Fractions help for education

Disclaimer:

Apparently the files with 'download' don't contain the numbers!!

I just uploaded 3MF files (which do contain the numbers) but the Printables website removed/merged them. When using EasyPrint the numbers are there. When using the download button, the numbers are nowhere to be seen!

Advise: if you plan on printing this model, please DO read the entire instructions before printing so printing will be easy, even when inserting magnets half way printing.

Furthermore, this is a model for a printer with a MMU. But you can print this model in just 1 color. In that case you need to remove all parts which are a number 0 to 9 or a - or a /. That leaves an empty space instead of text in a different color. This is also still usable. You might try to use a sharpy (or something) to make the text stand out more.

About this model

A set to help kids to learn fractions. Adding, multiplying, and so on.

This set contains 14 bars 20cm long and 14 discs 10cm diameter. Each bar and disc is devided into one of the fractions from 1 to 14.

7 plates on which the different parts can be used and stored. Put all the same fractions into one hole for disc or bar and in one glance it's clear if the set is complete.

The 7 plates contain 6 magnets inside to keep the plates together. The magnets are inserted while printing (pausing the printer of course!)

A box to put the 7 plates in. The box also has magnets (6 or 12, it's up to you) to somewhat prevent the plates from sliding out. I used 12 magnets (6 on each wall of the box)

To be able to get the parts of a disc out of the hole, I put an opening in the plate at the center of the discs.

To be able to get the parts of a bar out of the hole, I created a little bump in the hole. Press on the top or bottom of a part and it will tilt upwards on the other end so it will rise above the surface of the plate.

For each fraction I added a separate 3MF file. Each file contains both fractions in bar and slice shape. The bar shape is added in 2 ways

1. 1 long strip of 20 cm containing all parts in 1 piece. When the print is finished, you can take the entire 20cm bar of the build plate and cut the bar into the separate parts. The bar has guides for a knife to cut in the right spot(s)

2. 1 small part which needs to be printed 1 to 14 times, depending on the fraction.

Why this setup? Not every printer has the same tolerances. In my case the big 20cm bar worked great for numbers 1 to 4. After that, the 20cm bar was cut into the separate parts but I guess the cut tends to somewhat flatten the material (in my case TPU), and with that, making the parts slightly longer. I only printed in TPU. No experience with other materials.

So you might want to print each part apart from each other. This also makes it possible to adjust the width of each part so that all parts (of that fraction) will end up 20cm in total when placed next to one another. 

Another material, another printer, another nozzle might end up with different results I cannot predict so you'll have to decide for yourself.

Extra needed

48 or 54 Neodymium magnets 10mm diameter x 2mm thick.
Each plate needs 6, so 7x6 = 42 magnets for the plates
The box can hold up to 12 magnets. I advise to at least put 6 magnets in the 6 lower slots. So for the box you need 6 or 12.
In case you use magnets in all slots, that makes 54 magnets for the entire set.

Printing

I printed the parts on my XL.

PETG for the plates and box
TPU for the fractions parts

Layer height 0.15mm

Infill 20% Gyroid

NO supports

Important printing tips

Neodymium magnets don't like heat! A 80 degree build plate might demagnetize them! I did the following things:

1) Of course I paused the printer at the layer where the printer is going to print on top of the inserted magnets. This is at heigth 2.7mm

2) 1 layer earlier I give the printer a GCODE to lower the bed temperature. The printer takes a while to print this layer so the bed has time to cool down enough to save the magnets from overheating. Inserted GCODE is:

M140 S55

This lowers the print bed temperature (on my Prusa XL) to 55 degrees C. You might want to check if your printer also uses M140 for print bed temperature

In the 3MF-file of the plates you see 8 small circles in the centers of the 2 holes for the discs. My advise: move them to a easy to reach place on your print bed (front, nearest to you). These small plates are 0.3mm thick and the same diameter of the magnets.

While printing I pull them of the build plate (that's why you should put them in an easy to reach place). I glue the small plates onto the magnets (all on the same pole of each magnet!). Make sure the small plates are flat. Let the glue dry while printing the bigger plates.

When the pause arrives, put the magnets with the small plates glued onto them into the slots,, small disc facing up. The top of the magnets-with-plates should be flush with the top of the print so far. And of course: Resume printing

This way the printer does not have to make bridges. Also the small printed plates provide a very good base for the next printing layer. This way you can print magnets into your models with just a very small combined layer on top.

Of course it's better to print the small plates before you start the print with the big plates. The buildplate can cool down so the little plates can be removed easily without bending them. It's up to you. I did the first method (using a heat gun to flatten the plates before glueing them onto the magnets)

For the magnets in the box you just need to pause the printer twice. First for the 6 magnets at the bottom, then for the magnets at the top.

Additional information

I created this for my wife. I wanted to put metal plates into the bigger plates so the parts would stick in place. But that meant more magnets, more metal, thicker parts resulting in a thicker, way more heavy set which she didn't want. So I stepped away from that idea (I already did order metal plates which can be sticked to the back of phones in order to place them on a magnetic car holder. But just those plates in crease the weight significantly so based on that, it's a good thing I didn't use them for this particular cause)