Post Processing 3D Prints: Removing Build Lines

As anyone who has a 3D printer can attest, there are visible build lines on printed objects. This is, of course, simply the nature of a machine that builds things layer by layer. A search of the web reveals a few options for removing build lines. With ABS, acetone can be used to “melt” a print smooth. However acetone if not handled properly can be disastrous. For PLA, chemical solutions are even more dangerous than acetone and probably should not be considered.

Methods that cause dissolving of a piece equates to loss of detail.  Sanding is an option but also causes loss of detail. Filler primer combined with sanding, Spot putty and even Bondo have been used. These all require proper ventilation and protective gear.

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I have another technique you may want to try. It harkens back to my traditional painting  days. Since I now paint in Photoshop my painting tools have languished unused for some time.

I grabbed a palette knife and a jar of acrylic modeling paste and set about applying it to a part printed at .3mm layer height. I applied it much like one applies joint compound to drywall. You can also use a damp paper towel when applying it to uneven surfaces. I’ve used it on resolutions of .1mm to .3mm with excellent results.

I lay on a thin coat filling in the tiny spaces between the build lines and let it dry then sand it smooth. It adheres well to PLA (I have not yet tried it with ABS ) and is a great base for painting with acrylic media. You can colorize the modeling paste before using it by adding acrylic paint . Probably the best part is its non toxic, relatively inexpensive and cleans up with water.

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Two identical parts printed in PLA at .3mm.

In the image above the top and bottom objects were both printed at .3mm (300 microns) the bottom one has been left just as it came from the printer; the top one had modeling paste applied and then hand sanded with 220 grit sandpaper. It is extremely smooth to the touch and with the naked eye its almost impossible to notice any flaws.

Although I have not tested them yet, additional acrylic paint mediums may also prove useful. There are several Gel Mediums that should prove just as viable. They all can be colored to a desired color by adding acrylic paint before use or painted after.

ZBrush Rope Making Technique

This is one technique for making braided rope in ZBrush. I posted this on Vimeo a couple years back but thought I would post it here as well. I’ve also included a step by step description.

Tutorial: Braided Rope or Cable using the CurveLineTube brush and a Cylinder Primitive.

Draw out a Cylinder3D and make the following adjustments
In Tool>Initialize subpallet:
Set X and Y size to 5; Set HDivide to 36 and VDivide to 128.

In Tool>Masking:
Click the MaskAll button; Set Select Count to 2 and Skip Count to 1; Click the Column button.

In Tool>Deformation:
Inflate to 8 on X and Y axis only.

In Tool>Masking:
Clear the mask.

Make this object a PolyMesh3D.

Now in Tool>Geometry:
Divide one time.

In Tool>Masking:
Click the Mask By Cavity button; Click the GrowMask button one time.

In Tool>Deformation:
Inflate to 8 on X and Y axis only; Inflate Ballon to 1 on X and Y axis only.

In Tool>Masking:
Clear the mask.

In Tool>Deformation:
Twist to 100 on the Z axis only and repeat up to 10 times. Rename the tool to something like: Twist_Base.

Now in Tool>Geometry: Delete Lower Subdivisions.

Select the CurveLineTube brush.

In Brush>Modifiers:
Click on MeshInsert Preview and select the Twist_Base tool. Now the CurveLineTube brush is set to draw out a curve using the Twist_Base tool.

Now draw out a new primitive Cylinder3D and make the following adjustments in Tool>Initialize subpallet: Set X and Y Size to 5; Set HDivide to the number of strands you want the braided rope to be (i.e. 3 or 4).

Make this a PolyMesh3D and snap it in position by holding Shift while rotating the tool.

In the Transform pallet:
Click the Activate Symmetry button and select the Z axis; Turn on Radial Symmetry; Set Radial Count set to match the number of sides on the PolyMesh (i.e. 3 or 4).

Set a fairly large brush size and draw out a curve along the length of the PolyMesh. Adjust the brush size and click on one of the curve end points until the instances of the curve tube touch one another without overlapping or leaving a gap.

In Tool>Deformation:
Twist to 100 on the Z axis only and repeat up to10 times. Rename the tool to something like RopeBraid_Base.

In Tool>Subtool:
Click the Group Split button to separate the braided rope from the PolyMesh used to support the Curve Tubes. You can delete the support mesh leaving the braided rope.