Sanding parts is a very important process in manufacturing and is often overlooked or skipped. Over-sanding and under-sanding is also very easy to do this will include some tips on how to properly sand a part. Hopefully this page will help one understand why sanding is important- and when it isn't, as well as how to sand a part properly.
Why is sanding important?
Sanding is important because it makes a part easier to handle by taking off sharp or rough edges. This is also helpful for when inspectors rub their grubby hands over your robot when looking for sharp edges. Sanding also help give your parts a little bit of tolerance.
When do I know to sand a part or not?
Typically, you want to sand parts for the reasons listed above. However you shouldn't sand every single part you make. If you are in a time crunch and you are the one holding up the team then consider whether or not the part really needs it, or maybe it just needs the corner taken off.
I don't know how much I should sand this part.
This is a very common question, or at least it's something that is very often done incorrectly. More often than not I see people over-sand rather than under-sand. Here are some quick tips to follow
If you have changed the dimensions of the part, you have sanded too much
If you are done sanding and you feel the part and it is still sharp (hard to do unless you miss a spot) then you need to sand more
Sanding is not meant to change the shape of a part - in most circumstances - think of it as 'part hygiene'
Make sure to sand all features - that you are sanding - evenly. If one portion of the part is under-sanded and the other side is over-sanded, you've messed up. Devbot!
Sandpaper vs. Belt/Disc Sander
As a general rule, if you are sanding external edges, then use the belt/disc sander, otherwise use sandpaper. In other words, only use sandpaper if you can't reach the feature with the belt sander.
It is sometimes hard to know when to sand and when to file some. A good rule of thumb is
Filing is for changing the geometry of a part by taking off larger amounts of material in a more sloppy manner, while sanding does not chance the geometry of a part and is a cleaner finish.
You will likely find two different types of files in the shop: metal files and wood files.
Obviously, use a wood file on wood and use a metal file on metal.
To get the best use out of a metal file, don't go back and forth aggressively on the part. Files typically cut in one direction, so one-directional strokes tend to work best.
What is a burr?
"During most machining processes, work pieces become burred, and sharp edges or material compression occurs. This affects the quality of the part and can create a potential sources of error during the assembly process."
Using a hand deburrer (see below) is a very quick and easy way to clean up edges- both internal and external- on a part.
Here is a video on various ways a deburrer can be used.