bootstrap

machine#construction: bootstrap
machine#designs_in_progress: bootstrap

Pull yourself up by the boostraps

Well, how else are you gonna fly?

Bootstrap is a multipurpose machine tool that can be made without the use of a machine tool in its construction. I will attempt to document all of the steps of brainstorming and designing, as well as actual construction and testing of the final design.

Regarding this document, I want you to consider the situation in both developed and undeveloped countries, so it will be of most use to those who actually need it.

The first point to consider is how to make the ways, which are really the heart of any machine tool.

*options for scrounged ways:

• polished chrome plated bar ways w/cast on zinc bearings
  • relatively expensive, alignment issues, may need to adjust bearings, hard to cut with limited equipment
• cold rolled flat rectangle with some scraping
  • can hand scrape to desired accuracy, hydrodynamic damping, use PushPull
  • requires flat mounting surface, may need to purchase mail order
• 80/20 style linear rail
  • may require complicated bearings (look into this), not necessarily accurate
• ball bearing linear rail
  • has very low friction
  • sometimes requires flat mounting surface, rarely in scrap yards, custom bearings unlikely with limited equipment

*options for homemade ways

• cast iron box
  • multiple gib strips (can use PushPull), must cast and scrape,
• cast iron dovetail
  • one gib strip
  • hard to measure, must cast and scrape
• cast iron double inverted Vee (prismatic)
  • tailstock can mesh with carriage to some degree, backup ways if external ways are damaged or worn.
  • twice as hard to measure, must cast and scrape
• roller bearing on square or round rail
  • common materials, very low friction
  • alignment, bearing adjustment, how to mount bearings, no hydrodynamic damping (see http://members.shaw.ca/axxus/m1.htm for a good example)
• ceramic versions of cast iron ways
  • kiln requires less fuel equipment and skill, highly wear resistant, high rigidity and dynamic damping, extremely common materials
  • high friction unless glazed, will sag during firing (must calculate how much - try standing upright on Z axis?), must scrape green form to desired accuracy, cannot correct after firing without expensive abrasives, fragile, uncharted territory - (well cutting edge at least, see http://pergatory.mit.edu/rcortesi/portf/grinder/machdsgn48-51.pdf )

overall design goals of the machine

• should be easy and quick for a novice to build
• should be as flexible as possible, able to perform many different operations with the same parts, including turning, shaping/scraping, horizontal milling, end milling/drilling, sawing, dividing, radius turning
• should include designs for mechanical as well as electrical/electronic auto feed, since some places don't have any electricity
• should be designed with the use of either castings or being fabricated/welded from stock in mind (right?)
  • discuss relative merits of both approaches