Hello everyone!
First I want to congratulate pretty much all of you because in every threads I read (mostly in the DIY section) I see a strong demonstration of respect, specially noticeable towards the newbies. I had no intention to post anything but to do my research on my own instead. Everyone's positive attitude convinced me otherwise. I'm confident I can ask for help without fear of judgment.
I'll just had a little side note to this, I love straightforwardness: If you think something is just a plain bad idea, please tell me. I like to believe that I can handle the truth. That's what I'm looking for.
Short story:
I started building a first CNC about 10 years ago and never finished it. The stepper motors and controllers are about all I intend to salvage from my first attempt.
Goal:
If I have to choose between precision and working surface area, I'll take precision. I'm aware that my current components are not the best for it, it's just to keep it in mind.
The components list up to now:
- Nema23 425oz/in 2.8A stepper motor with KL5056 drivers (it's the analog version, now they are digital)
- SBR20 supported rail & bearings (300/600/1000mm) + Ballscrews, bearings & nuts ( 350/650/1050mm) Kit is from Amazon.
- Bosch Colt palm router as spindle
I'm still in the design phase and I'd love to get your inputs on few questions.
Q1 - I'll use 8020 extruded aluminium for the base frame. I designed the first draft with 1515 extrusion and it seems a bit bulky for what I consider to be a fairly small machine. Is the 15 serie (1.5" x 1.5") an overkill or does it bring added value in rigidity? And the rail supports are larger than 1.5" so like with the 1" version, the "floating" portion of the bearing rails would be sitting on the transversal frame supports. There is way less unsupported surface with the 1.5" though.
Q2 - I had in mind to install every rails with the supports parallel to the table. It was easy to do for the Y axis. It a bit more complicated for the X travel (on the gantry). On most of the designs I see, the rails are installed on their side. I'm pretty sure it's less of a problem with the carriage block type rails. Can this be an issue for SBR bearings? Would it better to design the gantry beam with a rail on top and one underneath? I also thought of installing the rails in the back of the gantry but my guess is that if I am to go with a side installation I better get as close as I can from the spindle holder assembly (Z) not to mess with the center of gravity.
Q3 - I noticed comments on ballscrews accessibility for maintenance. On all axis, I installed the lead screws between the rails and they're all pretty jammed up and surrounded by framing components. Should I consider making them more accessible, like bringing the X axis lead screw behind the gantry per example?
Q4 - I planned on making the gantry out of 3/4 inch baltic birch because I'm well equipped to work with wood. Could this be too heavy?
Thank you very much for your help.