This instructable shows an easy way to make your own personalized leather coaster to protect your desk from nasty tea stains. All you need are some basic tools and a 3D printer to print your stamps.

Why leather? Because leather is easy to process and gets a beautiful patina over time and with every spilled drink.

Supplies

10x10cm piece of 2-4mm thick veg tan leather (I prefer 4mm for a sturdier coaster)
leather oil, bee wax,..
PETG filament

Tools:

one coin
Leather knife or cutter knife
metal ruler
3D printer (FDM)
computer with a CAD Software
edge slicker or wooden stick
clamps or vise
cotton rag
600 grid sandpaper

Step 1: Preparing the Leather

The base of the coaster is a 10x10cm piece of leather, which fits perfectly for the size of cups and bottles I use.

To cut the leather I use a cutter knife and a ruler made of circuit board. Do not us a plastic one, you will damage it and lose the straight edge. I also used the cutter knife to mark the size before cutting.

I decided to give the coasters round corners with a diameter of about 26mm. You could use a corner punch, if you have one. I used a 2€ coin instead. I placed the coin in the corner and fixed it with one hand while cutting with the other hand. The perfect knife for this job is a leather knife, like the one in the photo, but you can also use a normal cutter knife. You do not try to make a round cut, instead you make many straight cuts which together forms a round corner. I aligned the knife to the coin and then did a vertical cut. Repeat it until you are happy. Now it looks nearly as perfect as it would, if done with a corner punch.

The last step is to round the top edge. I used a wooden edge slicker, but a cylindrical wooden stick will also do the job. Just rub the straight part of it on the edge of your leather piece until its round and smooth. Apply some water for a better and faster result.

Step 2: Designing and Printing the Stamp

Basically the stamp is just a rectangular base with a raised text or logo on it.

You can use every CAD Software. I use Autodesk Fusion360, but the steps are the same.

First create a rectangular shape with the size of your final stamp. Then extrude or raise it by 5mm to get a sturdy base. And finally add your text on to this base und raise it by 3mm. If you want to stamp a logo, you need a svg (vectorbased version). Simply place it on your base and also raise it by 3mm.

Finally you must mirror your stamp or you can not read it afterwards. This is the most important and most frustrating step. Most of the time I notice this error only after printing. I use one of the side planes of the stamp to be the mirror plane.

The numbers are based on my experience and many tests. The size of your text or logo also depends on the force of your press. I just use two clamps, so I can not do big stamps or stamps with a big raised area. But the best way to find out, is to try it with your own design. Learning by doing. The possibilities with leather and 3d printed stamps are gigantic and the learning curve is steep.

I use the Prusa Slicer and a modified Ender 3 Printer with PETG Filament which is stronger than PLA (should also work). I set it to 0.2mm layer height and 50% infill for a sturdy base.

On my Ender3 the print was done in less than an hour.

!! Do not forget to mirror your stamp!!

I added the files for both stamps shown in this instructable, the "place drink here" and the "make tea not war" stamp.

Step 3: Preparing the Stamp

My printer do not deliver perfect prints, so there is some work to do to get a perfect stamp.

I remove all the strings and bits of filament with a knife and also trimmed some edges to get crisp looking letters. After this, I used some fine 600 grid sandpaper to flatten all the printer lines on the top of the stamp. Sand it until you cant see printer lines on the top surface anymore.

Then I used a left over piece of the leather to test the stamp. The next chapter shows how to do this. If you can see any printer lines or other imperfections, you have to do more cleaning, trimming or sanding. The attached photo shows two perfect imprints with no leftover printer marks.

If you get a weak imprint in the leather, you need more force to press or have to redesign your stamp with smaller text.

Repeat this steps until you get a perfect imprint.

Step 4: Stamping

Now it is time to use both prepared parts and stamp them together.

First you prepare all your tools and stamps. Then let the leather soak in water for about 10 seconds until it becomes darker and smoother. Bend it to feel the difference. When it is wet, dry the surfaces with a towel.

Place the leather on your surface and carefully place the stamp centered on it. Next step, mount the clamps. Place them centered with no big gap between them, to prevent the stamp from bending in the middle section. Also watch the stamp being leveled, not tilted. So your result is an evenly deep imprint of your motive.

Now you have to wait until the leather is mostly dry, before you can losen the clamps. Et voila, the first imprint of your motive. If there are drips of water, you can dry them with a rag to prevent stains.

Instead of clamps you could also use a vise or a hydraulic press.

Step 5: Finishing

Finally it is time to apply a coat of leather oil on your finished coaster to give it a nice shine and better resistance against water. I used leather balsam from our horse gear, but you can also use oil or bee wax. I applied it on both sides and the edges and refreshed it after one week.

There are more ways to personalize your coaster like dyeing or stitching or or or...

I added a photo of one of my older coaster which get a beautiful dark patina over time.

Thank you for reading :D