3D Printer (Prusa Bear Mod) Build

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Netpackrat
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Re: 3D Printer (Prusa Bear Mod) Build

Post by Netpackrat »

So, a couple posts back I mentioned maybe working on the extruder unit next, which is a different mod than the bear frame, even though they were both designed by the same guy. The Bear Exxa (extruder/x-axis) can be installed on a standard Prusa, and conversely a Bear frame modded Prusa can use the bog standard Prusa extruder and X axis. Really the main reason I am going with the Bear Exxa is it lets me use the 10mm Z rods, which will stiffen up the 100mm taller Z axis a little. This has me jumping back and forth between the assembly guides for the Bear frame and the Bear Exxa, and in the end it made more sense to assemble the Z and X axes first. At least it got some of the parts onto the machine and off the workbench.

Image

In the meantime, here is a preview of the printed parts that go into the extruder. These are all black PETG with the exception of the part cooling fan shroud (upper left), which is printed from ASA (an ABS variant that prints a little better) for additional heat resistance. I printed up an extra of these since it is the printed part that is most vulnerable to heat damage.

These are all printed in black instead of the blue, because the extruder uses an IR filament sensor that lets the controller board know if the filament runs out. Only some of the parts need to be black, but I figured having pieces of both colors in the same assembly would look silly.

Image

Printer as it sits now. Same deal with the X motor as the Y; I ordered the wrong parts, so I am going to have to wait a few days for the new drive pulleys I need to install the belts. The extruder will ride on the 3 bearings you can see on the X rods. The orientation is marked on the back with sharpie marker so I can turn them the correct way. The idea is to have them turned 45 degrees from straight up and down, so the weight of the extruder will be supported by 2 rows of balls at 1:30 and 10:30 for better wear characteristics than having all of the weight on a single row at 12:00.
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HTRN
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Re: 3D Printer (Prusa Bear Mod) Build

Post by HTRN »

When you finish getting it together, I found your first project!

https://www.thingiverse.com/thing:4702158/makes

:mrgreen:
HTRN, I would tell you that you are an evil fucker, but you probably get that a lot ~ Netpackrat

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Netpackrat
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Re: 3D Printer (Prusa Bear Mod) Build

Post by Netpackrat »

HTRN wrote: Tue Apr 26, 2022 5:36 pm When you finish getting it together, I found your first project!

https://www.thingiverse.com/thing:4702158/makes

:mrgreen:
That's awesome. How did you know I have a spool of yellow PLA?
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blackeagle603
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Re: 3D Printer (Prusa Bear Mod) Build

Post by blackeagle603 »

They had me at chocolate
Scientists Say They’ve Created Crispier Chocolate Using 3D Printers
Applying the science of metamaterials to make chocolate even harder to resist...

Researchers from the University of Amsterdam realized that the metamaterials approach could be used to further enhance the texture and experience of biting into high-quality chocolate. This happens via creating even more snaps and fractures through a structure that is more complex than what’s created by simply pouring melted chocolate into moulds. The idea doesn’t replace the tempering process, however, which actually provided some unique challenges when the researchers turned to 3D printers to manufacture their chocolate treats.

RTWT with graphics
The results were shared in a recently published paper, “Edible mechanical metamaterials with designed fracture for mouthfeel control,” in the journal Soft Matter.
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HTRN
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Re: 3D Printer (Prusa Bear Mod) Build

Post by HTRN »

Netpackrat wrote: Tue Apr 26, 2022 6:15 pm That's awesome. How did you know I have a spool of yellow PLA?
Because I'm under your bed, with a knife. :mrgreen:

Edit, here's something else you might find cool:
https://www.thingiverse.com/thing:4259458
HTRN, I would tell you that you are an evil fucker, but you probably get that a lot ~ Netpackrat

Describing what HTRN does as "antics" is like describing the wreck of the Titanic as "a minor boating incident" ~ First Shirt
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Netpackrat
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Re: 3D Printer (Prusa Bear Mod) Build

Post by Netpackrat »

HTRN wrote: Wed Apr 27, 2022 12:14 pm Edit, here's something else you might find cool:
https://www.thingiverse.com/thing:4259458
Not familiar with that franchise at all.
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Netpackrat
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Re: 3D Printer (Prusa Bear Mod) Build

Post by Netpackrat »

Image

Extruder body with the motor installed and the pieces of the E3D V6 hot end. The hot end for the Prusa came preassembled, and the Bear Exxa build manual assumes you are removing your hot end from a stock Prusa extruder, so I had to go to YT to see how this was supposed to go together.

