Posted by Matthew Bollom Jun 29, 2012 We have been investigating possibly replacing the current motors on the claw machine with motors that NI sells. This would allow us to use our C series motor drive modules and to use SoftMotion in LabVIEW. I took the gantry down so we could get a better look at the current motors. 1
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The motor on the left moves the claw up and down (Z direction). I also removed the cord between the wheel and the claw because we are going to replace it. The motor on the top moves the gantry left and right when you are looking at the machine (X direction). Note: a cover on the gantry was removed so we could see and work inside of the gantry. 3
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This motor moves the gantry forwards and backwards (Y direction). Based off of the labels on the motors, they are 12 V DC motors manufactured by Brevel Motors Inc. I've searched the internet for information on these motors regarding power requirements, torque, etc., but I haven't had any luck. These motors are more than likely more than 25 years old. The motors are connected to a gearbox which then turns the necessary wheels to move the gantry or claw in the desired direction. The gearbox is the box between the motor and the metal plate in the picture below. If we cannot find a motor that has the same shaft size as the current motor, we will need to make a new gearbox or gears to fit a new shaft size. 5
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The Z direction motor was also removed because it was the easiest to gain access to. The shaft is geared, which will increase the cost if we wish to use the same gearbox. Another thing to note is that these motors do not have encoders in them already. Ideally, we should add encoders so we know where the gantry is at all times. This will be important in the automatic mode. Two of the motors (Y and Z) have a dual shaft with a diameter of 0.185", which would allow us to easily add encoders if we find some with the same shaft size. The X motor does not have the double shaft because there was no room for it. You can see this in the first image above. Without the dual shaft for the X motor, a linear encoder will most likely be needed. We brainstormed some ideas for options regarding the motors: 1. Use the current motors. This would be the quickest. However, we do not have any C series modules that control DC motors directly. We could potentially use a DO module, but in order to reverse the direction of the the motor, the voltage polarity needs to be reversed. My first thought on a way to solve this is to use a H-bridge and a DO module to control the direction of the current flow through the motor. 2. Find motors that have the same shaft size, are geared, and have the same form factor as the current motors. This is because there is a rod connecting wheels on opposite sides underneath the motor (see the above picture). There is very little room for a larger motor. 3. Get new motors and have a gearbox built. Stepper motors would be ideal if we went with options 2 or 3. Stepper motors are generally pretty accurate and sells a few different ones. The NEMA 17, the smallest stepper motor we sell has a shaft size of 0.1969" and an overall motor width of 1.68". Unfortunately, this motor is too large for the space that we have available to work with and the shaft size doesn't match so a new gear box would be needed. In addition, the cost of getting a geared stepper motor from an external source also increases to $400. For now, we will have decided to continue to work with the current motors. 7 Views There are no comments on this post 7