Saturday, February 25, 2012

Cost Reduction in Manufacturing

I have been looking for ways to reduce materials cost, scrap material wastage, and labor on the telescope caster assemblies that I build--and each time I look for a way to do this, I find more opportunities.  The units that slide inside the Losmandy G-11 and Celestron CI-700 tripod legs have been a particular length, mostly because my first design relied on length to hold them in place.

This never worked very well, because a tight enough fit to make them fit snugly in some units would be too tight to fit in others.  (The manufacturing tolerances on the tripod legs for these models are actually astonishingly good, but even .005" variance was the difference between holding tight or slipping out.)  I came with a different scheme that uses a screw to hold the inserts inside the legs.  This works very well--but it means that the length of the inserts is now substantially more than is required--and acetal rod this diameter isn't cheap.  So I have been experimenting with a shorter length of insert.  This requires material costs a bit.  It also reduces labor, since I have to turn these 2 3/8" rods to a size just a bit smaller than that.  If I have an inch less acetal to turn down to diameter (and that typically takes several passes), that reduces the time I spend.

Perhaps the most significant discovery I made this evening was serendipitous.  I start out with cylinders that I turn to size, then I cut a 30 degree angle on one end of the cylinder in a chop saw.  That is just wasted material that I throw away, and I can't recycle.  Why not turn down a long piece of the material to diameter, then make the 30 degree cuts from that long rod?  The 30 degree cut produces two mirror image pieces.  Now I don't throw anything away.

In addition, to hold the cylinder in position on the chop saw without putting my finger anywhere near that blade, I have traditionally drilled and tapped a 3/8"-16 hole in one of the cylinder, so that I can clamp a fixture to the chop saw back fence, and use a bolt from the fixture into that hole.  I can no longer need to hold a short piece of acetal in the chop saw--and I can use some of my other fixtures for holding round objects securely in place.  This alone is a major reduction in labor.

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