I’m putting together mechanical and electrical demonstrations. I need to print a bench rail, and mounts I can use to hold equipment.
I think the Picatinny rail might be a good choice. I found a nice design here: Picatinny Rail (Fixed STL) by gxl117 - Thingiverse
The rail section in the file is very short. I want a longer strip of rail. How can I modify this file to make longer sections of rail? I can use FreeCAD a bit, but I’m not a designer.
Once you have it on the bed, you can scale the X or Y to the length you want…uncheck Uniform Scale.
Scaling it will change the proportions of the object. I should have said that I would like the features of the object to remain in the same proportions.
My only idea so far is to to clone the object, overlay the two so that the features on the rail line up perfectly, and then merge them in some CSG operation. I don’t know how to line up pieces that perfectly. Yet
If you just need it longer, you could add 2 on your build plate,align them correctly and merge them to make a longer one.
*Move the pieces via coordinates in the move function. That will align them properly.
CTRL+click to select both parts, right click and merge.
I’m not sure if that statement is entirely true. Yes, I am aware that the specifications of a Picatinny Rail require precision but that’s only in one vector. You can scale in one vector and leave the rest alone.
All you need to do is uncheck the Uniform Scale box to ensure that you’re only scaling in one axis.
Yes, I am aware that this will make the holes oval and will place them in the wrong spots but if your not using the holes it won’t matter.
Now, if that solution is not acceptable to you and what you really want to do is add segments to the rail… well… the right tool for this is CAD, not the slicer. However, if you believe that the right tool is the one you have, not necessarily the one you need, then what follows is a method equivalent to using a pipe wrench as a hammer. It won’t be pretty and the nail head might look ugly, but it can be done inside the slicer. It involves many steps and requires much patience and a certain amount of trial and error. We’ll use the model you cited off of Thingiverse as the example.
Cut out the section you want to use as the “extender”. You will have to do this twice in order to cut out the segment we will later use as an extender piece.
Clone the Center Piece(CTRL-K) and make as many segments of the extender piece and rename it something else by selecting the model in the objects menu, hitting Space and then start typing the new name. Type CTRL-E to show the model names.
Now comes the beginning of the tricky part and the part that will most likely be challenging. “ALLIGNMENT” Select each object one at a time, right-click and center all objects. This will align all objects from their respective center points.
Now in this example I have created 3 sections and named them and changed the filament color to make them easier to see. You will want to use the Object Menu to select each item.
Selecting the object and then select the move tool. Now either use the arrow key’s and move them with your mouse or you can get more precision by typing in the correct position by hand. This allows for sub-millimeter precision.
Select all of the models. This can be done by using shift-click in the models menu or holding down the shift key while dragging the left mouse button around the objects. Once all of the objects are selected, Right-click and assemble them into one assembly. Then slice your model. If you used separate colors it will look multicolored and you will want to remove those if you have an AMS. Otherwise if you don’t have an AMS, it will simply ignore the colors on prints.
If you did this correctly, the sliced model should look like this.
Creating a single model isn’t necessary for printing but ensures a stronger model with fewer artifacts by eliminating interior walls caused by the joining of two models within the slicing process. This works well if you followed the initial steps above correctly. If there are visible seams in your model, they will appear in the Boolean model too. Go back and fix them.
Repeat this for every section and when you’re done, you will only have a model called “Assembly”.
This is what the sliced model looks like next to the original we used to make this model.
If you aligned everything correctly, it will produce an accurate piece. Again, I want to emphatically state that this is best done in CAD. Both Onshape.com and Fusion360 have free versions that work well with this kind of concept but they both have a steep learning curve. If you want to be a 3D Printing ninja, I would recommend at some point climbing that curve. You will be rewarded with the ability to independently modify almost any ‘mechanical’ model with geometric lines that you might find on the web. This technique does not work well for organic models like Dungeons & Dragon figurines.
What an amazing answer! Thank you. Several great ideas. I had not thought to use the slicer. And you are right, scaling the rail out along one axis won’t mess up the railing, it will just stretch out the raised and lowered sections.
I’ll use the slicer. I’ll fire up Orca and see if I can get the union function to work. Once again, thank you for such a thoughtful and thorough answer.
