Hotend Fan Mount 50mm for Printrbot
by sfcgeorge, published
The benefits of using this are twofold. Firstly, each layer of a print cools faster, enabling higher quality at faster speeds and on smaller objects. Secondly, it helps cool down the hotend so that it is less likely to warp the extruder body.
I made the mount quite thick at 6mm to raise the hotend up a little and give more z space. On my Printrbot up to 10mm of extra z space could be gained by raising the hotend.
Note, this style fan mount should only be used with insulated hotends, otherwise the hotend will cool down too much and perform poorly.
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I have had some de-lamination issues with too much cooling, but you should be able to fix this and popping off the print bed with settings.
I have my printbed at 72 for the first layer, 71 after that, printing onto kapton tape on a glass surface. The fan probably cools the bed surface a few degrees from what the thermister is reporting, so try raising the temp a few degrees. I've heard people raise their beds to over 100 but I think t
hat's a bit crazy. Also if you are using plain glass don't go above 80 or it might shatter.
Raise the hotend temperature a bit too as again the fan might cool the tip a little so the thermister reading is higher than it should be. And you don't want the plastic to set as soon as it leaves the nozzl
e. I was printing ABS at 115 without fan, now 225, 230 for first layer to get it to really stick. Different plastics have varying melting points, but the RepRap wiki says ABS melts at 215-250. I'd say it's better to be a bit too hot than too cold and risk de-lamination or a blocked hotend.
e minimum fan speed if you can. If you set it too low the fan wont start at all, so you need to find your fan's limits (mine is 30%). For this use Pronterface. Send the command "M106 S100" where the number after 'S100' can be any value 0-255. Then issue "M107" to stop the fan. Repeat until you find
the lowest value where the fan starts reliably. You then need to convert this to a percentage for Slic3r. E.g. if your value is 76, the math to convert to percentage would be (76/255)*100 = 30%.
You can also lower the maximum fan speed if you still have problems, say 80%. Then the fan will only spi
n in the min and max range.
Make sure fan is disabled for the first layer.
I have enable fan if layer print time is below 50, and slow down if layer print time is below 10.
Originally I thought ducting was a great idea, but the airflow seems pretty even so I think a duct would just add weight.
I've put a 40mm fan on the same type of mount on my printrbot, what cooling settings are you using in Slic3r? I've noticed that it actually cools the print too fast that it snaps off the bed and curls up at the stock slic3r settings. maybe only having the heated bed at 70 is causing issues, also I think a more directed airflow would help.
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Use longer M3 bolts to mount this between the extruder and x-carriage. Use another two M3 bolts and nuts to attach the fan, cable ties may also work.
The SCAD file is provided, though a little messy. In the current configuration it fits a 50mm diameter fan where the holes are spaced 40mm apart.
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