Posts Tagged ‘hoeken’

12 Ways to Fight Warping and Curling

This article was written about printing with the MakerBot Thing-O-Matic and MakerBot Cupcake CNC. Click one of the following links for a similar article on the Fifth Generation MakerBot Replicator, MakerBot Replicator Z18, MakerBot Replicator Mini, MakerBot Replicator 2 or MakerBot Replicator 2X.



As printed plastic parts cool the different areas of the object can cool at different rates. 1  Depending upon the parts being printed, this effect can lead to warping and curling.  Although PLA has a much lower shrinkage factor than ABS, both can warp and curl, potentially ruining a print.  There are some very common ways to deal with this potential problem, the most notable being a heated build platform.  However, sometimes that might not be enough.

1. Use a heated build platform.  A heated build platform helps keep the lowest levels of a print warm as the higher layers are printed.  This allows the overall print to cool more evenly.  A heated build platform, sometimes abbreviated as HBP, helps tremendously with just about any ABS print and large PLA prints.

2. Print with a raft.  Rafts are a printing option in ReplicatorG and Skeinforge.  They’re basically a large flat lattice work of printed material underneath the lower-most layer of your printed object.  They’ll also help reduce warping and curling by allowing your printed object to adhere better to your flat build surface.  Other variations on this are to print with a larger raft and/or a thicker raft comprised of more layers.

3. Calibrate your starting Z height.  A good first layer makes all the difference.  If your starting Z axis height is too high, the extruded filament won’t be able to make a good bond with the platform.  If you think your Z axis starting height is too high, try lowering it by 0.05mm increments until you find a good first layer.

4. Get the right build surface.  Some people have experimented with different surfaces such as steel, titanium, glass, different kinds of plastic, different kinds of tape, and foam board.  However, I find both ABS and PLA seem to stick really well to hot or warm Kapton tape.

5. Clean your build surface.  ABS and PLA stick better to a clean build surface.  Keep it clean of dust, pieces of old prints, and any other debris.

6. Print slower.  Printing slower allows finer detail, better adhesion to the build surface and lower layers, and gives the printed part more time to cool evenly.

7. Print cooler.  Printing at a lower temperature isn’t always an option.  Ideally, you should be printing at the lowest temperature required for extrusion and that allows good interlayer adhesion.  However, trying lower temperatures isn’t for the faint of heart.  Printing at a too low a temperature could cause harm to your extruder motor or extruder.

8. Eliminate drafts or enclose your robot.  Forrest Higgs found that having his 3D printer too close to an open window caused very uneven heating across his build surface.  This in turn caused the side of his prints closest to the window to curl.  Since keeping the window closed wasn’t an option for him, he compensated for the window drafts by adding a heat lamp.  Cupcake and Thing-O-Matic owners might have an easier time of eliminating drafts by simply enclosing two or three of the sides of their robots.  It will also have a fortunate side effect of helping to control fumes.

9. Design with mouse ears.  Zach Smith’s solution was to add little discs to corners of an object to help those corners stick to the platform.  These essentially serve as “mini-rafts” to give those corners more surface area and better adhesion without having to print an entire raft.

10. Design with aprons to hold down corners.  Forrest Higgs suggested adding “aprons” around an object to be printed, while that object was being printed on a raft.  These low thick pieces of plastic help keep the raft flat and help prevent any curling or warping from affecting the desired printed object itself.

11. Design with surrounding thermal walls.  While Forrest Higgs’ apron approach provides a mechanical advantage of essentially holding down corners with a chunk of plastic, Nophead has added thin surrounding walls to his designs to act as baffles to keep warm air around the printed object as it moves around.  He’s postulated that a very thin surrounding wall could have the same beneficial effect as printing inside an enclosed build chamber.  Interestingly, it seems that Nophead suggests that designing objects with more rounded corners might also help avoid curling and warping at those corners.

12. Reduce infill.  When printing a model you can chose to print it hollow, completely solid, or some percentage between zero and 100.  However, as Nophead points out even the plastic inside a model exerts a force on the entire printed object as it cools.  It stands to reason that the more plastic you have, the more those pieces of plastic will pull against themselves and the build surface as they cool.  By reducing infill there will a reduced amount of internal tension as the object cools.  Reducing these internal forces by printing with a lower infill ratio can help reduce curling and warping as well.

