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Feed Rate vs. Flow Rate in 3D Printing. The Differences Explained

All of the different terminology used in 3D printing can leave you feeling lost and confused when trying to discuss an issue with a peer or a technical support team. Feed rate and flow rate are two very different things in the world of 3D printing, and confusing one with the other could lead you to inaccurate information if you’re trying to fix an issue with your printer.

Feed rate measures how much filament your printer extrudes in cubic millimeters per second. Flow rate is measured in percentage and controls the amount of filament allowed through the extruder at any time. Flow rate is a setting, whereas feed rate is a measurement.

In the following paragraphs, I’ll go into more detail about what feed rate and flow rate are concerning 3D printing and what makes them different concepts even though they seem like the same thing.

What is Flow Rate?

Flow rate is measured numerically by percentage and correlates to the amount of filament allowed to flow through your extruder at any given time. This measurement correlates with how quickly you can print and how tall or thick your layers are. 

The higher the flow rate, the more your filament is allowed to flow through the extruder.

People print with a flow rate between 90% and 110%. However, some materials may require a higher or lower flow rate to come out well.

What Happens When Your Flow Rate Is Too High or Low?

When your flow rate is too high or too low, you will experience issues in your prints. If your flow rate is too low, your printer will under-extrude, resulting in inaccurate dimensions. Your printer may over-extrude if it’s too high, causing blobby and dimensionally incorrect prints.

For either of these issues regarding flow rate, the solution is a simple one. Either adjust the flow rate percentage on your printer up or down. Whether you are experiencing over or under extrusion, your flow rate is the best thing to check.

Under Extrusion Due To Low Flow Rate

Under extrusion is when you may have holes or missing spots in your prints because the flow rate is not high enough for the filament you chose to use for this project. You can fix this by adjusting the flow rate setting on your printer and raising it by 5% until your print reaches the desired quality.

Under extrusion is an issue that is not only caused by problems with the printer’s flow rate but other hardware issues like a clogged nozzle, low print temperature, or overly rapid print speed. 

Suppose you’ve adjusted the flow rate setting on your printer and gone over 115% to accommodate for under extrusion and still can’t see any improvement in the quality of your prints. In that case, the flow rate is not the issue causing your under extrusion in your objects. 

Over Extrusion Due to Flow Rate

If you find that your prints are coming out blobby or with extra filament in places that it shouldn’t be, then you have an issue with over extrusion that may be related to the flow rate setting of your printer.

Over extrusion happens when your printer extrudes too much filament through the nozzle at once. There are a few steps that you can take to fix this problem:

  1. Adjust the flow rate setting on the printer, lowering it in 5% increments until your prints start to look better.
  2. If lowering the flow rate does not improve the quality of your prints, then you have a different issue causing the over-extrusion of your filament.
  3. Lower the print temperature so that the prints harden faster.
  4. Check your nozzle for damage. Over extrusion can also be caused by eroded or damaged nozzles. A nozzle eroded by abrasive filaments will throw off the extrusion.

Keeping your flow rate reasonably low is critical if you want straight walls with little to no artifacts. Properly adjusting this rate will also ensure that you capture as much detail as possible in your prints since over-extrusion can “smush” and blur fine details. 

What Is Feed Rate?

Feed rate measures how much filament your printer extrudes per second as the print head moves. Feed rate has more to do with the speed of your prints than how much filament makes it onto the print bed. 

This definition makes it easy to see why many people get flow rate and feed rate mixed up.

However, the main difference is that flow rate is a setting that adjusts how much filament comes out of the nozzle at any given time. On the other hand, the feed rate is a measurement of how much filament comes out of the nozzle per second.

The feed rate measures your printer’s speed, so a lower feed rate means your printer is running more slowly. 

If your prints are dropping in quality, try lowering the feed rate. Doing so will slow down the entire process and minimize the opportunity for imperfections in your models. 

Small prints that don’t require much detail can be done quickly with high feed rates up to 150 millimeters per second. However, this rapid speed is only ideal for small prints that do not have much detail.

Most people print at anywhere from thirty to fifty-five millimeters per second. This speed is slow enough to provide high-quality prints, especially if you have a high-speed printer with suitable hardware.

Conclusion

Flow rate is like opening or closing a dam. It is a setting that you can raise or lower to determine the amount of material allowed through the nozzle. 

Feed rate measures how quickly the printer extrudes the filament across the printing surface. It has more to do with the printer’s internal components than the extrusion itself.

So, while these concepts are similar, they represent different properties of your 3D printer. Remember, feed rate means speed, while flow coordinates with how much filament comes out of the nozzle in a split second.