McWire 4 inch extension springs too long for Y and Z stages - can I cut/trim them?

To keep the stages on straight paths over the rails, there are bearings with springs that keep them up against the rails (doc is here [reprap.org]).

I bought the suggested McMaster part (can be found here [www.mcmaster.com]; actually, I bought the replacement part, as that specific part is discontinued), which is a pack of extension springs, each of which measures 4 inches from one end to another.

One works on the X stage, extending a bit and keeping the stage straight as it moves along the rail. Unfortunately, when I tried them on the Y and Z stages, they turned out to be too long, and are slack (unextended) when the ends are placed on the bent nails. This is no good, as the stages can move perpendicular to the rails, defeating the point of the bearings.

I'm sure the springs would work if they were a bit shorter. Would it be a bad (possibly unsafe?) idea to cut the springs to length with wire cutters?

Interestingly, the parts list suggests the 4 inch springs and using 1 for each stage, while the pictures in the documentation seem to show the use of 2 smaller springs for each stage.

Edited 1 time(s). Last edit at 08/26/2008 12:05AM by Joshua Merchant.

I think the springs are bent before being tempered. That might make it hard to bend a new hook without breaking the metal. Perhaps you would be better off finding some shorter springs at your local hardware store.

You can soften the end of a spring by heating it until it glows red and letting it cool slowly. Once formed you can harden it again by heating red hot and then cooling it quickly in water or oil.

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[www.hydraraptor.blogspot.com]

There is no need to heat the springs. I got the same 4" springs in my order and yes they are to long for what I built. All I did is figure out how long they needed to be and cut them off with an 8" wire cutter. Then I took 2 needle nose pliers and bent out the end I needed to attach to the connection point.

No problem with this at all.

Bob

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Bob Teeter
"What Box?"

I agree with Teeter, I did the same thing and the springs worked fine.

Did you guys also find that the 80mm long vertical bearing arms are too short to reach the stage and still screw into the vertical bearing supports?

My Z-rails are 3/4" thick, my vertical base is 1/2" thick, my teflon bearings (for sliding on the rails) are 1/4" thick, and my Z-stage is 1/4" thick. That's 3/4+1/2+1/4+1/4= 1 3/4" = 1.75" = 44.45mm.
On a vertical bearing arm, the distance between the center of the hole for the bearing and the center of the hole for the attachment screw is 40mm. The radius of the bearing is about 10.5mm, and the radius of the screw is about 3.5mm (and that's not counting the width of material [acrylic/plywood] necessary to keep the screw in place), or 10.5+3.5=14mm.
This means the maximum space between the edge of the support (where the screw is attached) and the surface of the Z-stage (where the bearing rolls along and keeps the stage pressed against the rails) is 40-14=26mm.

So, the maximum space for the bearing arm is 26mm, and the minimum distance necessary to hold the stage is 44.45mm... am I missing something here? Or did someone else (not mentioning names ) really mess up?

I considered reversing the vertical bearing supports such that they stick out towards the Z-stage from the vertical base (currently they stretch away from the vertical base and Z-stage, as shown in the docs [flickr.com]), and then attaching the vertical bearings, which would then be close enough to the z-stage. When I thought about it a bit more, I realized that the nuts on the bearings on the z-stage (which are used to keep the stage aligned with the rails) would collide with the nuts on the vertical bearing arms' bearings (which are used to keep the stage pressed against the rails).
So I figure I'll just have to make longer vertical bearing arms tomorrow. Because I know we're all only human, I won't comment on the accuracy of the documentation .