Ok, it’s been a while since my last post again. I may make a separate post with all the details, all the changes, jobs, experiences, ect. But it isn’t this post. This post is about an arm…..
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This is a CMM arm, or a coordinate measurement machine. This arm is incomplete and broke, but that has never stopped me from making useful tools from unloved parts piles. The purpose of this arm is that you fix the base firmly in space (like to a table where it won’t move), and you use the other end to probe an objects shape.
This is the end the probe goes in, I’m gonna have to build one. This arm is so old you can’t get parts for it unless you luck out on Ebay or some other online antique shop. Once you have the probe up against the object you want to measure, press the button. This will cause the software (don’t have that either, lol) to measure the angle of al the joints in the arm and create a data point in 3D space using the fixed base as the reference point. Move the probe to another spot on the object to be measure and press the button. Doing this repeatedly creates a Point Cloud that is a digital outline of the object that can be used in modern CAD software. It’s a very useful tool to digitize large parts like the missing pieces of my various projects. If there is a left side part on my project, but I am missing the right side, I can digitize the side I have, and then mirror it in software and have one of my machines make the missing part.
So why but a broken arm missing pieces with no software? Because these arms new go for tens of thousands of dollars. Used arms go for multiple thousands of dollars. This arm was a couple hundred dollars, with a bunch of metal bits I don’t have to machine from raw stock, and expensive encoders that measure the angles in the joints for accurate point data. Bonus is the arm has carbon fiber tubes that make the machine accurate in almost any temperature or humidity level. So……
I pulled it apart to see how bad it is.
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Not gonna lie, it’s a mixed bag. On the bright side it’s a known major manufacturer, using good hardware, so that’s a win. On the down side, it’s going to need some major work. I applied power to the unit and checked voltages. It should use 12VDC in, which is knocked down to 10VDC using a LM33T, followed by a 78M05 to give me 5VDC. The 10VDC and 5VDC test pads are showing the full 12VDC. The whole arm is getting unregulated voltage that may have wiped out sensitive components elsewhere in the arm electronics.
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First things first, have to get my voltage under control. So I will be replacing the LM338, the 78M05, and any other item I find out of spec in the power regulation section. Once I have done that, I will continue posting the progress on this. I may also make a smaller arm from scratch using the ideas I see in this arm for inspiration. It will have much simpler electronics though……