how to apply MK4 upgrade on Bear 2.1

[bgiot]

Hi, it's more a question: I have a bear 2.1 mk3s with bondtech extruder. Will the MK4 upgrade work outofthebox ? Or do I have to comeback to the original frame design and wait for bear 3.0 design ?

[stahlfabrik]

It cannot be compatible - 10mm z rods for example are not compatible, the electronics and display parts are not compatible. Parts of it should be compatible: the motors for example:-)

[PRGeno]

I'd think the Z rods could be easily accomdated with some minor Z rod mount alteration. The electronics and screen should also be easy to accomdated with a new electronics box and display mount alterations.

I'm sure I'm missing something but I just don't see much standing in the way of supporting the Mk4 upgrade.

[Pyroschnueffler]

I hope that too, that Gregsaun make a Update to go on the MK4 I love the Bear Mod, and i hope so that the MK4 Update comes.

[akbiocca]

The MK4 4.0 upgrade may create a lot of interest in the Bear frame as the parts removed from the MK3 in this 4.0 upgrade process will almost complete a bear frame less what, a power supply?

On Tue, Apr 11, 2023 at 1:38 AM Pyroschnueffler @.***> wrote:

I hope that too, that Gregsaun make a Update to go on the MK4 I love the Bear Mod, and i hope so that the MK4 Update comes.

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[PRGeno]

From what I can tell (we'll have to wait to see the final BOM for the Mk4 upgrade kit) the upgrade is essentially an electronics upgrade (main system board & control panel screen), a new extruder (Nextruder), and a new set of motors (the Mk3.9 is the same upgrade but without the 0.9 stepper motors).

The only structural things that matter with the Bear frame is how the X & Z axis mounts might differ (and they can't change by that much - the X axis looks to stay the same), and how to mount the electronics.

It appears to only need some minor alterations to a few printed parts (many of us already use custom printed parts instead of the stock Bear parts). We'll have to wait to see what Prusa actually delivers in the upgrade kit when it becomes available, but it should be relatively easy (far easier than what Greg did to create the Bear upgrade in the first place).

I'm sure it's just a matter of time before someone figures out how to interface the new Mk4 parts onto a Bear.

[DesC21]

I started to work on updating the necessary parts (I do hope Greg will recover soon and can do a proper update @gregsaun get well soon). I don't have a MK4 yet but the original parts (STL only) are online. I think all that is needed is changing the following parts:

z_motor_mount z_top lcd_support_a lcd_support_b mounting parts for the new xbuddy case (since it is not 3D printed anymore we don't have the CAD data, I guess it is directly screwed to the frame but I haven't looked into it yet)

From what Prusa said the y-axis should work without problems. But since the carriage and design changed a little bit, maybe the height did too? But since the upgrade kits work with the old MK3 frame it should not be necessary to change anything.

So far I finished the z-axis parts. Greg's design is so well made, the z-axis changes were quite easy. The LCD and xbuddy case parts need a bigger update though. I'll try to finish the LCD supports today.

Does anyone know how I can publish these? I guess I have to release the source files as well or can I simply release the stl and mark them as remixed? Never looked into these details tbh...

[Pyroschnueffler]

I works on in it too, but i am not a CAD Profi. I switch all MK4 Parts from Prusa to Solid objekts in the Moment. I hope Your Work is better than my.

[DesC21]

I works on in it too, but i am not a CAD Profi. I switch all MK4 Parts from Prusa to Solid objekts in the Moment. I hope Your Work is better than my.

That's great let us know how it goes! I am no expert either, just trying to make it work ;)

Have you checked the new LCD cover and supports, yet? I noticed that on the original Prusa parts there is a collision when you align the mounting hole from the support part and the xlcd case (right side). Not sure if I am doing something wrong but aligning the holes should work?

Anyway I updated the LCD_support_a and b. Looks okay so far. The right mount is around 2,5mm over the edge of the case, not happy with that ;-). The angle of the display is the same as on the stock MK4.

and a little comparison between the new and old LCD case. The new one is actually more compact.

