# 3D Printing > General 3D Printing Discussion >  crazy story [printed a hook to hand bikes]

## threedee4me

crazy story printed a hook to hang bikes on the garage wall.  i have a flashforge finder.  printed the hooks great, screwed them into a beam and hung 2 bikes.  a couple of days later i find the bikes on the floor i was like what the...  one of the hooks cracked off.  lucky it only nicked my car.   Bottom-line a few questions arise: 

[1] i think there is a way to print the hook with more density and will that help? if so how?  

[2] can i start to print the hook then pause and lay a piece of metal down then continue printing over the metal?  

[3] other options?

[4] would the heat level in garage weaken the pla material?


thanks

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## printbus

IMO, hanging a bike was probably gutsy... I wouldn't want to trust the strength of the layer laminations.  How much weight were you putting on each hook?

You might show a picture of the hook that shows how it failed.  The picture should also help us understand how the part was oriented when it was printed.  Provide more information like what you are used for a slicer and the settings you used to prepare the print.  Settings like temperature, perimeter info, infill type and infill percentage are examples of what people are going to be looking for.

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## Talon 3D

You might want to try PeTG or something like that which is very tough. There is some even enhanced ABS. The bikes were quite heavy.
PLA is definitely not going to hold them up well.

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## threedee4me

LOL...  i embarrassed myself so i didnt take too many pics of them mess.   see attached pic of the broken hook.  

Downloaded it from Thingiverse
Slicer: Flashprint
PLA
no supports or raft
standard setting

layer
-----
layer height 0.18MM
First Layer Hieght 0.27 MM

shells 
------
primeter shell 2
top solid layer 3
bottom solid layer 3

infill
------
fill density 15%
fill pattern HEX
combine infill every 2 inner layers

temp 220

thanks!!

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## Talon 3D

The PLA was not strong enough especially if it got hot in there. You can see where it pulled apart.
Use ABS or PeTG for stronger hooks.

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## threedee4me

thanks.  i think my printer only takes PLA...  so I need a new printer.    can i print over metal?

my idea would be this print in PLA then at a certain point pause print layer a piece of metal down cut to fit over the partial print then resume? waste of time??

thanks

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## printbus

Yeah, I think you'd be wasting your time trying to add metal to the print.   Could actually be weaker in some ways since the printed material won't bond very well to the metal.  This is the point where you go to the hardware store and buy what they have instead. It'll be money well spent and you won't keep checking to see if the bikes have fallen yet.   :Smile:  

That said, here are my comments, beyond what Talon suggested.  For starters, I think it's a weak design for what you're wanting it to do.  I couldn't quickly find an example of what I'd suggest, but I think the wall facing part of the hook should have extended down a ways below the bottom of the curve, with something like a reverse arch carrying load from the bottom of the curve into the wall.  This is NOT what I mean, but at least this item on thingiverse seems beefier than the one you printed: http://www.thingiverse.com/thing:1014663

Your hex infill has the most strength 90 degrees from how you need it, which is not easy to fix with the print orientation you're pretty much stuck with.  A simple criss-cross infill like rectilinear would possibly be a better choice.  I would have went with 80% or so infill, shooting for a print that was almost solid.  And I'd have likely went with double the perimeters and top/bottom solid layers from what you have.

EDIT: But I still don't know that I would have trusted it.

EDIT #2: This isn't a wall mount hook, but the shape of the curved part reflects what I was trying to describe.  Note the reinforcement under the hook. http://www.thingiverse.com/thing:1195175

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## threedee4me

Thanks for all your input and thoughts.  http://www.thingiverse.com/thing:1014663  this is the hook i printed.  

I think your right a trip to home-depot for the hook i need is much easier  :Wink:    its just more fun to try to print it  :Wink:

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## curious aardvark

Hmm, there is no reason at all not to use that hook. 
Pla should have been strong enough. 

For strong parts, though,  you need a lot more shells and layers - also more infill. 

basically you have bugger all skin and sod all infill in that model. 

Print that with 6 shells and layers at 0.3mm layer height and 50% infill and it shouldn't have any problem at all holding a bike.

