How To: Easily Smooth and Finish 3D Prints with XTC-3D

An inherent part of FFF 3D printing is layer lines and striations. For prototyping and iterating, it isn’t a problem since the 3D print isn’t intended for anything more than checking fit and feel; does the part fit in place, does it feel right, is this corner too sharp or too round. But if you’re making gifts for friends and family, selling prints, or creating unique props and costumes, then those layer lines are something you’re going to want to remove or hide to elevate your 3D printed project from basic to incredible. For some filaments, like ABS or PolySmooth, you can use chemicals to treat the surface of a print to dissolve it and smooth it out. For others, you’re limited to sandpaper and fillers to cover it all up, and that defeats the purpose of printing in the variety of colors that filaments are offered in. XTC-3D is a great alternative to sandpaper to preserve the color and give your print a super shiny finish. You can even sand XTC-3D if you’d rather use that than filler primers and body fillers. Let’s dive into how to actually use XTC-3D, then compare it to other smoothing processes.

Step 1:Gather Materials

Conveniently, XTC-3D is packed with almost everything you need, but there are a few things you’ll need from elsewhere:

• XTC-3D which includes:
• XTC-3D Part A
• XTC-3D Part B
• Mixing Stick
• Graduated Medicine Cup
• Sponge Brush
• Disposable gloves
• Paper Plate
• 3D print
• Heat source (optional)
• Plastic/Paper sheet (recommended)

Step 2: Prepare your Workstation

XTC-3D is an epoxy resin, and as such anywhere you drip will be impossible to clean up once it has cured solid. You’ll have to sand it away or try and chip it off your work surface, so it’s best to prepare beforehand. Take the aluminum foil and tear it off into two squares, lay them flat on each other, and crumple up the edges to form a small plate. This is where you’re going to pour the epoxy resin once it’s mixed so it doesn’t cure as quickly.

Step 3: Prepare your 3D print.

Make sure that the 3D print you want to coat is completely clean. Any print errors, like stringing, blobs, zits, or brims, are going to be even more apparent after you apply XTC-3D, so take the time to remove these blemishes before you get started. You’ll also want to consider how you stand up your print while you’re brushing on XTC-3D. Suspending it will help prevent getting “elephant foot” where the resin pools and flares out the base. You can print a small base and post the hold up your 3D print, or making something quick out of what you have on hand. Once that’s all set up, you’re ready to start mixing.

Step 4: Measuring and mixing the first batch

XTC-3D is an epoxy resin that mixes by volume rather than weight, which is a lot easier. A very small amount of XTC-3d is needed to coat a 3D print. With 1oz of mixed XTC-3D you can cover three Phil’s. Now, let’s get started:

• Start off by shaking Part B vigorously before pouring.
• Like any resin, you need to be accurate with your measurements, otherwise it will cure too quickly, or not cure at all.
• Mixing by volume is the easiest method, and with the included graduated medicine cup you can easily see the volume.
• Once the two parts make contact, the clock starts ticking before the mixture cures solid. XTC-3D is mixed in a 2:1 ration, so I poured Part A up to the 1/2oz line, then poured in Part B on top of it up to the 3/4oz line.
• Mix the two together using the supplied mixing stick, making sure to scrape the sides and bottom, and mix for about 1 minute.
• After thoroughly mixing the two together in the medicine cup, pour it out onto the paper plate. This increases the working time of the mix by increasing the surface area and reducing its ability to heat up the entire mixture. Pouring out the mixture increases working time by 50%.

Step 5: Applying XTC-3D

Once it’s been poured out, you have 15 minutes to apply it to the 3D prints you prepared, so act quickly, but you don’t need to rush.

• Use the supplied foam brush, soak up some resin and apply it to the 3D print.
• Don’t try to do it all in one coat; many thin coats will produce a much cleaner final product than one thick coat.
• If your model has some small crevices, use the edge of the mixing stick to help pull resin from within them.
• To avoid drips and runs, keep brushing until it starts to set and gets harder to work with.
• If you need to apply more than one coat, wait until the first coat is tacky but hard before applying more.

Step 6: Curing and Post-Processing

To accelerate cure times, you can apply mild heat of 150 degrees Fahrenheit, or 60 degrees Celsius. Be mindful if your print is made from PLA, because 60C is right at start of its glass-transition range and may warp at that heat.

• One layer will cure tack free in about 2 hours, but heat speeds this up to a quick 15 minutes.
• Should you want to smooth your print any further, you can either sand it for a matte finish, or apply a second coat for a glossy finish.
• If you intend to paint your model, lightly sand with 320 grit sandpaper, then apply your paint.

I hope that this article was informative and has inspired you to finish your 3D prints with XTC-3D, and given you some ideas on how to incorporate it into your workflow.

Is there something you'd like to see Alec create using 3D printing? Let us know in the comments below, or send an email to support@matterhackers.com.