[PatB42]

so far very nice job, if any need i can help , i have modified several parts from the 2.1 bear for me , i redo a complete new rambo box as i wanted to use the Duet2wifi , apparently you work on fusion this is perfect for me ..the problem is i can't find even the STL for the new xbuddyboard ? there isn't in the printable mk4 ? any idea to find cad from this board or exact dimension size.....

[Pyroschnueffler]

Hello when i am finished i can check the collision with the parts

[Pyroschnueffler]

Yes u are right its a collusion, you not have made it wrong.

[Pyroschnueffler]

Any new Updates here? i am thinking to bye the mk4 complete Kit and i will see what changes i must made.

[ciscokeb]

I purchased the MK4 KIT, but I’m going to dial it in before I do untested modifications (updates). 😊

Keith

From: Pyroschnueffler Sent: April 30, 2023 10:50 AM To: gregsaun/prusa_i3_bear_upgrade Cc: Subscribed Subject: Re: [gregsaun/prusa_i3_bear_upgrade] how to apply MK4 upgrade on Bear 2.1 (Issue #138)

Any new Updates here? i am thinking to bye the mk4 complete Kit and i will see what changes i must made. — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you are subscribed to this thread.Message ID: @.***>

[DesC21]

Any new Updates here? i am thinking to bye the mk4 complete Kit and i will see what changes i must made.

I ordered a MK4 kit but I guess it won't be here until june (earliest). So I can't test anything. I haven't done the missing parts for the new xbuddy case. Does anyone have the measurements for the holes in the frame (they are the same on the MK3)? Otherwise I have to dig out my old frame.

Another thing, can anyone say anything on how warm the new board/case gets? Prusa uses the case as a heat sink and I guess that's why it is also directly connected to the frame. This won't be possible for the bear, as far as I can see. So it would be good to know if the case gets warm and even needs the frame to dissipate heat (I think this won't be necessary but you never know).

[HK-Moebius]

I guess the case as heatsink is more than enough. The new board uses the same Trinamic 2130 as the MK3 which had no heatsinks for the drivers.

[PatB42]

I design this for the rambo https://www.printables.com/fr/model/153464-the-ultime-einsy-rambo-case-for-the-bear-frame/related

since i added other part for cable with the stock part housing cable i can post it and i presume !! the xbuddy board will fit in but it's seems that not easy to get the drawing design at least dimension of this buddy board which is made by prusa itself !! so far can't find any cad files on internet !!

[PRGeno]

It seems to me, if you can make due without the new motors and Z axis components, the Mk3/S/+ to Mk 3.9 upgrade should be a much easier upgrade to apply to a Bear. It will provide the new electronics and extruder/hot end with only needing to create mounting bracket solutions for the metal Buddy board case and the new screen (actually they don't even need to be mounted to get operational). The Nextruder should fit directly without any changes at all.

Support for the full Mk4 upgrade, especially with it being only an additional $80 for the new motors and Z axis, would be very nice to have. But upgrading to a 3.9 model should be very quick and simple to accomplish without much effort at all, and would still a be very a useful and significant upgrade.

[akbiocca]

The 3.9 upgrade reuses the frame, power supply and motors. The Z axis is apparently replaced in the 3.9 upgrade. The only addition in the 4.0 upgrade is the motors. At least that's the way I read it.

On Sat, May 13, 2023 at 3:01 PM PRGeno @.***> wrote:

It seems to me, if you can make due without the new motors and Z axis components, the Mk3/S/+ to Mk 3.9 upgrade should be a much easier upgrade to apply to a Bear. It will provide the new electronics and extruder/hot end with only needing to create mounting bracket solutions for the metal Buddy board case and the new screen (actually they don't even need to be mounted to get operational. The Nextruder should fit directly without any changes at all.

