Experiment with filling PLA object with hot glue as it prints.
I'm doing my first test with hot glue. I don't know anything about gcode, so i looked up how to pause and just found the line in the code between layers and added:
@pause
G28
In retrospect, I think i have the order reversed here. oops
I found that if I restarted the printer from the home position that it would SLOWLY creep down to the print bed. I need to add a command to return it to the approximate print level.
ANYWAY...
My test was badly planned. and the pictures were a last minute decision, so they were planned on the fly. also, I didn't add supports because i figured it would support the top of the structure and I didn't want that.
Is there a way to add supports for small nooks and crannies but not for the overhanging surfaces? In my pictures you can see how my curved ceiling needed more support and I had to pause more often so it wouldn't collapse
Another reason I paused so much was because I didn't trust that it would pause on it's own. I THINK it paused for the first pause command but that may have been a pending command from me sending it twice. as I write I'm waiting for the second pause...
I took pictures every time I added a layer of glue:
In case you're wondering, The print is a collectible card plywood box end. I need about 40 of them and quality isn't so important. I've even saved some of the failed prints for smaller boxes. so I use it to test out new techniques - I highly recommend finding a model like this that fits your own needs.
first layer of glue
[img]
http://i.imgur.com/13SdJ1G.jpg[/img]
first layer of glue
[img]
http://i.imgur.com/9oXyFGC.jpg[/img]
Second layer
[img]
http://i.imgur.com/KOeXTZC.jpg[/img]
second layer
[img]
http://i.imgur.com/TZMsqCD.jpg[/img]
third layer empty
[img]
http://i.imgur.com/mllf5IU.jpg[/img]
third layer filled
The last hot glue i used was circa 1995, and that stuff was probably 10 years old. I was surprised to see how fluid hot glue is. It doesn't flow into all the small spaces, but it will slowly ooze into smaller spaces you can't reach. Also the top settles down to almost flat after awhile. the old stuff would solidify almost as soon as it left the gun!
[img]
http://i.imgur.com/kSlD0WQ.jpg[/img]
So, now I'm waiting to see if it will pause before it starts printing the roof. and nothing to do but sit here, so I thought I'd summarize my thoughts:
PROS
decreases print time enough that you could do a couple extra prints on the weekend when your technique is dialed in.
I hope it makes a more durable object than the filling at 30% that I've been doing
the glue is fluid enough to fill some smaller gaps
If you overfill a little the hot end passes through the bumps like butter - it doesn't seem to have affected the print
CONS
i started at 6PM it is now at layer 105/123 at 10:40; Print time is not drastically reduced.
if it pauses and you're not there, it will drastically increase print time. kinda useless for work days unless you have a REALLY hollow print
The hot glue I have is: $5 for 48 2" sticks (It's about the volume of a large grape fruit) at this price it may be worth strengthening smaller objects, but not filling in large art pieces
The hot glue gun DOES melt PLA. not so much that it ruined the print, but I'm glad I only had to get near the inside edges
adding @pause to the gcode didn't work. anyone have tips on this?
After the 3rd layer I think I nudged the build plate a little. You can't really tell in the pictures but it's off by a fraction of a mm.
[img]
http://i.imgur.com/DUYfdqk.jpg[/img]
and the final product - I think I could have added a mm or so more glue, but it seemed to print the roof fine with no sagging. It is taking a while to cool. When I match it up to another version it seems slightly bigger by ~0.2mm. I was cleaning my garage as I printed and can't find my calipers right now.
[img]
http://i.imgur.com/tu5U6gA.jpg[/img]
OK, lets wait a couple years and see if it held up!
Not really, but everything is relative. You can get glue sticks in bulk for really cheap, check amazon. I think they chose glue sticks because of compatibility. Most are just some formula of a thermoplastic. Which could work to your advantage if the property of the glue stick enhances whatever characteristic you're looking for in the finished part.I don't know the cost of hot glue, but it seems like this is an expensive alternative.I would assume for convenience. Probably just as easy to plan an "injection" port in your CAD. I think we've just scratched the surface of what's possible "in process" with our printers. I would be interested to hear if anyone has done some pausing to insert something or whatever? I've thought about it, but haven't actually tried it yet.I don't understand why the article says to drill holes in a completed print... why not just pause the printer and apply it up to the current layer. this seems sufficient as long as the object doesn't need to be perfectly balanced.
It's this kink of experimenting that will move us forward in our endeavors 
