The Best Glues for PLA 3D Printed Parts

3D printing with PLA filament has become increasingly popular among hobbyists and professionals alike. PLA is affordable, easy to print with, and produces quality parts. However, joining multiple PLA parts together can be tricky. Using the right adhesive is key to creating strong, long-lasting bonds between 3D printed components.

In this comprehensive guide, we’ll cover the top glues for bonding PLA and discuss how to get the strongest, most durable joints for your projects.

Why Properly Bonding PLA Prints Matters

When 3D printing objects in sections or designing prints with removable parts, proper adhesion is critical. With poor bonding, components can separate over time or with use. This can lead to print failures or accidents if glued parts come loose when they shouldn’t.

joining PLA properly ensures:

• Structural integrity of multi-part prints
• Tight, secure fit of parts
• Prevention of accidents or injuries from components detaching
• Professional, high-quality finish of assembled objects

Choosing and applying the right adhesive avoids frustrations, disasters, and disappointments down the road.

Challenges of Gluing PLA

PLA has characteristics that make gluing a bit tricky. Keep these factors in mind when selecting and using an adhesive:

• Semi-porous surface – PLA has a slightly porous surface that absorbs glue unevenly. This can lead to weak bonding if the glue doesn’t penetrate effectively.
• Poor chemical bonding – PLA doesn’t form strong chemical bonds with all glues. The adhesive must be compatible with the thermoplastic.
• Cooling and shrinkage – Freshly printed PLA can still be cooling and shrinking slightly when glued. As it stabilizes, it may contract and pull away from the joint.
• Flexing – PLA has some flexibility and bendiness, so joints can be stressed by movement over time. The glue must maintain grip despite flexing.

Accounting for these tendencies is important when gluing. The adhesive choice and application technique must overcome the challenges.

Glue Types for PLA

There are several major glue categories suitable for PLA:

Cyanoacrylate (Super Glue)

Super glues are a type of cyanoacrylate adhesive. They form fast bonds by reacting with moisture on the gluing surfaces.

Benefits:

• Extremely fast cure time
• Works well on semi-porous materials like PLA
• Allows repositioning during initial bond
• Generally creates a strong, rigid joint

Drawbacks:

• May not withstand flexing or shock over time
• Can become brittle as it ages
• Requires very precise application for ideal bond

Overall, cyanoacrylates make a great quick-bonding glue for PLA. Look for “super glues” designed for plastics.

Epoxy

Epoxy is a two-part adhesive with a resin and a hardener. Mixed together, they chemically react to form a rigid bond as they cure.

Benefits:

• Very strong, rigid bonds with PLA
• Withstands flexing and vibration better than super glues
• Fills gaps effectively between uneven prints

Drawbacks:

• Long cure time – may take hours to fully harden
• Mixing equal resin/hardener ratios can be tricky
• Bond may weaken over time with heat or chemical exposure

Epoxies are ideal when you need added strength and shock resistance. The long work time allows precision alignment of PLA parts before the bond sets.

Plastic Welding Adhesives

These glues partially melt the surfaces of plastic, fusing them together. Dichloromethane is a common solvent used.

Benefits:

• Chemically bonds plastic together like welding
• Doesn’t just coat surfaces but penetrates joint
• Creates very strong, rigid, permanent bonds

Drawbacks:

• Vapors from solvents may be harmful – work in ventilated area
• May not work as well on porous, textured prints
• Requires care to not “over-melt” the PLA

Plastic welders cause true melting together of PLA components. Take safety precautions and test first on scrap prints.

Hot Melt Glue

Hot melt adhesives are thermoplastic compounds applied molten then hardened through cooling. They create a strong adhesive layer.

Benefits:

• Fast bonding with quick set time
• Simple to apply from electric applicators
• Allows repositioning before setting
• Produces rigid, permanent joints

Drawbacks:

• Messy strings and drips from applicator tip
• Cooling glue may shrink and pull on joint
• Strength decreases as it ages

Hot melt glue guns are a handy way to tack PLA components in place quickly. Let the bond fully cool before stressing for best results.

Glue Selection Criteria

Consider these factors when choosing an adhesive for your PLA bonding project:

• Joint Strength Needed – If the bond will see heavy stress, an epoxy or plastic welder may work better than super glue.
• Cure Time Allowed – Super glues set fastest, while epoxies require hours to fully cure. Hot melt and plastic welding bond quickly.
• Working Conditions – Epoxies bond best at room temperature. Plastic welders require ventilation. Super glue needs some ambient moisture to cure.
• Appearance – Will the adhesive line be visible? Super glues and hot melt can be messy. Epoxy and plastic welding give cleaner results.
• Rigidity vs. Flexibility – Rigid bonds from super glues and epoxies may crack if flexed repeatedly. Plastic welders penetrate better.
• Shock/Vibration Resistance – Epoxies stand up to these forces better than super glues. Plastic welding is strongest.
• Age Resistance – Epoxies and plastic welding remain more stable over time. Super glues can become brittle.

