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Topic: Help with T8 Lead Screw Issues, Please.

Hello, I'm hoping someone can help me solve this issue I'm having, So I'll get to it.

I have the GEEETech Prusa i3 PRO-B Printer and when finished building it, I noticed one of the Threaded rods was buckled quite a bit. So I did some research and noticed the majority of people were actually swapping out their rods for lead screws.

So, I purchased these T8 L350mm Diameter 8mm Lead 4 Start lead Screws and the Specifications are as follows.

Specifications:
Lead Screw Diameter: 8MM 
Lead: 8mm
Screw Length: 350mm 
Screw Pitch: 2mm

My stepper motors are a Hybrid stepper motor 42SHD0034-20B http://www.geeetech.com/hybrid-stepper- … -1011.html


My problem is, I'm coming up with differing figures when working out the steps per millimetre with leadscrew driven systems.

I download a version of the Marlin firmware from this post over on the GEEETech forum which as apparently already been edited for the use of a BLTouch for the Prusa i3 Pro B and the T8 Lead Screw from this post here >http://geeetech.com/forum/viewtopic.php … mp;t=60826  and in his firmware, the steps are 400.96, see code below.

//#define DEFAULT_AXIS_STEPS_PER_UNIT   { 81.5, 81.5, 2577.46, 94 }
#define DEFAULT_AXIS_STEPS_PER_UNIT   { 81.5, 81.5, 400.69, 94 }
/**


Bear with me, Please?

Now, with this other guys Firmware, using the T8 Lead Screws here https://www.geeetech.com/forum/viewtopi … 647#p30268 the guy is using 2560 steps per mm and not 400.


Moving on, So I tried using this calculator here https://www.prusaprinters.org/calculator/ and this is where I become even more confused,... This is what I enter into the settings.

Motor step angle: 1.8° (200 per revolution)
Driver microstepping: 1/16 - uStep (mostly Pololu)
Leadscrew pitch: 2
Gear ratio: 1:1


The last one is the "Pitch presets" a few people have said use the: 1/4"-16 Acme (1.5875mm per rotation) and others have told me to use M8 - metric (1.25mm per rotation) and others have told me to just leave it, there's no T8 Lead Screw setting, as it's not been added.

I have noticed that none of the options in the "Pitch Presets" says 8mm per rotation, which is what my lead Screws move with one rotation.

Anyway, after I add the settings I get a figure of only 1600.00... now if my Lead Screws are a 4 Lead Start, do I then divide that 1600.00 by 4?  which would give me 400?



Why are so many people giving me different figures for the same lead screws?  It's gotten to the point now, where I'm virtually scared of entering any figure, lol... I don't want to get it wrong and break something, you see.

I do realise I have got a lot to learn and sadly, Maths was never my strong suit, could someone please, help me understand whats going on in Layman's Terms, please?


I thought I could just use the firmware that has already been edited for the BLTouch and the T8 Lead Screws, as I've already got the BLTouch also and if that firmware is already correct, I could just use that and then take my time learning everything else later, once I have this printer up and running.


I appreciate your Patience on this one, Please.

Thank you, so much.

I Want To Believe

2 (edited by yizhou.he 2018-05-22 22:22:53)

Re: Help with T8 Lead Screw Issues, Please.

Don't worry, use wrong STEPS_PER_UNIT is unlikely damage anything. Different people use different step motor driver and Driver microstepping, therefore the number is different even for the same lead screw. If you are not confident with your calculation, start with the smaller number, you will find the z axis move slower that what it supposed to be if the number for z axis need to be bigger. Let say if you try to raise z axis by 40mm, it only raise 10mm, then your number is 1/4 of what it supposed to be.

http://reprap.org/wiki/Triffid_Hunter's_Calibration_Guide

(Da Vinci 1.0, Jr. 1.0 RAMPS, miniMaker) X4, (Creality CR-10S, CR-10 mini, Ender-3) X4, Anycubic MEGA X4, Anycubic Chrion X1, ADMILAB Gantry X2 (MonoPrice Maker Select V2, Plus, Ultimate)X4--Select mini X1, Anycubic photon X4, Wanhao duplicate D7 X1.
iNSTONE Inventor Pro X2, CTC Dual X2, ANET-A8, Hictop 3DP-11, Solidoodle Press, FLSUN I3 2017X1

3

Re: Help with T8 Lead Screw Issues, Please.

With all the info given 400 steps sounds Right. Like yizhou  stated easy adjustment to make. You can change through reptier host as long as your chitchat is turned on in marlin.

