In Chapter 1 of my book, A Tale of Two Hittys, readers learn that the author, Charles Dickens, commissions a woodcarver to create a small wooden doll in the image of his beloved granddaughter, Mekitty. She instantly falls in love with her new doll, “Kitty,” who then comes to life. Mekitty begs her grandfather to retell the story about his encounter with the wooden doll named, “Hitty,” when he was on a reading tour in America.
That is how my book begins. My two inspirations are the book, Hitty: Her First Hundred Years by Rachel Field, (see Who is Hitty?) and an antique paper mache doll named, “Kitty,” (see Meet Kitty). Kitty’s little wooden boots were what attracted me to her in the first place, because they look a lot like Hitty’s boots. But unlike Hitty, Kitty does not make a good travel doll. She does not pose well. And the real Kitty has no hair, so I had to make her a wig from mohair. I love this doll, but she is too fragile to play with (see Restoring Kitty).
I want a doll that resembles young Mekitty (see Mary Angela Mekitty Dickens) with light brown hair pulled back from her face and secured with a headband, a hairstyle known as “Alice in Wonderland.” She needs to have jointed arms and legs, so she will be easy to dress and pose. And like the real Kitty, she must have little blue boots. The solution: a customized 3D printed doll.
Designing a 3D Printed Doll
To make 3D printed Kitty a reality, I started with a bust of her head. I thought it would be a good way to test the 3D printing technology (see Virtual Kitty). The software I used, called ZbrushCore, takes some effort to learn because it is not very intuitive. After some trial and error, I sculpted a bust, which I painted to look like antique Kitty. The bust turned out pretty well. Originally, I had planned to carve a wooden body for the bust, but as I got more confident with my digital sculpting skills, I decided to attempt a complete doll.
Digital sculpting is very different from woodcarving. On the plus side, I discovered that digital sculpting can be a lot more forgiving than woodcarving. If a change needs to be made, I can simply reshape the object instead of having to carve a new one. I can also duplicate an arm and “mirror” it to instantly make a left arm from a right. With a digital sculpting brush, I have nearly unlimited abilities to shape and reshape to my heart’s content. And best of all, I can print multiple copies of the doll without having to make a mold and cast it in resin.
Working with scale with Zbrush was a challenge. Since I was using ZBrushCore (a simplified version of the software), the “Scale Master” plug-in was disabled. This made it hard to predict what size the file would be when printed. I suspect this was done deliberately to encourage people to purchase the full version. My workaround was to add a 1” square cube to all the individual body parts. The square would act as a reference when preparing each part for 3D printing.
I spent a couple months designing a body for a 6.25” tall Kitty doll. Since I did not want a figurine, Kitty needed a way to move her arms and legs. I found inspiration by looking at other 3D printed items. When I saw these 3D printed dinosaur puzzles by Manabunlab on Cults3D, I thought that magnets would work well for the joints. Magnets would eliminate the need for peg holes, and they would never need repair.
For even more posability, I designed a stand for Kitty with two magnet holes. Then I added matching magnet holes in the bottom of each foot. I used an online 3D drawing program called, “Tinkercad,” to design the stand. Tinkercad was MUCH easier to learn than ZBrush, but it has limitations on file size, so it works best for simple, geometric shapes.
Here is a screen shot from ZBrush showing the completed doll and stand. Each individual body part must be exported as an .obj file for 3D printing.
Printing the Doll
Before the doll could be printed, each .obj file had to be prepared with slicing software that literally slices the design into layers. My son, Steven, who is a software engineer, took care of this part. He used a program called Bambu Studio to prepare the files for printing. Steven’s printer is a Bambu Lab X1-Carbon which uses fused deposition modeling (FDM). A plastic filament on a spool is fed into the printer, melted, and extruded onto a flat area called the print bed. After each layer is printed, the printer bed descents a tiny amount to allow space for the next layer. Many parameters, such as nozzle size, layer height, wall thickness and infill pattern/percentage, have to be adjusted to achieve the best result.
I purchased three colors of 1.75 mm filament made from PLA (Polylactic Acid). PLA is a type of polyester which uses less energy to produce and generates fewer greenhouse gases than conventional plastics made from petroleum. PLA is derived from renewable resources like corn starch and sugar cane. Unlike resin, it does not emit toxins or fumes when melted. The disadvantages are that it can fade in the sunlight, and it will deform in high heat. This might be problematic for a travel doll, so I will need to be careful with her.
