How to 3D Print Large Parts 1

Layer Adhesion

Layer and surface adhesion is a critical component of 3d printing. 3d printing issues increase as object size increases. Large 3d printers can be more difficult when it comes to bed leveling. As the extruded layers bond together they are fused with heat. Proper surface adhesion decreases warping that can decrease part quality.  Even at higher chamber temperatures, large ABS parts will warp without correct surface adhesion. If extrusion temperature is too low, layers will not adhere to previous layers. Layer delamination occurs when the layers separate or don’t properly bond together. To avoid layer separation, increase your printer’s hotend temperature.

Adjusting Hotend Temperature

To dial-in extruder temperature:

  1. Start a print as normal with a basic print temperature
  2. Increase it in 5-°C increments until you see some improvement.
  3. Get temperature settings from filament manufacturers.
  4. Blobbing or over-extrusion is caused by high temperature.Strongly adhere the part to the build plate

Print Speed

Layer separation can be caused by high print speeds. The extruded plastic will not have time to properly bond to the previous layer. To adjust print speed decreasing print speed in 10mm/sec increments until print results improve.

Flow Rate & Extrusion

Hotend flow rate Increases part strength and stronger bond between layers. A 3d printer’s flow rate also known as the extrusion multiplier in slicer software. As the molten filament comes out of the nozzle. This will result in a stronger bond between layers.

  • Start with your normal extrusion rate
  • increase it in 5% increments
  • observe print issues caused by over or under extrusion 
  • adjust the flow rate 

Heat Containment

Containing heat is required for some plastics. PLA is known to contract at higher rates as it cools.  Thermal contraction can cause layers to delaminate and decrease print quality. Enclosing the build area will keep more heat inside the chamber and slowdown the thermal contraction process. 

Part Cooling & Air Flow

Check that the part cooling fan is correctly blowing on the 3d printed part.

  1. Decrease part fan speed in 10% increments. You should see a significant decrease in layer separation and cracks in your print.

Heated Bed Temperature

Heat bed temperature is critical for printing large parts. Larger objects require higher build plate temperatures. The build plate surface should be from 135C to as high as 150C (ABS) to prevent warping. Bed temperature tends to increase the chamber temperature of the printer which results in better thermal contraction.While higher heated bed temperatures can draw much more power from the  power supply. Make sure you have enough amperage.

Temperature Control

Temperature-controlled chamber heaters can precisely control the chamber temperature.  When used in connection with a heated bed, the chamber heaters can also quickly warm the chamber to reduce standby time.  Chamber heaters are also beneficial because they can be adjusted to work with a wide range of materials. This feature can be especially important in large scale 3D printers.  For instance, with polycarbonate and nylon, we raise the chamber temperature hotter than with ABS.

Nozzle Diameter & Layer Height

Nozzle diameter and layer height plays a critical role in overall print time. The more material that flows through the print head, the faster a print will finish. The quicker you finish a print the less likely you are to have a failed print. A wider nozzle will also increase print temperature and flow rate. This will allow you to print wider layers, which should result in better layer adhesion. 3d printing large parts can take days to weeks and can use a great amount of filament. Print time is directly related to nozzle flow rate. Print speed is a healthy balance of X and y-axis travel speed and extruder flow rate.