Considering these factors will lead you to selecting the best PLA glue for your specific 3D printing application.

Applying Glue to PLA

Once you’ve chosen an appropriate adhesive, proper application is key to creating strong joints. Here are some tips:

• Ensure mating surfaces are clean and free of oils, dust, etc. Wipe with isopropyl alcohol.
• Roughen smooth PLA with fine sandpaper to create more surface area and “tooth” for the glue.
• Apply adhesive thinly and evenly on both bonding surfaces. Avoid globs that may weaken the joint.
• Clamp components tightly together as the glue sets. Constant pressure ensures a tight bond.
• Allow the full recommended cure time before stressing the joint. Test a scrap piece first.
• For larger parts, add fillets of adhesive at joint edges for added strength.
• When possible, design interlocking joints like puzzle pieces. This mechanically strengthens the bond.

Proper adhesive selection paired with good application technique will result in PLA joints that hold up to whatever strains your print will see.

Best Glues for PLA Recommendations

Based on experience and testing, here are my top picks for bonding PLA 3D printed components:

Best Overall: Loctite Plastics Bonding System

This two-part epoxy kit from Loctite is specially formulated for bonding plastics, including PLA. It strikes a great balance of strength, cure time, and ease of use. The syringe applicator allows precise glue placement for clean joints. After full cure, the rigid bonds withstand vibration, shock, and stress. For the best all-around PLA adhesive, Loctite is hard to beat.

Pros

• Strong rigid bonds with PLA
• Made specifically for plastics
• Applicator syringe for neat, precise application
• Withstands vibration, shock, chemicals
• Full cure in 6-24 hours

Cons

• Long cure time
• Mixing equal resin/hardener ratios can be tricky

Fastest Bonding: Loctite Super Glue Plastics Bonding System

When you need to glue PLA in seconds, Loctite’s plastic-formulated super glue is excellent. The cyanoacrylate formula penetrates the semi-porous PLA surface quickly, forming rigid bonds in just seconds. The bottle applicator allows controlled glue placement. Just beware of drips solidifying instantly. With proper precision, this super glue is unbeatable for fast PLA bonding.

Pros

• Bonds PLA in seconds
• Made for plastics
• Applicator bottle for precision
• Creates rigid, permanent joints

Cons

• Not as impact/shock resistant as epoxy
• Can become brittle over time

Best for Flexible Joints: Gorilla 2 Part Epoxy

Gorilla makes an excellent flexible epoxy that works well for PLA. The putty-like consistency fills gaps nicely between uneven 3D printed surfaces. The adhesive remains slightly flexible when cured. This prevents cracks from flexing or vibration. Handy syringe tips provide great control for a neat bond line. Just be sure to clamp tightly as it sets.

Pros

• Stays somewhat flexible when cured
• Fills gaps effectively between prints
• Syringe applicators for even dispensing
• Bonds various materials including plastic

Cons

• Slightly longer cure time – around 24 hours
• Not quite as rigid as more brittle epoxies

Best Plastic Welder: Bond It Plastic Welder

For creating truly fused welded joints in PLA, Bond It plastic welder is very effective. The dichloromethane solvent melts and fuses plastic pieces like glue “welding”. The thick gel consistency prevents runoff so only joint surfaces melt together. Just be sure to work in a well-ventilated area. Clamp pieces securely as it cures. The fully hardened bond is extremely rigid and strong.

Pros

• Chemically welds plastics together
• Thick consistency prevents drips
• Creates the strongest permanent bond

Cons

• Use care to avoid over-melting the PLA
• Requires good ventilation

Conclusion

Properly joining PLA 3D printed components requires using the right adhesive and proper application technique. Cyanoacrylate super glues provide fast rigid bonds. Epoxies create the strongest joints that withstand stresses over time. For flexible bonds, flexible epoxies work well. For “welded” joints, plastic welding adhesives penetrate and fuse the PLA together.

Carefully consider the joint strength, cure time, working conditions, appearance, and age resistance you need when selecting a PLA glue. Prepare the mating surfaces properly and apply adhesive thinly and evenly. Allow full cure time before stressing the bond.

With the right glue choice and careful application, you can create professional, long-lasting PLA joints that hold up to whatever your 3D printing project demands. The adhesives recommended above provide high quality bonding for all types of PLA prints.