Adding a bottom or joining  

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gkas
(@gerrykaslowski)
Eminent Member

I have a two part question.

1. I have a tall box that I want to shorten. I don't want to resize Z because the top lip is formed for stacking. I can use the CUT procedure and throw away the bottom. Can I then force PrusaSlicer to print a bottom on the box?

2. Question #2. If I cut the box in two, I can then resize the bottom. Can I force PrusaSlicer to stack the 2 parts together and print them as a single part?

I've been doin this in CAD, but it would be nice if I could do it in a few clicks in the slicer.

thanks,

Gerry

Posted : 04/08/2020 3:40 am
Neophyl
(@neophyl)
Noble Member

Question 1 - if you cut the bottom off an object then the new cut surface becomes the bottom so it will behave like a normal model bottom with whatever bottom layers you have set.  Its basically the same as doing a boolean difference on anything below your cut line if you choose to get rid of it.

Question 2 - not easily no.  You can cut it off and keep it, then resize it without problem.  However the only way that slicer lets you print an object that is not on the bed is to have the second model as a logical part of the first.  When you cut an object in 2 it gets separated into 2 objects.  
You could resize the cut part and then choose export as stl to save the modified version.  Then right click on your first part and choose add part and select the object you exported.  This would import the saved part as part of the same object which will allow you to move it around in the air and 'stack' it on the first.

Frankly it would take a lot less time and be much better and more precise to just modify the original object in some proper CAD software as that's what it is designed for.  Something like Blender or Meshmixer where you can easily manipulate existing geometry.  There will be loads of others you could use but I'm not familiar with anything else.

Posted : 04/08/2020 7:25 am
towlerg
(@towlerg)
Honorable Member

@neophyl

Perhaps I'm not understanding correctly but I think the answer is yes. Try this, make cut saving upper part (lets call it part A) and save it, reload the whole part, make a cut saving the lower part, now import part A and line them up (with a little overlap jic), save as .stl, load the stl.

Post the part and I'll try to show what I mean. 

Posted : 04/08/2020 11:33 am
gkas
(@gerrykaslowski)
Eminent Member

Thanks.  Stackable boxes

Posted : 04/08/2020 8:45 pm
Neophyl
(@neophyl)
Noble Member

What do you want to do to the boxes ?  If you want to make them not as deep or deeper (changing z height) but keep the bottom thickness and top lip section the same then that would take about 30 seconds in Blender.

Its possible to achieve in slicer but its not trivial to do.  You would have to cut the model into 3 parts, the bottom, middle and top.   You would then resize the middle to whatever new height you need for the extra or less  You would then have to export at least 2 of the parts and save them as stl files.  Personally I would export the middle and top sections and leave just the bottom in Slicer.  
Then you would right click the bottom section that is in slicer, choose 'add part' and then select the middle section.  That would then import the middle and add it to the existing object rather than adding it as a separate object.  When added in this manner it can be placed such that its not on the bed and 'above' the bottom part.  You would have to carefully place it and scale it and make sure that there was a slight overlap with the bottom part.  Once you have the middle section in place you would repeat the process to add the top section back in at the correct height. 

The resulting project could then be printed.  Doing that rather than just importing into blender, selecting edit mode, selecting the top vertices, moving them up or down to the desired height and then saving the modified stl.  Basically 30 seconds work.  A lot less effort and one where you dont have to worry about placement or positioning etc.

However as you want to know how its done I have attached a project file where I have cut up one of the boxes and exported/reassembled it as I describe above for you to study.  I hope it is useful and I hope you try it with another of the boxes and then do the same thing with some proper cad software.  You will see that it is MUCH quicker and easier to do in  software that is designed to do that job.

Posted : 04/08/2020 10:41 pm
towlerg
(@towlerg)
Honorable Member

@neophyl

I'd thought that Blender was more targeted at "art", figurines and such. The problem I find with trying to edit an existing .STL model is that it just isn't an appropriate format for most CAD packages. I'm trying to learn DesignSpark and it just doesn't deal with .STL very well. Prusaslicer seems to handle .STL without problems. The advantage of moding in Prusaslicer is that you don't have to learn a CAD package.

I've downloaded Blender and give it a spin.

Posted : 05/08/2020 1:15 pm
towlerg
(@towlerg)
Honorable Member

@gerrykaslowski

Is this what you want to do?

Posted : 05/08/2020 1:17 pm
towlerg
(@towlerg)
Honorable Member

I just ran Blender for the first time, IMO the learning curve to do the simple thing the OP requested is unreasonable. I would suggest that if a CAD type solution was desired something more engineering based (the obvious being Fusion 360 but that's cloud based and personally I neither trust or would use a cloud based app but thats just me) DesignSpark is painful but I'm beginning to suspect the CAD is just a big learning curve, whatever package you pick. 

