Thinking Outside the Box

This article encourages you to spice up the average downloaded part further by focusing on the concept of hollow parts. This isn't exactly a feature of Creatr 2.1 software, so it requires a bit of a hack - at least in the way the printer and print settings are set up. We'll explain how to in just a bit.

Pyramids not Cubes - Infill and Gravity

It first must be said that you can't just make any part hollow. Having infill in a part serves a purpose other than just making a part stronger; it creates a printed build platform for the top solid layers (a.k.a. "upskins") to print upon without gravity effecting the shape of the part. In other words, just as you would use generated support material to support overhangs on the outside of your part, infill provides support material for the top layers that overhang inside the part.

To further explain, imagine the top side of a cube. If you were to print a cube with no infill, the bottom side and the 4 sides of the cube should print just fine. However, when your printer gets around to printing the top side of the cube without any infill, it would be extruding filament on no printable surface (air). Gravity would do it's thing, and the extruded lines making up the top side of the cube would fall, most likely leaving a stringy mess on the top side of an otherwise good part.

However, a hollow pyramid might print just fine as the printer can print parts with some overhang without the need for support (or infill, in this case). Spheres may work too. Therefore, any part that has top layers that do not have greater than a 45º angle over the middle of the part is a good candidate for this hollow print hack. 


                        Hollow pyramid gcode.

Yeah... But Why Do It?

Other than saying, "Just because I can..." There may be some practice uses for hollow prints. Maybe you want a part that is more buoyant than a 15% infill part. Maybe you're just looking to save money on filament (no infill certainly would cut back on filament usage - assuming your model fits the criteria mentioned above). Since this article is all about thinking outside the box, you maybe can think of some better uses that we can. The point is, it is possible given the right circumstances. AND if your model doesn't fit the criteria, here is an article on how you can take the same concepts mentioned in this article and apply it to printing infill with PVA so that parts with top solid layers with great than 45º overhangs can still be printed:

How to Print PVA on the Creatr HS Using Materialise (Creatr Software)

 The only catch to using PVA infill is that your part would need a hole in the model so that water could get inside the part to break down and dissolve the PVA.

How to Print Hollow Parts

If you're like many of our customers and have skipped over all the previous sections of blah blah blah, we really recommend that you look again at the criteria of what models this will work with and which models it won't. 

Printer Setup

For this hack, it's really important that you only have 1 roll of filament loaded, leaving 1 extruder empty. This extruder will be printing the "infill" (so printing nothing even though the print head will be going through the motions of printing an infill). FOR THIS EXPLANATION, we are going to not load any filament in our LEFT extruder and use it to print the imaginary infill.

If you were wanting to use PVA as the infill (as mentioned above), you would load it into this extruder.

Creatr 2.1 Setup

First load everything as usual: select your printer model, import and transform (if necessary) your .STL model, and then go to the Print tab.

Setting the right nozzle to Contour print mode automatically sets the left nozzle to Infill print mode. Since we will not have any actual filament loaded in the left, the print head will only "dry print" (go through the motions of printing infill).

So this can make a hollow print build just as slow as a print that has an infill. How might you speed it up a bit?

Click the Edit Profile button on that tab:

Find the Build Strategy profile that you plan on using and click the plus button next to it to make a copy:

Rename it to indicate that it is for HOLLOW parts (this step is merely to keep you from accidentally using it on another print):

Then, with this copied (and renamed) profile selected, change the INFILL Density to around 1 or 2%* (causes less number of movements of the print head when printing this imaginary infill). Also change the INFILL Print speed factor to about 150%.**

*Note: Creatr 2.1 will not allow you to set an infill less than 1%. But there is a workaround (please see the link below)

**Note: 150% is 150% of your print speed that you set in you Material Profile. You never want any of your speeds to equal a speed greater than 300mm/s. Therefore, if your print speed in the Material profile is faster than 200mm/s, you should not use 150% in the INFILL print speed factor (200mm/s X 1.5 = 300mm/s).

Since you're basically only printing contours, upskins, and downskins, you may want to increase the number each of these by 1 or 2 values (though it's not necessary; the hollow pyramid printed above had 3 contours, 4 upskins, and 3 downskins).

When you're done, click the Save button; this will close out your Edit profiles window.

Finally, make sure that you select the Hollow version of the Build Strategy:

It's just a matter of generating the .GCODE and running the print! We hope that it goes well for you.

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