<p>I have make a little test with 4 dots aligned with A tower, B and C tower. Distance W and S are the same in the stl but not in the print. I have tried diferent values of diagonal root but S always is smaller than W, and all S are equal (more or less 38.20mm) and all W are equal (more or less 40.80). I expect that W and S will be 40mm. How can fix this problem?</p>

<p><a href="https://i.stack.imgur.com/hkUAj.png" rel="noreferrer"><img src="https://i.stack.imgur.com/hkUAj.png" alt="enter image description here"></a></p>

<p><strong>Update:</strong></p>

<p>Here is the stl I use: <a href="https://www.dropbox.com/s/2vwjbo387cmk5qa/DeltaCalibration%20v15.stl?dl=0" rel="noreferrer">https://www.dropbox.com/s/2vwjbo387cmk5qa/DeltaCalibration%20v15.stl?dl=0</a></p>

<p><strong>Update:</strong>
I have replaced the steper motor in tower B but same result.</p>

[{'answer_id': 4638, 'author': 'Fernando Baltazar', 'author_id': 4454, 'author_profile': 'https://3dprinting.stackexchange.com/users/4454', 'pm_score': 2, 'selected': False, 'text': '<p>Well, you have two main issues:</p>\n\n<p><strong>1.-</strong> Your calculation for stepping is a little wrong, for example your firmware indicates 2315.84 when you need 2321.70 (REMEMBER this is an example and is not accurate), So you will see a diference about 2.0mm along your printing. If your printing is bigger more diference you will get.</p>\n\n<p><strong>2.-</strong> Misalignment, your printer is not angled correctly to 90° and also Z axe if has the same condition. with this uncalibrated parameter are you going to have pisa towers on every tall part. \nFor delta Printers this not apply</p>\n\n<p><strong>3.-</strong> Tension. Your belts are a little weak; avoid weak tension band to eliminate something called backslash, of course this is for screw parts but is the same efect and even bigger. Also you will get an accurate dimension of the parts.</p>\n'}, {'answer_id': 4659, 'author': 'darth pixel', 'author_id': 1211, 'author_profile': 'https://3dprinting.stackexchange.com/users/1211', 'pm_score': 3, 'selected': True, 'text': '<p>I bet your towers are not standing straight (vertical) or\nyour bed is not clearly horizontal</p>\n<p>I\'ve recreated your picture with some assumptions (for example that your SW calculates properly and your steppers and motors act well).</p>\n<p>Take a look here:\n<a href="https://i.stack.imgur.com/O4lKx.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/O4lKx.png" alt="enter image description here" /></a></p>\n<p>If you deliver your printer dimensions</p>\n<ul>\n<li>tower height (from the base)</li>\n<li>tower distance from the center</li>\n<li>bed distance (height) from the base</li>\n</ul>\n<p>I can calculate what the inclination angle on all towers is, but, I suppose it\'s not really important.</p>\n<p>The important thing is to set them straight/vertical (perpendicular to the bed).</p>\n<p>We can see from the picture that tower A is the most inclined to the center or\nthe bed highest point is next to tower A (and I bet one of those or both cause the issue).</p>\n<p>As an example, I\'ve made some calculations based on imagined assuptions of the tower height\nhere are details:</p>\n<pre><code>    towerH | inclination\n-----------+----------------\n    300 mm | 0.11°\n    400 mm | 0.08°\n    500 mm | 0.06°\n</code></pre>\n<p>It seems to be quite small but in fact your differences in dimensions are also small!</p>\n<p>The inclination of tower B is bigger as there is bigger difference in dimensions, so maybe the issue is more in bed &quot;horizontality&quot;.</p>\n<p>It would be good if you would check and measure these parameters.</p>\n<p>As for the explanation why bed the inclination causes dimension distortion:</p>\n<p><a href="https://i.stack.imgur.com/4jfG1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4jfG1.png" alt="enter image description here" /></a></p>\n<p>This is exaggerated but it\'s just to show the issue.</p>\n'}]
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