Hi all,
I've spent a good amount of time over the past few weeks reading up on homebuilt CNC. I'm still in the planning stages, but i'm pretty sure about what i want.
my requirements:
a)-cheap! Need to keep within a tight budget so i can spend more money on airplanes/woman.
b)-I plan on cutting balsa and lite ply for model airplanes, perhaps other stuff, but I can build a second machine as my needs grow. cutting area should be at least 24" long, maybe 12" or so on Y axis. I have access (and skills to use) 3D cad, so i'd like full 3D cutting capability, not just 2.5D.
c)-has to fit in a storage closet: no wider than 30" to fit through the door. length is not so much of a problem, it can take up most of the closet.
d)-no table saw: can't cut dadoes. might be able to get around this.
design choices:
a) has me leaning towards an MDF frame with 75-100 oz/in. steppers, and either a dremel or a 5.5 amp cutout tool (just saw a DeWalt at lowes for $65). I'm also thinking rollerblade bearings on steel pipe, and allthread for my screws.
b) balsa/ply: dremel will work fine. 24" cutting area to keep the size down and tolerances tight, but I'll want an open-ended workbed so i could feed 36" or 48" stock in for 2 cuts. I'm looking for around ten thousandths (.010") precision.
c) 30" wide should be plenty for 12" usable length on the Y axis. I am building a board-and-mdf table that's 30"x48" for in the closet and will have space for an aging pentium underneath. since space is a concern, a rolling gantry/stationary bed seems like a good choice here.
d) should be able to work MDF and delrin to a reasonable precision, but I'll have to design around what I can do.
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Given my desired specs, the JGRO machine is pretty close to what I'm looking for. I have a few concerns about the design, and I wonder if anyone can comment on a few of my modification ideas:
1) I don't like the bearing arrangement on the guide pipes. I would prefer to go with 3 points of contact arranged either at 90 or 120 degrees. this will slightly increase the cost, but not hugely. would 120 degrees have a significant advantage over 90 (which would be just contact points on the top and sides), and would this be worth the added complexity of building it to a weird angle? I've seen someone do 120 deg, but I dunno where I could get non-right-angle angle stock. any thoughts?
2) I don't really see the need for two torsion boxes, especially as this machine will sit on a table that is already pretty stable and flat. I think i'll skip the bottom torsion box, add some simple bracing, and keep the torsion box on the cutting bed base. this should also speed up the build, as it looks like one of the most time-consuming parts. convince me that this is a bad idea?
3) If i skip the dadoes designed into a few of the gantry parts, will I have to be more concerned about losing strength or alignment?
-also, have I missed any threads with good additions/omissions/upgrades/mods to an mdf rolling gantry design?
-barrett lawson