This article is part of our Learn.colorFabb section
HOW TO PRINT WITH LW-PLA
At colorFabb material development never stops. We’re starting the 2019 with a fascinating new material, first of its kind in FFF 3D printing materials.
We’re proud to announce, colorFabb LW-PLA. This filament uses an active foaming technology which is triggered by temperature. At it’s peak the filament will expand nearly 3x it’s volume, meaning users can decrease flow by 65% to obtain lightweight parts, or use the expanding properties to speed up print time by using big layer heights or single extra thick perimeters.
colorFabb LW-PLA is available in two colors, natural and black. The foaming also gives printed parts a rough matte surface finish, which makes parts look very appealing.
HOW DOES IT WORK?
For the filament to expand it is necessary to put a certain amount of energy into the filament. The amount of energy a filament can absorb during printing depends on the length of the hot-zone and the time it takes for the filament to pass through the hot-zone. The longer a filament will reside inside the hot-end, the more energy it can absorb which will increase the amount of expansion.
Assuming nozzle size and layerheight are fixed, our main input variables are Temperature, speed and flow to determine the amount of expansion.
HOW TO DETERMINE THE EXPANSION OF THE FILAMENT
If you want to print lightweight parts which are dimensonally accurate, it’s important to first determine the possible expansion of the material. This can be done by printing single perimeter test cubes without top and bottom layers. We use the following 4 step process to determine the maximum expansion at a certain speed, temperature and flow.
PRINT CUBES AT A SET SPEED IN TEMPERATURES VARYING FROM 200°C UP TO 280°C
MEASURE PERIMETER THICKNESS OF EACH CUBE, NOTE TEMPERATURE WITH HIGHEST EXPANSION.
PRINT CUBES WITH DECREASING STEPS OF FLOW, USING TEMPERATURE FOUND IN STEP 2.
FIND THE CUBE AT WHICH PERIMETER THICKNESS EQUALS NOZZLE SIZE.
EXAMPLE – PRUSA I3 MK2S
Print speed – 25mm/s
Part cooling – 0%
Printing temperature – 200°C to 280°C in steps of 10°C.
Layer height – 0.2mm
Nozzle diameter – 0.4mm
STEP 1. PRINT CUBES AT A SET SPEED IN TEMPERATURES VARYING FROM 200°C UP TO 280°C
STEP 2. MEASURE PERIMETER THICKNESS OF EACH CUBE, NOTE TEMPERATURE WITH HIGHEST EXPANSION.
Cube at 200C – no expansion of material.
Cube printed at 250C – perimeter measured at 1.05mm, which yields a 260% increase of perimeter thickness. Between 240-250C the expansion of the filament was highest.
STEP 3. PRINT CUBES WITH DECREASING STEPS OF FLOW, USING TEMPERATURE FOUND IN STEP 2 (IN OUR CASE 250C).
STEP 4. THE CUBE WITH THE PERIMETER THAT EQUALS THE NOZZLE DIAMETER IS THE LOWEST USABLE FLOW. EXPECT FLOWS AROUND 35-50%.
In our case we found the cube with 30% flow to be equal to the nozzle size.
So when printing on our Prusa MK2s at 25 mm/s we can print accurate model using 250C and using 30% flow rate. Increasing the speed will be possible however we need to make sure the filament can absorb enough energy, so to account for the short residence time of the filament in the hotend, the temperature should be increased in order to keep the expansion of material the same.
|Flow||Down to 35%|
|Print speed||Up to 40mm/s|
Lightweight printing can be done by using the settings determined in the paragraph above. Keep in mind that if the flow is decreased to low values the hot-end might clog due to the filament expanding before exiting the nozzle.
LARGER LAYER HEIGHTS
On the left we printed the same gcode using regular PLA, on the right our colorFabb LW-PLA showing the expanding properties enabling 0.6mm layerheight from a 0.4mm nozzle.
|Temperature||Up to 260+°C|
|Max layerheight with 0.4mm nozzle||0.6mm|
Due to the expanding behavior of the material it is possible to 3D print with larger layer heights the nozzle itself, this means short build times for quick draft models.