The short version: warm soapy water, a soft brush, air dry, never the dishwasher if it is PLA.
Why not the dishwasher
PLA softens at around 60 C. A domestic dishwasher wash cycle runs hotter than that, and the drying cycle hotter again. A PLA cutter that goes through a dishwasher comes out curled, and it does not curl back.
PETG softens at around 80 to 85 C, which is above a typical wash but can still be reached by a heated dry cycle. If you must put a cutter in the dishwasher, use PETG, put it on the top rack, and turn the heated dry off. Even then, expect it to warp eventually.
The method that works
- Rinse straight after use, before the dough dries. Dried dough in layer lines is much harder to shift than wet dough.
- Warm soapy water, not hot. Warm enough for your hands is warm enough.
- A soft brush, an old toothbrush is ideal, along the layer lines rather than across them.
- Rinse and stand it on edge to air dry. Do not put it near a radiator, on top of a running printer, or on a sunny windowsill in summer.
Where dough hides
The inside face of the blade, right where it meets the flange. That inside corner collects dough and a cloth will not reach it. This is what the brush is for.
Imprint ribs and stamp relief collect dough in the recesses. A brush and a toothpick get it out.
Heat is the enemy, everywhere
Things that will deform a PLA cutter that people do not expect:
- A car in summer. An Australian car interior in February will comfortably pass 60 C.
- A drawer above a dishwasher or an oven.
- Leaving it in hot washing up water to soak.
- A hot dish sitting on it.
Store them in a drawer or a box, out of direct sun.
How long do they last
Treated like this, years. The realistic failure modes are:
- Snapped blade, usually from being dropped or from twisting while cutting. Press straight down, lift straight up.
- Warping from heat, which is avoidable.
- Staining from strongly coloured dough. Cosmetic, not structural.
Because these are printed, the recovery from any of them is to print another one. That is worth remembering when weighing up how much effort to put into preserving a single cutter, and it is also part of the food safety picture: a cutter that is showing wear costs a few cents of filament to replace, which is not true of a stainless steel one.
Cleaning a cutter you are worried about
If a cutter has been used with raw egg dough and then sat unwashed, throw it out and print another. It costs about 20 cents of filament. This is the single biggest practical advantage of a printed cutter over a bought one, and it makes most of the hygiene argument moot.