<p>You have to know:</p>

<ul>
<li>distance between belt teeth (usually 2mm)</li>
<li>number of teeth on pulley</li>
<li>motor step angle 1.8 deg?</li>
<li>microstepping count, probably 16?</li>
</ul>

<p>Then you can enter all these numbers info the calculator here:
<a href="https://www.prusaprinters.org/calculator/" rel="nofollow noreferrer">https://www.prusaprinters.org/calculator/</a></p>

CC BY-SA 3.0
2018-01-16T07:47:47.997Z
I changed it to the result from the calculator (80 steps per mm) but the extruder heater stopped working and I couldn't try it deeply. I am waiting for a new one, I will update this when I can do the tests.
Alberto Méndez
CC BY-SA 3.0
2018-01-24T07:54:48.697Z
I finally could try it and thanks to the calculator I could set the right steps per mm, I noticed too that the extrusor steps per mm I had set in the firmware were wrong, I had them in 98 and the default value is 158.8308. After changing these (X, Y and extrusor steps per mm) values the print size is the expected. Thank you
Alberto Méndez
CC BY-SA 3.0
2018-01-10T07:52:19.927Z
This helps but I had to do some manual adjustment in the `step per mm` option to solve it. Thank you very much
Alberto Méndez
CC BY-SA 3.0
2018-01-11T20:07:26.447Z
Yes, the result of the calculation should be entered as the `steps per unit`, and if the information is correct this should be a first-time accurate solution. Experimenting as described in Alberto's answer will work if you don't know the mechanical parameters, but may not be very accurate and will take multiple iterations to get "close enough".
mbmcavoy
CC BY-SA 3.0
2018-01-12T14:59:43.473Z
I will try it again because as you say my method can lead to errors, when I have done it I will update all the information. The changes didn't work as expected, some pieces keep giving size problems (usually too small now)
Alberto Méndez
CC BY-SA 3.0
2018-01-09T20:26:16.273Z
2018-01-09T20:26:16.273Z
Gunslinger
<p>I finally solved it by manually adjusting the <code>steps per unit</code> in the printer firmware. </p>

<p>The process is easy just move the extruder to one position and draw two marks, one at the extruder position and another one 10 cm in the X axis from the extruder position then with Repetier or with the the printer controls move the X axis 100 mm, if the extruder stops after the mark reduce the <code>steps per unit</code> or increase them if the extruder stops before the mark, do until the movement matches both marks. Repeat for the Y axis.</p>

<p>You can see the changes I made to the firmware in my <a href="https://github.com/amendezcabrera/geeetech-prusa-i3-pro-b-firmware/commit/f6ba29998ccfd0dc0f0e2cba2c3ef3176f6e487f" rel="nofollow noreferrer">GitHub</a></p>

CC BY-SA 3.0
2018-01-10T08:12:20.133Z
2018-01-11T09:18:38.113Z
2018-01-11T09:18:38.113Z
Alberto Méndez
<p>After a long time tweaking my new 3D printer I solved all the unexpected errors and I can print succesful pieces but I am facing a "problem", they are over sized, I found this problem trying to print a Raspberry Pi Case and an smartphone case, the printed pieces are bigger than the objects. </p>

<p>Here some related information</p>

<p><strong>Printer</strong>: Geeetech Prusa i3 Pro B</p>

<p><strong>Firmware</strong>: <a href="https://github.com/amendezcabrera/geeetech-prusa-i3-pro-b-firmware" rel="noreferrer">My GitHub</a> (Marlin)</p>

<p><strong>Software</strong>: Repetier Host with Slic3r</p>

<p>Does somebody know how could I solve it?
Thank you very much</p>

CC BY-SA 3.0
2018-01-09T14:47:31.690Z
Is this with every print? Or did you hit the scale multiplier by accident? And have you changed/modded your printer?
Granny
CC BY-SA 3.0
2018-01-09T14:50:46.130Z
I could sure it is with every print, I tried to print yesterday another fixed size piece (the third one, in different dates) and it is bigger than it should be. I am suspecting about the `step per mm` option in the firmware.  let me mention they aren't too much bigger, just some mm, but enough to don't fit the objects
Alberto Méndez
CC BY-SA 3.0
2018-01-09T14:52:03.840Z
If you have changed any poulies or belts your steps per mm could have changed and with this your printer will go further or shorter than its actually supposed to be.
Granny
CC BY-SA 3.0
2018-01-09T14:54:18.777Z
I didn't changed them, the oversizing problem is probably there from the beginning but I didn't noticed it until now, when I tried to print fixed size models. This evening I will try to check the `step per mm` configuration and let you know. Thanks @Granny
Alberto Méndez
CC BY-SA 3.0
2018-01-09T15:22:52.827Z
It would be helpful (to say the least!) if you posted the model of your printer and all the info you can find about the firmware & software on the printer as well as the application you're using to do the slicing.
Carl Witthoft
CC BY-SA 3.0
2018-01-09T15:30:41.783Z
Hi @CarlWitthoft I didn't do it because I'm away from my printer, I will try to add some info which I can remember now and the rest later.
Alberto Méndez
CC BY-SA 3.0
2018-01-10T07:53:08.387Z
I finally solved it by reducing the `steps per mm` in the printer firmware. Thank you all
Alberto Méndez
<3d-models><marlin><stepper-driver>
Oversized pieces
Alberto Méndez
# Oversized pieces

