ABS printing with a gcode pause for nut insertion

[cbrayton 0]

I have been experimenting with printing an ABS part with a pause in the gcode to insert a stainless steel nut.  I have successfully printed numerous ABS parts with my Ender 3 Pro using a glass plate and an enclosure.  Printing ABS in general is not the issue.  Normally I run the hot end at 255C and the bed at 115C, with the Print Cooling disabled.  

With the experimental component, I pause at a height above the bed of approximately 7.5 mm.  At the pause point the bed and extruder temps remain as set while parked, and usually the interior of the enclosure is around 45C.  Although I have tried to estimate at what time the pause occurs, if I miss it by more than few minutes, after the insertion of the nut and the release of the pause the next layer does not adhere.

First question:  is there a way to view the time in Cura at a particular layer?

Second Question: what's the fix for missing the "pause window" by a few minutes?  Hit it with a heat gun prior to resuming the print?  Lightly brush the interface surface with acetone?  

[geert_2 557]

What about staying around and keeping and eye/ear on the printer? Or via a webcam? Me being a simple man, I myself would go for simple solutions...

 

Alternatively, if the design allows it, and depending on the load-direction, you could go for other methods of inserting the nut, for example via side-openings, or by melting-in threads or nuts with a soldering iron.

 

I have successfully used these methods (the cone-shaped opening is only for inwards-directed loads obviously):

 

 

 

 

 

[cbrayton 0]

Thanks for your input geert_2, I'm with you on the "keep it simple" method, but that wasn't the point of the experiment.  The point was, could I imbed a nut.  And sure, the first shot at trying this I used your exact method:  I just stuck around until it was time.  The second time I printed the part, I was doing (once again) more than one thing at a time, and missed the window, I think by only a few minutes.  That's when I discovered the flaw in that method.  So now what I do, is use a post-processing gcode routine that displays the current layer being printed on the controller LCD.  That works pretty well for estimating when I should be there.  

But here's the more general case I was working towards:  what if you have a model that might need to run overnight or simply over many hours and you need to insert a nut or some other part into the assembly at different layers.  I was hoping that someone had come up with a more elegant solution that allowed a more precise estimate of the times that certain layers started and finished, or some great method for prepping the already printed ABS material for the next layer if you insert gcode pauses at the layers requiring the insertion of a part.

[geert_2 557]

Yes, I understood that. But your question has come up here regularly, and I have never seen a good solution yet, except for staying around the printer. That doesn't mean there isn't one, just that I haven't seen it.  :-)

 

I am afraid that you have to go to post-processing methods: inserting the nuts or special threaded inserts after printing. Or maybe print it in two parts, insert the nut, and glue them together? Preferably with a sort of dovetail mechanism or similar, to get mechanical retention in addition to the glue? And in such a way that the part does not see too much load in that direction? For example a sort of drawer that you slide in from the side, and that contains the nut. And then the whole drawer is glued or acetoned in place, so it becomes one solid block?

 

Or relocate the fasteners, or add a flange, so you don't have to insert them while printing, but you can do it afterwards? It all depends on the design and requirements of course.

 

Like with all great inventions, maybe someone just needs to see the light? Often the inventions were simple, but no one saw them up till that point...

 

Anyway, if you would find a solution, let us know. It could help a lot of people.