Steven printed an arm to test out all three of the filaments. (Technical note: it took a little less than one hour per arm, printed with the 0.2mm size nozzle at 0.06mm layer height). The colors and textures varied quite a bit. Top to bottom:
Hatchbox “Beige” PLA – very shiny texture and the lightest color
Overture “Matte Skin” PLA – a nice color with the least shiny texture
Elegoo “Matte Beige” PLA – has more of an ivory tone, somewhat shiny
I chose the Elegoo, the darkest color, with an ivory tone to look antique. Finally, Steven could print all the parts: two arms, two legs, a lower torso and and upper torso with head. It took about four hours to print the entire doll.
Finishing the Doll
After the doll was printed, Steven glued in the magnets. Kitty has eight 6 mm x 3 mm neodymium magnets (purchased from Amazon) which are glued into cavities in the shoulders and hips. Smaller .1” x .15” magnets are glued in the stand and feet. Steven posed her in front of his computer monitor with some of his toys.
Then Steven mailed me the completed doll. He lives over 1,000 miles away, so poor Kitty was stuffed in an envelope padded with bubble wrap for the journey. It was an exciting day when the doll finally arrived. I was pleased with the way her joints worked. It was very satisfying to hear the “snap” of her arms and legs clicking into place. At first, the magnets for the legs did not have enough grip to stay posed. The solution was to add more friction by sanding the legs and torso to make them less slippery.
I spent the next couple days painting the doll. The PLA plastic was easy to paint using acrylics. There were some visible layer lines, due to the printing process. This was minimized by adding a clear coat of Minwax Polycrylic sealer before painting. I used additional coats of Polycrylic on top of all the painted areas to protect the paint.
Here is Kitty… the first ever 3D printed, magnet-jointed Hitty doll!
The next version of the doll will have a few changes. This doll is quite slender, which means all of Hitty’s dresses are too big for her. The name, “Kitty,” is printed on her back, like the doll in my story. But the letters are too small, and I am not happy with the font. I also want to try out different filaments to see how they compare. But in the meantime, I am going to enjoy playing with my new doll.
UPDATE: October 9, 2024
Recently, I received a new doll that Steven printed. She has several improvements. Most importantly, her new, stronger magnets work much better. Her arms no longer fall off when I try to dress her. I purchased the new magnets from K&J Magnetics, Inc. The arms use 1/4” x 1/8” D42-N52 Neodymium Disc Magnets and the legs use 5/16” x 1/8” D52-N52 Neodymium Disc Magnets.
Neodymium magnets come with some risks, especially with young children. Although Kitty’s magnets are glued in, if they came loose they could be swallowed and pose a choking hazard or worse… become attached inside the intestines, causing a medical emergency. Also, the magnets should be used with caution around medical devices, such as pacemakers. The K&J Magnetics’ site has a useful Safety Sheet which you should read if you are looking for more information about neodymium magnets.
One of my goals was to make the Kitty doll the same size as Hitty, so I made the torso a bit thicker. It’s now made in one piece instead of two to simplify printing. The arms and legs are also less slender. She is still more petite than my other Hitty dolls, and next time I want to try making her head and torso even bigger.
Her hands are still mitten-shaped, but now they have the suggestions of fingers. Steven found a way to print the arms vertically. Now they are a lot smoother on the underside and need less sanding. Take a look at this video of Kitty being printed. The movie has been sped up a lot. The actual amount of time it takes each doll to print is around four hours.
Here is what the doll looks like after printing, while still attached to the print bed.
Painting such a tiny doll is a challenge. I spent a few days practicing and perfecting the paint colors. Here is Kitty after painting, wearing a sleeveless prairie-style dress. I also completely redesigned the stand, using a green filament which looks nice with her blue boots.
I used a blue permanent ink pen for the letters on her back. Cool fact: Charles Dickens preferred to use blue ink because it was less likely to fade.
Although she’s still not perfect, this new doll is shaping up quite nicely. So what’s next? I’ll make some minor modifications before I will call her finished. I am also considering making an alternate version with elastic joints, for anyone concerned about the magnets. Until then, I will keep enjoying Kitty. She has many fun adventures to look forward to.
