Printing small items out of ABS or HIPS on a PULSE

  • If you are running the Bed at 100C or therabout as necessary for ABS or HIPS and you print small items make sure that the fan speed does not exceed 25% or you will force a thermal runaway bed at layers below 20mm (eg printing a chess piece) Reason is bed cannot go above about 80C with the Fan running full blast.

    Same holds true when printing some Nylons for example and Nozzle temp is >265 on layers below 15mm in distance to the bed the airflow will cool the nozzle to about 260 and cause another thermal runaway error (or clog before that depending on material).

    When printing higher temp material and printing at lets say .2mm layer height it pays to turn off the fan for the first 30-40 layers alltogether and if neccesary when slowing down does not provide enough cooling put another item accross the build plate far away or a 3rd or 4th to increase layer time.

    This holds true on the C frame for sure - IDK if there are other fan solutions available but would like to know. What it would need is a feature something like keep fan off for first 20 layers from layer 20-30 dont exceed 25% from layer 30-40 dont excee 30% etc

  • MatterHackers

    The Bed thermal runaways (TR) is likely due to the positioning of the printed part on the build plate. If the small part is centered on the bed and the fan is turned up, this will cause the fan to cool the section of the build plate where on the opposite side of the plate is the thermistor. So you are essentially sinking out the heat in one section of the build plate so the system forces the TR error.

    Keeping your settings all the same and moving the printed part forward 2-3 inches will more than likely eliminate the false positive on TR.

  • Tried that - within 75 mm of center. If you tell me where I send you some STL's set to turn fan on if print time < 30 sec. Slice with a slicer of your choice tried to upload them here but it tells me I don't have the priviledges. they are 15 tooth htd pulleys. Or print 3 16mm tall 18mm diameter cylinders with a 13mm hex hole in the middle at least 2 in away from the edge of the plate as the edge does not carry the temp and set the fan to 100 % heck even 50 % does the trick. And just to make sure it isn't something melted on the hotend mount I reprinted that. when I installed the new E3D V6. Alternatively create a circular plate 196mm in diameter 4.8mm thick with a 29mm hole in the center 4 6mm holes on a 50.4 mm circle and 6 8mm holes on a 112mm circle and print it with a .8mm nozzle and .4mm layer height - sold (6 bottom, 6 top layers and turn the fan to 50 % and a nozzle tempt of 275 and roll the dice who is going to have a thermal runaway first the nozzle of the bed. So either there is something wrong with my printer or it just cant do it. The solution to this one is to turn the fan off and slow the print speed quite down. Heck this one even fails with PLA and the bed at 85 to get a heat resistent annealed dimensional correct pla sheet. It becomes particularly challenging with low bridges that need a fan on pretty much any material like this
    0_1560802686932_ToughBoxMiniHolder.jpg bolded text
    or this
    Both will cause a Thermal runaway on the bridging when printed in HIPS (270 nozzle 100 bed) The 2nd item luckily can be printed on a 45 deg so there are less bridges (its 267mm lon and prints diagonally) the first one is 215x167 thereabouts and the first bridge section is 13mm off the plate. Only choice on that is set bridging fan to 10% and design it so its about 1mm lower than need be so you can file a lot of hanging stuff out to get it dimensionally correct. (first part also is about 180mm tall). So anyone know a change to the design that would allow better bridging and cooling - I am all ears. Until then this is just for anyones info. If you got a pulse and need to bridge at high temps close to the building plate or print small items - do it without a fan or with the fan at < 20% depending on distance from build plate. BTW both items are used in multiple configs on the "bumblebot" I posted here

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