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Embedding objects?

Posted by anode505 
Embedding objects?
January 02, 2011 10:20AM
Just ordered a mendel and a boat load of 'ink' winking smiley

One of the first items I want to print needs a steel ring in it. This one should be easy, it would be on the bottom face.
Should I just draw it up with it the 'dimple' in place?

And for future ref, what about items in a more fully suspended position? (I'm thinking nuts and such)
Should I just make it 2 parts and stack them on top of each other? Is there a stop code? (the CNC lasers I fix for a living offer an M1 for this)

Thanks guys
Re: Embedding objects?
January 03, 2011 11:37PM
Especially if you need an air-tight fit, that would require some type of custom extruder tip. You need to extrude right next to the part. With current tips, at best you would always have a roughly 1mm gap due to the thickness at the nozzle tip. If the part you are embedding is tall, then you would have an even bigger gap due to the profile of the hot end.

My extudrer carriage has a couple of screws with the heads embedded in plastic, but I didn't print them this way. I printed the part with an undersized hole, then heated the screw with a 20w soldering iron till I could push it into the pocket. With your steel ring, maybe you can do something similar. Just lay out a sheet of foil or wax paper over a stove top and turn it on low. Once it gets close to your extrusion temperature, press the ring into an undersized groove. Don't use the stove top directly or you might get melted plastic on it. Pressing a heated ring into your printed part might deform it a bit, so if your printer can hold good enough tolerances, you would be better off to make the grove a press fit then just press the ring in by hand.
Re: Embedding objects?
January 04, 2011 08:35AM
The extruder tip shouldn't be a problem, so long as the part can fit into a convex hole. You simply stop the print at the top of the hole, insert the object, and keep printing. This is usually done by splitting the gcode file in two at that layer, print the first half, insert the nut, and print the second file. For best results, heat the object and press into a very slightly undersize hold as described above. Be careful to avoid moving the part or the bed while inserting the object.

Avoid printing while the embedded object extends above the printing layer. The head will crash and even if you tweaked the g-code to avoid that, you wouldn't be able to print close enough to the part. Better to print an insert to cover the parts of the object that the printer can't fill in itself.
Re: Embedding objects?
January 07, 2011 12:09AM
Instead of splitting the G-code into two files, couldn't you just put an M00 command at the end of that layer to pause execution?

Re: Embedding objects?
January 07, 2011 05:52PM
No, but you might be able to use M226, assuming that the host software recognizes that this is a pause command and can issue the resume command. Last time I saw this being discussed, it was done by splitting the files.
Re: Embedding objects?
January 07, 2011 09:40PM
I assume this is specific to the RepRap host software? Under Mach3, I just toss in M00 for a pause when I need one...

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