<p>I know that the actual printing time is longer than the time estimated by Cura, due to acceleration and jerk factor.</p>

<p>However, I have printed a small pyramid for which Cura estimates 4.0 minutes, while the measured printing time is 2 minutes and 40 seconds. 
What reasons could produce this difference?</p>

<p>For clarity, I'm using a Delta Wasp 20 40 equipped with a clay extruder for which parameters such as E-step (for E axis) are unpredictable since I have no filament.</p>

[{'answer_id': 4081, 'author': 'Mark Walker', 'author_id': 305, 'author_profile': 'https://3dprinting.stackexchange.com/users/305', 'pm_score': 1, 'selected': False, 'text': "<p>As you note, the estimates are usually optimistic because they're calculated without knowing the printer's actual acceleration as well as communication overhead time losses, etc.  However, many estimation algorithms put in a bit of a fudge factor to approximate a typical printer or to approximate startup time. I think in this case, you're just on the wrong side of the fudge factor.</p>\n"}, {'answer_id': 4240, 'author': 'Brison', 'author_id': 7477, 'author_profile': 'https://3dprinting.stackexchange.com/users/7477', 'pm_score': 0, 'selected': False, 'text': "<p>Estimating time for any CNC based machines are measured in this formula:</p>\n\n<p><em>The length of pulses that machine travels x The feedrate of the pulse itself</em></p>\n\n<p>It gives you the time for whole movements. If you're familiar with NC codes, information of any movement is listed in a single line, having its own <code>feedrate</code>, that's what we call pulses.</p>\n\n<p>As machines are not ideal, some delay occurs between pulses, approximately <em>1 or 2&nbsp;ms</em> according to machine type. That's what is not measured in the formula.</p>\n\n<p>If you were able to measure that <code>delay time</code> and multiply it in <code>number of pulses</code>, by adding it in the <code>estimated time</code> found by machine, you could find a much more definite estimated time, for your process.</p>\n"}, {'answer_id': 4440, 'author': 'Tim Kuipers', 'author_id': 7956, 'author_profile': 'https://3dprinting.stackexchange.com/users/7956', 'pm_score': 2, 'selected': False, 'text': '<p>If you properly define your own machine with a <code>delta_wasp.def.json</code> file you can fill in the acceleration and jerk settings of your printer, so that Cura will use the correct values for print time estimation.</p>\n\n<p>For example, take a look at <a href="https://github.com/Ultimaker/Cura/blob/master/resources/definitions/ultimaker2.def.json" rel="nofollow noreferrer">how the Ultimaker 2 is defined.</a></p>\n\n<p>Exposing these settings to the Custom FDM Printer wizard hasn\'t been implemented (yet).</p>\n'}]
['https://3dprinting.stackexchange.com/questions/4066', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/7089/']