Support for the full Mk4 upgrade, especially with it being only an additional $80 for the new motors and Z axis, would be very nice to have. But upgrading to a 3.9 model should be very quick and simple to accomplish without much effort at all, and would still a very a useful and significant upgrade.

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[PRGeno]

My interpretation is slighting different than yours. It looks to me that the thicker Z axis rods are not part of the 3.9 upgrade (why would they be without the new Z axis motors?). So from my take, it should not require any new parts for the Z axis, or any other truly functional parts (I don't consider Buddy board case or display board mounts as functional).

I ordered my 3.9 upgrade under that assumption. We will see if how I am interpreting ends up being correct or not when it arrives whenever Prusa is able to fulfill the order.

[DesC21]

My interpretation is slighting different than yours. It looks to me that the thicker Z axis rods are not part of the 3.9 upgrade (why would they be without the new Z axis motors?). So from my take, it should not require any new parts for the Z axis, or any other truly functional parts (I don't consider Buddy board case or display board mounts as functional).

I ordered my 3.9 upgrade under that assumption. We will see if how I am interpreting ends up being correct or not when it arrives whenever Prusa is able to fulfill the order.

You are correct, on the Prusa website they added what will be kept from the MK3 and it states the z-rods.

I haven't checked yet but my assumption is that the whole x-axis assembly stays the same then and the nextruder just fits.

So upgrade kits 3.5 and 3.9 need parts for the LCD and electronics (if you want them on the frame) and full MK4 needs additional upgraded z-axis as well.

Let's see if MK4 kits starting shipping soon. If there are any volunteers to test the parts I updated (at least until my kit arrives), let me know. I'll hopefully finish the xbuddy case mounts this week.

[akbiocca]

I see now their descriptions are inconsistent. But they do state that Z rods and bearings are part of the motors-only Mk4 upgrade. :)

When I compare prints from my well used Mk3 and my new Mk4 the quality difference is noticeable. But I don't know how much of that is the extruder vs the worn bearings, belts, etc. I would consider replacing the bearings at a minimum during the upgrade. The larger Z rods would likely have more impact on speed (input shaping) than on VFA, so they should be upgraded if speed is the goal or input shaping with standard values is planned. If the bearings are being replaced anyway the cost of changing diameter and new rods is small. Hence people doing 3.9 upgrades may also be doing Z rods on their own.

Perhaps this is an opportunity to upgrade to rails instead of, or provide the option. That would differentiate the Bear from the Mk4 and close the gap with the Switchwire to some degree.

On Sun, May 14, 2023 at 1:25 AM Dennis Schuldt @.***> wrote:

My interpretation is slighting different than yours. It looks to me that the thicker Z axis rods are not part of the 3.9 upgrade (why would they be without the new Z axis motors?). So from my take, it should not require any new parts for the Z axis, or any other truly functional parts (I don't consider Buddy board case or display board mounts as functional).

I ordered my 3.9 upgrade under that assumption. We will see if how I am interpreting ends up being correct or not when it arrives whenever Prusa is able to fulfill the order.

You are correct, on the Prusa website they added what will be kept from the MK3 and it states the z-rods. [image: image] https://user-images.githubusercontent.com/26366384/238175325-1fd5b32c-cfea-4789-a431-198ee825d41d.png

I haven't checked yet but my assumption is that the whole x-axis assembly stays the same then and the nextruder just fits.

So upgrade kits 3.5 and 3.9 need parts for the LCD and electronics (if you want them on the frame) and full MK4 needs additional upgraded z-axis as well.

Let's see if MK4 kits starting shipping soon. If there are any volunteers to test the parts I updated (at least until my kit arrives), let me know. I'll hopefully finish the xbuddy case mounts this week.

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[PRGeno]

I suspect the Z axis and motors will allow some increase in speed, although the Z axis has the least effect on speed with this type of machine. I also suspect that the larger rods together with the 0.9° steppers should have a significant affect on quality, and the $80 price difference for the full Mk4 upgrade is a better bang for the buck in my opinion. But it will require much more effort to get it running (properly) as a full Mk4 Bear upgrade.

