Some parts of the revised CNC would benefit from a little more accuracy and precision than my current set of tools can manage. It may be possible to make a crude hand-operated mill out of my drill press. I purchased two steel plates from Lowes and two drill-press clamps from Home Depot, which I will slap together tomorrow morning. Total cost was around $40.
The idea is to create a stencil, trace the image on the material, and use the improvised mill to cut it out.
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I will purchase some thin aluminum flashing to use for making stencils of the parts I will cut out of HDPE. This way, if I mess up while machining a piece (or need multiple copies), I do not have to painstakingly measure and redraw the cutting marks each time. Not sure why I wasn’t doing this before, but it seems like a no-brainer.
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I spent more time building the mini CNC than updating the site. After completing the mini CNC, I discovered many shortcomings. Sleeve bearings are simply not a good choice for this kind of machine. Too close a fit, it tends to bind on any debris that is picked up; too loose and the assembly is no longer rigid. The play compounded horribly on the x-z axis, which deviated 1 to 2 mm under load. Therefore, I will use roller bearings that ride on rails instead. Polycarbonate is also a little too flexible and expensive, so I am going with 3/4″ HDPE sheets. The threaded drive rods had a lot of friction and are slightly warped right out of the store. I may cave in and buy some Acme lead screws. Lastly, to maximize the amount of workable area, I am going to go with a moving gantry design instead of a moving bed.
My first task is to think about how to making the linear bearings- stay tuned!
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Removed stepper motors because slight misalignments caused the assembly to jam. It may be necessary to include a flexure shaft coupler between the drive shaft and the lead screw. Finished all 3 translating stages and reinforced the chassis.
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Put in drive screw for Z-axis and mounted a stepper motor for direct drive. I am a bit concerned about whether or not the stepper has sufficient torque for direct drive. I will not know for sure until I finish the controller.
Started work on the dremel/cutting tool housing.
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Built linear rails for Z-Axis translating stage, which was by far the most time consuming to design and build of the three. There was considerably less room to work with while integrating it into the Y-axis and must later house the cutting tool assembly.
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Built linear rails for the X-Axis and the main chassis for the CNC router
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Built and tested linear rails for the movable bed (Y-Axis.) Acquired stepper motors from 3 used printers and 1 flatbed scanner from Allgen Computers for around $12. Pictures soon.
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Initial research about home-made CNC machines. Searched Home-Depot and Lowes for parts I can gerbil into linear rails for each axis. Purchased 4 old CD-ROM drives for a total of $2 over at Allgen. Although I the drives lacked the stepper motors I was seeking, I may eventually use the PIN diode sensor arrays I found for the interferometer.
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I have a secret project in the works this year which requires a fairly sophisticated interferometer setup. While I have gotten quite skilled at improvising parts from things I find at Home Depot, it is often a time-consuming and injury-prone process. After much deliberation, I have decided it will take marginally more effort to first build an ad-hoc CNC router. The deciding factor was mainly that the machine would reduce costs and greatly speed the development of future projects. This may be the most involved project I have taken on single handedly, but I am up for the challenge.
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