CNC Precision Multimachine Specification

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The CNC Precision Multimachine is defined as a modular construction set for heavy duty (1000 lb lateral and vertical tooling loads) precision (down to 10 microns or 1/3 mil) subtractive manufacturing system that can accommodate any tool head for subtractive machining and grinding operations. It is the equivalent to machining as LifeTrac infrastructure is for modular heavy equipment construction, and it is the equivalent of the Universal Power Supply Construction Set for power electronic devices, and it is the equivalent of the Modern Steam Engine Constructin Set for the power infrastructure.

The CNC abegins with a Cartesian x,y,z Precision Motion Construction Set. This motion system is mounted on solid concrete bases, either horizontal or vertical. The precision drive is opposing - ie., the work piece and tool head move on the same linear drive to facilitate alignment. Second, rotary precision motion is added to the system to allow for 5 axis machining operations.

Cartesian Precision Motion Construction Set

This is a 3 Cartesian axis (x,y,z) motion systems for precision machining.

The basic design is for a precision motion system (down to 10 microns with zero backlash) based on a modular design of structural holding table, drive, and structural precision rail system for linear motion. Further, this precision motion system is extensible, or scalable – via a mechanism for attaching consecutive motion system members to extend the length of the precision motion system.

  • Force requirements are 1000 pounds of downward pressure in drilling operations
  • Force requirements are 1000 pounds of sideways pressure in milling operations
  • Table workpiece holding requirements are up to 500 lb workpieces
  • Basic size of precision motion module is 9 by 18 inches for the rail and table
  • These modules can be added linearly to accommodate any length of machine, such as a lathe with a 6' bed
  • The componentized structure of each motion axis should include: (1) precision drive: precision drive system such as a ball lead screw; (2) Rail system: rail/slide system to provide both precision and structural holding strength of the motion system while under the stresses caused by machining operations; (3) Reinforcement - a reinforcing component placed on the rail/slide system may be used whenever the motion system is scaled, which may be necessary to accommodate the additional strain associated with increased machine size
  • Structural scaling may be obtained via addition of a strengthening module to the motion assembly. To accommodate this, a block with a large section modulus may be bolted or otherwise fastened to the surface of the rail/precision drive assembly. Typically, a workpiece-holding table is attached to the rail/precision drive assembly. In the case of machine scaling, an intermediate reinforcing piece may have to be used.
  • Module can be arranged horizontally (lathe for holding chuck and tailpiece, or table of a mill) or vertically (such as the holder for the drilling head on a drill)
  • Module is attached to a monolithic, concrete block to provide mass and structure to counteract vibrations
  • Modules can be stacked one upon the other. This is clear for the x and y axes, but this is also the case for z motion, where the x and y axes can be attached to the z via a right-angle bracket
  • These modules are operated manually with a turning wheel, but the turning can readily be retrofitted with stepper motors or servos for CNC control

Design for Fabrication: Simplicity and Modularity

  • Simplicity and modularity are the keys to keeping the fabrication costs of this precision motion system as low as possible. For this reason, a structural block of concrete is used as a base for the machine (horizontal or vertical). Modularity stipulates that once the design for a single axis is obtained, it can be used on the other axes – thereby simpifying both design time and reducing fabrication time as the same pieces need to be fabricated.
  • Design for fabrication should be employed to simplify fabrication procedures, reducing cost
  • The design should be such that the precision motion element is an off-shelf device such as a lead screw, but the structural rail holding system should consist of stock steel or metal. Stepper motors may be bought.
  • Design assumes that in order to reduce material costs, stock steel can be machined, hardened, and precision ground. It is assumed that the fabricator of this machine has access to a surface grinder, milling machine, and a heat treating system such as an induction furnace that can be used to harden materials as needed.
  • Modular rotary axis of motion for rotary motion
  • Modular reinforcement for scaling linear axes
  • Assumes stock steel, case hardened and surface-ground to precision
  • Assumes surface grinder and mill are used in its construction up to a 4' working bed
  • Can be used to make a mill or lathe
  • hydraulic motor drive, flow control for speed control
  • Interchangeable heads
  • Indexing head is also motor head