switching from PLA to PETG

How to switch from PLA to PETG

Almost every beginner to the 3D printing world starts this incredible journey using simple PLA filaments. PLA is relatively easy to print, and yields high-quality surface finishes with the least problems. However, this material has its own shortcomings, like low glass transition temperature, that makes us think about an alternative; that’s when PETG comes to mind. 

How to switch from PLA to PETG? (briefly):

Start by changing the printer/slicer settings. Slow down the printing speed to 40 mm/s. Set the extruder temperature between 230 to 260° C and the bed temperature to 60 to 80° C if necessary. You can also turn off the fans to increase layer adhesion and decrease the retraction speed. The last step is to double-check bed leveling and surface adhesion and remove the remaining PLA filament in the hot end.

Now that you get the big picture, let’s dive into the details about finding the optimum setup for your 3D printer and preparing for some upcoming issues.

Adjust temperature

Different manufacturers recommend various extruder temperature ranges for their filaments. However, the norm for the extruder temperature for PETG is regularly between 230 to 260° C. But keep in mind that Bowden tubes that guide the filament into the hot end deform at 250° C, so temperatures higher than that will damage your 3D printer.

The quality of your finished product is heavily dependent on the nozzle temperature. Too high temperature can cause stringing, warping, and oozing. On the other hand, in low temperatures, pushing the extruder’s filament is more demanding and can cause extruder skipping.

Finding the best temperature based on your filament and 3D printer brand is somehow superficial. You need to start the printing process with low temperatures like 230° C. If you hear a clicking sound from the extruder, increase the temperature a little until the clicking sound disappears.

A heated bed can help the first layer of filament stick to the bed, But PETG tends to stick too much and cause damage to the foundation when you remove it from the surface. The recommended bed temperature for PETG is in the range of 60 to 80° C.

Set the heated bed temperature to 50° C. If the first layer did not stick to the bed, increase the temperature.

Keep in mind that the sticking problem may have other causes like incorrect bed leveling, insufficient adhesion, large z offset, etc.

Make sure your bed is leveled

Before you do any printing, you should make sure that the bed surface is perfectly leveled. This way, you will get a uniform and even first layer that becomes a good foundation for the rest of the layers and lowers the chance of warping.

To level your bed:

  1. Clean the tip of your nozzle from previous filaments.
  2. Bring the nozzle to the bed corners and adjust the distance from the nozzle to the bed’s surface by a 0.3mm feeler gauge or something with the same thickness, like a notebook’s cover or paper.
  3. Do the same process for the remaining sides.

As you may have noticed, printing with PETG requires a bigger nozzle gap. That’s why we recommend a 0.3mm feeler gauge.

Use correct adhesives

PETG tends to stick too hard to the bed and damage the bed’s surface, especially if you use PEI or glass surfaces. Using an extra adhesive layer between the surface and filament is the solution.

The most reliable option here is to use blue painter’s tape. This way, you will have a disposable surface, and thus you don’t need to worry about your bed getting damaged. The downside is that the finish on the bottom layer is not as good as printing on a glass surface. You can apply the blue tape on top of any building surface.

BulidTak surface also works well with PETG and other filament materials. However, it wears down after 3 to 6 months of constant use, and then you should replace it. Incorrect temperatures or small nozzle gap can result in a strong permanent bond between PETG and BuildTak surfaces, Resulting in the part tearing off chunks of the plate as you try to remove it.

Printing PETG on a glass surface requires a heated bed and a medium layer. The blue tape is a suitable medium. But, glue and unscented hairspray can also be used.

It’s not a good idea to use PEI sheets to print PETG. It can stick too much to the part and thus damage the surface.

Decrease the printing speed

High printing speed can lead to lower quality and damaged products. 40mm/s is an ideal speed for the first try. you need to keep it between 40 to 60mm/s. Printing faster results in extruder jamming, bad first layer adhesion, and low-quality surfaces. On the other hand, if it’s too slow, it will cause deformed parts, increases oozing and creates more strings.

Printing speed for the first layer should be lower than the rest. The best first layer speed is around 20mm/s though you should find the sweet spot for your setup after some experiments.

Extruder’s high temperature can make the PETG filament melt much faster, and the melted filament tends to drip from the nozzle. This phenomenon can create oozing. Increasing travel speed can solve this issue.

Modify retraction settings

The ideal retraction setting varies from one 3D printer to another. However, lower retraction speed usually prevents stringing and oozing if not eliminate it.
Set the retraction speed to around 30mm/s and see if the results are satisfactory; if not, you can try decreasing it to 25 or 20mm/s.

Turn off cooling fans

Cooling fans can help with a temperature drop and reduce stringing though it will decrease the layer adhesion.

Unlike PLA, which requires cooling during printing, it’s better to turn off fans while printing with PETG. Using fans can only help with smooth surface finishes and edge quality, so it’s better to turn off the fans, at least for your first tries printing with PETG.

Dry PETG filaments if necessary

If you put PETG spools in a humid environment for a long time, you need to dry the whole thing before using it. Drying filament is easy; you can put the spool in an oven or fruit dehydrator for four hours at 65° C. However, in many cases, PETG doesn’t need to be dried. You can also check the article about ‘Does PETG need to be dried?’

Bring out the remaining PLA filament

To switch from PLA to PETG, Heat the nozzle to 240 to 260° C. Pull the PLA filament out and replace it with PETG. This process may vary based on your printer’s structure, but it’s usually a simple task. You need to extrude the new filament for a few minutes until it cleans the nozzle from the remaining PLA.

Common issues:

What to do if the extruder does not extrude?

Slow down the printing speed. The PETG filament needs time to melt and pass through the nozzle. If you don’t let it heat up, the extruder can’t push it inside the nozzle.

Check the nozzle and make sure whether it’s hot or not and make sure the drive gear works correctly. The next thing to check is the nozzle’s hole. See if the nozzle is clogged and remove any obstruction in the nozzle’s tip.

How to fix disordered infills and rough surfaces?

The best way is to increase the nozzle’s temperature around 5 to 10° C and decrease the printing speed by 5mm/s. You can work with these parameters and reach the desired quality. Turning on the cooling fans can also improve the print quality.

What to do when PETG does not stick to the bed?

You can read our article about PETG not sticking to bed problem.