud, but until I did that I ran long prints with a small table fan set next to the printer on extruder motor side. Fan airflow was angled upwards to not affect the bed and nozzle much, but the extruder motor would pass into the airflow when it was on the right-hand side of the prints. That kept the extruder motor noticeably cooler.

Quote:

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Originally Posted by printbus

Although you could do it, replacing the motor or going with a different extruder should not be a prerequisite for you to get your i3v up and running. Continue the dialogue in your print problems thread so we can help figure out what is going on in your case.

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Yep, planning to post some latest findings and results there, just a bit busy with work lately. I'm determined to make it work with all the current hardware, before moving on with new motor and/or extruder.

I have just assembled an 8" I3v and printed several things successfully using makerfarm stock firmware and makerfarm's supplied slicer config settings. PLA. I did not measure or calibrate the driver voltages since everything was working fine. the only calibrations performed were bed leveling using a sheet of copy paper to measure, and the eSteps on the filament feed rate.

Observations: the stock makerfarm slicer settings came with max 60mm/s for infill and 130 for travel. Obviously a lot slower than Clough42 is tuning to.


At these speeds nothing gets hot and the retractions work fine.


So it seems like either the stock settings or motors have been changed. The printer works well as delivered and doesn't have to have upgrades to work. I can certainly understand how upgraded motors or added cooling could be required for maximum performance. When I get a chance i'll update this with identifying information from the motors themselves to see if they are shipping the same ones Clough42 measured. I'll also experiment with upping the speed and see what happens. I've got a non contact thermometer somewhere so I should be able to get decent temperature figures.

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Originally Posted by TopJimmyCooks

So it seems like either the stock settings or motors have been changed. The printer works well as delivered and doesn't have to have upgrades to work. I can certainly understand how upgraded motors or added cooling could be required for maximum performance. When I get a chance i'll update this with identifying information from the motors themselves to see if they are shipping the same ones Clough42 measured. I'll also experiment with upping the speed and see what happens. I've got a non contact thermometer somewhere so I should be able to get decent temperature figures.

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Cool. What retract rate are you using? Are you using RAMPS? Can you measure the reference voltage setting on the drivers?

The speeds I'm using were stock at the time I purchased my kit.

I provided some feedback to Colin regarding the current settings, but he didn't seeme very receptive. He just told me the heat shouldn't be a problem, and for the most part it isn't. I wonder if he's tuning something differently now.

I'll get some more info up toniight or in the next few days. However I strongly suspect based on my lack of vibration issues, belt slapping and heat that you reported, that the makerfarm provided slicer print speed settings are slowed down significantly. I can't see anything else that's different.

Quote:

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Originally Posted by TopJimmyCooks

Observations: the stock makerfarm slicer settings came with max 60mm/s for infill and 130 for travel. Obviously a lot slower than Clough42 is tuning to.

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I'm not seeing these values in the current config files available through the Slic3r download link in the site's current build guide. Sometimes MakerFarm has more than one download path for what should be the same material, but isn't. So, through what link did you get the config files? What hot end type & size, and filament diameter are you using? Maybe not all the different config files have the same speed values. I didn't compare line-by-line, but at a glance the current config files for the 0.40mm nozzle 1.75mm hex hot end appear to have the same speed values as the files in late April.

In addition to the questions clough42 had, how long of a print have you ran without noticing the motors getting hot?

Quote:

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Originally Posted by TopJimmyCooks

Observations: the stock makerfarm slicer settings came with max 60mm/s for infill and 130 for travel. Obviously a lot slower than Clough42 is tuning to.

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These are the default values built into the Slic3r software. You're not running with the MakerFarm config files unless you manually load them. I assume you haven't been doing this?

I did in the beginning but I've messed around quite a bit. I know I have more than one instance of slicer floating around because pronterface installed a second one. I'll report back. .50mm J Head.

looks like I'm using the config given for the .50mm 3mm j head. This hotend may not be capable of supporting the higher speeds.

Edit: confirmed - max speed with this hotend is 60mm limited by extrusion.

Code:

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# generated by Slic3r 0.9.9 on Sat Apr  5 14:38:22 2014avoid_crossing_perimeters = 1
bed_size = 200,200
bed_temperature = 90
bottom_solid_layers = 3
bridge_acceleration = 0
bridge_fan_speed = 100
bridge_flow_ratio = 1
bridge_speed = 60
brim_width = 0
complete_objects = 0
cooling = 1
default_acceleration = 0
disable_fan_first_layers = 0
duplicate = 1
duplicate_distance = 6
duplicate_grid = 1,1
end_gcode = M104 S0 ; turn off temperature\nG28 X0  ; home X axis\nG28 Y0  ; home Y axis\nM84    ; disable motors\nM190 S0 ; wait for bed temperature to be reached
external_perimeter_speed = 70%
external_perimeters_first = 0
extra_perimeters = 1
extruder_clearance_height = 20
extruder_clearance_radius = 20
extruder_offset = 0x0
extrusion_axis = E
extrusion_multiplier = 1
extrusion_width = 0
fan_always_on = 1
fan_below_layer_time = 60
filament_diameter = 3
fill_angle = 45
fill_density = 0.4
fill_pattern = honeycomb
first_layer_bed_temperature = 90
first_layer_extrusion_width = 200%
first_layer_height = 0.35
first_layer_speed = 30%
first_layer_temperature = 225
g0 = 0
gap_fill_speed = 20
gcode_arcs = 0
gcode_comments = 0
gcode_flavor = reprap
infill_acceleration = 0
infill_every_layers = 1
infill_extruder = 1
infill_extrusion_width = 0
infill_first = 0
infill_only_where_needed = 0
infill_speed = 60
layer_gcode =
layer_height = 0.4
max_fan_speed = 100
min_fan_speed = 35
min_print_speed = 10
min_skirt_length = 0
notes =
nozzle_diameter = 0.5
only_retract_when_crossing_perimeters = 1
output_filename_format = [input_filename_base]I38_50.gcode
perimeter_acceleration = 0
perimeter_extruder = 1
perimeter_extrusion_width = 0
perimeter_speed = 30
perimeters = 3
post_process =
print_center = 95,95
raft_layers = 0
randomize_start = 1
resolution = 0
retract_before_travel = 2
retract_layer_change = 1
retract_length = 1
retract_length_toolchange = 10
retract_lift = 0
retract_restart_extra = 0
retract_restart_extra_toolchange = 0
retract_speed = 30
rotate = 0
scale = 1
skirt_distance = 6
skirt_height = 1
skirts = 1
slowdown_below_layer_time = 30
small_perimeter_speed = 30
solid_fill_pattern = rectilinear
solid_infill_below_area = 70
solid_infill_every_layers = 0
solid_infill_extrusion_width = 0
solid_infill_speed = 60
start_gcode = ; 8" i3 & i3v 3mm PLA for .50mm Jhead 4-5-14\nG28 ; home all axes
support_material = 0
support_material_angle = 0
support_material_enforce_layers = 0
support_material_extruder = 1
support_material_extrusion_width = 0
support_material_interface_layers = 0
support_material_interface_spacing = 0
support_material_pattern = rectilinear
support_material_spacing = 2.5
support_material_speed = 60
support_material_threshold = 0
temperature = 225
threads = 2
toolchange_gcode =
top_infill_extrusion_width = 0
top_solid_infill_speed = 50
top_solid_layers = 3
travel_speed = 130
use_relative_e_distances = 0
vibration_limit = 0
z_offset = 0

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