Soft Robotic Gripper With Exoskeleton

 Hello,

this is a fully functioning soft robotic gripper. You can use it on its own or print the exoskeleton around it. You can use the exoskeleton to mount it to a robot. 

It has the dimensions of approx.

200 mm in diameter and 17 mm in height (26 mm with the optional exoskeleton)

The optional exoskeleton has room for 3 M4 screws so that you can fit it to your robot arm.

It is air powered: As soon as you increase the air pressure inside through the hole on the top, the arms of the gripper will move towards the center of the gripper. If you remove the air from the gripper it will open again.

This is a video showing how it works without the exoskeleton:

Please note: Making this gripper can be difficult! 

How should you print it?

The mold consists of only one part and can be printed in around 7 hours without supports. I recommend a 0.2 mm layer height, a 20% gyroid infill (you can use a higher infill to make it even more durable if you like) and PLA. 

The seperator must be printed 3 times. It takes around 1 hour each. Use the same settings as for the mold.

Before you can print the exoskeleton, you must print the mold and and the seperators to create the gripper! Otherwise it will not work! The exoskeleton also consists of one part, it is printed in around 1.5 hours. I reccomend the same settings as for the mold. Be careful though, it is designed to be printed around the existing gripper. It is quite tough to get it to print properly and you need to pause the print to insert the gripper. 

How do you build it?

You need the following parts:

• 3 x Screw M4 (optional)
• 3 x M4 Hex Nuts (optional) 
• 1 x M6 Air Hose Fitting (optional) 
• 1 x Printed Mold
• 1 x Ecoflex 00-30 silicone (around 200 ml, but I reccomend to buy more)
• 1 x Knife/scalpel/scissors
• 1 x Old piece of cloth
• 3 x Printed Seperators

1. Print the mold.
2. Print the 3 seperators.
3. Pour the ecoflex into the mold. 
4. Place the sepators onto the mold:
    
    
5. Let it dry. STICK TO THE MANUAL OF THE ECOFLEX!!!!!
6. Remove the seperators. (If you can see through as in this photo, the ecoflex still needs time! Be patient. I was not patient and it was not worth it)
    
7. Remove the gripper from the mold. Destroy the mold if necessary. Be careful not to rip the gripper apart. 
9. Place some ecoflex on the old piece of cloth and then put the gripper on top of it so that it closes the gripper. Be careful not to use too much ecoflex on the cloth. If it is too much the gripper will not work. Also use a spoon to put some ecoflex around the edges to create a good air tight seal.
    
10. Let the ecoflex dry again. Be patient. 
11. Use your knife, scalpel or scissors to cut through cloth around the contour of the gripper. Be careful not to cut yourself or the gripper!
12. Test the gripper. The arms should move towards the center and grip anything that is placed between them.
     
13. The gripper is finished!

If you want to add the exoskeleton proceed as follows:

1. Print the exosleketon and pause the print right before the top of it is printed.
2. Place the gripper inside the exosleketon.
    
3. Coninue and finish the print. This part is very difficult. You might need a couple attempts before it really works.
4. Place the hex nuts in the exoskeleton so that you can insert the screws.
5. Insert the air hose fitting into the top of the gripper. You can pull it apart to widen the hole in the top. 
6. The gripper with exoskeleton is finished!
7. If you want you're allowed to make a remix of the exoskeleton. Splitting it into two parts would make everything easier for example. (I used the single part design because I wanted to experiment with silicone as support material)

How do you use it?

Place it above an object you want to grip and increase the air pressure, the arms will move towards the center and grip the object. My test object was a ball with approx. 80 mm in diameter and a weight of 20 g.

Here are some outtakes of the progress (different early prototypes of the gripper):

I hope you have fun with it!