{"action":"created","issue":{"url":"https://api.github.com/repos/MarlinFirmware/Marlin/issues/1209","labels_url":"https://api.github.com/repos/MarlinFirmware/Marlin/issues/1209/labels{/name}","comments_url":"https://api.github.com/repos/MarlinFirmware/Marlin/issues/1209/comments","events_url":"https://api.github.com/repos/MarlinFirmware/Marlin/issues/1209/events","html_url":"https://github.com/MarlinFirmware/Marlin/issues/1209","id":52594209,"number":1209,"title":"Testers NEEDED","user":{"login":"boelle","id":3832239,"avatar_url":"https://avatars.githubusercontent.com/u/3832239?v=3","gravatar_id":"","url":"https://api.github.com/users/boelle","html_url":"https://github.com/boelle","followers_url":"https://api.github.com/users/boelle/followers","following_url":"https://api.github.com/users/boelle/following{/other_user}","gists_url":"https://api.github.com/users/boelle/gists{/gist_id}","starred_url":"https://api.github.com/users/boelle/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/boelle/subscriptions","organizations_url":"https://api.github.com/users/boelle/orgs","repos_url":"https://api.github.com/users/boelle/repos","events_url":"https://api.github.com/users/boelle/events{/privacy}","received_events_url":"https://api.github.com/users/boelle/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":13,"created_at":"2014-12-21T12:41:21Z","updated_at":"2015-01-07T18:32:54Z","closed_at":null,"body":"We are in the process of getting the issues list down to 0, or as close we can.\r\n\r\nFor this we need a lot of people, with as much different machine setups as we can, that are willing to load the latest development and report back any faults, the goal is not to do features but just to test for faults.\r\n\r\nTesters so far:\r\n\r\n@MagoKimbra -  one Prusa I3 with Ramps 1.4 and 4 extruder and autobed level with servo & one Kossel mini with ramps 1.4.\r\n@a4jp-com - Scoovo X9H\r\n@darkjavi - PrusaI3 with megatronics V2 & coreXY printer with ramps1.4\r\n@fmalpartida - H-Bot mechanics (with auto level) and  AT90USB1286 controller\r\n@gregrebholz  - Rumba on RigidBot\r\n@avluis - Phoenix with RAMBo, 1 extruder, heated bed, inductive touch probe\r\n@vandarin - Phoenix with RAMBo, 1 extruder, heated bed, switch touch probe\r\n@Grogyan - RAMPS 1.2 derivative with on board MAX6675 & test bed electronics is RAMPS 1.4 with a RepRap discount full graphic display, Max6675 \r\n@thawkins - Scratch built machine with autoleveling inductive probe, ramps, 330x200 bed, based on zentoolworks cnc chassis, dual jhead hotend, qubd thermistors. Ballscrews. Reprap discount Full graphic display. Heatbed. & Scratch built machine with autoleveling servo and microswitch, ramps, 210x210 bed, jonbot, printed chassis. Single ubis hotend, qubd thermistors. Gt2 belts. Reprap discount 20x4 display. Heatbed.\r\n@arno-millenaar - Rumba with external DM422C drivers (will add the extra delay in the stepper code)\r\nLCD + SD (RepRapDiscount Smart Controller)\r\nBed Auto-Leveling\r\nBulldog XL Extruders with E3D v6 hotends (not sure this is relevant :) ) setup for > 300C\r\nBed 500W with temperature reach of 185C (or more not tested)\r\nThermistor for Bed and Thermocouples (AD597) for the hotends\r\n@Lukelectro - I have a Mendel90 (Melzi electronics), gt2 belts and modified (low power, run a 24V hotbed on 12V) hotbed, otherwise standard)\r\n@pacaj2am - Rebelix with Ramps 1.4 and Heated Bet.\r\n@JoshyuNL - MendelMax 1.5 custom, Rambo 1.3, Heated bed + dual extruder, Filament Diameter Sensor\r\n@alhirzel - modified MTU MOST delta printer on Sanguinololu 1.3a\r\n\r\nTest object: http://www.thingiverse.com/thing:525888"},"comment":{"url":"https://api.github.com/repos/MarlinFirmware/Marlin/issues/comments/69067836","html_url":"https://github.com/MarlinFirmware/Marlin/issues/1209#issuecomment-69067836","issue_url":"https://api.github.com/repos/MarlinFirmware/Marlin/issues/1209","id":69067836,"user":{"login":"galexander1","id":3728591,"avatar_url":"https://avatars.githubusercontent.com/u/3728591?v=3","gravatar_id":"","url":"https://api.github.com/users/galexander1","html_url":"https://github.com/galexander1","followers_url":"https://api.github.com/users/galexander1/followers","following_url":"https://api.github.com/users/galexander1/following{/other_user}","gists_url":"https://api.github.com/users/galexander1/gists{/gist_id}","starred_url":"https://api.github.com/users/galexander1/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/galexander1/subscriptions","organizations_url":"https://api.github.com/users/galexander1/orgs","repos_url":"https://api.github.com/users/galexander1/repos","events_url":"https://api.github.com/users/galexander1/events{/privacy}","received_events_url":"https://api.github.com/users/galexander1/received_events","type":"User","site_admin":false},"created_at":"2015-01-07T18:32:54Z","updated_at":"2015-01-07T18:32:54Z","body":"If I read correctly, G28 X0 Y0 will not change the robot's sense of its Z\naxis position at all.  So if you power on and G28 X0 Y0 is the first and\nonly command you enter, then the robot's sense of its Z position will be\neffectively undefined (probably 0?).\n\nIt took me a little while to understand, but the reason you're using G28\nX0 Y0 is that the subsequent G29 is expected to initialize the Z axis so\nthe G28 doesn't have to?  And the G29 doesn't do a good job if the Z axis\nposition is completely unknown when it begins.\n\nI am not 100% certain, but I think that's because G29 starts with an\nassumed location of the bed, and if it doesn't trigger the contact sensor\nthen it stops at that assumed location to prevent driving the head into\nthe bed for very long in case your probe breaks.  So if it already thinks\nit is at the Z=0 position, it won't go below that position and the\nprobing won't complete correctly.  That's why you would generally tell it\nthat Z_MAX_POS is a few mm bigger than your actual printer (wouldn't\nyou?).\n\nThat seems like a pretty good reason but I don't know if it's really the\nbest.  Is it better to have an unreliable heuristic to prevent damage\nwhen the probe fails and G29 is issued?  Or is it better to support the\nsmall time savings of G28 X0 Y0\\nG29\\n as a startup sequence?  I suppose\nreally that depends on if a popular slicer is shipping with G28 X0 Y0 as\nits default prologue?\n\nAnyways, I don't use G29 so I don't have a preference.  I just figured\nI'd speak up just to answer why it works the way it does.."}}