My previous comment was only intended to point out that a 3.9 upgrade is still a significant upgrade which should require very little Bear side design effort except for a few non essential mounting brackets.

I agree that it would be a neat Bear exclusive to use linear rails instead of the rods, but again I suspect the Z axis would gain the least benefit from rails on this type of machine and might not end up being worth that extra effort.

From an economic view, the Mk4 upgrade appears to be the better deal, but the Mk3.9 upgrade looks to be a pretty simple plug and play upgrade option for a Bear.

[Bob6y]

Glad to see this topic, indeed I have a mk2 and was prospecting to replace it.
I really liked the bear chassis, so I bought a kit, then in the meantime came the announcement of the mk4 and the discovery of the installation of rails! Lots of new!
I have a few rail products in my Ali express basket but I don't know which one to take for the tray (Y axis) .

And I think it is no longer necessary for the Z axis because the steel rod is a more suitable diameter. For the X axis I started on a rail + the steel rod but I have the impression that the mk4 extruder is more compact, with a center of gravity that does not induce rotation. So one rail will suffice.

Here I am in full reflection on the bear chassis + mk4 kit + rails.

Hope I am in the good thread, has I will apply the bear chassis on the mk4 full kit and not do an upgrade. It is my first post on git...

Regards

[gregsaun]

Hi Everyone,

Thank you so much for your interest in the Bear frame, it is very nice to read those posts ♥️! It is a good point regarding the 3.9 kit, absolutely.

We already have mods for 10mm Z axis and X ends made by Shaun Doe, you can find them on bear-lab.com -> Community -> Community's Optional Parts: https://guides.bear-lab.com/Wiki/community_optional_parts

The biggest problem is that I am pretty sure the MK4 Z rods are longer than the MK3 rods as the specs says 220mm Z axis where the MK3 was 210mm. I don't think it will be possible to accommodate this difference and modifying the firmware involve breaking the tab on the main board. Unfortunately, as usual with Prusa, source files are missing for everything, including the Z rods specs and the Z frame, so it is hard to get the length. I guess it is 335-340mm (nextruder has more room under like the bearexxa and they added 10mm over the MK3).

Regarding the rails, I highly recommend to keep going with 10mm Z rods instead of rails on Z as this is the widest axis and the most difficult one to align. Also you are not going to see print improvement between Z rails and 10mm rods, unless your rails are not aligned well enough and then it will be worst than 8mm rods. For Y axis I recommend to check some mods with single rail in the center (no alignment issue, easier to assemble and maintain, cheaper, more than stable enough) but you then need a rail with light preloading or you will have some play.

I am not yet recovered unfortunately but I am slowly getting better 🤞. I can't wait to be back on the project!

Happy bear print!

Edit: some typos and mistakes (writting with my phoney sorry)

[gregsaun]

Mmmh I might be wrong, 3.9 keeps the rods and frame of MK3 but has 220mm Z axis. So how they went to 220mm? Did they made the two bottom bearings of the X axis even closer to the bed? Did the made the Z top higher up a little (I mean the printed part only)?

[PRGeno]

Hi Greg, I had not heard you had a health issue, but I wish you the very best and ultra speedy recovery.

I think the 3.9 upgrade 220mm Z axis spec must be be related to the Nextruder and a difference in height where the cable bundle comes into the extruder in relationship to the nozzle. I can see how they might gain 10mm there without changing the Z axis, since the extruder cables could provide more clearance at the top of the frame.

There is no way of telling until we can get our hands on the upgrades, but if this were true it should work fine on a Bear with not only the 3.9 upgrade, but also the full Mk4 upgrade (obviously with upgraded Z axis parts), without the need to customized the firmware.

At least I hope that is the case, and I can't think of any other way the 10mm gain could be possible without changing the Z axis.

