The finishing operation for PLA is harder to achieve compared to the ABS-based parts. This is because of the fact that the dissolvent of PLA is generally more dangerous than of ABS. This section intends to explain finishing/cleaning methods of PLA with tetrahydrofuran (THF) and dichloromethane. Please do not experiment or apply without being positive you can handle every safety issue.
There are two basic methods for finishing the PLA part with THF, which are similar to the finishing operation of ABS. As a first method, one can apply vapor treatment to the part. The method should work as acetone works for ABS; the important point here is to have the jar big and wide enough to let the vapor achieve every point of the printed part. However, it may not always be useful for every application. An experience with THF reveals it may not give the intended result.
Another method with THF would be hand polishing. For this purpose, one needs to have Nitrile gloves and a piece of cloth which is white –to prevent taints on the surface. The direction of application may affect the final look. After the polishing operation is done, it would be necessary to let the part dry to get free from dangerous chemicals –it is better if the part is dried outside the house or building.
The important point here is to keep in mind that THF is not good for human health and should be avoided especially in applications to toys.
Dichloromethane for PLA is also said to work as acetone does for ABS. The necessary safety arrangements will still need to be applied to assure a healthy working environment. As a general comment, dichloromethane is more powerful for PLA than acetone is for ABS as a dissolvent. Therefore, the timing issue matters more in terms of the use of dichloromethane. A RepRap user's previous experience with PLA underlines the issue.
Finally, it should be stated that the 3D Refiner also works for the finishing operation of the PLA part.