Post Print Processing

For some parts, precision and smoothness is vital. Printing with higher resolution can help, but it can add a lot of print time. To achieve precision and smoothness while avoiding extra time, after the print is completed it can be machined. There are multiple techniques to increase the smoothness of our 3-d print and to increase its precision.

Smoothing processes
There are several processes that can be done to smoothen 3-d printed parts. Some of the most common techniques include sanding, bead blasting, and vapor. The type of material used should be considered when choosing a smoothing method.

Sanding
Sanding process can be used to reduce the visibility of layer lines on 3d printed parts. 3d printed parts can be sanded by hand or with belt sanders, like wood or automotive parts. Sanding is inexpensive, effective, and proven method to reach a smooth finish. It is consistently the most widely used finishing techniques for 3D printed parts. When parts must hit benchmarks for accuracy and durability, it’s important to keep in mind how much material sanding will remove. Removing too much could force adjustments in part design and wall thickness before printing. Benchmarks will also help determine which sanding technique to use — hand sanding or power sanding — and which tools to employ.



Bead blasting
Bead blasting is the process of removing surface deposits by applying fine glass beads at a high pressure without damaging the surface. It is the second most-commonly used finishing process. It includes spraying tiny beads of media at a part to remove layer lines. The process is quick and takes only 5 to 10 minutes to complete. The process leaves the products with a smooth finish. It is a flexible process and it works with most 3d printing material.

Bead blasting does have some limitations, one of them is part size. Due to its process which takes place in an enclosed chamber, the maximum part size is 24 x 32 x 32 in. And, given that parts are bead-blasted by hand, they are finished one at a time and, thus, cannot be mass finished.

Solvent smoothing
Solvent smoothing is an alternative to sanding and bead blasting. Solvent smoothing uses a chemical agent to smooth a part’s surface. It modifies the surface by eliminating layer line while preserving feature detail and part accuracy. The smoothing agent can be applied either as liquid or a vapor and it is quick and nearly labor-free.

Common chemical agent for PLA
Jewelry polisher (tumbler), XTC-3D (coating/paint), Tetrahydrofuran (similar to acetone, more toxic), Dichloromethane (similar to acetone), Heat Gun/Flame, Dishwasher, Hand polish/sandpaper, Sand blasting

Machining processes
Machining processes can be done to a part after it is 3-d printed to increase its dimensional accuracy.

Milling
Parts made with the MakerBot can be milled in the shop to bring them within tolerance and to create smoother surfaces. Speeds for milling PLA plastic are similar to aluminum and aluminum speeds can be used. Milling provides a higher quality detail compared to a 3d printer.

Drilling and reaming
To make a hole precise for sliding and press fitting, the finished part can be reamed. If a hole is intended to be reamed, it needs to be .005” smaller in diameter when designing the part. The Gcode should be set for "2" shells. Reaming should be done on the drill press so the reamer will find the hole.

Tapping
PLA can be tapped so long as the shell thickness has been set to at least "2". Tapping is done the same as for metal. Be careful when tapping hole because PLA is soft and can strip easily.