Basics for printing the components

Material Selection

The original prototype printed with PETG filament. I believe it is an overall best compromise for;

• heat resistance
• printability
• dimensional stability
• strength

If you prefer a different material, please keep in mind that electronics, hotend, motors and power supply creates significant heat.

Part orientation

All parts are oriented according to required strength and printability. I recommend printing all parts in their original orientation.

Nozzle and layer height

Printable parts are designed to print with 0.4mm nozzle and 0.2mm layer height. If you prefer less layer height, prefer 0.1mm. Other layer heights may cause loss of sacrificial layers for hole bridging.

Printing precise parts

Almost everything about FDM printing is relative and it is not simple to print precise parts.

Understanding temperature effects

Printing at a correct temperature is critical to achieve precision in FDM parts. Filament manufacturers have their own material blends. Therefore, a very best temperature value for a filament wouldn’t be the best for another brand. The manufacturers mostly recommend best temperature range for their filaments. Usually, printing at lower end of this range gives better surface quality, which is very important for precision. However, lower temps. also reduces the fusing between layers and part becomes weaker. So you would prefer to find best compromise spot between the surface quality and the strength.

Printer’s positioning accuracy

Especially the 3D printers come as kits, mostly don’t have a good positioning accuracy. You would expect 0.1mm deviation on dimensions. Parts of the babyBear designed to have 0.2mm tolerance to each other and off the shelf components. Make sure your printer’s positioning accuracy is better than 0.1mm. If it is not, then calibrate your printer’s hardware and stepper motors.

Squareness of the printer

Very less 3D printers come with a good square frame. If your printer came as kit and you assembled it yourself, it is probably not square at all. If you are into printing precision parts, I recommend you to get machinist right angle squares.

Using right angle, check all the linear rails and adjust them until they are square to each other. To get more information about squaring, it is called Tramming in machine industry. Check youtube for cnc machine/3d printer tramming.

Let’s say if your printer is not square enough; In this case Z axis wouldn’t be parallel to the rotary axis of the babyBear. This means, in higher Z distances, your part will become narrower or wider. Rotary axis rotor won’t be cylinder enough and it will wobble. This wobble will be amplified by Z height.

So the squareness of your printer is very important.

Dimensional accuracy of the parts

To make sure the 3D printed parts in a good tolerance, first print some test parts and try if they fit properly.

For example, I printed a section of rotary axis rotor to check 16010 bearing ID tolerance and again printed a section of the main body to check 16010 bearing OD tolerance.

Especially the bearings must fit to the place with a little tightness. If it is too tight, it will deform the printed body while mounting. If it is loose, it won’t create precise movement under load.

On the bearing mounting surfaces, only use sanding to remove imperfections. If the surface is not accurate enough, then I recommend to print the part from scratch.

Post processing

Even under best circumstances, 3D printed parts still can have problems. FDM printers tend to smooth inside corners and make bulgy ends on outside corners. So you have to sand down these imperfections, if necessary.