I’m looking at all the plans, photos and parts and I can’t seem to find how the CNC stays “centered” on the table/bed. Shouldn’t there be wheels or bearings on the side parts to keep it from moving left-right?
Why would it move left to right?
All the wheels should be pointed in the same direction and only move in that direction. If for some reason your build has an issue the Z rails can act as a guide. If you follow the getting started guide and start the machine square, and pre drive your entire job length you should have no issues with this.
The wheels may only move in one direction, but what about drift? Nothing seems to prevent the machine from drifting left or right, cutting in the X-axis will push the machine horizontally.
https://printrbot.com/wp-content/uploads/2014/10/Crawlbot-Electronics.jpg
If you see on the crawlbot there is two sets of three bearings on each side that roll against the side of the table, to prevent such movement.
Or are you saying that LowRider relies on wheel friction alone to prevent such drift?
Yes, correct CAM has very little forces on the machine. If you want to use guides like that your table will have to be built with extremely good tolerances. Trust me it is easier to roll in a straight line than build two perpendicular edges 5’ apart. With a perfect table that is the best way, with a really good table the best way would be 1 guide wheel as to not over constrain the system. 4 wheels do a very good job of not moving, 8 even better.
It is harder than you think to slide 1 wheel across a table.
Alright, thank you for the information.
I’ve started printing the “standoff” parts yesterday so I still have some way to go before I can start assembling my LowRider.
Thanks again for all your excellent designs and sharing them with the world.
1 Like