Part of testing every printer is printing an object at full height to test the Z. For one of our recent XLT printers in testing, we printed a rocket. If you look closely, you can see the top of the rocket is colored differently than the rest of the rocket. Why is the color different? What could you do to make the rocket all the same color on the next print?
You need to change the the temperature of the nozzle.
The rocket is PLA and was printed with a nozzle temperature of 210C. What temperature should it be changed to? Why change the temperature?
Here's my first guess. I would slow the print head down during the last portion of the print. Because the diameter of the object is getting smaller, and the temperature of the nozzle is constant (assumed), the material does not have time to cool sufficiently before the next layer is extruded. Therefore the nose portion of the print is getting too hot and causing it to change color. To fix it, I would change the Speed Override settings in S3D to allow the print head to slow down, and also decrease the temperature in the Per Layer Temperature Settings of S3D by 5C-10C during that portion of the print. Finally, I would print just the nose section alone first to make sure the settings give you the desired results.
Cheers to all!
Darrel
Pretty much what Darrel said - enable speed over rides. It's not exactly a structural part so overkilling it shouldn't hurt too much; have it reduce speed below 30 sec layers or something along those lines. Could also reduce temp for the last layers, increase fan if it isn't already 100% or introduce a secondary fan on the printer.
I think the color of the filament was transparent. the layer thickness at the top of the rocket may have been somehow decreased vs the rest of the rocket. the less numbers of layers, the more transparent the model is.
that is my guess!
The rocket printed at default Simplify settings. It had the same layer height (0.3175mm) throughout, same temperature (210C), and slowed down to a max of 25% for layers less than 7s.
In the picture below, the middle cone is the original settings top of the rocket. The left cone is the same, but no slowing down based on layer time. The right cone has the slowing down to a max of 5% speed for layers less than 30s.
How do you make the rocket all the same color?
For this material, I think that the color or degree of transparency is related to the temperature of the base layer related to the temperature of the subsequent layer deposited. Where the extrusion path length for a particular layer is long, then new extrusions are deposited on (practically) fully-cooled substrates. However when the path length is short for a given layer, there is not enough elapsed time for a given layer to cool to the steady-state temperature before the extruder begins depositing a new molten layer of plastic on top of it. As the circle-layers approaching the rocket tip get smaller, the path-length and the time per layer is shorter and thus layers are deposited upon layers without preceeding layers having the chance to cool to steady state.
To account for these, we can increase cooling or use strategies to keep time-per-layer at least as long as necessary for the preceeding layer to cool to steady state before depositing subsequent layers. The strategy of
if(layer time < 30s), then {MaxSpeed <= 5%;} was used on the right-side cone.
Using pigmented filament or post-processing such as sanding and painting are other strategies to enhance color consistency.
Are these ideas correct?
You are correct that the smaller layers have heat build up and can't cool down and the way to fix it is to slow down the layers, but that doesn't change the color much. That affects the warping of the very tip of the rocket. If you look at the very tip of the small cones in the second picture, you can see that the faster the tip the more warped it is.
There is another setting that affects the temperature which affects the color/translucence. Can you guess what it is and how to make the rocket the same throughout?