McWire construction problem and solution

For those of you that are building an McWire "Seedling". One large word of caution. The Bill of Materials call for galvanized pipe to be used. USE IT. In my haste to get started the local Ace Hardware did not have any 12" galvanized pipe so I got some black pipe instead. Wrong thing to do. Here is a picture of the pipes with one hole in it and it ate 7 screws after drilling the hole. 2 screws had to be cut off and drilled out. The others just were machined smooth where the threads were. It also took 3 hours of putzing to prove to myself that this was not going to work. So today I went and bought 2 - 12" galvanized pipes from Home Depot and spent 1 hour and finished the job correctly. See pictures below.



So word to the wise get only galvanized pipe for the frame or you will have more work that you can believe.

Edited 2 time(s). Last edit at 01/31/2008 10:40PM by Robert Teeter.

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Bob Teeter
"What Box?"

I used the galvanized pipe also. I'm a little unsure of what the black pipe is made of. Just a harder steal? I don't think I saw that in Diamond Home Improvement where I went.

I like how you made your 'Strap much wider than normal. Good move. I'm limited with mine currently but it will do to make me the parts for a Darwin.

Demented

My McWire is made from the black steel pipe. Didn't have any problems with the screws, but maybe I was using different screws.

I don't have it working yet - the X and Y are in place, but the bearings aren't right and I haven't even started on the Z. I've been distracted by getting the steppers to work - using the arduino with a found stepper driver board.

The pipe I think you want is Malleable Iron as opposed to steel.

The Malleable thing makes it easier to work with.

The stuff I was looking at today was available either galvanized or not but didn't come painted black. The ungalvanized is so Grey as to be able to be called black pipe but isn't painted.

Umm duno if this is of any value but there you go.

Cheers

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

I think you're right. The pipe I have isn't painted, it's coated in some sort of oily substance. Home Depot labeled it as "black steel pipe" but it's not wielded pipe, so I suspect that it's not steel, or is a really low-grade steel.

Bottom line of course is that it worked for me. Drilled OK, the screws self-threaded, and it went together without much fuss, or requiring a pipe wrench.

I didn't find the design for the "improved" wcwire, only the parts list. So I got (approximately) that list of parts, and did what I could figure out. Haven't had as much time to work on it as I'd like, so it's still incomplete. It'll get there eventually, but I think it'll take awhile.

The bearings in particular I didn't grok - but my found steppers have plenty of muscle, (2A/phase, 1000 steps/second, 200 steps/turn ) so I don't think a little extra friction is going to be a problem.

which bearings? the roller bearings are fairly crucial to keep everything orthogonal.

the PTFE bearings are also rather crucial, unless you want to replace your acrylic stages ($100+) every few hundred hours instead of some PTFE strips ($5) the fact that they also make things much smoother is just icing on the cake.