Jump to content
Oliveros

Best way to reinforce PETG for snap on type application

Recommended Posts

Posted · Best way to reinforce PETG for snap on type application

I have an application where I'm trying to get a PETG object to snap onto rails, I've printed one so far and it just snapped the piece being snapped in. 

 

What do you guys recommend for making something like that stronger? I made it 2MM thicker but I'm thinking it might not be enough. It was with 20% infill and just 2 walls.

Share this post


Link to post
Share on other sites
Posted · Best way to reinforce PETG for snap on type application

You may need to print it in a different orientation so the weakness of layer adhesion isn't causing the problem. Check out This Thread.

Also you might want to show us the model.

Share this post


Link to post
Share on other sites
Posted · Best way to reinforce PETG for snap on type application

I guess the snap-areas are the two "keyhole" openings?

 

First I would make the splits a bit wider, so the clamps would deform less while snapping over the rails. That should still give enough retention.

 

Depending on the load it has to see, I would also use a higher infill, maybe 50...70% or so? And the layer-lines should definitely go in such a way that they cause no weaknesses. Just like when you cut wood along the grain. You also need to print hot enough, and slow, to get a good layer-bonding and no underextrusion.

 

Personally, I have no problems with PET snap-fits, like these chains. In PLA they crack after some time, due to the PLA being too brittle and stiff. But PET is flexible enough.

 

The cream ones are PLA, and they begin to crack and deform after repeated use. The green one is PET: no cracks, no deformation.

DSCN6055.thumb.JPG.c9f2aa4f551f913408727e004905b944.JPG

 

For reference: text caps-height is 3.5mm (=hollow watermark in the model). I printed these solid 100% infill, at 215°C, and slow at 25mm/s, 0.1mm layers.

karabijnhaak7b2.jpg.5af2e3a94d542181304efcc4670463d7.jpg

 

Share this post


Link to post
Share on other sites
Posted · Best way to reinforce PETG for snap on type application

Yes, you are correct on the snap opening.

 

I thought about making the keyholes larger but I fear that if I do that, it will unsnap from the rails too easily. Perhaps I can try it and see how it works.

 

Good to see that PETG can survive it better than PLA, this application won't be repetitive snapping and unsnapping, just snap on once and ideally stay there for a long time.

Share this post


Link to post
Share on other sites
Posted · Best way to reinforce PETG for snap on type application

Hey Oliveros

You could try something like this.

Make the walls 2 line widths thick.

Shaft_Clip.png.f28dde1c06f9655a9be9416d1eeecca8.png

Shaft_Clip.obj

Share this post


Link to post
Share on other sites
Posted · Best way to reinforce PETG for snap on type application

Hey Owen,

 

That;s not a bad idea, I could give that a shot.

 

I tried making the wall thickness 7 MM, 2MM, 1MM and 0.5MM and the one that seemed the most promising in terms of snapping on was the 2MM thick one.

 

I'm going to keep experimenting today so any advice is helpful and than k you so far.

Share this post


Link to post
Share on other sites
Posted · Best way to reinforce PETG for snap on type application

Owen,

 

Your idea was great, it lead me onto the right path, after making one of those shapes, I decided to print it standing up to avoid having to brace the sections and it turns out PETG is WAY more flexible when printed across and not lengthwise, like day and night difference. 

 

So I tried 3 or 4 different versions of your idea and they are almost too flexible to work, I don't know if they'll stay on the rail but I'm still experimenting.

Share this post


Link to post
Share on other sites
Posted · Best way to reinforce PETG for snap on type application

Great work Oliveros. Thanks for the updates.

Share this post


Link to post
Share on other sites
Posted · Best way to reinforce PETG for snap on type application

Thank you. 

 

Got any advice for making PETG stick to the bed? It's driving me nuts when it gets partway through the print and then starts sliding around.

 

On a seperate note, your idea may just be the key, I tried printing a partial object with the full solid piece like it was on the original and it couldn't quite flex far enough without snapping, so now I'm printing one with your idea. 

 

One of which just came off the bed so now it's round 2.

Share this post


Link to post
Share on other sites
Posted · Best way to reinforce PETG for snap on type application

I haven't printed with PETG but I think it's similar to NEXT GEN. I use UHU glue and a Brim and make spharp corners on the base base round where possible.

Share this post


Link to post
Share on other sites
Posted · Best way to reinforce PETG for snap on type application

I print PET on clean bare glass. Sometimes I use the "salt method", however this does not increase bonding for PET (contrary to for PLA), but rather reduces it slightly, but it makes it a lot easier to remove parts. To prevent warping, I use no cooling fans, or the absolute minimum. But no fans makes it more difficult to bridge gaps, so this is not suitable for every design. Most of my designs are long flat models without bridges.

 

I tried dilluted white wood glue too a couple of times (ca. 10% glue in water), but this bonded way too strong: it tended to chip the glass while cooling, even before I started pulling the model off. So if you need a strong bond, this should work.  :-)

 

But the bed has to be hot enough: 60 or 70°C won't do for me. I need to set it to ca. 80...85°C.

 

The photo below is what the bottom of my PET parts looks like: no corners lifting, and no problems making tiny holes. These are small models (see ruler behing in mm and cm), but it looks the same for my bigger models. Printed with the salt method to facilitate removal: you can see the tiny pits caused by the salt (looks like corrosion pits).

DSCN6083.thumb.JPG.6fa2f0776aca10a340718c2065decdbf.JPG

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...

Important Information

Welcome to the Ultimaker Community of 3D printing experts. Visit the following links to read more about our Terms of Use or our Privacy Policy. Thank you!