Lower left of the hot end parts is the heat sink, which is the part actually held in the extruder body, upper left is the heater block, top center is the heat break that goes between the heat sink and the heater block and actually holds the two together, and continuing clockwise are the PTFE tube, collet clip, and collet, with the brass nozzle in the center. Not shown are the heater cartridge and thermistor which also go in the heater block once the rest is assembled. One of the printed parts for the Bear design was a different collet clip which I used instead of the one shown, although I don't think it makes any difference.

Assembly was not difficult but once the printer can be powered up, I will need to heat the hot end to some high temperature and re-tighten, so nothing will loosen in use due to heating and cooling cycles. The PTFE tube is inserted from the top and is held in place by the collet. There's a printed tool for trimming it to exact length and putting the specified taper on the nose, then the upper end gets a 60 degree internal chamfer which I did with a small center drill. The PTFE tube is a wear part so I made up several of them.

Image

Assembled hot end placed in the extruder body. The extruder cover goes over this and holds it in place.

Image

This is the fully assembled extruder, ready to go on the X axis. The fan on the left is the cooling fan for the hot end, which blows air across the heat sink. I used a fan that is supposed to have a higher flow than the stock Prusa fan. The fan on the front is the part cooling fan, which blows cooling air across the part as it is being printed. This is the same part as the stock Prusa extruder uses (I bought it directly from Prusa along with some other spares). One of the benefits of the Bear extruder over the Prusa is the Bear mounts this fan vertically instead of at an angle, which is supposed to extend the life of the bearings.

The printed ASA fan shroud attaches to the bottom of the print fan and directs cooling air to the part. This is the part closest to the heater block and the work piece which is why it is printed from a higher temp material. Because it's vulnerable to damage in the event of a failed print, it's a good idea to have extras on hand. Once I have 2 printers running, having spare printed parts will be less important since I'll be able to use the printer that's not broken to print pieces for one that is.

Image

Extruder hanging on the printer. I have gone about as far as I can with this until the drive pulleys show up.
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HTRN
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Re: 3D Printer (Prusa Bear Mod) Build

Post by HTRN »

Netpackrat wrote: Wed Apr 27, 2022 6:43 pm Not familiar with that franchise at all.
Go watch here:
https://gomovies.sx/tv/watch-the-expanse-gomovies-39357
HTRN, I would tell you that you are an evil fucker, but you probably get that a lot ~ Netpackrat

Describing what HTRN does as "antics" is like describing the wreck of the Titanic as "a minor boating incident" ~ First Shirt
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HTRN
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Re: 3D Printer (Prusa Bear Mod) Build

Post by HTRN »

HTRN wrote: Tue Apr 26, 2022 5:36 pm When you finish getting it together, I found your first project!

https://www.thingiverse.com/thing:4702158/makes

:mrgreen:
Aaaaaannnnnndddddd it's gone. :(

But have no fear! You're friendly neighborhood Machinist has the answer!
https://archive.org/details/thingiverse-4702158
HTRN, I would tell you that you are an evil fucker, but you probably get that a lot ~ Netpackrat

Describing what HTRN does as "antics" is like describing the wreck of the Titanic as "a minor boating incident" ~ First Shirt
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Netpackrat
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Re: 3D Printer (Prusa Bear Mod) Build

Post by Netpackrat »

Yeah the forces of censorship are alive and well on the 3d printing sites. Speaking of which, that Honda snow blower that I was definitely going to buy this year, and the Honda Rancher I was thinking about getting, are definitely not going to happen now.

https://www.thedrive.com/news/honda-ord ... ommunities
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"People come and go in our lives, especially the online ones. Some leave a fond memory, and some a bad taste." -Aesop
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