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This topic contains 8 replies, has 8 voices, and was last updated by  feste 2 weeks ago.

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  • #3673
    Josef Průša
    Josef Průša
    Keymaster

    Please post here your calculated and tested values along with the printer name or setup description.

    #3792

    Dr. FrakenPrint
    Participant

    Motor Step Angle: 1.8 (200 per rev)
    Driver MicroStepping: 1/16 (Pololu)
    Belt Pitch: 2 (GT-2 rubber w/fibreglass reinforcing)
    Pulley Tooth Count: 20 (GT-2)

    Result: 80.00
    Resolution: 12.5 micron

    Setup:
    Prusa Mendel i2
    RAMPS 1.4
    Marlin
    Budaschnozzle 2.0

    Handsome and Super Sexy: Yes

    #3793

    ruggb
    Participant

    help me understand this please.
    I have 3 belt driven screws — lead = 8, pitch = 2 (4 start).
    i have a 36T pulley on each screw and stepper and a gt2 belt. That is basically the same as driving each screw with a separate motor. The result == 44.44 steps/mm

    I am assuming the lead screw driven system means a direct drive since the gear ratio is 1:1. result == 1600 steps/mm.
    Why are they different?

    #3803

    paulscott56
    Participant

    Motor Step Angle: 0.9 (400 per rev)
    Driver MicroStepping: 1/16 (Pololu)
    Belt Pitch: 2 (GT-2)
    Pulley Tooth Count: 20 (GT-2)

    Result: 160.00
    Resolution: 6.25 micron

    Setup:
    Prusa Mendel i3 (MODIFIED)
    RAMPS 1.4
    Marlin
    Standard 0.4mm J Head

    #3804

    dintid
    Participant

    Lots of confusion regarding what pitch and leads really are. Mostly because the US (Again) uses their own set of rules.

    Anyway, I bought this nice stepper with attached leadscrew and nut included for my Z-axis:

    Partnno.: SM42HT38-1684AL
    Specification: Size 42 x 42mm
    Length 38mm
    Rated Voltage 2.52V
    Rated current 1.68A
    Resistance 1.5 Ohm
    Inductance 2.3 mH
    Holding Torgue 4.2 kg.cm
    1.8 degree/step
    Axis length 205mm
    Lead screw TR8x8mm (P2)
    Include screw nut, wire and connector

    What we want to pay special attention to here is the “Lead screw TR8x8mm (P2)” which Means it is 8mm diameter and we need to enter 8mm pitch. Why is that? Because it has 4 lead starts with 2mm pitch between each = 8

    It Means I can set my Z-axis like this:
    1.8 steps (200 pr revolution).
    Screw pits 8.
    1/4 multistepping
    Result: 100 steps
    Resolution: 0.01mm (10micron)

    Why do I choose as I did? 0.01mm (10micron) is more than good enough resolution, as I will never print Z-layers that can’t be divided by 0.01 and the lower multistepping the higher torx I get.

    Also, and that is most important: I get fewer missed steps with 1/4 multistepping as opposed to “standard” 1/16 for no reason.

    #3815

    ledaero
    Participant

    There’s no 1/32 step calculation in the belts calculator – you have 2x 1/16, then 1/64, but no 1/32.

    Not that it’s hard to work out, but I thought you should know.

    It’s a popular resolution with more advanced Marlin/RAMPS boards using DRV8825 drivers.

    Your screw calculator gives 1/32 figures when you select 1/64.

    And for both types of calculation, your presets don’t preset anything.

    Has this website been tested? Sorry – I won’t be trusting your calculations, I will use a micrometer and calculator as usual.

    #3821

    edson
    Participant

    I modified my prusa 3d printer of 5mm to 8mm Leadscrew, but the printer pieces had been printed with 30% greater. I need change program or G-code to return size for the original?

    • This reply was modified 1 year, 7 months ago by  edson.
    #3823

    ruggb
    Participant

    I don’t have a prusa, I built my own coreXY unit, but maybe this will help u.
    I use Marlin firmware. This line in the configuration.h file
    #define DEFAULT_AXIS_STEPS_PER_UNIT {200,200,800,317.48}
    defines the steps/mm (UNIT=mm) for each axis and extruders.
    I have an 8mm dia, 4 start screw so the lead is 4mm and the pitch is 2mm
    That says it rises 8mm for each revolution.

    Look at the stepper and driver. Mine has a 1.8° step angle with 32x microstepping Or 360/1.8 x 32 steps/rev = 6400 steps/rev
    so — 6400 steps/rev x 1 rev/8mm = 6400/8 steps/mm = 800 steps/mm
    Which is what that 3rd number is.

    How u get that information into ur prusa is another story.
    I do not know anything about the prusa electronics or firmware.
    BUT it has to have firmware and it has to be modifiable and uploadable to the electronics. U might better look for a prusa forum to get that information.

    • This reply was modified 1 year, 7 months ago by  ruggb.
    #4898

    feste
    Participant

    Motor step angle 1/8
    Driver Microstepping 1/32
    Belt pitch 2
    Belt presets 2mm GT2
    Pulley count 20

    Result 160

    on a HTA3d

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