Typically 3D printing with the DMS plastic is around 10¢/gram, if you buy your own plastic it is closer to 5¢/gram.

The hard part is drawing a 3D model. That and the 8"X8"X8" limitation.

You draw it, I'll print it.

 

What's the density of the finished plastic? I can estimate the volume I need. If I can come up with something in the $5 range, it could be a go.

I'm a 2D guy. What software is preferred for feeding the printer?

 

There is a free program out there called SketchUp, it has some good video tutorials on the site. Feed me a iso drawing and I'll see what I can do.

 

Thanks Bill. It'll take me a while but I'll be back.

 

Here's a prototype using the spider hub recommended by killivolt in #4. The tubing is a little too flexible and makes it a tad wobbly at this size of orb, but I love the hubs. If I had one for 5/8" OD PEX tubing, I'd be done.

 

Here's a prototype using the spider hub recommended by killivolt in #4.

No silly.. thats an octopus hub.. not spider..

 

Here's a prototype using the spider hub recommended by killivolt in #4. The tubing is a little too flexible and makes it a tad wobbly at this size of orb, but I love the hubs. If I had one for 5/8" OD PEX tubing, I'd be done.

View attachment 81040 View attachment 81039

The (O.D. of 3/8" pex is .500) and the (I.D of 5/8" is .574) with a difference of ruffly (.050) that should leave (.025) in the circumference that you maybe can fit the 5/8" tube over the 3/8" ?

Never tried it before.


kv

 

You draw it, I'll print it.

Well it's been a struggle but I have a pretty nice 3D model drawn up. I think it's ready to print but that could be my naiveté. I'm ready for professional help.

[update] The SketchUp model is drawn so that 1.0m in the drawing scales to 1.0 inches in the final piece. It should be 4.17" square, 0.9" thick, and ~5 cubic inches in volume.

 

I can supply the STL file if that helps. I don't care about the color of the finished object.

Would it be prudent to test print just 1/8th of the model - one of the "arms" - to verify that PEX tubing fits into the hole? I'd hate to make an expensive paper weight, although that seems to be the main use for 3D printers.

 

I can supply the STL file if that helps. I don't care about the color of the finished object.

Would it be prudent to test print just 1/8th of the model - one of the "arms" - to verify that PEX tubing fits into the hole? I'd hate to make an expensive paper weight, although that seems to be the main use for 3D printers.

Since these objects can be printed at 25% fill rate (e.g. honeycomb fill), the density of most of my prints is not high enough for paperweights. You are right though, mostly show-and-tell pieces that end up in the fire wood pile (for outdoor burning).

Buy the way, since you are 3D printing them, you might want to ask the octopus designer if they want all PEX pipe in the same plane exiting the core. It would look a little more 'organic' if it had some variation to it. Granted, it still has to be 3D printable - printed in layers without un-supported bits levitating until they can be joined by another layer.

 

...you might want to ask the octopus designer if they want all PEX pipe in the same plane exiting the core. It would look a little more 'organic' if it had some variation to it.

Well, I'm the designer, so I can speak for ... me.

I'm not sure I follow your comments. My goal is something like the hub in #25, so that two can be used to make an orb. I have considered tilting the arms just a hair towards the central axis, towards the center of the sphere, to give a more rounded look, but I think that's an unnecessary trifle compared to the flexing of the PEX.

 

Since these objects can be printed at 25% fill rate (e.g. honeycomb fill)...

I had no idea. That doesn't seem to be an option at the online print shops but maybe I missed it.

Cost is definitely a factor in this project, so using less plastic is an option to consider. I need enough strength to hold together and remain firm agains the tension of the flexed PEX. I have no feel for what printed material I require to do that.

 

Well, I'm the designer, so I can speak for ... me.

I'm not sure I follow your comments. My goal is something like the hub in #25, so that two can be used to make an orb. I have considered tilting the arms just a hair towards the central axis, towards the center of the sphere, to give a more rounded look, but I think that's an unnecessary trifle compared to the flexing of the PEX.

I am getting projects confused... a bit. In your first post, you said you were doing this for a friend. I assumed it was an octopus project. Now I remember the octopus was for my wife's friend (her daughter is an octopus in a school play and needed a costume. Another story associated with 8 ). Anyhow, you said "All in the same plane" and you have what you need.

As per the fill rate, the .stl file must get processed by a .."slicer" program to dictate how each layer will be drawn. There you can specify fill rate and number of solid fill perimeter layers for each exterior surfacE.

CHEERS

 

Wayne,
What size PEX again.. (whats the OD).. I think 5/8's is 3/4" OD
And how many do you need?

 

The PEX is 5/8" OD with an ID just under 1/2". The 5/8" OD is the controlled dimension, they let the ID vary more than the OD.

The "quality check" I would perform on the prototype hub is to verify that the PEX tubing goes into the arms and that the part seems solid enough to hold an orb together. I could rely on someone else's eyes to assess both issues as long as they have actual PEX tubing to test with.

I might need as many as 6 or so of these - three pairs with one pair for each orb - but that's a rough guess. If you need a better answer I can press my friend. The answer may depend partly on the cost per unit.

 

The PEX is 5/8" OD with an ID just under 1/2". The 5/8" OD is the controlled dimension, they let the ID vary more than the OD.

The "quality check" I would perform on the prototype hub is to verify that the PEX tubing goes into the arms and that the part seems solid enough to hold an orb together. I could rely on someone else's eyes to assess both issues as long as they have actual PEX tubing to test with.

I might need as many as 6 or so of these - three pairs with one pair for each orb - but that's a rough guess. If you need a better answer I can press my friend. The answer may depend partly on the cost per unit.

You could also make the 5/8" inlet larger and add a nut-cage to your design. Slide a nut for a #8 screw into the cage and tighten the screw through the nut (held from turning by the cage) and the screw goes into the PEX to either wedge it into place (if you leave a rib on the far side of the screw for the PEX to deform against) or you could drill a hole into the PEX to accept the screw. In this case, the tightest tolerance you need is to prevent the nut from turning in the cage. My son designs the cages into everything he makes because they are so easy to make in 3-D printing. The only work is the design and he claims that is easier than holding a wrench on the nut when he assembles something.

 

That's a great idea, leaving a hole for a screw and building in the nut cage. I've been planning to use mere friction or an adhesive if needed. This thing shouldn't have to move much except for extreme wind. Friction alone seems pretty good so far for the wooden prototype and the black plastic one. But if I get more time to tinker with the drawing, I'll definitely consider adding those refinements, just in case.

For anyone following, there is a useful PEX fitting example in the SketchUp archive. It's called "SharkBite-1-2-x-1-2-FNPT.skp" I just looked again and notice that they use a diameter of 0.63" to receive the PEX tubing, which is 0.005" larger than my drawing. I suppose they sized it for the largest possible diameter rather than the average. Hmmm....

 

Wayne,
What size PEX again.. (whats the OD).. I think 5/8's is 3/4" OD

I'm sorry, what I've been calling 5/8" is actually know as 1/2" PEX. It's actual OD is 5/8". The industry's nominal 5/8" is indeed 3/4" OD, but that is not what I'm using.

 

Cute... is this one of the two cats shown in your avatar?

 

Haha, good catch. Yes, that is Pork Chop, aka Porky, on the left. His 'sister' FuzzMo is on the right. They're sitting on top my little Seadoo boat in the garage. They seem to think it's a special cat hammock just for them.