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This doesn't fit the original Prusa MK3  

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rbish
(@rbish)
Active Member Customer
Joined: 8 months ago
Posts: 6
27/11/2019 5:38 pm  

Two problems:

1.  Z-height calibration won't work- the purge mechanism interferes with the proper Z-height calibration as the mechanism strikes the front of the upper z-brackets before topped out and bends them upwards.

2.  The purge mechanism itself is at least 10mm higher than the nozzle.

Any ongoing work to make this work with an original MK3?


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BigBrain3D
(@bigbrain3d)
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Joined: 12 months ago
Posts: 181
28/11/2019 2:15 pm  

1. We just reran the calibration on our machine and the issue you mentioned doesn't show up here as the z calibration completes successfully. Can you please record a video of the calibration problem you are seeing? 

2. As soon as prusa sent out the free upgrade kits we installed them so we cannot test this here. Would you mind help us with this since we don't have an MK3? You would just need to 3D print the brackets and try them. We downloaded a 3D model of the i3 MK3 from grabcad. It shows that the difference is 5.75mm in height. Attached is an updated stl for the bracket that is longer by 5.75mm. If you can try this out and take a photo/measurement then we can adjust as needed.

Thanks 🙂


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rbish
(@rbish)
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Joined: 8 months ago
Posts: 6
29/11/2019 8:10 pm  

I agree that the calibrate does complete, but I don't like how it bends the upper z bracket as it does so.  I can't seem to attach or upload a video that I made of this interference.

I had already modified the bracket in Fusion 360- Mine is 5.875mm longer, and that seemed to do the trick.  I also found that the bracket needed to be spaced an additional 2.54mm forward (towards you as you are looking at the printer).  I modified the Purge Mount Right bracket to do this.  Both modified parts are printed and mounted and purges are successful now.

Let me know how I can upload the short video showing the calibration concern I have.

Thanks!

 


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allen.r.marion
(@allen-r-marion)
Active Member Customer
Joined: 8 months ago
Posts: 8
01/12/2019 2:34 am  

I have the z axis brackets from JLTX on thingiverse on my machine and had the same interference. What I did was modify his bracket to not use the filler plate on the bottom side (extended the recess flush) and created a 3mm recess on the top for clearance to the purge mechanism.  With this I had to use shorter screws  in the front two holes of the motor mount.  Hope this helps.


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BigBrain3D
(@bigbrain3d)
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Posts: 181
01/12/2019 2:55 pm  

@rbish

I've attached the files with the changes you mentioned and posted them to the google drive too.

Also, putting the files into a zip will probably help with uploads to the forum posts.


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BigBrain3D
(@bigbrain3d)
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01/12/2019 2:56 pm  

@allen-r-marion

Could you please attach a photo of the installed unit? Thanks!


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allen.r.marion
(@allen-r-marion)
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Joined: 8 months ago
Posts: 8
01/12/2019 3:02 pm  

@bigbrain3d

Don't have a picture right now, but it is just a motor mount.  I put the .stl on thingiverse for everyone.

https://www.thingiverse.com/thing:4013705


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BigBrain3D
(@bigbrain3d)
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01/12/2019 3:40 pm  

@allen-r-marion

Thank you  🙂


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Googliola
(@claude-scagliola)
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Joined: 7 months ago
Posts: 2
22/12/2019 7:47 am  

@allen-r-marion printing your replacement for jltx bracket now.

I ran into another problem: mechanism cannot work below z=14 as it gets block by the bed see picture at ?dl=0?dl=0

?dl=0

This post was modified 7 months ago 3 times by Googliola

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BigBrain3D
(@bigbrain3d)
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Joined: 12 months ago
Posts: 181
22/12/2019 1:48 pm  

Yes that is why there needs to be a z lift in the on tool change like this:

G91;Change to relative position
{if layer_z < 15.0}

G1 Z15

{endif}
G90;Change to absolute position


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Googliola
(@claude-scagliola)
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Joined: 7 months ago
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23/12/2019 3:54 pm  

@bigbrain3d

should have RTFM but was too excited to try it ? ..well, thx anyway for the quick reply


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BigBrain3D
(@bigbrain3d)
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23/12/2019 3:56 pm  

@claude-scagliola

You're welcome 🙂


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allen.r.marion
(@allen-r-marion)
Active Member Customer
Joined: 8 months ago
Posts: 8
08/01/2020 4:57 am  

@claude-scagliola

Did you get it working?  I had some issues with the repeatability of where it locates the bucket under the nozzle due to flexing of the bracket.  I designed a brace that attaches to the bracket and couples it to the smooth z rod.  I can’t give you my files as they are modified for my machine, but here are some pics of the cad design to give you an idea.  I’m testing now and the repeatability is spot on now for the bucket placement.

 
 
This post was modified 6 months ago by allen.r.marion

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flyers6667
(@flyers6667)
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Joined: 5 months ago
Posts: 2
11/03/2020 11:08 am  

Hello,

I printed the files you send on Thingiverse: https://www.thingiverse.com/thing:4048193/

It doesn't fit on my MK3 (not MK3s), the PINDA is hitting the purge mecanism.

I've haven't change my gcodes yet. 

I was just trying the first step (assembling on the printer).

Is there any issues that I haven't seen?

 


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BigBrain3D
(@bigbrain3d)
Supreme moderator Admin
Joined: 12 months ago
Posts: 181
12/03/2020 12:40 pm  

Hi @flyers6667,

You need the parts for the MK3.

Also we've made an updated connecting arm (Rev B) so please make sure you printed that part from thingiverse.

It's likely that you will need to raise your PINDA probe. Lower the nozzle to .2mm about the print plate. Then adjust the PINDA until it barely senses the bed, then lower by 1/2 turn. Make sure the cable is twisted out of the way of the action arm too. Then redo your first layer calibration.

 

 


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