[akbiocca]

Prusa has said additional Z range is due to Nextruder.

The thicker Z rods allow greater accelerations in X. Together with input shaping can improve speed.

I could measure the new MK4 Z rods length if that's helpful, when I get to the printer next, day after tomorrow.

On Tue, May 16, 2023 at 9:05 AM Grégoire Saunier @.***> wrote:

Mmmh I might be wrong, 3.9 keeps the rods and frame of MK3 but has 220mm Z axis. So how they went to 220mm? Did they made the two bottom bearings of the X axis even closer to the bed? Did the made the Z top higher up a little (I mean the printed part only)?

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[gregsaun]

I look at few pictures and it seems the distance between the nozzle and the X bottom bearings is very close. We can see this here:

I think this is a dangerous choice from Prusa, the bottom of the carriage might grab stuffs, get warm and deform a bit and affect the bearings, the arm leverage is big with the heaviest part higher on on the axis and single bearing on top, etc.

I am wondering if when you upgrade to MK3.9 you have to swap the Z tops and motor mount, and even maybe the X ends. First thing is that the double bearings is now on the bottom so we will need to remove x ends anyway. Second, on this picture it looks like the Z tops might be a little higher up which could also help to get few mm more:

Finally, when looking at the X carriage STL, the spacing between the two X bearing is wider, meaning this extruder is also wider and so maybe the X ends are shorter:

While searching for pictures I could note a weird position for the top bearing:

@akbiocca would be nice if you could measure, like we would beb100% sure. No stress with this.

[DesC21]

@gregsaun good to hear from you, all the best and stay positive!

Good to hear your input. I do hope that there will be no collisions with the frame due to the nexttruder, especially with the cable coming out of the carriage so high now (corner plates might get close). I guess the weird position for the top bearing is only to have it centered to the stepper/hotend (even load on the bearing?). But I also noticed that the x-carriage must be slightly tilted because the top bearing is slightly offset to the lower two bearings. Not sure what's that about :). Ignore the values, scaling is wrong, should be 1/10.

@akbiocca would be great if you could measure how high the nextruder is over the top edge of the frame, when the z-axis is at the top. Personal question of mine because my enclosure height is a bit limited ;).

EDIT: It also appears the the x-axis rods are 4mm closer together, so that means MK3.9 needs new x-axis end stops. I guess they will release a version for the old bearings then.

[gregsaun]

@DesC21 thank you very much for those info! I wish I could be able to work on my computer but it is impossible at the moment.

The top bearing should ideally be aligned with center of gravity, maybe it is not that far but the motor is light and there are a lot of things on the left side (nozzle fan, wires, bottom bearing, etc.). Anyway probably not the biggest issue.

Those bearing alignement you show is also very curious. Are the X ends rods aligned the same way?

For your scaling issue it is probably because Fusion took cm instead of mm or something like, not very important.

[DesC21]

I just checked and the x end are aligned the same way (so extruder is not tilted ;-)). But that confirms that the nextruder can't be used with the old MK3 x-axis. So as I speculated Prusa will have to provide x-axis parts which fit the old bearings to make the MK3.9 work.

PS.: yep sure, you are correct, used the wrong settings on import! But only did a quick check of the parts after reading the last few posts ;).

@DesC21 thank you very much for those info! I wish I could be able to work on my computer but it is impossible at the moment.

The top bearing should ideally be aligned with center of gravity, maybe it is not that far but the motor is light and there are a lot of things on the left side (nozzle fan, wires, bottom bearing, etc.). Anyway probably not the biggest issue.

Those bearing alignement you show is also very curious. Are the X ends rods aligned the same way?

For your scaling issue it is probably because Fusion took cm instead of mm or something like, not very important.

[gregsaun]

Thanks for that and yes it confirms that new X axis will be needed. Just to be sure, have you check the spacing is 2mm as well on the x ends?

[DesC21]

Yes, it matches the 2mm of the carriage, It looks different on the images right ;).

