How do I print solid & strong pieces?

[titanhusker]

I am using a Printrbot Simple Metal. I have printed many times with this printer, and for the most part all of the prints look great, (primarily using PLA+) I need to print a few pieces for my MIG Welder, specifically the clapper mechanism (Which means they need to be strong). I have tried to print with both PLA+ and ABS (which is recommended for this part). Each print looks great in appearance but, the parts are brittle and break easily. When I first got Simplify3D, I adjusted the extrusion multiplier to 1.05, (seems like I read somewhere to do that if the prints had gaps, may be wrong). I had it set to 1.05 using 1.75mm filament. I checked the filament with a mic, it measures out to be 1.70, so I adjusted the multiplier down to 0.93, and the width to 0.42, the prints look better, but they are still cracking. Speed is set to 50 and the temp is at 210C, since I was using PLA+ ; I didn't use the heated bed, but when I do, it is usually set to 45C and reduced down to 30C then to 0, changing about every 8 layers. I am using a 100% infill with fast honey comb, I even tried rectilinear.

Is there some sort of calculator or method of math to figure the specific figure it should be set to perfectly. In a nut shell; How do I produce strong & reliable prints for mechanical function. Any insight would be helpful.

[greybeard]

Strength depends on several factors. I print only engineering parts and find the best settings for me (and my prussa printers) are:

[*CORRECTION - what was I thinking...}

Temp = 230(PLA) & 250(ABS). Depends on brand and age... I use eSun PLA+
Infill = Rect & Rect…
*infill = 10% (with rect/rect, that means 20% infill total). Bump it up if not what you need...
Shells = 3 (unless for threaded boss, then I use 5 shells)
Layers = 3
Height = 0.2mm (sometimes 0.3... ) always depends on the part....

see image

[arhi]

when you print cold, especially PLA, it looks great but is easy to break, delaminate .... you need to up the temp (in my experience the "nice but not strong" is ~20C for PLA and ~30C for ABS below optimal temperature for strong prints)

[tonyno]

You will not get much strength in the Z-direction. Keep this in mind when designing/printing.

[zemlin]

I get pretty sturdy parts with ABS. The parts I build are fairly large so I print with a 0.6mm nozzle.

I print vase-mode calibration cubes (no top or bottom layers) to check layer bond strength and then extruder calibration. The speed reduction and cooling settings for short build times are disabled. No cooling fan. I build ABS on PEI with a 100C bed temp. Have the extrusion multiplier set to 1 when running these so you can find the correct extrusion multiplier. It will change depending on material, speed, temperature, and layer thickness. There is not one number you should use for everything.

I normally set the software for an extrusion width equal to the nozzle diameter.

I generally run a .25mm layer thickness.

Layer bond strength will depend on the material, speed, and temperature. ABS is a fairly brittle material, but if you need a rigid part it's a pretty good choice. You should be able to flex the side of a single layer calibration cube with a fair bit of stress before it cracks. If it splits real easily, you're not there. It might take a lot of little empty cubes to find the sweet spot. Once you get a cube with the layer bonding you want, measure the wall thickness with a micrometer. Compare this to the extrusion width you have set in the software. If you have the extrusion width set to .6mm in S3D and you measure a wall thickness of .6mm, then 1 is the correct answer. If you measure a thickness of .612mm, then an extrusion multiplier of .98 will reduce the amount of material extruded by 2% and the resulting wall will be .6mm. Using the same material, same speed, same temperature, but a layer thickness of .3mm vs .25mm gives me very different multipliers, so don't take this likely. It has a big impact on your part strength.

side note: PETG tends to build up on the printer nozzle if there's any over-extrusion, so I deduct 5% from the calculated multiplier. I also run no retraction vertical lift with PETG, as that causes a lot of stringing which builds up on the nozzle.

I print Hatchbox black ABS at 260C and 80mm/s I print with at least 3 perimeters, 40% hex infill and 4-6 top/bottom layers.
I just bought some eSun ABS. I've used it before, but haven't dialed it in using my latest methods. I'll find out how it compares. I don't like their ABS+ - it's softer than straight ABS. If I want a part that flexes, I print PETG.

Accel and and jerk settings will be very dependent on your printer, but I run a post-processing script to get faster printing of infill and support.

My start scrips includes:

M201 X1600 Y1600 E5000 ; acceleration
M205 X12 Z1.0 E5000 ; jerk
M204 T7200 ; travel accel

{REPLACE "; outer perimeter\n" "; outer perimeter\nM204 P900\nM205 X9\n"}
{REPLACE "; inner perimeter\n" "; inner perimeter\nM204 P1600\nM205 X12\n"}
{REPLACE "; solid layer\n" "; solid layer\nM204 P1600\nM205 X16\n"}
{REPLACE "; support\n" "; support\nM204 P7500\nM205 X60\n"}
{REPLACE "; infill\n" "; infill\nM204 P7500\nM205 X60\n"}

the lower accel and jerk settings on the perimeter and solid infill improve part appearance by reducing ringing and overshoot. I run 50% speed on outer perimeter and solid layers. The higher accel and jerk for support and infill keep the print speed up in all the little direction changes involved with those features. Cuts many hours off a large print, and doesn't impact final appearance, as those features are either inside the print or removed.

Raise3D N2, N2+, and Makergear M2, fwiw