When you add a primative (i.e Cylinder) to an object, is there a way to automatically CENTER the primitive on the associated object vs just moving it freehand? Seems like there should be a way to do this.
Also, when a primitive is floating above the plate, is there a way to tell Studio to drop the primitive to the build plate? I know you can manually move them but that’s pretty tedious, is there an automatic way to do this?
These examples are using Orca Slicer 2.2.
Right-click on the object and select Center for both objects you want to align. This will move each object to the middle of the build plate. Repeat this process for all other objects in your model.
However, note that this tool calculates the center as the geometric center of the bounding box of the model. This works fine for symmetrical models, but if you’re trying to center the object on a specific point or location within the model, slicer software does not support this. For precise placement, you would need to use CAD.
Similarly, to drop a model onto the build plate, use the Right-Click → Drop command.
In the example below, the Center option is greyed out because I have already selected it, and the cylinder is now at the center of the build plate. However, the model is still suspended above the plate.
Selecting Drop will place the object at the bottom of the plate. In the final example below, the cylinder is now both centered and dropped to the plate, which is why both options are greyed out.
Although you didn’t ask, I’ll anticipate another common question:
“How can I select a specific spot on the surface of a model and center another object to that spot so they are flush?”
The answer: You can’t. Slicers are not CAD, and this is a function that CAD handles easily.
The only workaround is to use the Move command and manually adjust the position using numerical inputs. Tedious? Yes. But it’s the only tool available in a slicer.
There’s an old saying: “When the only tool in your toolbox is a hammer, all the world begins to look like a nail.”
In 3D printing, I often see questions like this where the best answer is simple: Use the right tool for the job. Use a screwdriver to drive screws and a hammer to drive nails. Likewise, don’t try to use a slicer as CAD.
Yes, you can force slicers to do some things that CAD handles much better, but as another saying goes: “Why train a billy goat to climb a tree when you can hire a squirrel?”
Sometimes you don’t have access to the CAD files, if I did then I agree with your statements. But it’s certainly easier in most cases to get the job done in the Slicer if possible, no need to make a task harder than necessary. Of course, if the Slicer can’t do the task then, of course, revert back to CAD to make the changes (if you have access to the CAD files).
I believe there’s a couple problems with your answers (at least when I try to use your suggested approaches, it doesn’t work as expected). And just to be clear, my questions pertain to working with PRIMATIVES not standard objects.
Positioning seems to be screwed up with combined objects (i.e. an object with an associated primitive and/or negative part), since the size of the object is shown as the combined size of the original object and any/all of the combined parts. So when trying to center, things get messed up and centering doesn’t appear work properly (at least that I can see). I wish it just allowed you to center associated primitives directly to the CENTER of the containing objects size (without any added parts).
I’m not seeing a DROP option when working with the negative part. Here is what I see when I try to drop the negative part (associated with object shown in RED):
As you can see, this negative part is up off the bed in Z. When I right-click it there isn’t a DROP option shown.
And all of the DROPping things don’t apply when working with standard objects, since Studio doesn’t appear to allow you to move a standard object in Z. When I try, it just automatically drops it back down to the plate. I guess I can understand that but it should just gray out all the Z selections if this isn’t allowed. It lets me grab the move handle (or type a value in the Z field) and move it and it shows it moved with the handle until I let go and then it resets back to the plate. Feel it should display an error message saying why it can’t do what your are asking vs just dropping it down automatically. Just seems odd to me.
First, let me say thank you for posting clear, annotated screengrabs. 
This really helps take the guesswork out of understanding your objectives.
It looks like you’re trying to solve multiple problems with one click. Let me suggest an alternate approach.
First, it’s clear that you’re using Bambu Studio. I recommend loading Orca Slicer on your machine. There’s no downside to using both, as they can coexist on the same system since they’re based on the same core code. However, as you can see, the drop feature is just one of many quality-of-life enhancements the Orca team has included in their version. It’s worth noting that Orca is based on Bambu, and the developers are printer enthusiasts whose sole goal is to enhance the user experience. In other words, they create features they actually want to use, not for commercial purposes. Bambu has borrowed back some of these enhancements, but it appears that Drop may not be one of them.