[gregsaun]

Cool thanks for those info!

[HK-Moebius]

Couldn't it be easiest to redesign only the Z upper and lower parts and use the complete MK4 X-axis as it is?

[gregsaun]

@HK-Moebius this will be mandatory as the extruder is wider. Someone explained me that they moved the Z axis to the outside to accommodate the larger extruder. Unfortunately we can't reuse the 10mm Z axis mod made by Shaun at the moment due to this.

[gregsaun]

One good news is that the firmware has a secret menu where you can set the Z axis length, so no need to have special firmware compilation and Bear frame should be compatible even if we have to use a shorter Z axis.

[akbiocca]

On my MK4, with the extruder at 221mm (max Z) there is about 38mm of the extruder sticking above the frame top. This is the wiring cover shroud. The filament inlet hole is only about 5 mm below this.

The 10mm rod appears to be about 228mm in length. The ends are inside printed plastic parts so it could be a bit less. The top end is visible about one mm inside the part but the lower end is not. There is a rubber gasket between the Z motor and the printed plastic part. The Z rod stops above the motor, but out of sight inside the PETG.

I estimate the nozzle tip to be about 6mm below everything else on the extruder.

These are measured with metric tape measure and mark 1 eyeball. I might be able to do better if it is important, but I thought I'd start with this.

-- Alan B

On Wed, May 17, 2023 at 4:24 AM Dennis Schuldt @.***> wrote:

@gregsaun https://github.com/gregsaun good to hear from you, all the best and stay positive!

Good to hear your input. I do hope that there will be no collisions with the frame due to the nexttruder, especially with the cable coming out of the carriage so high now. I guess the weird position for the top bearing is only to have it centered to the stepper/hotend (even load on the bearing?). But I also noticed that the x-carriage must be slightly tilted because the one top bearing is slightly offset to the lower two bearings. Not sure what's that about :). [image: image] https://user-images.githubusercontent.com/26366384/238928530-1b525e4f-58a7-45a5-961d-5b6bd1354557.png Ignore the values, scaling is wrong, should be 1/10.

@akbiocca https://github.com/akbiocca would be great if you could measure how high the nextruder is over the top edge of the frame, when the z-axis is at the top. Personal question of mine because my enclosure height is a bit limited ;).

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[DesC21]

On my MK4, with the extruder at 221mm (max Z) there is about 38mm of the extruder sticking above the frame top. This is the wiring cover shroud. The filament inlet hole is only about 5 mm below this. The 10mm rod appears to be about 228mm in length. The ends are inside printed plastic parts so it could be a bit less. The top end is visible about one mm inside the part but the lower end is not. There is a rubber gasket between the Z motor and the printed plastic part. The Z rod stops above the motor, but out of sight inside the PETG. I estimate the nozzle tip to be about 6mm below everything else on the extruder. These are measured with metric tape measure and mark 1 eyeball. I might be able to do better if it is important, but I thought I'd start with this. … -- Alan B

thanks for checking, sounds good about the extruder for me, I have 6cm to the enclosure :). For the z-rod you mean 328mm right? MK3 rods are 320mm, so 330mm might be possible. X and y rods are already mentioned for the MK4 on the webshop, the z rods are not...

After all the input from @gregsaun I went ahead and assembled the x-axis with the original MK4 parts. The good news is, the general form of the z-axis parts works perfectly fine.

The bad news is, Prusa moved the z-motors more to the outside to make more room for the wider nextruder (thanks for the tip Greg, I didn't catch that...). That means the z motor mounts and z-tops won't be such an easy fix as I thought previously...

And even more bad news, as soon as the motors are moved more to the outside, the cable holder will collide with the top corner bracket (right now with the old position of the motor it would fit barely ;).

So the z-motors won't be able to sit in the middle of the extrusion anymore, if we fix it with the 3D-printed parts :-(. Another solution would be two new extrusion for the base and the one on the z-axis, to make the whole frame a little bit wider... decision time :-(...

