<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>

[{'answer_id': 5248, 'author': 'Gunslinger', 'author_id': 5395, 'author_profile': 'https://3dprinting.stackexchange.com/users/5395', 'pm_score': 3, 'selected': True, 'text': '<p>You have to know:</p>\n\n<ul>\n<li>distance between belt teeth (usually 2mm)</li>\n<li>number of teeth on pulley</li>\n<li>motor step angle 1.8 deg?</li>\n<li>microstepping count, probably 16?</li>\n</ul>\n\n<p>Then you can enter all these numbers info the calculator here:\n<a href="https://www.prusaprinters.org/calculator/" rel="nofollow noreferrer">https://www.prusaprinters.org/calculator/</a></p>\n'}, {'answer_id': 5253, 'author': 'Alberto Méndez', 'author_id': 9549, 'author_profile': 'https://3dprinting.stackexchange.com/users/9549', 'pm_score': 2, 'selected': False, 'text': '<p>I finally solved it by manually adjusting the <code>steps per unit</code> in the printer firmware. </p>\n\n<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>\n\n<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>\n'}]
['https://3dprinting.stackexchange.com/questions/5245', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/9549/']