That’s exactly what my example showed, but I think you may be getting hung up on terminology. A primitive is just another object—the only difference is that the slicer generates it internally.
In your example, I believe I understand what you’re trying to do, but it seems like you’re attempting two different things that require different approaches. Let’s tackle the easy one first.
This only happens when the object is isolated. If, for example, you want to suspend a part/object above the build plate, it must be part of an assembly. Select the object from the objects menu, and you’ll be able to move it independently.
In this example, we have a dragon model with a cube primitive that was created as part of the assembly. Note that the cube(tiny red dot lower right) is the lowest part of the geometry, serving as the build plate anchor.
You are absolutely correct. The slicer calculates the center based on the combined size of the “assembly.” It sure would be nice if there were an object alignment tool built into the slicer. In fact, I suggested this, and many users voted in favor of it.
Sadly, that was back in 2023, and despite 95% yes votes, the response from Bambu Labs has been nothing but crickets.
Link to the alignment request poll: Align to grid/align to object
So, the only workaround—just like in your example—is to independently create a single instance of the model and perform all necessary operations on that one model. Then, using the Clone tool, recreate the required number of models and use the Auto Arrange tool to realign them onto the build plate.
If the model is a pre-arranged grid you acquired elsewhere, you’ll need to use the Cut tool to isolate the segment. If the grid has specific spacing requirements, you can use the more granular Arrange Objects tool in the toolbar (Shift-A), which allows you to precisely set object spacing.
If row distances differ from column distances, first create the row alignment, then clone that assembly and make a second alignment using the first set of rows as reference.
Clumsy? Yes. But this isn’t CAD. 
In CAD there is a pattern tool that does this very quickly.
There are many CAD packages out there. I use free versions OnShape, Fusion360, and FreeCAD. I also use Solidworks for Makers($50/yr) but I don’t recommend that since it’s got a very, very steep learning curve and unless you’re using it professionally like I am in my day job, there is no advantage.
My go-to CAD is OnShape for easy of use and it is much better suited for 3D printing. What’s more, it is cloud based so whatever hardware you have is not a factor, only a browser is needed. I have a contemporary desktop computer with an advanced GPU so hardware is not an issue in my case nevertheless, OnShape is just easier to use.
This YouTuber’s videos is what convinced me. He does a side by side comparison to many CAD programs, all from a bias of a 3D Printer enthusiast. His tutorials are world class.
Here’s an updated version of his beginners video that got me started. https://www.youtube.com/watch?v=d4QzBdcQoe0
Thank you so much for all the details that really helps. I’ll dig through it all and let you know if I have any questions. Again, really appreciate your time.
Regarding Orca. I use both Studio & Orca (I also have a couple FlashForge 5M Pro printers and a few older printers using Orca). I really miss the Calibration processes built into Orca when using Studio, I wish they would use the same Calibration routines in Studio. But I generally use Studio with my Bambu machines & Orca for others. Things are “mostly” compatible but it’s not perfect as I’m sure you’re aware. I find odd things happen when I try to move projects back and forth between the slicers. Are there any documentation that you’re aware of that describes what things work & which things don’t when crossing projects between Orca & Studio?
Regarding Orca, I also started having another problem last week. Since you use Orca, maybe you can help me. After months of use, Orca suddenly crashed last week and wouldn’t allow me to re-open. I can start it and it displays the main screen for a few seconds and then crashes with a Crash Report but no specific error dialog. I’m running on MacBook Max under MacOS. I worked with Apple Support to isolate what appeared to be the problem - I was on an older version of Sequoia (15.0.1) and there is a newer version 15.3, which I’ve now upgraded to late last week. And Orca started working properly again, until yesterday. It crashed again with a Crash Report but no error messages telling me what the problem is. And again, it’s doing the same thing as before, it starts, waits a few seconds and then crashes. So at the present time I can’t run Orca. The other odd issue here is that I was on 15.0.1 for several months and Orca was running fine. So, not sure if the update to 15.3 solved the initial problem or just hide it for a bit. Have you ever heard of this type of a problem and if so, any suggestions on how I can get this resolved so I can run Orca again?
Appreciate any guidance.
I’m afraid I won’t be much help on diagnosing the issue with a MAC since I use the Windows version. Sorry. 
