Ordered Bear upgrade!  

RE: Ordered Bear upgrade!

Posted by: charles.h13

Would an upgrade thread be something of interest?  

I for one would certainly enjoy it.

I am creeping my way into upgrades. I have printed my Improved X axis, which I can't use until I do the Bear extruder...

RE: Ordered Bear upgrade!

I will start a thread tonight for everyone to post their upgrade lists so you can ask questions,  

RE: Ordered Bear upgrade!

Posted by: matthew.m63

Is it worth it? What can i expect? will it reduce ghosting?

Usually people are asking this questions before they order something 😉

RE: Ordered Bear upgrade!

OK,

I have completed my Prusa Bear build and it is working.  I need to tighten up a few things.  After a couple successful prints, it is now jamming after about 2-3 hours during long prints.  Multiple types of filament.  I am determined to get this working.  

RE: Ordered Bear upgrade!

@charles-h13 can u give us an update to your Bear Upgrade. Does it improve something - except the better look ??????:>

RE: Ordered Bear upgrade!

I am not certain.  I have been using it for a month plus and mine is slightly skewed.  I need to work on it this weekend.  

RE: Ordered Bear upgrade!

I have a question about the Bear upgrade. What is gained? I understand it's supposed to be more rigid, but are the travels any larger?

RE: Ordered Bear upgrade!

@neil-1

No change to print dimensions.  Slightly more rigid.  So far, not noticeable difference.  

RE: Ordered Bear upgrade!

@charles-h13

Interesting.

I've only had my MK3s for about three weeks so I'm not an expert on 3d printers but I have designed and built a few industrial automation machines and it seems to me that if one is going to go to all the trouble of replacing the frame with structural extrusion why aren't the travels increased? The only thing even a little hard would be changing the program for maximum travel and since it's open source I'd assume that wouldn't be a problem. All the rods, bushings, steppers and other hardware are available on-line. It's not rocket science. X and Y axis should probably go with 10 mm rods and bushings but that's just a new back part of extruder where the bushings are. I think someone with a 3d printer could handle that. Longer belts and a larger heated bed. Maybe a larger power supply. All these printer parts are amazingly cheap. I'd like to hear from other people about why they're keeping the same travels because I'm getting itchy fingers. A larger print envelope may be in my future.

RE: Ordered Bear upgrade!

Hi folks.  Original MK3S owner as of September; but also a multiple Bear 2.1 MK3s ("Bear") owner as of October.  I actually liked the Bear upgrade version so much, I sold my Original MK3S ("OG").  I'm currently running two MK3S Bear 2.1's, with a third one sitting in a box in my garage waiting to be built.  Lots of opinions here in this thread, so I'll lend mine as well.

Features of the Full Bear 2.1 that I like:

• Easy x-axis belt tensioning with two screws, vs. OG which requires tilting the X-axis motor.   On the OG Prusa, I struggled a little bit with the hand-eye coordination required to hold the tension on the x-axis motor whilst also tightening its three screws to secure it in place.  I always ended up a little tighter or a little looser than where I wanted to be.  In the pic below, you can see that to tension the x-axis belt on the Bear, you just turn two screws, and then the whole "shuttle" inside the x-axis end moves in and out.  Easy peasy.     
• Easy y-axis belt tensioning, without tipping over the machine or peering underneath the heat bed.  Bear moves the Y-axis tensioner device to the front of the machine which is easily accessible, and it eliminates the second "set screw" required on the OG design.  I also found the Bear tensioner easier to install vs. the OG tensioner.  In the pic below, you can see the tensioning screw in the front of the machine.  Turn the screw and your belt tension changes with it.
• Completely adustable y-axis rod positions.  I have found with some bearings (i.e. Misumi), and even OG bearings, that it helps to put "outward" force on the y-axis rods to eliminate the annoying "bed rattle".  These rods make that very easy to accomplish.  The pic below shows the direction I would push the rods to eliminate bed rattle.
• Free y-rod clearance under the machine.  I ran into that issue with OG frame where the actual U-bolts on the bearings were ramming into the frame.  It took some finagling to get the OG frame pre-tensioned in just such a way as to have the y-axis bearings / U-bolts clear the frame without hitting it.
• "Pillow blocks" on the y-axis bearings.  Again, my hand eye coordination.  I struggled getting those U-Bolts on the OG design tightened juuuust right.  The Bear upgrade leaves tons of room underneath the heat bed and ergo allows you to go with plastic blocks for installing the y-axis bearings in lieu of U-bolts.  Also, did anyone notice the U-Bolts were never quite the right width so you had to bend them back and forth to get them installed into the y-carriage?  I found the Bear design a ton easier to get installed correctly vs. the OG U-Bolts.  Pic below shows the "pillow block" that I'm referring to, and also shows the immense amount of clearance left underneath the machine.
• I run this LED light bar mod.  With 2040 extrusion of the Bear, I can hide the 24VDC power wires by running them down the middle of the extrusion.  On the OG, with the light bar mod, I had to resort to one of many undesirable options: a large akward bracket, drilling and tapping the OG frame, or 3M command strips to secure the wiring coming down the z-axis from the top of the machine.
• Speaking of that 2040 aluminum extrusion.  2040 aluminum v-rails gives room for upgrades.  Octoprint LCD?  You can bolt it on the front of the machine right next to the LCD display.  Gently bolt-on spool holders and other attachments vs. wrenching on your z-axis frame to get the spoolholder on and off.  Pic below shows a standard single-spool holder that only needed one screw to secure (red arrow is not pointing at the screw, the screw is actually in the top).   In any case, 2040 aluminum extrusion means easy swap out of anything that can bolt to slots.

Those are my favorite features.  Generally speaking, I'd say the Bear frame is more difficult to assemble - you need extra tools such as a carpenter's square, clamps help, and you have to print out several extra "build tools" for gauging and measuring.  However, once the frame is assembled, I found the remainder of the installation faster and easier, and generally less quirky and demanding than the OG design.

Also worth mentioning that I did go with the Bear Extruder.  The Bear Extruder triggers the need for custom firmware in order to pass the XYZ calibration test.  For me, it's worth it, since the "Bear firmware" is literally two lines of code different from the main Prusa firmware.  And once you pass XYZ calibration, if you desire, you can flash back to OG Prusa firmware.  I could see this being a dealbreaker for some people however.  I found the Bear Extruder a lot easier to put together, and it makes hot-end swapouts and other hot-end maintenance a lot easier.  You do not have to use the Bear Extruder, you can go with the standard Prusa MK3S extruder.

What about print quality?  "Out of the box", I had less ringing in the corners and less ghosting on my prints coming out of the Bear 2.1 design.  Now, before I start a huge argument and flame war, I am NOT CLAIMING that the Bear 2.1 design is better quality.  What I will tell you is, for a lesser experienced printer like myself, the steps required to install the Bear Frame lends you to having a more "compliant" and properly tuned machine once you're done building.  This as compared to the OG design which requires a whole bunch of tweaking, and playing, and tuning after you've built the machine to get it working just right.  For example, the Bear Frame instructions had me download an app for my phone and tune all of my belts to 90 Hz.  So easy this idiot could do it.  The Prusa instructions have you run the Belt Test, which we all know doesn't work.  Seriously, just google for Prusa MK3S Mystery Y-axis Crash Detection.  Tons of folks gave up and just turn crash detection off.  Surely it's just wrong belt tension or another installation or maintenance issue, but the point is, it's finicky and hard to solve this issue on the OG design and lots of people have run into it.  Lord knows my last OG MK3S had about 25 y-axis crash detections before I got the belts and U-bolts set juuuust perfectly on my y-axis.

In any case, "out of the box" so to speak (or rather, right after assembly is completed) I am getting no layer shifts, zero crash detections, no waves in my corners, no ghosting, no bed-rattling.  The result is a happy dude who has two Bear 2.1's and a third on the floor of his garage waiting to be assembled.  Long story short, Prusa is an awesome machine, and Bear makes it better.  Just like any upgrades can make any things better.