The print orientation is correct. It needs to be lying flat.
Speedwise - print at about 50mms. 
The temperature is a little high, I suually go to about 215 max for pla. 
You also want your infill combined every layer - ie: it needs to form a solid internal matrix.

You could invest in some stronger pla for this kind of model. polymaker, polyplus and polymax are probably your best bet: http://www.polymaker.com/shop/polymax/
You should be able to print with pet-g on blue tape or pva. 
Obviously a heated print bed is best - only things I print on a cold bed are flexible filaments on pva. 
But as you don't have that option - you can play with different filaments.
Would be worth getting a sample of pet-g and testing: http://www.globalfsdusa.com/?target=main
trying samples is a great way to work out just what you can and can't print.
It will print on a cold bed, thibk they recommedn blue tape - but I'd try pva (gluestick) as well

One thing you absolutely cannot use is abs - that not only requires a very hot build plate, but a lack of smell and an enclosed printer as well :-) 

You could print that hook in polyflex of ninjatek semiflex - both are super strong and pretty stiff if printed as a largish model. 
I'd expect to be able to hang off a polyflex hook and I'm around 90kg. 
It would probably bend but never break - polyflef is virtually unbreakable. Short of using powertools I'd defy anyone to break a decent polyflex print with their bare hands.  

But as far as your failed hook goes - you just printed it incorrectly. Needed lots of shells and layers and at least 50% infill. Triangular pattern I find best,  if you've got the option.

Pla is a very strong material - as long as you use it correctly.

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## threedee4me

> Hmm, there is no reason at all not to use that hook. 
> Pla should have been strong enough. 
> 
> For strong parts, though,  you need a lot more shells and layers - also more infill. 
> 
> basically you have bugger all skin and sod all infill in that model. 
> 
> Print that with 6 shells and layers at 0.3mm layer height and 50% infill and it shouldn't have any problem at all holding a bike.
> 
> ...



Thanks for all the information and direction its very much  appreciated.  like mentioned above i might just go buy a hook.  however  if i do feel brave from the picture attached what settings do I use?  do  i make all the layers 6?  Also not sure how to set the layer to "0.3mm layer height" .   Layer height set to 0.3mm and what do i set first layer height too?

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## curious aardvark

yep change all three to 6 - that will give you perimeters made of 2.4 mm of solid plastic and top and bottoms of 1.8mm. 
so perimeters and top and bottom layers. 
resolution needs to be 'low (faster)'
Combine infill should be every layer - if it will let you. 
Otherwise it offsets every other layer - which looks pretty, but is nowhere near as strong. 

Have to download a copy of that software and have a play with it. 

I've just bought an electroplating with copper kit to make some of my prints super strong.  But I've used pla for some pretty tough items.

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## threedee4me

thanks again for your help!  much appreciated!

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## awerby

Get a piece of steel. Drill a couple of holes in it, and bend it into a hook shape. Install it in your garage and hang your bike on it - end of story. 

Or keep experimenting with home-printed plastic hooks, but don't count on missing your car each time...

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## curious aardvark

you've got no sense of fun :-)

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## threedee4me

> Get a piece of steel. Drill a couple of holes in it,  and bend it into a hook shape. Install it in your garage and hang your  bike on it - end of story. 
> 
> Or keep experimenting with home-printed plastic hooks, but don't count on missing your car each time...


 :Big Grin:  :Big Grin:   lol actually cry out loud.  my poor car!  








> you've got no sense of fun :-)


why print one when you can print two.  this thing is solid now...  THANKS!

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## printbus

Well, let us know how they hold up! 

Is that the same hook as the one you referenced?

For the record, what settings did you go with?

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## threedee4me

They are holding up great so far, yup same hooks.  I followed curious aardvark reco.  All layers 6 and a triangle pattern, plus 50% infill.  Solid as a rock.  actually as 2 rocks since i doubled up on the hooks just to be safe.  




> Hmm, there is no reason at all not to use that hook. 
> Pla should have been strong enough. 
> 
> For strong parts, though,  you need a lot more shells and layers - also more infill. 
> 
> basically you have bugger all skin and sod all infill in that model. 
> 
> Print that with 6 shells and layers at 0.3mm layer height and 50% infill  and it shouldn't have any problem at all holding a bike.
> 
> ...

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