Headband [rinting issue

Tom R

(@tom-r-2)

Active Member

Headband [rinting issue

Hello:

Can anyone make a suggestion?

I am trying to print a headband but the two ear sections keep failing. The ear sections are being grabbed and pulled up by the extruder or the end sections do not print with any definitive shape. (I got one print to actually finish printing but the others failed about 15 to 30 mins in the print). See attached photo. The rest of the headband prints perfect.

PETG
70 speed (that speed is where I got 1 to print but the ear sections look terrible as the photo displays).
Speeds of 60 and 50 failed within 15 to 30 mins.
Auto support activated.

Any suggestions?

Thanks in advance.

Tom

Tom Rauscher

Posted : 27/03/2021 7:44 pm

bobstro

(@bobstro)

Illustrious Member

RE: Headband [rinting issue

I can't see your pic. Try dragging & dropping the image into the edit area or using the Add Media button above.

From your description, it sounds like narrow parts of the print are coming loose. This is usually due to poor adhesion. Here's an info dump on the subject:

Your underlying issue is bed adhesion. This is a common problem that can be caused or aggravated by two factors that need to work together well for successful prints. Filament should lay down cleanly on the PEI print surface and hold throughout the print. There are 2 main causes of bed adhesion issues: PEI cleanliness and Live-Z height adjustment. Even if you're dubious that these are the cause of your problems, they're 2 fundamental troubleshooting steps that you need to complete to rule out the basics:

A dirty PEI print surface. Even if you don't think this is the cause, it's always a good idea to make sure your PEI surface is clean before trying any other fixes. If it's a smooth PEI sheet, take it to the kitchen sink and give it a good dunk with Dawn (original formula, no vinegar or hand softener variants) dishwashing soap or your local equivalent (e.g. Fairy in UK). Use a clean paper towel to clean it off, and another to dry it. Avoid using any sponge or cloth that has been in contact with grease. Above all else, avoid touching the PEI print surface. Once it's good and clean, you should be able to use 91%+ isopropyl alcohol between prints, 100% acetone when that fails , and another dunk when acetone fails. Worst-case, use a 3M 7445 ScotchBrite (1200-1500 grit) pad or equivalent on smooth PEI to give it a very light buff, but only infrequently. If you've got a textured powder-coated PEI print surface, the official instructions are to use 91%+ isopropyl alcohol on it only. Rumors persist that some have had good luck getting started with these sheets by giving them a wipe with 100% acetone and a dunk with Dawn. Either way, there's no real warranty on these sheets. YMMV.
If you have not already done so, try using Jeff Jordan's "Life Adjust" procedure for calibrating your Live-Z setting. It is much easier to use and understand than the onboard routine and much easier to make mid-print adjustments accurately with. In general, start high (less negative) and work lower (more negative) in large increments (e.g. 0.1mm) until the filament starts to stick on its own. When you've got your Live-Z setting adjusted properly, you should be able to gently rub the extruded lines on the PEI surface without dislodging them. Then start lowering (more negative) the level until there are no gaps between layers. You should not be able to peel the lines apart after printing, but the top should be regular.

Remember that the effectiveness of a solvent such as isopropyl alcohol is going to depend on concentration and volume relative to the amount of grease you're trying to remove. 71% pads work... on very tiny amounts of grease. A squirt of 91% works better, but if there's a lot of grease, you need a lot more alcohol. This is why a wash under the sink with Dawn is so effective: There's a much larger volume of Dawn-and-water attaching to grease and rinsing stuff away instead of just moving the broken-down grease molecules around.

And above all else, avoid touching the PEI print surface.

Glue stick is NOT necessary for PLA on the PEI print surface. You paid the big bucks for a Prusa with a removable spring still sheet with PEI, so clean it up and take advantage of it. Save the glue stick for printing sticky stuff like PETG that might adhere too well. Even then, I only find I need glue stick when printing high-temp PETG at 260C+ temps.

Try those 2 steps. If you're uncertain of the Live-Z results, post pics here of the 75x75 print bottom and you'll get quick help. If you want more detail, I've consolidated my notes on Prusa PEI adhesion, bed cleaning, and Live-Z calibration.

If, after doing all this, you still find narrow or tall parts popping off, you might try using a brim, adding mouse ears to corners and thin parts, or applying some additional adhesion booster to your bed.

A bit of trivia - The reason higher concentrations of alcohol seem to be harder to find is that isopropyl alcohol is most effective against bacteria at roughly a 71% concentration. A bit of distilled water helps slow evaporation, making the alcohol more effective. If you're looking in pharmacies, that's why 91% and higher seem to be hard to find.

My notes and disclaimers on 3D printing

and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

Posted : 27/03/2021 7:56 pm

Tom R

(@tom-r-2)

Active Member

Topic starter answered:

Headband printing issue

@bobstro

Hello:

Thanks for all the info. I am up on most of it.

Tom

headband-failure-collage.jpg

Tom Rauscher

Posted : 27/03/2021 9:25 pm

Dan Rogers

(@dan-rogers)

Noble Member

RE: Headband [rinting issue

head band shapes can be difficult to print because of something called warping - it is due to long linear shapes that build up many layers in the same direction. The problem is linear shrinkage. It builds up layer after layer imparting a shrinking force at each horizontal layer. As the layers grow taller, the forces from each layer combine and have a vertical element, that results in the ends of your print part separating from the bed before them other parts. for a linear part (and curves don't change the rules) this means the ends typically start lifting up and separating from the bed mid-print - which causes all kinds of mischief.

Learn about - Brim. This is a 102 to 204 level learning element (out of 440 as top difficulty learning curve stuff) - so freshman year.

Learn about mouse ears (330 - 402)

Posted : 28/03/2021 2:54 am

Tom R

(@tom-r-2)

Active Member

Topic starter answered:

RE: Headband [rinting issue

@dan-rogers

Dan - thank you. Going back to school to learn. 🙂

Tom

Tom Rauscher

Posted : 28/03/2021 2:21 pm