I'm converting my LEAD1515 to a 1010 with linear rails and a 1.5 spindle. I'm trying to decide between MGN15's or 12's for X. Also, would I need four rails on the X c-beams or would two work? Thank you
I can’t answer most of your questions but the answer to 2 or 4 rails is 4. This prevents rolling of the C-beam channel subsequently preventing racking of the rail within the carriage blocks.
Thanks, Rick. Anyone have some input on MGN 15 or 12's? Since I'll be using four I could probably use mgn12's.
15's, 12's are to fragile, but I don't understand the recent trend to double up on linear rails? Cheap ones which are very tight typically cause much drag as well. 15's are four bearing rows which resist roll and won't bind from some side torque. lots of cost for very little benefit, this is all just my opinion. I work with automation and many of the robots have one rail for an axis, the loads are not like machining but it works fine for years. Bracing the two C beams on the x axis together, will be much better than using 4 rails, and less drag and cost. Cheers Gary
So two 15's on the very bottom and very top position of the cbeam and possibly a 1/4" plate or two somewhere on the back side of the cbeam?
I'd use HGR15 rails for the Y axis- they roll easier and have zero issues having that gantry sitting on top of them for extended periods of time. MGN is fine for X. I'd use two rails per axis because the friction of four is too much, but! Rick is correct, you still have to stop the C-Beam from twisting. You may have seen how I approached that, but if you're willing to put the screw outside of the extrusion (ie. directly between the two rails) it's much easier to tie the two C-Beams together on both sides using maybe 3/16" aluminum strips as Gary says. Or build a rectangle block with 4020s in between them to spread the rails out a little further. Maybe even epoxy it all together and lock it up. Gary is also correct in that profile rails are far, far stronger than anything they're attached to here and a single rail can take any force a lightweight extrusion machine is going to apply to it while effectively resisting any torque forces. However, the extrusion that it's attached to is far less effective at resisting those forces, and the rail is not a structural element. You need the two rails spread out to resist the leverage of your Z axis assembly as best that the C-Beam can do so. The wider the gap between those X rails, the stiffer that axis is going to be- the extrusion doesn't get stronger, but you give it more mechanical advantage to resist the torque.
Here's the latest version with Fusion 360 file attached. Using advice given here and some other changes I think it'll be an upgrade. HGR20's on X,Y and HGR15 on Z. Plates are 6.6mm and 9.8mm. The plan after this version is to eventually upgrade to ball screws and spindle. I appreciate everyone's opinion and guidance. Link to Fusion file https://drive.google.com/file/d/1XbpHZHwHu8dzy_jXfYTU4kcl8v2-SmVH/view?usp=sharing
