Dear all,
newbie here trying to build a cnc. I've been reading up for the past several weeks, but as I'm putting together a design I have a few questions I can't find an answer to. My goal is learning, machine won't be working 24/7 or need high precision, will be primarily cutting 1/2 wood and plastic and if possible do some little engraving of aluminum. Table should be about 3"x2". Budget is ~$500 if possible at all. I have a dremel I intend to start with. Speed isn't an issue at this point, in fact I'd rather start slow with "bad" parts and replace them as I go so that I can actually observe the difference they make. I'm no mechanical engineer, but I'm not afraid to tinker and study so feel free to pass on links for me to read on.
As far as options go these are the ones I found, please let me know if I miss any:
- aluminum profiles with special v cats that fit v bearings . seem standard on all machines on openbuilds.com
- 45deg angled aluminum profile with skate bearings, probably most common solution in MDF/cheap builds
- unsupported rods with SBR bearings, either open or closed , mostly for Y axies, x and z seem to use closed ones for the most (for some reason I never saw anybody using the round ones, even tho they are for sale on amazon)
- supported linear round rails with open or closed SBRs
- flat rails with flat bearings, seems top of the line/pricey hwin stuff
am I missing any option?
So here's my questions:
Here's my questions:
1. why are homemade skate bearings carriages more common at 45deg than orthogonal? do they offer more support? better distribute the weight? I'd like to avoid them because attaching the 45deg rail is quite a bit of a pain (at least to do solidly filling the inside with a properly 45deg cut wood)
2. some designs have the gantry fall on the rails/bearings, others have a little L/extension with the rails/bearings orthogonal to the gantry arms and the gantry connected underneath, like in the Joe 2006 CNC. Is one solution better than the other? Is it better to avoid putting the weight of the bridge straight on the rails? Does it actually help to connect the gantry underneath in terms of stiffness even tho that means raising the bed and attaching to the table with 4 feet only?
3. some design with skate bearings carriages have only one carriage on the Y axies while others have two, one above and the other below the side panel. Are two substantially better than one in terms of stability? (two carriages are standard on X & Z). Same goes for support rods/linear bearings, some have two like the Joe CNC I used an inspiration, but many others only have one.
I need to figure out exactly the costs, but right now making orthogonal skate bearing carriages attached horizontally and connect the gantry underneath the table is my favorite option. Should I prefer something else? Here's a pic of what I'm thinking, just images than instead of the two rods I'll have to profiles of aluminum and 4-skateberaings orthogonal carriages (either one or two of them depending on question above):
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That said, I'also love to hear comments on how that compares to this in terms of rails (the classic 45deg):
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thank you in advance for your patience and input and I'll go make another thread about threaded rods and leadscrews.
you all take care,
Spike
