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Unread 25-11-2013, 19:15
Oblarg Oblarg is offline
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Re: Practical 3D printed parts

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Originally Posted by ToddF View Post
Thus far, we haven't broken any plastic parts. The bearing blocks were an experiment to see if semi structural parts could hold up if made beefy. These have lasted through two off-season competitions and at least half a dozen demos.
What material do you use?
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Unread 25-11-2013, 21:33
MrRiedemanJACC MrRiedemanJACC is offline
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Re: Practical 3D printed parts

Here's a project my senior students worked on. I don't have access to the printed part (at school right now and I'm home), but the second one fit extremely well to a VEX Versa hub. The original intent was for our 6 WD test bot and the driven wheels would used this design. Last year's bot used an 8" drive wheel and 6" driven wheels, but we used chain drive. This year we want to use belt drive and we couldn't find the tooth ratio we wanted so we started to draw this in Inventor. The tooth profile wasn't too hard to get, but the hard part was getting the right diameter for the circular pattern of the tooth to work out in Inventor and in real life. So, this one is 39 tooth to match the Andymark double pulley, so if we use this design, wheel sizes will be common. But I'd like to cheat the driven ones to be smaller to increase the wheelbase of the bot. Therefore we redraw it with the right tooth ratio and off we go. The problem will be getting a smaller tooth profile to fit with the part. If we keep the 39 tooth drive with a 6" wheel, we need a 26 tooth driven for a 4" wheel. Not sure how that 26 tooth will match up with the Vex Versa Hub Pattern. But in the classroom that becomes an absolutely great design exercise to go through!

BTW, Project Geometry is your very good friend in Inventor. Just make sure you have the parts in an assembly, constrained correctly, and then you can modify the part you are working on to match very, very well with the mating part.
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Unread 25-11-2013, 23:13
yash101 yash101 is offline
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Re: Practical 3D printed parts

ABS is a very nice plastic and is very strong. After 3D printing technology improves enough, it will be feasible to start producing things like pulleys and other highly used parts. Pulleys should already be an easy one to 3D print as long as you use an aluminum or steel axle because the load is distributed throughout, reducing the stress on the plastic!

I have gotten many things printed in ABS. They are very strong, and lightweight and take compression forces quite well, as long as there is no sheer or bending force on it. My Stirling Engine crankshaft broke because of the high sheer force I accidentally placed on piece, when removing the building material. I should have used an abrasive instead, to get rid of the black building material.

Our school has either 2 or 3 of those Dimension 1200ES printers! Out of that, we use only one!
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Unread 25-11-2013, 23:32
Bald & Bearded Bald & Bearded is offline
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Re: Practical 3D printed parts

Lots of good examples out there. I am impressed with everything Triple Helix has done with the parts.

Last year we had only started getting into printing. On the robot we printed a couple of things. One was some bushing which fit inside the outer tube of our lift and let the inner tube slide up easily. We also, printer out our gyro holder and some thin flexible fingers for our shooter to help keep the frisbees aligned.

Oh, and we printed out a bunch a little key chain wrenches to hand out.

This year we are looking for opportunities. I can certainly see some manipulator parts depending on the game this year.

For FTC we have a couple of teams already doing some things. One team CAD'd and printed flippers to pull the blocks into their bot. We also had some of the old clip style samanthas so one of the kids found a CAD of the back and we added some bolt down tabs. (Pic attached)

We also started experimenting with plastic parts with hole textrix hole patterns. Specifically to get different heights through different thicknesses (pic attached).

As another poster commented layer separation can be a problem. For other projects at home (like the robot hand I posted earlier on another thread) I have used acetone painting and acetone vapor baths (safety is a huge consideration). Other than that though ABS is very strong. Even with 20% honeycomb in-fill and 3 shells the parts I have printed are very strong. Just look at how well the 3d printed extruder gears on RepRaps hold up. The one on my Prusa I2 has thousands of hours on it.

The other issue mentioned is print time. I have had parts take 6-8 hours to print (parts of the robot forearm) and an hour or so is not un-heard of and you will have failed prints usually after half the print. If you have other CAM capabilities (CNC mill, laser cutter, etc.) they can be much more efficient. And yes the commercial printers generally can be run faster than the RepRaps we use but for complex prints.

The other big limitation is build area. The printers we use have an effective build area of 180mm x 180mm x 170 mm. So you may need to cad bigger things as separate parts that can be joined. ABS glues very well with Acetone and bolts are easy.

I really look forward to seeing what neat ideas teams come up with. I hope to see more threads like this one. Maybe, we should look at tagging FRC and FTC parts when posted on Thingiverse or having a standard thread hear on CD so folks can always see what is new.
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Unread 01-12-2013, 08:20
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Re: Practical 3D printed parts

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Originally Posted by Oblarg View Post
What material do you use?
Standard ABS filament for a Makerbot 3D printer.
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