PETG filament is a variant of the widely used PET polymer, its use in 3D printing is booming due to the fact that the ratio between printing difficulty and mechanical characteristics is very good. It is widely used in industry because it is chemically very stable and has a high impact resistance.

Advantages

  1. Good mechanical properties: it is a material with high impact resistance, great durability and its resistance to temperature is above 80ºC, which is when the material starts to deform.
  2. Food grade approval and ability to be sterilised: FDA certification (US agency responsible for the regulation of food, drugs and cosmetics).
  3. Chemical resistance: as a very stable material, PETG is chemically resistant to both acid and base attack.
  4. Transparency: PETG without dyes (natural) allows 90% of light to pass through, making it the ideal material for making translucent or transparent parts.
  5. It is recyclable.
  6. It does not produce odour when printed.

Disadvantages

  1. Finding the "sweet spot" of the filament is the biggest drawback of this material, obtaining the correct printing parameters.
  2. Need of hot bed for proper adhesion.
  3. Loss of colour due to long term exposure to the sun. UV rays can generate a discolouration of the piece and make it more brittle. To solve this problem we have a PETG that is resistant to this discolouration.

Main printing parameters

Extrusion temperature

The temperature range for printing with PETG is between 220°C and 250°C, and the ideal temperature is primarily dependent on the size of the nozzle and the extrusion equipment. In case your 3D printer has a Teflon barrel, you should not raise the temperature above 235°C to avoid deterioration of the barrel. Very high temperature levels will cause the filament to drip, resulting in the "stringing" effect. Very low temperature may cause the extruder to lose steps, resulting in poor material flow. A temperature test must be performed to determine the correct temperature.

Printing surface

A hot bed between 70°C and 90°C is required for proper adhesion with this material. Any specialty adhesive for 3D printing will be helpful in avoiding the notorious 'warping' effect; we therefore recommend these adhesives for large components. If you are printing on a smooth PEI surface, a barrier must be created between the PEI and the part using an adhesive (glue stick or lacquer), or it will be difficult to remove the part from the surface.

Layer fan

Using a layer fan is not required with PETG filament, but it is helpful if the part has a lot of detail or a lot of overhangs to improve adhesion between layers. If the part begins to delaminate or crack, reduce the layer fan speed (set it above 20%) to reduce airflow and increase adhesion between layers.

Printing speed

The speed of a 3D printer is very dependent on the whole set of parts that make up the printer, but having some sort of benchmark value is helpful. The optimal speed for most cases would be between 25mm/s and 55mm/s.

Layer height

The optimum layer height is usually 50% of the nozzle outlet diameter, but it can be lowered to 25% or raised to 75-80%. For a 0.4mm nozzle, an optimum layer height would be 0.2mm within a range of 0.1mm and 0.3mm.

Flow

It's crucial to determine the precise value for each material's dimensional tolerance in order to set this parameter. During regular printing, this parameter should not vary by more than 5%, i.e. 95% to 105%. If our extruder is badly calibrated after we conduct a flow test, we must first calibrate it to obtain optimal outcomes.

Retraction

The retraction factor is dependent on the hotend-extruder assembly and must be determined through a retraction test. The initial values can be as follows

  1. Direct drive: 1-2 mm & 25 mm/s
  2. Bowden: 5-6 mm & 30 mm/s

Avoiding clogging with PETG

Retraction

If the material's extrusion temperature is poorly defined and very long retraction periods are used, the molten material will accumulate on the walls of the barrel, resulting in a jam. To avoid this, a shrink test should be performed as described previously, but first you must determine the correct extrusion temperature of the material.

Hotend cooling

When heated, this material becomes very liquid, so it tends to ooze out of the nozzle if the temperature is high. In order to prevent the material from overheating before it reaches the heating barrel area, a very good cooling of the hotend is necessary to generate a thermal shock and prevent the molten material from moving up the barrel into the cold zone.

Cleaning

When printing with PETG, you may notice a few small particles sticking to the nozzle or to the element you are printing. When the hotend is clogged, the material may not flow properly, so you should clean the nozzle with a "cold pull" technique or utilising cleaning filament. Carbonised dirt may become trapped on the nozzle or heating cube, so it is beneficial to brush them periodically with a wire brush to dislodge it. Using a silicone "sock" to clean the nozzle and heating cube is advantageous because the particles do not stick to it and can be easily removed.

Storing the filament

The material is sensitive to humidity (hygroscopic). It must be stored in a dry place when it is not being used. Vacuum-packing the spool with an extra desiccant bag is advisable when you receive it at home. Since it is a costly procedure, we include an airtight bag with every spool in which you may store the filament together with its desiccant bag when not in use.

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