<p>I have just finished building a Tronxy P802M Prusa i3.</p>

<p>When I try to move the Z-axis, using the hardware buttons in the LCD menu (without a computer connected), it only goes down, when I both increase, and decrease, the value of Z.</p>

<p>Any suggestions?</p>

[{'answer_id': 4162, 'author': 'Greenonline', 'author_id': 4762, 'author_profile': 'https://3dprinting.stackexchange.com/users/4762', 'pm_score': 2, 'selected': False, 'text': '<p>It could be a hardware fault. </p>\n\n<p>First check, and compare, the control board connections to the motors of the three axes. You don\'t state it in your question but, presumably, the X and Y axes move correctly? If so, then compare the connections for the Z-axis motors with the connections for the motors of the axes that work as expected.</p>\n\n<p>If they are correct then the problem is likely to be with the firmware.</p>\n\n<p>Have you...</p>\n\n<ul>\n<li>homed the Z-axis yet?</li>\n<li>installed the endstops?</li>\n</ul>\n\n<p>From <a href="https://makerware.thingiverse.com/groups/prusa-i3/topic:7370" rel="noreferrer">X Y Z axis only move one direction?</a>:</p>\n\n<blockquote>\n  <p>Using Marlin? Before you do a <code>G28</code> homing the axes will only move\n  towards the endstops. But also check your endstops with <code>M119</code> to make\n  sure they are triggered at the right time. On older Marlin, you may\n  need to set <code>DISABLE_MAX_ENDSTOPS</code> (on a machine that has no max\n  endstops). Newer Marlin uses <code>USE_XMIN_PLUG</code>, etc., to specifically\n  set which endstops are connected. If the switches show the opposite\n  state (off when triggered) then set the\n  <code>[XYZ]_(MIN|MAX)_ENDSTOP_INVERTING</code> flags, as needed.</p>\n</blockquote>\n\n<p>Likewise, from <a href="http://www.instructables.com/id/Building-a-Prusa-i3-3D-Printer/" rel="noreferrer">Building a Prusa I3 3D Printer</a>:</p>\n\n<blockquote>\n  <p>You will probably also find the motor will turn only in one direction. This is normal for now as we don\'t have end-stops installed and haven\'t homed the axis - so the software doesn\'t know how far it can go in one direction or the other.</p>\n</blockquote>\n\n<hr>\n\n<p>As Mark states in his <a href="https://3dprinting.stackexchange.com/questions/4158/prusa-i3-z-axis-only-goes-down-even-on-up-command#comment5758_4162">comment</a>, the P802M uses a Melzi board. From <a href="https://github.com/repetier/Repetier-Firmware/tree/master/boards/Zonestar%20P802M" rel="noreferrer">Github: Repetier-Firmware/boards/Zonestar P802M/</a>:</p>\n\n<blockquote>\n  <p>There are some printers sold under different names like \'Zonestar\n  P802M\', \'Prusa i3 P802M DIY kit\', \'Anet A8-B\', etc, which have LCD\n  20x4 with 5 keys controller connected to Melzi V2.0 board via 10 wires\n  cable. Keys are connected to a single analog input using resistive\n  divider.</p>\n</blockquote>\n'}, {'answer_id': 4171, 'author': 'Avshalom Mizrahi', 'author_id': 7296, 'author_profile': 'https://3dprinting.stackexchange.com/users/7296', 'pm_score': 2, 'selected': False, 'text': "<p>Thank you guys, it took me a while but it was a faulty cable, \nOne stepper motor worked but the other did not. But, apparently, both have to work for even one to turn. </p>\n\n<p>The cable had one wire isolation still in place, so there was no connection from the board to the stepper. </p>\n\n<p>I also had another cable with the wires connected in the wrong order, as well.  </p>\n\n<p>Bottom line - it is working. And printing well. </p>\n\n<p>Now it seems like I have problem with the z-sensor (stopped working after a few hours of printing). But I'll figure it out tomorrow. </p>\n\n<p>Thank you for your help.</p>\n"}]
['https://3dprinting.stackexchange.com/questions/4158', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/7296/']