Hmm... interesting.  Will it be strong enough?  Interesting question.  I've heard that while PETG is a bit stronger than PLA, it is less rigid.  It has more flex than PLA.   So the benefit, as I understand it, is it will give a little rather than breaking, but that may not be the feature you're looking for on this part.  If you print it with a thicker shell and a stronger infill (like 3D honeycomb?  I've heard that's one of the strongest infill patterns) you might get a better part from PLA than PETG.  I dunno.

But it certainly won't be as strong as making it from metal.  Nor will it be as much effort!

The biggest concern I'd have is the latching mechanism for the bucket.  Maybe make that from metal parts?

Don't you love advise from someone who know's less than you about your project? 

Kim

Great comments!


The petg may give a bit more than the pla, but the pla will snap if flexed too far. Prusa, maker of my printer, actually prints a lot of the printer parts from petg, as solids with no infill. This part is fairly thick. My experience with the  parts I printed for the subs is that petg is a lot more durable if thick enough to be rigid, though pla gives much better details.


The door, struts to the boom, and the moving latch parts would need to be metal. I'm  thinking the bucket itself would work as petg, and as you say would take a Lot less work than metal, just a couple minutes to set up the printer and hit Go!      worst case, it gets remade in steel.


Just for laughs, I  went to places like Shapeways to see what they would charge to print/cast the bucket in aluminum. Even scaled down by a third to fit thier casting limits, the cost was about $800.     Just having them print it in plastic would cost more than another roll of filament  for my printer!


 

Hmm... interesting.  Will it be strong enough?  Interesting question.  I've heard that while PETG is a bit stronger than PLA, it is less rigid.  It has more flex than PLA.   So the benefit, as I understand it, is it will give a little rather than breaking, but that may not be the feature you're looking for on this part.  If you print it with a thicker shell and a stronger infill (like 3D honeycomb?  I've heard that's one of the strongest infill patterns) you might get a better part from PLA than PETG.  I dunno.

But it certainly won't be as strong as making it from metal.  Nor will it be as much effort!

The biggest concern I'd have is the latching mechanism for the bucket.  Maybe make that from metal parts?

Don't you love advise from someone who know's less than you about your project? 

Kim

Had the printer going in the background today, and had it make a sample dipper bucket for the shovel. The little square stub I'm holding on to would be the end of the dipper stick - this print is to the same scale as the model, so it will give me a reference when making one out of metal later on, as well as a double-check now that the sizes look right with the model so far. Looks like a grinning muppet, sorta?! Or a big version of those RockEmSockem Robot toys from when I was a kid!    The door on the bottom is a separate piece, as are the struts holding the dipper stick on.  Looks like it should work out fine for the model.


Another angle:

Going to be interesting to make one of these in metal. I wonder - would printing it in solid PETG be strong enough? This was done in PLA, with only 5% infill, so its very light and not rigid enough, but PETG with 100% infill might work. The struts would have to be metal, and the dipper stick will be made from some 5/8" square steel bar that I have.  Hmmm... Can't hurt to try, could always make it from metal if the plastic doesnt work out. This prototyoe doesn't have the mechanism on the door for the tripper bar, might be good to make at least the door from metal so it has enough weight to swing back shut when the bucket is lowered down - they are a gravity closed door, which is why the hinge is so far up the back wall. Maybe I'll add some horizontal ribs across the back wall between the vertical ones too.

Cool, thanks!

This is an interesting process, is there a reason that you didn't use a sodium silicate bonded core?

Dave