3D printer flow rate, or the extrusion multiplier, refers to the slicer setting that determines the amount of plastic to extrude. By default, the flow rate is set to 1.0 or 100% depending on the slicer. When you set the flow rate to 1.1 or 110% you are increasing the flow rate by 10%.

Why is the flow rate of my 3D printer important?

The correct flow rate is the first step in getting attractive and dimensionally accurate 3D prints. Incorrect flow rates can lead to both over and under-extrusion which are two of the main issues that cause your prints to come out looking “ugly.”

Why would I ever need to change the flow rate on my printer?

Different filaments not only have different densities, but they can have different extrusion properties that can lead to under or over-extrusion issues. Calibrating your flow rate for each filament can help improve the accuracy of your prints.

Tip: Write the calibrated flow rate on your spools of filament so you don’t forget!

How do I quickly determine the optimal flow rate for my filament?

Finding the “sweet spot” when it comes to flow rate starts with a planned trial where you choose a small model and print it using different flow rates to find the best results.

For example, you could start with a flow rate of 105%. If the printed part is over-extruded, you could then choose a lower flow rate like 100%. If the 100% flow rate results in a part that is too under-extruded, you now know that the optimum flow rate is somewhere between 101% and 104%. You could try the same process with flow rate values between 101% and 104% to narrow down the best flow rate for that filament. It is that simple!

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What happens when you print with too high of a flow rate?

When you print with a flow rate that is too high, it can lead to over-extrusion. Over-extrusion happens when your 3D printer extrudes too much material. Over-extrusion is characterized by oozing, blobs, stringing, and drooping.

But how do I fix over-extrusion? If over-extrusion is happening to you, there are a variety of ways to fix it.

  • Lower your flow rate.
  • Lower your printing temperature.
  • Check that your filament dimeter input is correct.

What happens when you print with too low of a flow rate?

When you print with too low of a flow rate, under-extrusion can happen. If you models are missing layers, have thin layers, or have layers with dots and holes in them you are likely experiencing an under-extrusion problem.

But how do I fix under-extrusion? If you are having issues with under-extrusion, there are a few simple things you can try to correct the problem.

  • Increase your flow rate.
  • Increase your temperature.
  • Make sure your filament diameter input is correct.

If you want some more information on under-extrusion and how to fix it, check out our How to Fix Under-Extrusion.

The flow rate of your printer determines how much plastic to extrude, and an incorrect flow rate can lead to ugly prints that are full of holes and mismatched layers. Take the extra time to determine each of your filament’s optimal flow rates to ensure that you are not only getting good looking prints, but also dimensionally accurate ones.


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