13. EDIT:  Sand the Kapton.  Charles Pax has suggested that sanding a Kapton tape build surface will increase the surface area, making it easier for the molten plastic to stick.

14. EDIT:  ABS surface.  Some have suggested essentially painting the build surface with liquid ABS.2  This is has the same effect of laying down a big flat raft.

If you’ve got some suggestions, tips, or tricks that you use to fight warping and curling, please leave a comment below!

  1. Photo courtesy of backpackphotography []
  2. ABS dissolved in acetone or ABS glue []
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Thingiverse All-Star: Most Things Uploaded!

Who has been rocking Thingiverse and doing cool and amazing stuff?  The Thingiverse All-Stars!

Most Things Uploaded - Zach "Hoeken" Smith

Most Things Uploaded - Zach "Hoeken" Smith

Thingiverse and MakerBot co-founder Zach “Hoeken” Smith has the most uploads to Thingiverse with 80 separate Things.  (MaskedRetriever was a very very close second with 79 Things).  Another great thing about Thingiverse is that you don’t actually have to have any tools other than a computer to contribute.  There’s no reason why you couldn’t snag this top spot tomorrow.  Just start looking at the world around you, think of all things you could replicate, improve, or invent, create the design file, and share it on Thingiverse to help everyone else too!

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Incomplete polygons – a dramatization

Posted by on Monday, December 13, 2010 in Uncategorized
I'm not a polygon, but I play one TV

I'm not a polygon, but I play one TV

One commenter posted that it took him a little while to really get the “incomplete polygon” or “open hole” method1 thought up by Zach to avoid oozing and threads around interior holes in objects.  Above you can see my dramatization of how this works. 2  With a normal closed polygon hole, Skeinforge lays down a regular path all around the edge of the interior hole.  However, the plastic extrusion is much thicker than the ideal mathematical path plotted out by Skeinforge.  As a result, it can cause little blobbies to appear inside the hole.

With the method depicted at the bottom of the diagram shows how creating an incomplete polygon/open hole method means that the only real bit of blobbies that occurs with an extrusion is where the two sides of the incomplete polygon meet.  And, if that gap is small enough, say 0.1mm or less, then although the Skeinforge path is drawn with them very close together – they end up fusing together.  The end result is a complete polygon or whole hole3 with little to no blobbies inside.

Zach Clarification: The main reason this technique works well is because of the outline continuity. Current DIY extruders are not very good at precisely starting and stopping exactly when we want them to. When you have an outline + 4 holes, the extruder must start and stop 5 different times. The effect is that your holes do not come out very nicely. When you use this technique, you have one continuous outline and your holes have much better definition. Furthermore, since the gap is so small, the tiny gap ends up getting bonded anyway and you end up with nicely defined, gapless holes.

  1. I thought up the names.  Like it? []
  2. I just want you to know that the above picture was rendered with perfect mathematical fidelity.  If it looks a bit off to you, well, that’s because of the limitations of your tiny monitor. []
  3. I’ve been waiting since Friday morning to make that joke. []
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Design Tip: Incomplete Polygons!

Posted by on Monday, December 13, 2010 in Uncategorized
Incomplete polygons

Incomplete polygons

3D printers can have a difficult time printing small holes.  This is never a catastrophic problem and really only requires a little bit of time reaming the hole out with a drill bit, bolt, etc.  One potential problem with printing small holes is that the print head could move across the hole causing a string to inadvertently be deposited.  One way to compensate for this is to make sure those holes are less complex – opting for a hexagonal or octagonal hole instead of  a circle.  With a circle the ‘bot has to make a large number of calculations relating to the various points along the edge of that circle.  One other issue is that even when the hole is a low-count polygon (such as the aforementioned hexagon or octagon) the extruder can leave extra plastic in and around that hole as it travels to and from the various points around the hole.

Zach thought up a new way to compensate for this issue.  In the above picture he’s printed a motor bracket where the holes at the base of the thing aren’t actually holes.  They are holes where there is a 0.1mm slice out of the edge.  The two ends of the “hole” are not touching, which causes Skeinforge to draw the two sides of the hole independently.  However, they are close enough together that the thickness of the molten plastic laid down at that layer touches – and they fuse together.

The result is that you end up with not-holes that really are holes – without the problems of filled in holes and the not-holes are just as strong as if they were designed as holes in the first place!

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