Posted : 05/08/2020 1:25 pm
Neophyl
(@neophyl)
Noble Member

@towlerg

Yes there is a learning curve but that is the case with all cad packages, your suspicions are correct about that 🙂  .  I found blender to be easier than fusion 360.  At least for manipulating already existing stl files.  For parametric technical design then 360 is probably better although once you learn more about Blender it is possible to do a lot of the same things, its just done in a completely different manner.

It just looks daunting.  Once you pick up the UI and some basic concepts it will make much more sense.

For example with the stretching/manipulating of the box example that the OP gives I would do the following.

Import the stl file into blender.
Turn the view to wireframe mode.
Change to edit mode (press tab to toggle between object and edit mode)
Select vertice mode (number 1 on the keyboard, not the keypad but there are select icons on screen too you can use )
Move the view to view the box from the side (this can be done by pressing 1 on the number keypad if you have one or you can middle mouse button and rotate the view around)
Box select the top area of the stl file  making sure to cover the top lip of the boxes (left mouse click and drag the box over the top)  because we are in wireframe mode all the vertices can be selected even those behind others.
Drag the selected vertices up or down however far you want using the manipulation handle for the z axis or if you want a precise amount then you could use the keyboard.  For example typing 'gz10' would move all the selected vertices up 10mm.  G is grab, z limits the axis to up/down and 10 is the distance.  You could type -10 to lower them 10mm.
Job done.  Change back to object mode and making sure the object is selected export it as an stl file.

So 4 keypresses and a couple of mouse selects once the stl has been imported.  As I said its 30 seconds work for such a simple model like these boxes.  You can pick the basics of the user interface up by watching one of the many youtube videos in under 30 minutes. 

Yes it takes time to get good and even longer to get quick.  I don't consider myself that as yet, as it takes me a lot longer than some of the guys doing these tutorials and I still go how the heck are they doing that all the time but don't be put off.  Its extremely powerful software. You can pretty much make it do anything you need.  Just don't try to learn it all at once.  I usually find myself wanting to do something and then watching a tutorial on how to do that specific thing.  Then trying it on my project.  That way it tends to stick more as I am actually using the knowledge gained practically. 

Its free and its not that big a download being under 150 mb.  Like you I do not like cloud based software.

If you are ever going to progress beyond printing off other peoples models then you have to learn some form of CAD.  Prusa Slicer can do some nice tricks and if all you do is a few tweaks you can get by with that.  You reach a point though where it cant do what you want.  Nor should it.  Its a Slicer, its designed to slice.  If they made it a CAD package too then you would have to learn its CAD rules and it would get way more complicated, I also doubt that it would be as good a CAD package as others already available.  

Posted : 05/08/2020 2:36 pm
gkas
(@gerrykaslowski)
Eminent Member
Posted by: @neophyl

What do you want to do to the boxes ?  If you want to make them not as deep or deeper (changing z height) but keep the bottom thickness and top lip section the same then that would take about 30 seconds in Blender.

I'll have to look at Blender again. I've looked a little bit before for my CNC 3D modelling, but I just went with Aspire. 

thanks again...

Posted : 05/08/2020 7:18 pm
gkas
(@gerrykaslowski)
Eminent Member
Posted by: @towlerg

@gerrykaslowski

Is this what you want to do?

This looks like only the bottom section. I'm trying to also save the top section, it has a flange.

Posted : 05/08/2020 7:21 pm
Neophyl
(@neophyl)
Noble Member

@gerrykaslowski

Did you look at the project file I linked ?  That has a box split into 3 with the bottom/middle/top flange.  

Posted : 06/08/2020 7:18 am
gkas
(@gerrykaslowski)
Eminent Member
Posted by: @gerrykaslowski
Posted by: @towlerg

@gerrykaslowski

Is this what you want to do?

This looks like only the bottom section. I'm trying to also save the top section, it has a flange.

Yes, looks good. I'm going to take a look @ Blender.

tnx

Gerry

Posted : 06/08/2020 8:32 am
towlerg
(@towlerg)
Honorable Member

Sorry, zipped up the wrong file.

Posted : 06/08/2020 11:41 am
gkas
(@gerrykaslowski)
Eminent Member
Posted by: @towlerg

Sorry, zipped up the wrong file.

Very cool... I will definitely take a good look @ Blender.

Posted : 06/08/2020 3:49 pm
towlerg
(@towlerg)
Honorable Member

@gerrykaslowski

just to be sure, I didn't use Blender, nor would I (in my limited experience) recommend it.

Posted : 08/08/2020 9:24 pm
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