PS.: such a pain to work with the stl, please Prusa release the step files already....

[akbiocca]

Yes, 328mm. I don't think they can be 330mm because the motor would be in the way, but perhaps they are 325mm as we can't see the bottom end of the Z rod inside the PETG.

On Fri, May 19, 2023 at 6:36 AM Dennis Schuldt @.***> wrote:

On my MK4, with the extruder at 221mm (max Z) there is about 38mm of the extruder sticking above the frame top. This is the wiring cover shroud. The filament inlet hole is only about 5 mm below this. The 10mm rod appears to be about 228mm in length. The ends are inside printed plastic parts so it could be a bit less. The top end is visible about one mm inside the part but the lower end is not. There is a rubber gasket between the Z motor and the printed plastic part. The Z rod stops above the motor, but out of sight inside the PETG. I estimate the nozzle tip to be about 6mm below everything else on the extruder. These are measured with metric tape measure and mark 1 eyeball. I might be able to do better if it is important, but I thought I'd start with this. … <#m-702917997879862360> -- Alan B

thanks for checking, sounds good about the extruder for me, I have 6cm to the enclosure :). For the z-rod you mean 328mm right? MK3 rods are 320mm, so 330mm might be possible. X and y rods are already named for the MK4, the z rods are not...

After all the input from @gregsaun https://github.com/gregsaun I went ahead and assembled the x-axis with the original MK4 parts. The good news is, the general form of the z-axis parts works perfectly fine. [image: image] https://user-images.githubusercontent.com/26366384/239544614-58437b43-9c90-4699-b3f6-4f29a3f53f63.png

The bad news is, Prusa moved the z-motors more to the outside to make more room for the wider nextruder (thanks for the tip Greg, I didn't catch that...). That means the z motor mounts and z-tops won't be such an easy fix as I thought previously... [image: image] https://user-images.githubusercontent.com/26366384/239545047-afe0658a-d019-404b-876c-9b13470b43f0.png

And even more bad news, as soon as the motors are moved more to the outside, the cable holder will collide with the top corner bracket (right now with the old position of the motor it would fit barely ;). [image: image] https://user-images.githubusercontent.com/26366384/239545358-8d4509cb-f718-4daf-b63e-6af41eb33a58.png

So the z-motors won't be able to sit in the middle of the extrusion anymore, if we fix it with the 3D-printed parts :-(. Another solution would be two new extrusion for the base and the one on the z-axis, to make the whole frame a little bit wider... decision time :-(...

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[gregsaun]

@akbiocca thanks for the info. MK3.5 has a Z axis of 210mm and MK3.9 has 220mm so I think yes they moved to 330mm Z rods. Interesting they have added a rubber between rod and motor, probably to reduce the noise some printer have when the Z axis is moving on the full range.

@DesC21 thanks for this great job! With STL is a pain to do. Not having CAD files and hardware list shows how serious Prusa is regarding open source. So yes cables will hit the corner plates, not sure this can be fixed. Their Z top seems thicker so maybe the spacing you have between Z top and X end is smaller. I would prefer to change the Z length in the firmware as they seem to provide this functionality and keeping the frame as it is.

[Novacat170]

The rubber may be a way to allow some "movement" due to tolerances stack up during assembly but at the same time procede some force so the rod doesn't depend only on friction to stay "fixed" vertically. As rubber will push it to the other side. Maybe rattling noises?

Regarding the z height even though firmware mods are an option, it implies breaking a tab and lose guarantee even though the rest is not changed... I understand they have to protect themselves from "broken boards caused by wrongly prepared firmware. Maybe move the cable slightly down as add a small tab in the center for the contact during z calibration? Other options are to "update the frame to get rid of that corner bracket. Smaller one? Higher vertical one and fit it inverted? One of those that fit in the "interior"? Blind joint?