(Asked by: username_0 on 2018-01-09)

After a long time tweaking my new 3D printer I solved all the unexpected errors and I can print succesful pieces but I am facing a "problem", they are over sized, I found this problem trying to print a Raspberry Pi Case and an smartphone case, the printed pieces are bigger than the objects.

Here some related information

**Printer**: Geeetech Prusa i3 Pro B

**Firmware**: [My GitHub](https://github.com/amendezcabrera/geeetech-prusa-i3-pro-b-firmware) (Marlin)

**Software**: Repetier Host with Slic3r

Does somebody know how could I solve it?
Thank you very much

**Tags:** 3d-models, marlin, stepper-driver

> **Comments:**
> **username_1**: Is this with every print? Or did you hit the scale multiplier by accident? And have you changed/modded your printer?  
> **username_0**: I could sure it is with every print, I tried to print yesterday another fixed size piece (the third one, in different dates) and it is bigger than it should be. I am suspecting about the `step per mm` option in the firmware.  let me mention they aren't too much bigger, just some mm, but enough to don't fit the objects  
> **username_1**: If you have changed any poulies or belts your steps per mm could have changed and with this your printer will go further or shorter than its actually supposed to be.  
> **username_0**: I didn't changed them, the oversizing problem is probably there from the beginning but I didn't noticed it until now, when I tried to print fixed size models. This evening I will try to check the `step per mm` configuration and let you know. Thanks @username_1  
> **username_2**: It would be helpful (to say the least!) if you posted the model of your printer and all the info you can find about the firmware & software on the printer as well as the application you're using to do the slicing.  
> **username_0**: Hi @username_2 I didn't do it because I'm away from my printer, I will try to add some info which I can remember now and the rest later.  
> **username_0**: I finally solved it by reducing the `steps per mm` in the printer firmware. Thank you all  

---

## 2 answers

### Answer by username_3 on 2018-01-09. Score: 3 | Accepted answer

You have to know:

* distance between belt teeth (usually 2mm)
* number of teeth on pulley
* motor step angle 1.8 deg?
* microstepping count, probably 16?

Then you can enter all these numbers info the calculator here:
<https://www.prusaprinters.org/calculator/>

> **Comments:**
> **username_0**: This helps but I had to do some manual adjustment in the `step per mm` option to solve it. Thank you very much  
> **username_4**: Yes, the result of the calculation should be entered as the `steps per unit`, and if the information is correct this should be a first-time accurate solution. Experimenting as described in username_0's answer will work if you don't know the mechanical parameters, but may not be very accurate and will take multiple iterations to get "close enough".  
> **username_0**: I will try it again because as you say my method can lead to errors, when I have done it I will update all the information. The changes didn't work as expected, some pieces keep giving size problems (usually too small now)  
> **username_0**: I changed it to the result from the calculator (80 steps per mm) but the extruder heater stopped working and I couldn't try it deeply. I am waiting for a new one, I will update this when I can do the tests.  
> **username_0**: I finally could try it and thanks to the calculator I could set the right steps per mm, I noticed too that the extrusor steps per mm I had set in the firmware were wrong, I had them in 98 and the default value is 158.8308. After changing these (X, Y and extrusor steps per mm) values the print size is the expected. Thank you  

---

### Answer by username_0 on 2018-01-10. Score: 2

I finally solved it by manually adjusting the `steps per unit` in the printer firmware.

The process is easy just move the extruder to one position and draw two marks, one at the extruder position and another one 10 cm in the X axis from the extruder position then with Repetier or with the the printer controls move the X axis 100 mm, if the extruder stops after the mark reduce the `steps per unit` or increase them if the extruder stops before the mark, do until the movement matches both marks. Repeat for the Y axis.

You can see the changes I made to the firmware in my [GitHub](https://github.com/amendezcabrera/geeetech-prusa-i3-pro-b-firmware/commit/f6ba29998ccfd0dc0f0e2cba2c3ef3176f6e487f)


---

