January 24, 2022

How do CNC probes work

How do CNC probes work

  1. Start by fixing the part to the machine table and make sure it is stable and clamp. That way, you get maximum performance and minimal mistakes.
  2. Define a rectangle where you want to apply the probing process, and the area is a bit larger than the model itself.
  3. Start moving the machine over the probing area and lower itself in the Z-axis until the probe tip triggers the internal switch in the CNC touch probe sensor.
  4. The machine control has to record the X, Y, and Z-axis locations at that point.
  5. The probe moves to the next position and repeats the process, identifying and recording the next point.
  6. Once the probing area is mapped out, it results in a point cloud that represents the part surface, and the software then takes the point cloud. It uses it to create a 3D surface area.
  7. One can now toolpath the newly created surface, the same way we would with a toolpath downloaded to the computer.

What is the primary benefit of CNC probes?

CNC probes allow you to copy parts and reverse engineer projects. That is how you tell that it is complete. Add a CNC touch probe to your CNC router or CNC plasma essentially to turn it into a parts digitizer. It is one of the best options for making complex 2D shapes or 3D geometry so you can use them in your CNC work. It is also available at an affordable price. 

How do CNC probes help the CNC machine

  • Thermal expansion compensation
  • 3D Surface measurement, inspection, and digitization.
  • It offers a preset setting
  • Setting the tool height and diameter 
  • Cutter compensation
  • Measuring the material 
  • Workpiece Alignment
  • Vice and work holding position identification
  • 3D Surface profiling.
  • CNC Machine Calibration.
  • Applying CNC probes to a CNC machine

CNC probe types

        centroid probe

The CENTROID probe is for probing (part setup, zero location setup, CMM type location and measurement of part geometry), component/fixture/workpiece setup, inspection, and 3D or 2D digitizing. The probe came from the USA with patented technology, and the probe’s low trigger force allows the use of small styli for maximum detail and accuracy.

        digitising touch probe for CNC router

It works repeatedly using standard hardware and does not require a lot of precision during assembly. Screw tips rest in shallow pockets in bolt heads, foaming replacement of spring mechanisms used. 

The foam also helps the triangular probe table from getting rocked off-center. It is a single-pole switch, and any movement of the probe tip disrupts the circuit that passes through the three screws.  Mount the probe under the portion of the router mount that holds the vac hose.  The screws pass through corners and slightly on the backside.  

        touch probe sensor

These are sometimes referred to as touch-trigger probes or triggering touch probes and work by touching parts of a workpiece or tool to collect multiple data points. What determines the position of the workpiece and updates the machining setting, is the user. 

        CNC digitising probe

Touch probes measure a variety of tools on the machine. Measurements are so accurate that they will not miss a single tool, and the CNC automatically saves the measured tool data in the tool memory for later use in the part program. 

Touch probes are inserted into the tool holder either manually or by the tool changer. They can automatically or manually perform depending on the probing functions of the NC control, and the functions include:

• Workpiece alignment

• The Preset setting

• Workpiece measurement

It is for accuracy, prevention of scrap or rework, and the overall quality of the finished workpiece. Touch probes are an ideal solution for monitoring tool wear or breakage during minimally-supervised operations. Probe contact is deflected from its rest position, sending a signal to the NC control during the three-dimensional probing of a stationary or rotating tool.

CNC probe applications

Workpiece Alignment

Workpiece Alignment is one of the applications and processes used with stock, components, tools, and system calibration. It is fundamental when machining and working on workpieces that have been machined. 

You can determine the component’s exact position and orientation to ensure that any machining operations are located. This is difficult to complete manually as the touch probe speeds up this process with precision.

You are allowed to clamp the workpiece in any position, since that may not be accurate in terms of aligning with XY coordinates. A touch probe has an automated program that analyzes the component’s position to define and correct misalignment. 

Data is processed by the control CAM software, and adjustments are made to the program. That compensates for manual positional errors. The system moves two datum points like hole centers or rotates the XY axis by 0.001 degrees to compensate. Start machining your operations with confidence.

Preset Setting

Your machine setup involved several preset positions. Precision vices are known as positions, and they use touch probes to adjust stock positions on preset positions using regular routines. You even run offset adjustments in your software to ensure that you do not waste stock positioned correctly. Reduce your safety material rules and save money on stock waste.

Cutting Tool Compensation

The machine components give high levels of accuracy consistently and repeatedly. Cutting tools are maintained and performed correctly and wear out. That is not avoidable. It is not necessary to replace worn tools as they may be useful. 

Tool wear may need to be compensated with predefined routines, touch probes measure a range of cutting tools types, and necessary adjustments to compensate for tool wear.

How to choose between a 2D and 3D probe

Choosing between the two depends on your use. A CNC digitizing touch probe works for capturing 2D surfaces Just like 3D. For an irregular 2D shape, use the probe to perform the 2D scan, and get the shape in CAD format without measuring or drawing. From that point on, tool pathing becomes easy.

The more detail a part contains, the closer the point samples will have to be and the longer it will take to probe the part. Once you start the process, the machine continues automatically with minimal human effort.

The 3D Touch Probe is for measuring workpiece geometries such as edges, holes, grooves, studs, angles, and corners or scanning surfaces. It works for high measurement precision; the touch probe must be mechanically calibrated so that its axis aligns perfectly with the spindle axis of the machine.  3D Touch Probe is not only a simple switch but includes electronics to ensure a stable and reliable switching behavior.

CNC probing software

A well-functioning interface between the CAM programmer and the machine operator is necessary for a reliable production process. Do not neglect clamping errors, stock inaccuracies, or operator errors on the machine. Manual interventions and the associated machine downtimes are hidden time sinks that increase throughput times. 

David D. Hughes
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