No 20mm is enough. I recommend 25mm screws and the frame is a bit more than 6mm. Happy building then

 

I wish you a happy build . Yes I am in the same case as you, waiting for the MK2.5 upgrade...

Good news for you, I will publish the V2.0 build today (on openbuilds at first first) !

 

It is something requested by several users, so I decided to add in all parts of Version 2 two parameters (in Fusion 360 files) : "rail_profile_width" and rail_profile_height". You can play with these parameters to adjust them to your Misumi profile. However, you cannot change the angle for two reasons :

1. Some parts are printed vertically which means you will need to add a support, which results in fairly low accuracy
2. When you print angles, the plastic will take a small shortcut which results in a rounded angle. All my "v-slots ergots" have a special shape to avoid this (advantages : more precise fitting, avoid stressing plastic parts on a small surface (on the shortcut), avoid bad alignments when building). Making this shape in parameter is not that easy.

By the way, V-Slot is 45° and as you could see it has some advantages over T-Slot even if you do not use wheels!

 

BTW, I have open a new build for the Version 2 : https://openbuilds.com/builds/prusa-i3-bear-upgrade-v2.6428/

 

I would love to see a HiWin linear rail on my upgrade, this is in my head since a long time

Yes all rods are original!

I am currently fixing several issues on full upgrade, so wait a bit. Should be good by end of the week.

 

Yes I am thinking about this (and much more)

Moving the horizontal vslot on top does not solve this problem. The vertical extrusion can be cut with a slightly different length (or not a perfect 90° angle) and depending how well the build is done you might have unequal small spaces on top and bottom of vertical vslots. The advantage of the small top vslot is that you can use it to set same distance in bottom than in top.

 

Precise cut does not mean perfect assembly, it depends how good you will square your frame (which depends on lots of factors). You also have to take in account that t-nuts are not centered in a hole like the screws on the prusa frame, they have a bit of play to help you square your build.

Something else that is not perfect with the Prusa method and screws is that the plastic part are going to be deformed by the screws. Plus, they slightly twisting the X axis (specially on the side of the X motor).

What I am doing to make a good alignment :

• Z motor mounts are touching the bottom vslots
• There is a smaller diameter on top of Z top smooth rod holes, if you push the smooth rod correctly you will get the perfect dimension. There is a hole to view that the smooth rod is correctly inserted
  
• Flat surface in bottom of Z stop to stop the X motor and X idler without twisting them

What do you think?

 

Sorry I was not clear, quite hard to explain without an image...



1. For now printer is quieter than original and maybe a bit quieter than Half Upgrade. If you prefer, you can add a piece of 1mm under the Z motor mount during the build (remove it when finished) and 1mm longer vslot. Bonus, you should win 1mm in Z axis (never tested this)
2. Corresponds to red arrow. During the build, the smooth rod has to be fully inserted until touching on top. Their is a little hole in center to see it is correctly inserted. Rod will then define the Z height precisely. (this will be explained in the manual)
3. Corresponds to green lines. When X idler (or X motor mount) will go up, it will touch the parts marked in green. For me it is way better than "half" of two screws head (as explained in my previous post)

Is it better explained now? Does it make sense?

 

I use Autodesk Fusion 360, everything will be open source!

Fusion 360 files are available on my GitHub here (dev branch for now) : prusa_i3_bear_upgrade/src at dev · gregsaun/prusa_i3_bear_upgrade · GitHub
STEP and STL files are available for each version as well

As explained before (or maybe in V2 thread), if you are using other extrusion, there are 2 parameters to set the rail width and height. Checkout this article if you do not know how to do this : Making Parametric Models in Fusion 360

 

Even more with my bad english. Ich verstehe ein wenig Deutsch aber ich bin from French part of Schweiz (yep we are speaking 3 languages in Switzerland + one for advance speaker :-D )

No it will not bend (hard to show you on this pic without the X idler), the x idler/motor mount will touch a L shape on the Z tops.

I think I answered this point in my previous comment. Sorry for know I do not plan to make Misumi version (only the parameters in the Fusion 360 files) I have to maintain 4 versions for now and it is not a small job :-D

 

Could we continue to discuss further points of the V2 in the V2 thread?
https://openbuilds.com/builds/prusa-i3-bear-upgrade-v2.6428/