This is my take on the character Pipo from the videogame Overblood. In his normal stance he stands at around 15 inches but if he stretches out he can reach a max height of around 27 inches. He is constructed from 30 some odd parts with custom friction pads in the hinges.

Problems

This model is a prototype and is in need of refinement. It has several known issues:

1. Joints - The joints do not work as intended. The joints were designed to make it easy to place Pipo in a variety of poses without using a tool. However, because the M3 screw that acts as a pivot also provides the clamping force that sets the amount of friction in a joint it tends to rotate a little each time the joint is moved. This causes the joints to loosen fairly quickly with use requiring them to be retightened. It is also difficult to impossible to set the right amount of friction in the various joints to accommodate the full range of motion of Pipo’s arm. As the arm extends the amount of leverage on the joints increases causing more torque.

2. Heat-set threaded inserts too close to the edge - Some of the holes for the heat-set threaded inserts are close to the edge of the material. This makes it difficult to install them without damaging the part. Two notable holes that suffer from this issue are the bottom two of the four in the Top Body in section where the Lens Bracket Mounts

3. Easy to damage - The use of heat-set threaded inserts make it easy to damage Pipo. This can happen if:
   An M3 screw is over-tightened.
   The wrong length M3 screw is used in a hole.
   If a part isn’t seated flush and square before the M3 mounting screws are tightened.
   If any of the above happens the heat-set threaded insert will be ripped from the plastic potentially destroying a part.

4. Too many different lengths of M3 caphead screws - There are too many different lengths of M3 caphead screws used in this design. Leading to an inflated BOM and a higher chance of mistakes where the wrong length screw is used in the wrong hole leading to a damaged part.

Hardware

Pipo is assembled using M3 caphead screws, heat-set threaded inserts, and rubber sheet cut into friction pads.

Rubber Sheet - Each joint except the wrist has a friction pad that fits around the pivot and is compressed when the joint is tightened. The wrist has two friction pads; one of either side of the Bottom Jaw. The rubber sheet specified is 1.7mm thick. This is the specific rubber sheet I ordered from Amazon:

Rubber Sheet, SBR, Rubber Width 12 in, Rubber Length 12 in, Rubber Thickness 1/16 in, 70A, Plain Backing

Heat-Set Inserts - The heat-set inserts used are threaded for M3 and are 4mm tall and have a diameter of 5mm. This is the specific kind of heat-set threaded inserts I ordered from Amazon:

120 Pieces M3 Threaded Inserts, Premium Heat Seat Inserts for 3D Printing, M3x4x5 mm Metric Knurled Nuts, Brass Threaded Inserts for Plastic

M3 Caphead Screws - The M3 caphead screws used have a cap depth of 2.8mm a cap diameter of 5.2mm and are of a variety of lengths. This is the specific kit of M3 caphead screws I ordered from Amazon:

mxuteuk 620PCS M3 Screw Kit,M3 Screws Suitable for 3D Printer,12.9 Grade Alloy Steel M3 Bolts,M3 x 6/8/10/12/16/20mm Hex Socket Head Cap Screws Bolts Nuts Kit

The lengths specified below refer to the threaded portion of the screw only. For example an M3x20 screw has a threaded portion of 20mm but an overall length (including the cap) of 22.8mm. The following screws are used:

• Left Front Leg -> Left Leg Bracket: (1) M3x12
• Right Front Leg -> Right Leg Bracket: (1) M3x12
• Back Leg -> Back Leg Bracket: (1) M3x12
• Left Leg Bracket -> Bottom Body: (2) M3x6
• Right Leg Bracket -> Bottom Body: (2) M3x6
• Back Leg Bracket -> Bottom Body: (2) M3x6
• Bottom Plate -> Bottom Body: (2) M3x6
• Bottom Body -> Middle body: (2) M3x8
• Middle Body -> Top Body: (2) M3x6
• Lens Bracket -> Lens: (1) M3x6
• Lens Bracket -> Top Body: (4) M3x6
• Male Arm Bracket -> Top Body: (2) M3x6
• Female Arm Joint -> Male Arm Bracket: (1) M3x8
• Female Arm Joint -> Bottom Arm: (2) M3x6
• Male Arm Joint -> Bottom Arm: (2) M3x6
• Female Arm Joint -> Middle Arm: (2) M3x6
• Male Arm Joint -> Middle Arm: (2) M3x6
• Female Arm Joint -> Top Arm: (2) M3x6
• Wrist -> Top Arm: (2) M3x6
• Top Jaw -> Bottom Jaw: (1) M3x8

Printing

The following parts need to be printed multiple times:

• (3) Female Arm Joint
• (2) Male Arm Joint

If holes and fillets are considered to be self supporting then the majority, if not all, of the parts can be printed without supports. When I printed mine I believe the only parts (if any) I printed with supports may have been one or both of the jaws. I honestly can’t remember.