# Posts Tagged vacuum gripper

Today I present my first Delta robot made with Arduino. The Delta robot structure was designed by a professor at the Technical University of Lausanne in 1985.  It is a parallel robot, and within two decades has become the star of pick and place industrial robots . The delta robot distinctive elements are two:

• The robot geometry which simplifies the equations of motion (kinematics)
• The great idea to anchor the robot upside down so that it has the motors connected to the base. This is very important because while the robot works, the motors remain attached at the base, allowing the robot to have arms very light. Lightness means low friction, low inertia, low power motors, precision, speed, fast acceleration and deceleration.

These are two examples of delta robot:

These aren’t laboratory prototypes, but commercial robots and they cost about 50-60.000 euros. I tried to build a simple delta robot with Arduino. My Delta robot works like the commercial Delta robot, ie, in inverse kinematics. Given a point x, y, z in space, in real time Arduino calculates the angles of the servomotors that allow  to reach that point in space.

The Delta robot has two triangular plates. A higher which is fixed and the lower is free. The servo motors are fixed to the top plate. The gripping tool (i.e. an electromagnet, a gripper, a vacuum suction cup), is fixed to the lower plate. The two plates are triangular equilateral, that is, equal sides and equal angles of 60 °.

The Delta  has 3 servo motors and two arms for each servo. One is integral with the servo. The other arm is free to rotate in all directions and it is connected to the lower small triangle. In order to ensure the free turning, the second arm is linked with ball joints. To find the ball joints has not been easy. I found something about the steering of the machine model. Just search on google “joint Uniball” and you can find little cheap joints.

A very good explanation about the the Delta robot geometry and a very effective explanation of inverse and direct kinematics formulas can be found here . You can find also the code that calculates the inverse kinematic.

These are some Delta robot pictures (with an ATtiny85 microcontroller).

The end effector can be used with different tools. I tried a vacuum syringe and  a drawing pen.

These below are some videos with different tools.

The first experiment with a simple trajectory (a circle).

The Delta robot drove by a mouse with Processing. The code is available here.

The Delta robot in  pick and place configuration. The code is available here.

The Delta robot drawing. This is a first draft. The code is available here.

This gripper uses an inexpensive syringe as the vacuum source. A gripper is the final part of a robot and usually is used to grab an object. It is also called “end-effector” and can be of different kinds: magnet, clamp, vacuum, welding electrode. But there are many others.
I thought to make a gripper wich can hold the things and carry them around. The gripper approaches the object to the suction cup, it create a vacuum and the object remains attached to the suction cup. At this point it can moved where you want. Eliminating the depression the object falls for gravity.The gripper will pickup any small light object that has a smooth exterior finish. On the market there are very few solutions that are affordable for a hobbyist. Some components of Lego or Fischertechnik but they cost a lot of money.

The solution I present is based on an idea from Lynxmotion and it is very cheap. The gripper uses a simple and inexpensive servo (in my case the Futaba S3003 a) that costs around 10 euros. The other things are: a rectangle of PVC foam, a pipe and a connector for micro-irrigation that cost a few cents and a 20 cc syringe which costs about 10 cents. Some screw and clamps. The suction cup is made from an arrow. Having a baby has advantages, such as I can reuse his toys! We are quietly under 15 euros, an interesting result for a device of this type.
Surely we can not define the gripper as a force of nature, basically using a simple syringe and a servo to go up and down, but does its job. It can hold comfortably 200 grams for a long time.
There are no particular complications, mechanical or electronic, so I leave the word to photos and video. Note that the cutting of PVC is made with a cutter and the holes are made on the PVC with a screw.

Tags: