Welcome to the Onshape forum! Ask questions and join in the discussions about everything Onshape.
First time visiting? Here are some places to start:- Looking for a certain topic? Check out the categories filter or use Search (upper right).
- Need support? Ask a question to our Community Support category.
- Please submit support tickets for bugs but you can request improvements in the Product Feedback category.
- Be respectful, on topic and if you see a problem, Flag it.
If you would like to contact our Community Manager personally, feel free to send a private message or an email.
Why are my dimensions rounding up?
graham_brown146
Member Posts: 6 ✭
I have sketched and extruded my design. However, in both areas the dimensions always appear rounded up. eg: 23.5mm will be added in the dimensions box but will always appear as 24mm on the sketch or 3d model. It's still 23.5mm if you click on the box. Is that just how it appears and will it print as intended?
Cheers
Cheers
0
Best Answers
-
NeilCooke
Moderator, Onshape Employees Posts: 5,596 
Check your decimal place settings in preferences and in the current doc (hamburger menu top left)Senior Director, Technical Services, EMEAI1 -
michael3424
Member Posts: 686 ✭✭✭✭
Depending on the filament type and profile, I often have to scale an STL-iimported part in the slicer by a small amount to get the nearly-exact-dimension that I want. In PrusaSlicer, the scale factor is often slightly smaller than 100%, say 99.7%. It gets more complicated if you want exact hole diameters.graham_brown146 said:Thanks Michael. Yes, I'm 3D printing. They are simple shapes but I didn't know about 'scale factor'. Wouldn't they print at the designed dimensions?
0 -
S1mon
Member Posts: 2,785 PRO
Scaling the whole model seems strange.
I have often added extra clearance on faces that will be touching mating parts. 3D printing will have certain types of dimensional errors depending on the technology, tessellation, calibration, maintenance, environmental conditions, and axis. FDM will often be off in Z (build axis) by something on the order of the layer thickness (either the layer is there or it's not). X+Y is more a matter the tolerances on the other variables.
For hole diameters, I recommend building a test part with a series of hole sizes. If you're also using bosses, build those too, as the material may cool and shrink differently in the middle of a large plate than it will in a thin walled boss. Keep in mind that a particular 3D printer may have different tolerances on different areas of the build platform, and at different build heights. If you really need to control this kind of thing, you might have to do a lot of careful testing.
This is a really good use for move face to add clearances where necessary. It makes it easier to have configurations for production vs prototyping.
The reality is that even with the best machines and processes, 3D printing will never get the precision and control of machining or injection molding - unless you start talking about some of the metal powder sintering/micro-machining stuff. I've worked on a project where the mold inserts were built this way, and those were almost as good as a tradition machined + EDM insert.0
Answers
I have often added extra clearance on faces that will be touching mating parts. 3D printing will have certain types of dimensional errors depending on the technology, tessellation, calibration, maintenance, environmental conditions, and axis. FDM will often be off in Z (build axis) by something on the order of the layer thickness (either the layer is there or it's not). X+Y is more a matter the tolerances on the other variables.
For hole diameters, I recommend building a test part with a series of hole sizes. If you're also using bosses, build those too, as the material may cool and shrink differently in the middle of a large plate than it will in a thin walled boss. Keep in mind that a particular 3D printer may have different tolerances on different areas of the build platform, and at different build heights. If you really need to control this kind of thing, you might have to do a lot of careful testing.
This is a really good use for move face to add clearances where necessary. It makes it easier to have configurations for production vs prototyping.
The reality is that even with the best machines and processes, 3D printing will never get the precision and control of machining or injection molding - unless you start talking about some of the metal powder sintering/micro-machining stuff. I've worked on a project where the mold inserts were built this way, and those were almost as good as a tradition machined + EDM insert.