Last updated on Tuesday, February 25, 2014 05:21:43 PM Eastern US Time Zone
3D Digitizing Probe, Digitizing Movie
Basic 3D digitizing steps: probe, mesh point cloud, convert to appropriate file type, CAM to g-code & then CNC the part.
Find the Mach3 3D Probing Plug-in, then
install & configure it under Mach3 Conf Menu.
Adds the 3D Probing tab to the right of Help. Creates an XYZ comma-delimited txt file.
Mach3 also has a Digitize Wizard but it is purportedly slower than the plug-in.
MachCloud reads the 3D Probing
comma-delimited txt file & creates an XYZ point cloud that can be meshed from the
menu & then saved as an STL file or just saved it as an STL file for use by other meshing programs e.g., MeshLab.
Raw point cloud file structure can vary e.g., comma, tab, or space delimited. Reading errors can result.
Convert meshed STL file (using any preferred method) into g-code for Mach3 with a CAM program e.g., FreeMill.
STL is a file
format native to the stereolithography CAD software created by 3D Systems. This
file format is
supported by many other software packages. It is widely used for rapid prototyping & computer-aided
manufacturing. STL files describe only the surface geometry of a three dimensional object without any representation
of color, texture or other common CAD model attributes. The STL format specifies both ASCII & binary
representations. Binary files are more common, since they are more compact. An STL file describes a raw
unstructured triangulated surface by the unit normal & vertices (ordered by the right-hand rule) of the triangles
using a three-dimensional Cartesian coordinate system.
Mesh generation is the practice of
generating a polygonal or polyhedral mesh that approximates a geometric
domain. The term "grid generation" is often used interchangeably. Typical uses are for rendering to a computer
screen or for physical simulation such as finite element analysis or computational fluid dynamics. The input
model form can vary greatly but common sources are CAD, NURBS, B-rep & STL (file format). Three-dimensional
meshes created for finite element analysis need to consist of tetrahedra, pyramids, prisms or hexahedra. Those
used for the finite volume method can consist of arbitrary polyhedra. Those used for finite difference methods
usually need to consist of piecewise structured arrays of hexahedra known as multi-block structured meshes.
Computer-aided manufacturing (CAM)
is the use of computer software to control machine tools & related machinery
in the manufacturing of work pieces. CAM is the next computer-aided process after computer-aided design (CAD),
as the model generated in CAD can be input into CAM software, which then controls the machine tool.
Traditionally, CAM has been considered as a numerical control (NC) programming tool, wherein two-dimensional (2D)
or three-dimensional (3D) models of components generated in CAD software are used to generate
G-code to drive computer numerically controlled (CNC) machine tools.
In Mach3, LPT1 pin 12 input is used for the probe.
3D Digitizing Probe
Shaft is ⅜" x 1.2", body is 1.8" diameter x 1.9" long & the probe is about 0.24" diameter x 2" long with ⅛" ball.
The shaft can be removed & the probe tip replaced with a rubber-boot sealed pedestal. The unit is then
mounted upside down on the mill table in a setup that would be used for automated tool length sensing.
Econo Probe instruction sheet.
Click to see digitizing probe movie.
Another probe tip was constructed of stainless steel with a 10-24 thread. A 2mm (0.078740") carbide tip from
a dial test indicator was used for the tip. The tip is seated in a reamed hole & held in using Loctite red #271.
Smaller ball tip mounted into the probe housing.
3D Digitizing Probe, Digitizing Movie