Soliddoodle 4 stock w glass bed------Folger Tech Prusa 2020 upgraded to and titan /aero extruder mirror bed
FT5 with titan/ E3D Aero------MP mini select w glass bed
MP Utimate maker pro-W bondtech extruder
Marlin/Repetier Host/ Slic3r and Cura

4

Re: Help with T8 Lead Screw Issues, Please.

@yizhou.he
@Tin Falcon

Sorry, for my delay in getting back to you, I've had a few things to take care of,...

Moving on, Thank you to both of you, I've added the 400 and the BLTouch to the printer, however, I'm not sure what I'm actually doing wrong, but the printer still doesn't work correctly.

When I press Auto Home, the carriage will now move all the way to the Left, and stops, then the print bed comes all the way forward and stops, then the carriage goes to the middle of the print-bed and stops,... then the Left and right Lead screws turn to lower the carriage about 10mm the right Screw stops but the Left Screw turns a few extra turns, bringing the left-hand side down, so now it's all lopsided.


I've not got a darn clue to what it is I'm doing as this is my first printer,... Is there a service I can call Via Skype?

I was thinking of showing what is actually happening via a camera on the mobile phone, and hopefully, they could walk me through what it is I'm doing wrong.


I'm more than willing to pay and I can afford maybe £20-30 quid for someone to calibrate this machine.



I can take my time and learn at my own pace, once its up and running,... If you know of any service and they can visit, I live in Blackburn, if you know of any in my area?


P.S
I've read the GEEETech forums, which aren't all that good or busy if someone does reply, they explain with the terminology of someone who actually understands, I don't think they know what Layman terms are.


Regards

I Want To Believe

5

Re: Help with T8 Lead Screw Issues, Please.

I don't have any experience with GEETech, so you are welcome to try my suggestion or ignore it if you don't trust it and wait for others comment.

Find //#define MANUAL_X_HOME_POS in your marlin configure.h and change following three lines to the following

#define MANUAL_X_HOME_POS 0
#define MANUAL_Y_HOME_POS 0
#define MANUAL_Z_HOME_POS 0

This will let your printer park hotend at home position, I think. Your previous setting ask printer to park the hotend to the center of the bed, I think.

About Z-axis, your left Left Screw and the right screw is not in sync, I think. Since you mentioned you replaced it, make sure the left screw and right screw are identical.

then double check if both step motor for z-axis got enough current, which means you can not easily turn then right after autohome finished. if you can easily turn one of then, adjust the motor current for that step motor. Google for instructions on how to adjust the motor current for your printer.

Lastly, turn off printer after autohome, and turn the left screw or the right screw so that the left and the right end of the carriage are at the same height. then turn on the printer and raise the z-axis from LCD screen and do autohome again and see if the problem is fixed. If it does, level your bed and do a test print, again, google for instruction on how to leveling the print bed for your printer.

(Da Vinci 1.0, Jr. 1.0 RAMPS, miniMaker) X4, (Creality CR-10S, CR-10 mini, Ender-3) X4, Anycubic MEGA X4, Anycubic Chrion X1, ADMILAB Gantry X2 (MonoPrice Maker Select V2, Plus, Ultimate)X4--Select mini X1, Anycubic photon X4, Wanhao duplicate D7 X1.
iNSTONE Inventor Pro X2, CTC Dual X2, ANET-A8, Hictop 3DP-11, Solidoodle Press, FLSUN I3 2017X1

6 (edited by Tin Falcon 2018-05-26 20:10:06)

Re: Help with T8 Lead Screw Issues, Please.

I'm more than willing to pay and I can afford maybe £20-30 quid for someone to calibrate this machine.
I can take my time and learn at my own pace, once its up and running,... If you know of any service and they can visit, I live in Blackburn, if you know of any in my area?

First of all you purchased a kit so IMHO you need to get it running. And i know of no service that offers help to get them running.
Also 3d printer kit building   is not for the faint of heart, And thirdly there are some cheap printers that were never designed to be completed.

That being said IMHO it sounds like you are very close to completion . And you likely only have one issue that being the z axis.

Sounds like your right screw is binding. preventing the probe routine from completing.

Also now may be a good time to verify yours steps per mm through manual control.

Soliddoodle 4 stock w glass bed------Folger Tech Prusa 2020 upgraded to and titan /aero extruder mirror bed
FT5 with titan/ E3D Aero------MP mini select w glass bed
MP Utimate maker pro-W bondtech extruder
Marlin/Repetier Host/ Slic3r and Cura