What to use for the most strength for PLA?

[Gamble]

I made a small wrench about 5" long, double ended. I tested it and it works great, what settings should I use for optimal strength?
I know it's not going to be a complete replacement for metal one, but it's for under 30ft pounds of torque for those that don't want to ruin the bolt heads.

[awerby]

Print it lying down flat, parallel to the bed of the printer. That way, the laminations, which are the weakest part of a FDM-type print, aren't running across the parts of the wrench which need the most strength.

Andrew Werby
www.computersculpture.com

[3dkarma]

Inter-lamination strength also depends on extrusion width and layer height in relation to nozzle size. Strength can be dependent on the amount of contact each individual strand has to the layers above and the strands to each side. The more contact, the stronger the bond. When you look at your printing settings, the closer your layer height is to your nozzle diameter, the weaker the print will be. General recommendation is that the layer height should be less than 80% of nozzle diameter, and extrusion width should be greater than nozzle diameter.

The next thing to look at is printing temperature. Printing at lower temperatures is often recommended to get better quality but can make layer adhesion poorer. Take a look at this video: https://www.youtube.com/watch?v=FSOPsRiiOZk - it's specifically for calibrating your printer temperature, but you can use the same method to test for the strength of your printer settings. Set up your printer, run through the procedure in the video, then tweak layer height / extrusion width (if you're not happy with the strength of your print) and try again. You should hit upon the best combination of layer height, extrusion width and printing temperature for your printer and plastic combination.

[curious aardvark]

another thing to look at are the number of shells.

For really strong parts I'll use 5 shells - these are solid plastic enclosing the infill.
If you work on a shell being the same width as the extrusion. 5 shells in and out will give you a solid 2mm plastic shell on the outside and inside of a model. And combines with a strong infill will produce an extremely strong part.

The other thing you can look at is the filament itself.
polymakr's polymax pla is a lot stronger and tougher than standard abs or pla.
Also - if you can make it work nylon parts are very strong and there are some new hybrid filaments that taulman claim are even stronger and actually printer friendly.

[ralphzoontjens]

I find layer adhesion to be the single most important factor in determining the strength of a part. One weak layer often causes the parts I print to tear.
The only way to really get decent strength is by printing at a very high resolution, say 0.1mm layer height, which often renders it impractical to print because it takes more than one workday to complete a print. Also reinforced filaments only add a marginal amount of strength, since we're working with very small fibers.

For infusing filament with carbon nanotubes one would have to be a millionaire, and resin coating takes too long.

The Mcore 3D printers run a nozzle with glue between each layer of paper it prints to create very strong bonds. This has already been done for decades with LOM 3D printers.

It should be possible to also with filament extrusion develop a special adhesive to improve layer strength, which runs after each layer has been printed. I imagine a simple rollerball with refillable liquid container can do the job. Does anyone know if this is already in development?