A good 1st layer with big prints
Good first layer adhesion is half the challenge for any FDM 3D printer!
Most 3D printer users agree that getting a good first layer is one of the most challenging and sometimes frustrating aspects of 3D printing. BigBot printers are significantly larger than most printers, and when part size increases, the potential for part warpage increases as well. Fortunately, advances in materials and practices should enable you print good and print large.
So many opinions…
RepRap and YouTube community based learning has provided a vast database of information regarding bed adhesion, but be careful…some information can be misleading. ABS prints cleanly and beautifully, but please don’t expect parts over 4″ to print well in ABS. Many RepRappers swear ABS is the best and only filament, but that mainly stems from the premise that ABS is easy for cheap extruder gears to grip, and does not require much extruder tuning. No RepRap printers operate in a 80C+ degree environment, so ABS will exhibit high warpage with large parts. ABS is, however great for small parts like decorative items and figurines.
Many Reprappers have many 1st layer practices. For our use, we do not consider any method that requires the following: nasty chemicals (like acetone), adhesive that is not clear or does not release from part, or platforms that do not fit our beds.
Best materials for large prints
Our printer nozzles will print nearly any filament you can find (1.75mm or 2.85mm), but it is up to the user to pick the right plastic for your application. Our continuing bed adhesion development is focused primarily on 2 filament materials: PLA and PETG. We’ve chosen these plastics because when compared to other filaments, they have superior low warpage and high layer adhesion. We are also working to incorporate nylon for it’s high strength and high layer adhesion, but it is more challenging to adhere to the build plate.
1st layer print settings
The goal for a good 1st layer is to get the hot filament to fuse to the build plate for the duration of the print, but then release cleanly once the print is complete. Your print settings have a large role in fulfilling this objective. These basic rules provide a good starting point:
- Ensure the nozzle tip is not more than the nozzle diameter above the build platform. If the nozzle is too high, the plastic will be cooler when it hits the build platform and/or extrude a distorted shape.
- Ensure the nozzle tip is not less than 1/2 the nozzle diameter above the build platform. If plastic cannot exit the nozzle your extruder gear can slip on the filament and therefore not extrude plastic.
- Try higher flow rates for the first layer. Most slicers include an option for % flow. 120-150% typically helps adhesion dramatically.
- Slow the 1st layer print speed down to 30-40mm/s. Give the extruder extra time to push the larger volume of filament into the tight gap between the nozzle and build plate. Also, the higher your print speed, the cooler the filament is when it exits the nozzle (even though the thermistor reads otherwise). Keep the speeds low to ensure the filament is hot and can be extruded easily.
Best bed adhesion methods:
1. PET tape and clear aerosol enamel spray
This video below shows the bed adhesion method we’ve used for over a year (and our printers run almost non-stop). This works well for PLA and PETG, but leaves a light haze on the printed surface. Most often, the build plate temperature can be reduced after 20mm of part height to conserve power.
Our 1-10 rating of this method:
Ease of use: 7* / PETG Adhesion: 7 / PLA Adhesion: 10 / Cleanup: 9 / Cost: 6
*Initial application takes 30min plus drying time
The video below shows this method:
2. Bare PET Tape
Using just 3M8992 (PET film with silicone adhesive), PETG adheres well with a build plate at 90C-100C, and PLA works well with the plate at 55-65C. Apply like the video in 1. above, without the enamel spray. Tape will often last more than 10 prints.
Our 1-10 rating of this method:
Ease of use: 9* / PETG Adhesion: 8 / PLA Adhesion: 7 / Cleanup: 10 / Cost: 7
*Initial application takes 30min plus drying time
3. PEI plastic
PEI has recently become a preferred build platform because of it’s excellent adhesion to hot filament and little or no cleanup and chemicals are required. Build plate temperature is proportional to adhesion…but be careful; if the temp is set too high it may fuse permanently! PETG works well around 60-70C. 12″x12″x.125″ PEI with 3M468MP double-sided adhesive is available from several manufacturers on Amazon. It is a bit expensive, and anything larger than 12″x12″ is not easily available for consumers. We’ve also found PETG lifts the PEI from the tape for large PETG parts.
Our 1-10 rating of this method:
Ease of use: 7 / PETG Adhesion: 7* / PLA Adhesion: 9 / Cleanup: 8** / Cost: 4
*Would score better if adhesive would stick better to the PEI.
**Be warned, if the PEI sheet is damaged, or a part gets fused, removing the 468MP from the build platform takes hours.
4. Scotch (3M) Blue paint tape
This method is likely the most popular among the RepRap community, and is nice because the tape is often available from a local hardware store. This method is easy to use, and easy to cleanup with a paint scraper. Just apply the tape to the bed evenly and print!
Our 1-10 rating of this method:
Ease of use: 9 / PETG Adhesion: 5* / PLA Adhesion: 6* / Cleanup: 7** / Cost: 9
*Adhesion is not ideal for 2 reasons: Sometimes tape will never release from the print’s 1st layer, and the tape will be pulled from the plate by a large part fairly easily. Fortunately, it’s easy to replace. The tape also looses it’s adhesion at 95C and higher.
**Cleanup is rated worse here because the tape typically lasts 2-5 prints.