A kit I have had my eye on for a while is the Maplin computer controlled robot arm. This arm, or kits like it can be found all over eBay and Amazon, but I have only found one which is computer controlled at Maplin.
I don't have any in progress pictures as I was pretty into the build at the time, so did not think to stop and take some. The kit itself largely consists of 5 electric motors, a control board and several plastic sprues of parts.
I was surprised to find that the motors are the standard 5v hobby motors that you get, rather than some sort of stepper motor. The fast motor movement is translated using a worm gear and a gearbox, so the first job after cutting out all of the parts is to build the gearboxes.
The arm combines the form and function well with these, and the gearboxes make up the bulk of the structure. 4 D cell batteries in the base keep the arm stable, one motor deals with the base rotation, while 2 make up arm joints and the final one open and closes the jaws of the arm.
The largest problem I had with the build was fitting nuts next to the motors. The motor cases were very magnetised and pulled the nuts out of slots in the case. The nuts were very small and needed to be sandwiched between parts of the case to bolt on the arm structure. Nylon nuts, or threaded holes would have made the process much simpler.
Once I was up and running I found that one of the major complaints for the arm was true. Gear lash made any movement unrepeatable with the flash based UI which is packaged with the arm. I have found a library on Github that provides more granular control. There is also no default position, and I found that the grip strength was practically non-existent, making this more of a show piece than anything practical.
Getting the software running on my PC was a task in itself because the drivers are untrusted you need to disable some protection to set them up, but thankfully Maplin have been keeping a page of drivers which is now bang up to date with Windows 10. It is also links to a how to for Rasberry Pi.
I has been some nice practice with gearing and made me think a little differently about what can be achieved with this. It is also a bit of a rabbit hole of other projects, from code that could handle some automation, to improvements to the gear chain. For now I am happy that I have a working robotic arm with 6 degrees of freedom.
I don't have any in progress pictures as I was pretty into the build at the time, so did not think to stop and take some. The kit itself largely consists of 5 electric motors, a control board and several plastic sprues of parts.
I was surprised to find that the motors are the standard 5v hobby motors that you get, rather than some sort of stepper motor. The fast motor movement is translated using a worm gear and a gearbox, so the first job after cutting out all of the parts is to build the gearboxes.
The arm combines the form and function well with these, and the gearboxes make up the bulk of the structure. 4 D cell batteries in the base keep the arm stable, one motor deals with the base rotation, while 2 make up arm joints and the final one open and closes the jaws of the arm.
The largest problem I had with the build was fitting nuts next to the motors. The motor cases were very magnetised and pulled the nuts out of slots in the case. The nuts were very small and needed to be sandwiched between parts of the case to bolt on the arm structure. Nylon nuts, or threaded holes would have made the process much simpler.
Once I was up and running I found that one of the major complaints for the arm was true. Gear lash made any movement unrepeatable with the flash based UI which is packaged with the arm. I have found a library on Github that provides more granular control. There is also no default position, and I found that the grip strength was practically non-existent, making this more of a show piece than anything practical.
Getting the software running on my PC was a task in itself because the drivers are untrusted you need to disable some protection to set them up, but thankfully Maplin have been keeping a page of drivers which is now bang up to date with Windows 10. It is also links to a how to for Rasberry Pi.
I has been some nice practice with gearing and made me think a little differently about what can be achieved with this. It is also a bit of a rabbit hole of other projects, from code that could handle some automation, to improvements to the gear chain. For now I am happy that I have a working robotic arm with 6 degrees of freedom.
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