And about the open source files... You are right that the STL is not cad dependent so more "open"... But at the same time it's not a cad file. Each one has its purpose. And there are many non proprietary cad files (like step or iges) where I.e. round holes keep being round (sorry I hate loosing the ability to joint to facetted holes in assemblies to work with...). And when the shape is unorganic ok but when they are sweeps and organic ones... Rebuilding them are a pain in the a**

[DesC21]

@gregsaun @akbiocca I think we can settle the rod discussion ;). It should be the same rod length as before, they archived the 10mm simply by the nextruder design. I mean the carriage is even a little higher than the x-end parts :-)

So to check the collision with the cable holder, I went ahead and moved the MK4 x-axis to the right position, each motor was moved roughly 6mm more to the outside of the frame. And of course, there is a collision :(. 3mm in z-height would be lost to avoid the collision. But the good news is, I can't see anything else giving us a headache.

solutions

1. redesign cable holder cover
2. calibrate with the cable holder not attached and limit z-axis (min. -3mm) in software
3. change the bear frame width (worst case I'd think, moving the motors more to the outside should be perfectly fine, just as the original). Advantage would be the z-axis parts would be finished already ;).

[DesC21]

just adding a slot to the cable cover should work just fine, I'd say.

[gregsaun]

@Novacat170 no need to break the tab, apparently there is a hidden LCD menu where you can set the Z axis length. In "open source" there are two words, open and source. If you want to be open and interroperable between software then you release the CAD, the STEP and the STL (this what I do). The source is missing and so you can't modify it and send the modification via a pull request on github like we do for software. Also the idea of open source is to share knowledge and not having access to CAD is a lost in that regards. Finally, STEP files are "deleting" a ton of constraints and parameters.

Regarding the rest we don't have the frame, the hardware list, the specs of fans, the files for the hotend, etc. It is just a fully close source printer at this point, just like a BambuLab.

@DesC21 nice job, maybe going back to zip ties would do it but we also have to consider some tolerances of the plate assembly. Another solution is to replace the top plate by printed part (not a very critical section of the frame) or new metal parts.

The bottom of the extruder is really too close to the nozzle tip, this is not a good decision from them.

[DesC21]

MK4 Z-axis for Bear is alive ;) Especially the z-motor-mounts are not pretty, but it should work as a first pre-alpha version :)

But I did notice something else on the Prusa design of both x-end parts. They have this weird bump at the top. But it doesm't fit into the Prusa z-tops. Especially that weird chamfer should be really close to a collision.

This is how it currently looks with my bear parts. That is currently the end stop and needs some fixing...

[HK-Moebius]

What's about to mount the corner bracket this way? I assume it will not give the same strength as the regular way, but it will not block the cable holder.

[gregsaun]

@DesC21 wow you are quick, cool work! Do you have 220mm length? We could fix the Z tops from the side of the frame with 2 screws on top of each other. It would help with clearance and stiffness. It is promising.

@HK-Moebius I thought about it but maybe with a different cable holder on the nextruder could avoid frame disassembly. Also I am not sure I like to top extrusion to be set with a single screw but needs to be tested.

[DesC21]

@gregsaun I don't know the exact position of the nozzle so I can't say for sure. When I move the whole x-axis assembly 220mm, I get a 13,9mm gap from the bottom of the nextrudr to the heatbed. Looking at pictures, the nozzle is really close to the bottom of the extruder so that should work I think.

Yeah, I also thought about mounting the z-tops from the side. Still lots of room for improvement ;).

EDIT: I made a mistake when aligning the cable holder, it actually is mounted a little lower so that gives us more breathing space! The standard parts just barely touch the corner bracket! I quickly sketched a new cable cover. Right now, there is a 3mm gap to the corner bracket. Should work fine with tolerances for everybody I would say.

[gregsaun]

@DesC21 This is promising, 13.9mm seems to be more than the nozzle <-> X carriage distance. This is promising! And good news for the cable holder!

@akbiocca do you think you could roughly estimate the space between nozzle and bottom of the X carriage?