Under extrusion is where the machine is not pushing enough filament through. This can happen for 2 reasons:

a) The drive wheel is not moving fast enough for the width of your filament. This is the FLOW RATE of the filament

b)The temperature is too low for your filament.

Understanding Filament flow rate

The FLOW RATE is literally how fast the machine pushes filament through. Some times filament can be a fraction (maybe .05mm) thinner than others. While the manufacture of filament is improving with laser measuring and other technological advances. This being said, it is important to understand that if yopur filament is a little thinner, for example, that it will result in less filament coming out the nozzle per mm, and this is called "under extrusion".

Understanding Temperature

3D Printers generally use a temperature sensor called a thermocoupler. This technology has been adapted from pottery kilns and is not as presice as we would like. As a result one machine may run 2-3 degrees hotter/colder than another.

PLA filament generally deals with this as you can print with most PLA at a range of 200-230 degrees.

Compensating and adjusting for under extrusion

Makerbot has three approaches to slicing within their Makerbot Desktop software.

a) Simple : This is where you select LOW   MEDIUM  or HIGH and using default settings 

b) Advanced : When you click "advanced options" you can edit the INFill density, No of Shells (wall thickness), layer height and speed the machine travels while printing

    At this stage you can not edit temperature on the 5th Generation machines (you can on Replicator 2 and 2X machines).

c) Custom Profiles : These are even more advanced options and let you control everything!

Bilby 3D has been a long term fan of custom profiles and would like to see more options in the standard software settings (which we suspect you may see soon)

Custom profiles are actually easy to set up and we have a step by step guide within our solutions bank.

We suggest you read the "Custom Profiles - Getting started - Decreasing support density"

Then read : "Custom Profiles-Flow Rates"

Bilby3D hopes you found this helpful