Friday, September 05, 2008
Moving the turnbuckle onto the inside of the floor mounting flange allowed for the use of one less nut per bolt, and moved the bearings closer to the flange, seemingly improving alignment somewhat. Excellent.
I haven't tried mounting additional flanges on the outside of the bolts yet. At nearly $4 each, they're already the most expensive part of the assembly by far. If I can get away without doubling the number of them needed, it's a big win.
You may want to give Sebastien Bailard a quick Personal Message on the forums Personal Messaging system.
Sebastien was interested in building a "Full Sheet" cartesian bot for some of his sculpture projects.
What you are doing here looks like a dead ringer for Gantry Mounts and Bearings.
You might also want to take a look at Pipe Clamps. They fit to the same ranges of pipe that you are using but are a slide on with a grub screw fitting.
The sort of things they make safety handrails from etc.
I looked extensively at the type of pipe clamps you're talking about. They're _perfect_ for this sort of application, but exceedingly expensive. $10 - $20 each. By comparison, the black pipe fittings I'm using cost around a buck a piece. They're not as nice, but MUCH cheaper.
Most of my design could be adapted to use kee clamps, and it would be a better machine for it. More easily adjusted and accurate. But that differers from my goal of building a repstrap that's inexpensive and easy to build by anyone who doesn't have tools.
Yes they are expensive you are right to use the less expensive parts.
Their alignment can be a touch pants too as their is a bunch of play in each fitting to allow for misalignment etc.
There are however some parts in the Kee Clamp range that are not available in the pipe fittings. That you might find complementary later on further down the line. If your aware of them then great your already a step or two ahead.
If you get to be concerned about accuracy and keeping the threaded joint tight (tapered threads are a bit like that) beg/borrow or long term loan a cheap stick welder and put tack welds on the pipe/fitting joints once you are happy with them.
Tack welds can be ground off again if you have made a mistake, but in conjunction with the threads fix some of those picky issues like getting a closed loop to align and be tight. (You generally get one or the other)
Obviously, since you're making it out of pipe fittings, it's going to require some heavier steppers to push the positioning table around.
Have you measured how much frictional load it generates?
He does use lots of flanges and bearings.
And 1" pipe. Heavy and more expensive.
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