Stepper motor control limits

One of the fundamental questions that arose during the control and testing of the SCARA arm was what is the maximum speed achievable and the torque available at that speed. Some digging around in the world-wide-web revealed the following: The speed is limited by the torque availability from the stepper to rotate. For steppers, as the torque drops exponentially with …

Achieving rotational accuracy with steppers

For the SCARA (Selective Compliance Articulated Robot Arm) that I’m building for the course project, the rotation accuracy at the joints is critical to achieving overall accuracy. The stepper motors that I have are 200 steps per revolution which amounts to 1.8 deg per step. The accuracy is +/- 5% which means a rotational angle uncertainty of 0.18 deg (best possible). …

Harmonic Drives

Harmonic drives (also called strain wave gear) was invented in 1957 by C.W. Musser. They offer several advantages over conventional gear systems, especially for high precision and high torque applications. Hence, they are commonly used in many industrial robots. High gear reduction ratios are possible in a small volume from 30:1 up to 100:1 in some cases! The patents regarding this …

How smoke detectors work

Recently when I was cooking in my home, some of the food spilled over from the vessel and came in contact with the heating element giving rise to a dense smoke with the smell of burnt food like charcoal! Then the alarms inside our house went off! After a while,the smoke left the building through the windows and the alarms …

Precision couplings

In one of my research meetings with my advisor, Prof. David Trumper, we were discussing about motors and motor couplings. He mentioned about how the metal bellows for precision couplings are manufactured using electroforming process. I did some more search on the topic, and found that they are very useful torque transmission elements which are very rigid torsionally and accommodate misalignments in …

How are ball bearings made?

When I was making the Kinematic Coupling for Lab-4, I was wondering how I would manufacture the wooden balls. In the first day of class, Prof. Slocum had given us a wooden hemisphere which looked almost perfect. The most number of balls that are used anywhere in the world is in ball bearings. They are mostly made out of steel, but …

The technology of Pilot FriXion erasable ink pens

My first encounter happened during a discussion with a Japanese customer at my previous work-place. He was writing down all the minutes himself and in between, I would see him erasing with the pen. I was amazed! It was better than even a pencil as it left no trace at all! Since then, I have been curious to find out how this …

Seek and Geek – 1 : Syringe Pumps

Make your own syringe pumps! http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0107216   Traditionally, these cost upwards of $1000. Now, it can be made in-house with easy to manufacture, readily available materials for $200 or less!