Polylactic Acid (PLA)
Polylactic acid or polylactide (PLA) is a biodegradable, thermoplastic, aliphatic polyester derived from renewable resources, such as corn starch (in the U.S.) or sugarcanes (rest of world). Although PLA has been known for more than a century, it has only been of commercial interest in recent years, in light of its biodegradability.
- Name: Polylactic Acid
- IUPAC Name:
- CAS No:
- Density: 1.23 - 1.25 g/cm³
- Melting Point:173-178 °C
- Glass Transition Temperature:50-80 °C
- Specific Heat:
- Water absorption rate:
- Elongation at break:
- Tensile strength: 2360 to 10000psi
- Compression strength:
- Flexural strenght:
- Flexural modulus:
- Coeff of expansion:
- Process temperature for rolling:
- Process temperature for extrusion:
- Ideal "ambient" temp for extrusuin:
Note the settings listed here are intended to be a good starting point for setting up your RapMan. They should enable you to obtain a good print with most basic objects. It should be remembered that you may need to experiment with them (especially the temperature settings) variables such as different colours of PLA, suppliers of filament, ambient temperature, overall size of object etc will all have an effect on the print quality.
Beware, Enrique has made some very recent changes (October 2009) to skeinforge that are not documented here! you will have to pick through the settings to see which are appropriate ... watch out particularly in the "speed" settings as the wording has changed and also in "raft".... Quote from the skeinforge powwow.... "I've changed the '..Nozzle Height over Half Layer Thickness' preferences in raft to '..Nozzle Height over Layer Thickness'. So 'Base Nozzle Lift over Half Base Layer Thickness' with a default of 0.75 is now 'Base Nozzle Lift over Base Layer Thickness' with a default of 0.375. 'Interface Nozzle Lift over Half Interface Layer Thickness' with a default of 0.9 is now 'Interface Nozzle Lift over Interface Layer Thickness' with a default of 0.45. 'Operating Nozzle Lift over Half Layer Thickness' with a default of 1.0 is now 'Operating Nozzle Lift over Layer Thickness' with a default of 0.5. If you have changed the nozzle lift preferences from their defaults, please go in raft and enter your nozzle lift preferences again at half their original values". This shouldn't be too much of a problem with a fresh install but if you copy settings from somewhere else (ie the blog, wiki etc) you may need to be careful.
Extrusion Width over Thickness (ratio): 1.5 Import Coarseness (ratio): 1.0 Infill Bridge Thickness over Layer Thickness (ratio): 1.0 Infill Bridge Width over Extrusion Width (ratio): 1.0 Infill in Direction of Bridges True Layer Thickness (mm): 0.4 Layer Thickness over Precision (ratio): 10.0 Clip Clip Over Extrusion Width (ratio):
Diaphragm Period (layers): 999999 Diaphragm Thickness (layers): 0 Extra Shells on Alternating Solid Layer (layers): 1 Extra Shells on Base (layers): 1 Extra Shells on Sparse Layer (layers): 1 Grid Extra Overlap (ratio): 0.1 Grid Junction Separation Band Height (layers): 10 Grid Junction Separation over Octogon Radius At End (ratio): 0.0 Grid Junction Separation over Octogon Radius At Middle (ratio): 0.0 Infill Begin Rotation (degrees): 45.0 Infill Begin Rotation Repeat (layers): 1 Infill Solidity (ratio): 0.3 Infill Odd Layer Extra Rotation (degrees): 90.0 Grid Hexagonal True Grid Rectangular False Line False Interior Infill Density over Exterior Density (ratio): 0.9 Outside Extruded First True Solid Surface Thickness (layers): 3 Inset Extrusion Perimeter Width over Thickness (ratio): 1.8 Infill Perimeter Overlap (ratio): 1.0 Calculate Overlap from Perimeter and Infill True Calculate Overlap from Perimeter Only False Remove Extrusion Overlap True Turn extruder heater off at shutdown True Start at Home True
Add Raft, Elevate Nozzle, Orbit and Set Altitude: True Base Infill Density (ratio): 0.5 Base Layer Thickness over Layer Thickness: 2 Base Layers (integer): 1 Base Nozzle Lift over Half Base Layer Thickness (ratio): 0.75 Bottom Altitude: 0.0 Infill Overhang (ratio): 0.1 Interface Infill Density (ratio): 0.5 Interface Layer Thickness over Layer Thickness: 1.0 Interface Layers (integer): 1 Interface Nozzle Lift over Half Interface Layer Thickness (ratio): 1.0 Operating Nozzle Lift over Half Layer Thickness (ratio): 1.0 Raft Outset Radius over Extrusion Width (ratio): 5.0 Support Cross Hatch: True Support Flowrate over Operating Flowrate (ratio): 1.0 Support Gap over Perimeter Extrusion Width (ratio): 1.0 No Support Material true Support Material Everywhere false Support Material on Exterior Only False Support Minimum Angle (degrees): 45.0 Temperature Change Time Before Raft (seconds): 0.0 Temperature Change Time Before First Layer Outline (seconds): 0.0 Temperature Change Time Before Next Threads (seconds): 0.0 Temperature Change Time Before Support Layers (seconds): 0.0 Temperature Change Time Before Supported Layers (seconds): 0.0 Temperature of Raft (Celcius): 210.0 Temperature of Shape First Layer Outline (Celcius): 200.0 Temperature of Shape First Layer Within (Celcius): 200.0 Temperature of Shape Next Layers (Celcius): 210.0 Temperature of Support Layers (Celcius): 200.0 Temperature of Supported Layers (Celcius): 200.0
Bridge Feedrate Multiplier (ratio): 1.0 Extrusion Diameter over Thickness (ratio): 1.5 Feedrate (mm/s): 16.0 Do Not Add Flowrate False Metric False PWM Setting True Flowrate PWM Setting (if PWM Setting is Chosen): 380.0 Maximum Z Feedrate (mm/s): 48.0 Orbital Feedrate over Operating Feedrate (ratio): 1.0 Perimeter Feedrate over Operating Feedrate (ratio): 1.0 Perimeter Flowrate over Operating Flowrate (ratio): 1.0 Travel Feedrate (mm/s): 64.0
Cooling with a fan is usually necessary. It is not necessary to use a raft when printing with PLA if your printbed is in good condition.
PLA as Support Material
When using a RapMan or BfB3000 printer with twin print heads it is possible to use ABS for printing the main object and use PLA as removable support material. The PLA can be removed mechanically or by soaking in Sodium Hydroxide solution (NaOH)(also known as Lye in the US.
Note NaOH is hazardous and can cause severe burns to the skin/eyes... take care!
Further information on the BfB forum RapMan second extruder
And in the T&L Resources Printing with Support
PLA is slightly more brittle than ABS once it's extruded, but that is more than made up for by it's almost complete lack of warping, the ease of part removal, and the lack of any bad smells. It gives off a faint odor of Candyfloss (cotton candy) when it's printing.
Due to PLA's relatively low glass transition temperature, manufatured parts can not be used in situations where temperatures are higher than about 70-80 degrees C... PLA cups cannot hold hot liquids
PLA sticks well to original print bed made from acrylic. .