If it is the first time you are printing a 3D model, you might have an impression that all you have to do is press a button and receive a finished item within a few minutes.
In reality, 3D printing involves more than that. For your item to look more realistic and have a metal appearance, you will have to put more work in it.
Does not really matter what type of PLA 3D filament you use for printing, almost every PLA 3D object requires post-processing or secondary metal finishing methods before it reaches the final state.
The technique you choose is an important consideration. Base your selection on the application requirements and the cost per object.
Most 3D printed objects have complex geometries requiring designers to consider various finishing techniques and their effect on every part. To metal-finish your PLA 3D prints, here are the steps to follow.
Sand the PLA 3D Printed Object
Almost every PLA 3D object will need some sanding. To get the best results, you will have to use multiple sandpaper grits – beginning with the course such as 200 grit and ending with the smoothest such as 4000 grit, when available.
When sanding, move the sandpaper in a circular motion against the object’s grain layer lines. Even though you might feel the urge to use a power tool, you will have to avoid using the tools because they make vibrations that can easily melt your PLA objects or deform the surfaces.
When sanding manually, remember that friction will generate heat that can damage the prints by melting the plastic.
When choosing the sandpaper, go for the “wet/dry” or the waterproof sandpapers because you can wet them to cool your plastic object.
Remember to rinse the print more often so that you can dislodge any particles resulting from the sanding operation.
One major benefit of wetting the object is that the water will stop the small particles from inhaled or airborne.
To distinguish the wet/dry sandpapers from the others, check the grit. They should have black grit and not beige or tan.
Cover the 3D Object
When you are through with the smoothing part, you will have to fill all the remaining lines with polishing compounds. You can never eliminate all the layer lines by smoothing the PLA object with sandpaper alone.
The manufacturers of polishing compounds mostly supply them as bars, which they grade differently –similar to the sandpapers. They design the compounds for use with metal objects but they will also work with your plastic objects.
To fill the lines, wipe a little amount of the compound onto a rotary tool attachment or a buffer wheel and apply it directly onto your plastic object to get a shiny smooth surface.
More like sanding, buffing will generate friction, which will heat the plastic. So, when using a buffer wheel to smooth your PLA objects, stick to slow speeds.
Heat the 3D Object
Heating is a less popular choice for smoothing PLA objects. To smooth your surfaces, you just need a heat gun but unlike the other two methods, heating requires more practice. The heating gun generates a lot of heat that can destroy the 3D print forcing you to start again from scratch.
By preheating the object before finishing, you will manage to pre-expose the plastic and make the last attempt more effective. Move the heat gun along the surfaces of your model and never keep the gun on one area for a long time because that can melt the plastic.
Even though PLA does not emit any noxious odours when extruded, it will produce fumes when the plastic softens due to heating.
So, regardless of the smoothing technique you choose, you will have to do it in an open well-ventilated room. Heated resins, plastics and spray emit potentially harmful fumes.
Give the Object a Metallic Appearance
In the following I will show you 2 methods you can use to give the 3D objects a metallic appearance:
Method 1: Use Elmer’s Glue and Metal powder Paste
Generally, metal filed filaments are the fastest way of making your 3D prints look like metallic items but such filaments are very expensive.
Fortunately, you can add hand-forged metallic appearance to any 3-dimensional print by applying the metal powder directly onto its surface.
The market offers metal powders that go for a few dollars. The method is only suitable for large objects where hammered rough appearance is necessary.
It is not a good choice when fine details are important. To use the method:
Buy fine metal powder
To make your PLA 3D prints look like real metal objects, you will have to buy some fine metal powder. You can get that from the online or local stores, which cater to sculptors.
Copper, iron and bronze powders are among the commonest choices.
In addition to the powder, you will require a plastic card or a palette knife to mix and spread the powder on your prints. You will also need plastic spoons, a container or empty lid, Elmer’s Glue, an air filter mask, extra-fine steel wool and paper towels.
Make the paste
For the best results, you will have to make a thick paste of glue and metal. Take Elmer’s Glue and the metal powder and mix two parts of metal powder in one part of the glue. Take one spoonful of your metal powder and add it into the container containing the glue.
Use the painter’s knife or spoon to mix the powder and glue. Using the painter’s knife, scrape up your Elmer’s Glue and press down onto your metal powder. Repeat the process until you get a properly mixed paste.
Loose powders might give your object a bad appearance. The air mask will be important in this stage because some of the particles are likely to become airborne.
Spread the paste on your object
Take the paste and spread a thick coat on your 3D print using your artist’s knife. If there is any need to coat on all the sides of the print, you will have to do that in sections.
Allow the paste to dry before you move to the next section. After you are through, use some water and soap to clean your hands and the tools.
Polish your 3D object
After the 3D object has dried for around 24 hours, it will develop a matte appearance very close to clay. To get a shiny look, use the fine steel wool to rub it. Ensure that it has attained a metallic surface.
Add a patina to the paints
You can add patina to metallic 3D prints. Even though most people use them for prints that they did with metal-filled 3D printing filaments, you can apply them on prints finished with Elmer’s glue and metal powder paste.
Brush some table salt and ammonia to your copper-coated print and leave it outside to corrode for a few minutes. The result should be dramatic and more like an object that has remained at the bottom part of an ocean for many years.
Method 2: Use Metallic Powder and Epoxy Paint
The other option of giving your three-dimensional PLA print a metallic appearance involves use of epoxy and metal paste. XTC-3D is among the epoxies marketed for 3D printing and it has a big name in the industry. However, other types of epoxy will also work. This cost-effective method will help you get metallic finishes faster and easily. Here are the steps to follow.
Prepare the workspace
Start by laying wax paper under your workstation for easier cleaning after the metal coating process is over. Make a simple aluminium foil tray by laying 2 aluminium foil pieces and fold their edges. The tray should hold the paste and allow you to work for a longer time.
Mix the metal powder and epoxy
Take 1 part of your metal powder and add it to 2 parts of the clear epoxy paint. Use a wooden popsicle stick to mix the powder until it dissolves in the epoxy clear paint.
Pour the two ingredients in a simple plastic container and mix them together vigorously until a smooth miscible blend forms. Ensure that there are no clumps or bubbles. Now, pour the paste into the aluminium foil plate.
Apply the paste
Use a brush to apply the solution on the 3D print lightly. The layer should be as thin as 0.04 cm. It should self-level when on the object.
Allow it to cure
Leave the object to cure untouched for around 3-5 hours. To speed up the process, use a light heat source such as a heat gun or a hairdryer.
Use steel wool to polish
After the curing process, use fine steel wool to polish the 3D print. For optimal results, vary the polishing time. The method creates a smooth, glossier metallic surface on the print.
The powder will mix with the epoxy paint completely making the application easier.
Keep in mind that if you add more powder than necessary, you will get a very rough texture in addition to the leafed gold look.
Even though most people rely on desktop 3D printers to make and test designs. However, at times you might want to make 3-dimensional objects great looking for presentation.
If you are familiar with 3D designs, you already know the many drawbacks expected with the appearance.
Aesthetic issues will always boil down to one problem, the surface quality. The above tips will help you get a metal looking PLA 3D object.