Gluing 3D prints: which glue for PLA, PETG, ABS, ASA and TPU?

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The short answer: for small PLA parts use super glue, and for large or loaded joints use two-part epoxy. ABS and ASA can also be welded with acetone. PETG is considered hard to glue, so two-part epoxy after thorough sanding is the safe choice here. TPU needs an adhesive that stays flexible itself. For all materials, preparation matters more than the brand of glue.

Which glue for which filament?

The assessments come from the Prusa and Polymaker wikis and from Henkel’s (Loctite) plastics bonding guide. Filaments differ depending on the manufacturer and additives, so test new combinations on an offcut.

Step 1: Prepare the surfaces

Polymaker calls surface preparation “crucial for all adhesives”. Here is how to proceed:

1. Check the fit. The parts should lie on top of each other without force. According to Henkel, super glue can only bridge narrow gaps, and larger gaps can only be filled by two-part adhesives.
2. Sand. Lightly roughen smooth surfaces, especially the glossy underside from the print bed, with sandpaper. In the Henkel guide, roughened plastic samples reached higher strengths than smooth ones with many adhesives.
3. Degrease. For almost all plastics, Henkel names isopropyl alcohol as the cleaner. Afterwards do not touch the surfaces with your fingers.
4. Fix in place. Clamps, tape or a printed holder hold the parts until the glue has set.

If you design the parts yourself, plan the glue joint in: according to Henkel, super glues hold well in shear and tension but poorly against peeling. Overlaps, tenons or dowel pins that enlarge the bonding area and take up forces as shear therefore hold better than a butt joint.

Super glue (cyanoacrylate)

The fastest way for small parts made of PLA, ABS and ASA. Henkel summarises the properties like this:

• Advantages: one-component, cures in seconds at room temperature, holds well on many plastics, available as a thin liquid and as a gel.
• Disadvantages: hardly fills gaps, weak against peel forces, low heat resistance, bonds skin instantly, can soften some plastics and trigger stress cracks.

Practical notes:

• Gel rather than liquid for vertical surfaces and small gaps. Polymaker describes gel super glue as easy to dose and cured transparent in under a minute.
• Remove excess immediately. With ABS, ASA and polyurethane, Henkel expressly points out that uncured super glue can cause stress cracks.
• A white haze around the joint appears, according to Henkel, when glue evaporates and settles on the part. Less glue and good ventilation help; there are also low-odour variants that are less prone to it.
• Activator speeds up curing, primer improves adhesion on hard-to-bond plastics. According to Henkel, depending on the plastic, up to 20 times the strength of the unprimed joint is possible with primer.
• Not for permanent load. Polymaker writes that super glue can fail under sustained load.

Two-part epoxy

For large surfaces, loaded joints and poor fits, two-part epoxy adhesive is the more robust choice. According to Henkel, epoxy offers high strength and good toughness and also cures through in thick layers. That is why it fills gaps where super glue fails. The disadvantages: the two components have to be mixed accurately, the working time is limited, and curing takes longer. For a tested two-part plastic adhesive, Polymaker gives 10 minutes to first holding strength and 24 hours to full strength. Stick to the times on the packaging.

Epoxy is also an option for PETG and nylon, where super glue often holds less well. With larger quantities, epoxy gets warm as it cures, and Henkel names this heat build-up as a possible disadvantage. Thin PLA parts can warp as a result, so apply only as much as necessary.

Acetone and solvents: only ABS and ASA

According to Prusa, ABS and ASA can be glued and welded with acetone: the solvent softens both surfaces, and as they dry they bond almost invisibly.

Henkel names disadvantages of solvent bonds: they trigger stress cracks more readily than adhesives, do not bridge larger gaps, and full strength can take weeks. The right timing matters; with too much or too little solvent in the joint, the bond stays weak.

According to Prusa, PLA can only be softened with acetone in some types. According to Prusa, PETG only dissolves in chemicals such as dichloromethane, which only trained laboratory staff should work with. For PETG this is not a route for home use.

There are also specialist adhesives for 3D prints that soften the surface and so weld the parts, each for PLA, for ABS and ASA, or for PET and PETG. Polymaker has tested such adhesives and describes the PET variant as particularly effective on PETG.

Gluing TPU

TPU is flexible, so the glue joint has to stay flexible too. According to Henkel, normal super glue cures to a rigid plastic and tears as soon as the part is bent. Henkel names these alternatives:

• Rubber-modified super glues, which have higher peel and impact strength.
• Polyurethane adhesives, which, depending on type, cure from soft and elastic to hard and, according to Henkel, are tough and good in the cold.

Henkel also points out that polyurethane can develop stress cracks from uncured super glue. Test your combination on an offcut and then bend it several times.

When gluing is not enough

For parts that come apart more often or have to take high forces, screws are often the better solution. Polymaker expressly recommends mechanical joints such as screws or clips for nylon. How to get threads into plastic permanently is covered in Melting in threaded inserts.

Safety

• Super glue bonds skin in seconds; according to Henkel this is a typical property of these adhesives. Protect your eyes and do not point the tube at yourself.
• Acetone is highly flammable. Work only with good ventilation, with no ignition sources nearby and with gloves. Polymaker urges extreme caution when handling acetone because of its flammability.
• Liquid epoxy is toxic according to Prusa, as is resin that has not fully cured. Wear gloves and keep to the mixing ratio exactly.
• Read the safety data sheet. Every adhesive has its own notes on ventilation, protective equipment and disposal.

More on fumes during printing and post-processing is under Safety in 3D printing. How to continue after gluing with filling, priming and painting is shown in Post-processing 3D prints.

Sources

• Henkel: Loctite Design Guide for Bonding Plastics, Volume 5 (PDF), sections Cyanoacrylates, Epoxy and Polyurethane Adhesives, substrates ABS, ASA, PET, Polyamides, Polyurethanes, and the table on stress cracking
• Polymaker Wiki: Glueing, ASA
• Prusa Knowledge Base: ABS, ASA, PLA, PETG
• Prusa Blog: Herstellung von lebensmitteltauglichen 3D-Druckmodellen (notes on liquid epoxy resin)