Sizing for snap-fit box?



I’m designing a snap fit mechanism for a case. The lid will have tabs, and the bottom will have grooves for those tabs.

Here is a groove I’ve made. I have some questions:

  1. I want to make a tab that exactly fits the empty space of the groove. How do I do that without a lot of manual work?

  2. Should the tab be exactly the size of the groove? Or should it be a little bigger (how much)?

  3. The depth of this groove is 0.75mm. My printer (a Monoprice, although I also have access to a FlashForge that I’ve never tried) has at best 0.1mm precision. Do you think my groove depth is something the Monoprice could handle?



Copy the geometry of the groove to use for the tab.

I would make it at least the same size and file it down a little until it fits. It’s easier to remove material later than it is to add material.

I can’t answer about what the printer can handle.

I think you should find some existing boxes with snap on lids and look at how they handle it.


Thanks, that’s really helpful!

I’ve now created a tab exactly the size of the groove on the base. I want to cut this tab off of the base so I can stick it onto the lid.

I’m struggling to figure out how to split that tab-solid from the rest of the base, so I can move it to my lid?


Sorry. I figured you’d already have made the box a component or group. Do that before copying the geometry of the groove. Then open it for editing, copy the geometry, close the box group and then use Edit>Paste in place. The tab will be in the same location but not stuck to the box.


Sorry, I’m confused…

I made the whole box a group. I hit ‘edit group’. I pulled the faces of the groove upwards to create an equally sized tab on the box. The group is still highlighted blue, now I go to edit and the ‘close group/component’ option is greyed out so I can’t do that?


No. Open the group, select the geometry of the groove and hit Edit>Copy. Then close the group and hit Edit>Paste in place.


Sorry for being dense! I don’t know how to ‘select the geometry of the groove’

Nothing was grouped when I made the groove. Now I’ve made a group out of the grooved box. I’m unsure of how to select the geometry of the groove, there’s nothing to select - the groove is a bunch of triangular faces that I’ve pushed into the box to create empty spaces?

(Also, my goal is to create a separate tab shape. Right now I’ve made a tab shape that is stuck to my box. Why would copying and pasting a groove shape create a tab?)


I may have missed you plans but, one of the fist steps must be what print technology will be used for your project. Do not assume just any thing will work. It has been some time but I did some research on what tolerance is required for snap together parts. Needless to ay I got answers all over the map.
Here is a link that may help you some:
Many of the processes used also use heat with materials which typically have high coefficient of expansion so when they cool they contract. When you select the print technology contact the printer if you are having it done they will probably give you some guide lines, same if you are buying a printer.
BTW the pics of you model seem to show some questionable edge artifacts you may what to check or post you model so Dave can check it.
Good Luck


This indicates you have not read the first two parts of the first chapter of the User Guide:


To try and convince you about approach I used your lid post above and made no changes except to export it as .dae ( dynamic asset exchange) so could open in different program.
It opened with 5761 vertices and 2026 faces;
Using some cleanup filters 7 duplicate faces removed; 4702 duplicate vertices removed; 13 null faces ( zero area ) removed; selected and removed self intersecting faces ( 1760 faces now); 1046 non manifold faces removed.
After re-import to SU non non-coplanar edges removed. You can see the results of that in attached model and also the holes in lid are not aligned correctly.
The reason is try to get your attention and convince you to spend time reading some of the help files and also the many excellent YouTube videos which will not take more than few days and then use the lid as a simple test case for testing you self.
I have many times told Engineers working for me to slow down and hurray up, think that applies to you.
Suggestion: Make the lid ribs, corners and flat section components so you can make a good accurate model. The corners have major issues now: slight_smile:case_base_partial_clean.skp (187.8 KB)


czar Update, attached some cleanup of lid, fixed rails, arcs in corners all and showed on case with what I call key. Still some work to do hope you get idea.case_base_partial_clean.skp (539.5 KB)
The small line spacing shown in the lid cross section may be issue with your print problem on box. More checking required
Attached is lid top all excep did incled the top prifle like you wanted , dleted holes because of the mis_align and thehand hole since it intersection with the ind edge detail. Then befor any more work had problems, think fixed nowAutoSave_case_base_partial_cleanA.skp (432.7 KB)
The corners now use 1 component iff you want to separate out latch key should be easy.
Goog Luck


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