3

I made a model for my 3D clock. Model has few vertical holes so I made one layer thick bridge for every hole. In Fusion 360 everything looks fine, but CURA (version 3.6.0) doesn't want to print those Bridges. Why?

The Full Wall is 1.68mm thick(in Fusion), infill is 20%, wall line count is 1, layer height is 0.28mm, the support-bridges are designed to be this thick too.

I'm not sure will be material stable above holes without Bridges.

Bridges in Fusion 360

Model in CURA 3.6.0

Hole at close

Trish
  • 20,169
  • 10
  • 43
  • 92
Pararera
  • 157
  • 1
  • 5
  • what's the line width and the width of the wall that should be printed there? – Trish Feb 02 '19 at 17:28
  • In Fusion walls are 1.68mm. Those Bridges are 0.28mm thick(same as layer height). – Pararera Feb 02 '19 at 17:32
  • layer height is Z thickness, you need to check Line Width, which is XY thickness. – Trish Feb 02 '19 at 17:33
  • While this isn't quite relevant to the question as asked, it looks like you are attempting to design supports for the top of the hole in your CAD program, which you will then remove after printing. I would not recommend this approach, but instead use your slicer (CURA) to generate the needed supports. These will be placed where they are needed, and should be easier to remove from the model. Alternatively, you can design so that you don't need supports (or as much). In the case of horizontal holes like these, you might make a "teardrop" shape that limits to overhang angle. – mbmcavoy Feb 04 '19 at 19:35
  • @mbmcavoy This "custom made support" is one layer thick(0.4mm), can't be thicker than this. Hole is tear drop shape because slicer cuts end of the hole. Why I did those supports? They use less time and material to print. Also, wall is less than 2mm thick. – Pararera Feb 04 '19 at 19:41
  • It seems what you are intending is one wall thick. What is the reason it cannot be thicker? Is that why you are not using supports generated by Cura? – mbmcavoy Feb 04 '19 at 19:44
  • Regarding the tear drop holes, I don't mean the appearance of your circular hole in Cura with the loss of precision. I mean to intentionally design a tear drop shape in CAD. Make a circle and add tangent lanes up to a point on top. The lines should have an angle of about 45 degrees (depending on your printer's overhang performance.) You should be able to print such a hole with no support needed. – mbmcavoy Feb 04 '19 at 19:48
  • @mbmcavoy Nozzle size? Stock 0.4mm nozzle that comes with printer. Whole model is printable without supports. Reason why I added those "support walls" is because I want to be sure that material above hole doesn't collaps. Not big deal to remove, print etc… Btw layer height is 0.28mm – Pararera Feb 04 '19 at 19:50
  • I guess I'm confused - you can always make a feature larger than your nozzle, just not smaller. You say you can print the model without supports, but this feature is specifically a support - that's what they do; make sure overhanging features don't collapse. – mbmcavoy Feb 04 '19 at 20:15

1 Answers1

5

Nomenclature help

  • A Layer is everything that is printed between the print head moving upwards.
    • Layer height is how tall each line is. It is in Quality.
  • A Wall is made up from lines put down next to each other.
    • line width is how thick a 1-perimeter-strong wall is in the XY-plane. It should never be smaller than the Nozzle Diameter. It is in Quality.
  • Nozzle Diameter is what is the physical diameter of your nozzle. It is located in the printer configuration.
  • A Bridge is printing horizontal layers that connect to walls at the sides but otherwise not connected to the printbed or print.

A simple bridge

Ultimaker Cura does ignore too thin walls

Your walls are 0.28 mm thick and your nozzle is most likely 0.4 mm thick. That can't be printed at all, in fact, you are way too thin to be printed: a printer should never print any object that is thinner than its nozzle as that is a perfect way to generate clogs.

Atop that, slicers ignore also what is thinner or exactly as thin as the line width. If the line width is 0.4 mm, and the wall is 0.4 mm, it gets ignored. If the wall is 0.45 mm, it is not. This can be remedied by setting the option print thin walls, but you still need to have one line nozzle-diameter as minimum line width - actually it is common to go about 10% larger for better extrusion.

Solution

Strengthen the walls to one line width (usually 0.4 mm) in your CAD-design and activate print thin walls under Shell.

A design with too thin walls

Trish
  • 20,169
  • 10
  • 43
  • 92