Layer fan and a dummy object makes printing difficult models.

I opened an account on 3D Hubs as 3D Printing service provider. The first order I had to print the Marvin. It looked a simple model but I had to print over sixteen samples before I managed to print an acceptable Marvin.

Filament: PLA 1.75 mm
Layer height: 50 microns (0.05 mm)
Printing speed: 60 mm/s
(I set the printing speed to 20 mm/s on bottom and top part.)

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The hook on top of Marvin gave me a lot of frustration because extremely slow printing or fast, 10 seconds of layer cooling time by Cool lift failed to produce decent shape. Cool lift left messy strings around the hook.

I thought ‘Is that all?’ and went out for Internet searching to find out how other users handle the Marvin. I forgot which site that a simple technique using a dummy object, which provide enough cooling time of tight layer such as the hook. So I added a cube object beside the Marvin on build platform in Cura.

The cooling time of target object’s layer is determined by travel speed and distance from the object, and shape of dummy object. Suppose travel speed is set 250 mm/s, five seconds of cooling time is derived by following formula.

Speed = distance / time
time = distance / speed
5 = distance / speed
distance = 5 * speed
distance = 5 s * 250 mm/s
= 1,250 mm

The nozzle makes a round trip so half of 1,250 mm is the distance between two objects, which is 625 mm. And we add average printing time of one layer of the dummy object to get the desirable cooling time of the target object.

By three to four test printing like below, I found dummy object’s size and separating distance from Marvin.
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Near finish of a successful Marvin printing.
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Air flow near the nozzle affects printing quality too. The ideal setup is to direct air tip of the nozzle in circular pattern.  The oval fan duct I installed today afternoon produced better quality of Marvin with 0.1 mm layer height, compared to the above one.

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About janpenguin

Email: k2.mountain [at] gmail [dot] com Every content on the blog is made by Free and Open Source Software in GNU/Linux.
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