A CNC Tool Height Setter is sometimes known as a Touch Off Setter or Z axis height setter.
There are plenty of considerations to mull over when it comes to the potential accuracy of a CNC machine. In fact, it is an utter minefield. The deeper you go, the exponentially deeper the rabbit hole becomes. I am not going to go into this much more as I am already having ‘nam like’ flashbacks. One thing is for sure and that is if you machine software doesn’t know the height of the tool cutter in your spindle, it’s safe to say you are going to get mixed results, even with the most precise of machines.
Depending on the application and operations required it maybe that simply zeroing off your Tool Height by eye with a known datum is sufficient. You maybe just cutting through some MDF and don’t mind going into your spoil board so you eye up by jogging Z, zero off, and add a millimetre or two to the depth of cut and your happy.
However, when it comes to much more precise demands, a piece of paper or a feeler gauge may not be enough, or it is simply too slow and means your machine downtime is too high with slow tool changeovers. You may also need to measure and re-measure the diameter of cutting tools with do change with wear. In this article we are going to focus on the Height of the Cutting Tool in relation to the traditional Z axis of a CNC Milling Machine. In particularly, we are going to focus on the use of a CNC Tool Height Setter, sometimes called a touch off setter or tool setter, to accurately measure your tool heights. We are also going to assume for the sake of this article that you require precise and effective tool height measurements.
The concept of using a Tool Height Setter involves the lowering of a pre-mounted cutting tool onto a measuring device. These Tool Height Setters are connected directly into the CNC machines controller and software and allows the automatic measurement of tools in a tool holder and the resultant data to be fed directly back to your machine program and Tool Table. These are the most sophisticated types of Tool Height Setter and allow at the touch of a button, or automatic part of a CAM programme to measure tool heights and make adjustments to Tool Table data. This is extremely useful for also re-measuring cutting tools when subject to tool wear that needs to be adjusted for if precision is to be maintained.
These systems require permanently mounting in a location of your CNC machine, most often with the touch plate perpendicular to the Z axis. They also require hard wiring into the CNC controller system and it is often required that basic programs are created for initiating the measurement sequence. This will be covered in more detail in the future with separate articles for a variety of CNC systems. These programs are often called macros and consist of programming language that tells the system to go and measure a particular tool and update a Tool Table database with the latest Tool Height data that was measured. In a fully automated system with a full auto tool changing carousel it is possible to perform a number of other functions that are extremely beneficial for your machining process flow. As previously mentioned, you can program the system to re-measure tool heights to apply cutting tool compensation for tool wear, but you can also take advantage of this functionality to identify if a tool has broken, evidenced by a lack of anticipated physical presence of a tool when a tool measurement is simulated.
There are literally hundreds of models available nowadays on Amazon and Alibaba, but many are poor quality in terms of repeatability and build construction. Many are not suitable in heavily polluting environments like using flood coolant. Many of the cheap and nasty variety have a short stroke distance and don’t have over travel safety functionality. Stroke distance on a Tool Height setter is the distance that the touch plate can be depressed safely by the cutting tool, without crashing the system and damaging the tool height setter, cutting tool or CNC machine. This distance, if only very small limits the speed in which your cnc machine can feed towards the height setter and still accurately take a measurement. Over travel protection is something that only the best Tool Height Setter’s offer. This system means that the Tool Height Setter can be wired into the safety circuit of your CNC machine so if whatever reason, the mechanical system fails to stop before crashing, the safety circuit is activated, stopping everything immediately, before any damage is done. Higher end systems also feature the connection of an airline which connects to a system to blow the touch plate clean of contaminants that would otherwise falsely effect the tool height measurement result.
EMG Precision's UTS-2 is a professional, ultra precision, uniaxial touch tool setter which performs a tool length measurement function, broken tool detection and automatic compensation. UTS-2 transfers the signals by cable. UTS-2 has 11mm of stroke distance which reduces the possibility of an accidental crash and a travel override protection circuit. This tool setter has an indicator light to show its operational status and utilises a 6 core cable. UTS-2 adopts original micro resistance technology guaranteeing excellent durability for a pro-longed life. UTS-2 is widely used on CNC professional machining centers and features an integrated Air Blower and is IP168 Rated, perfectly suited for harsh flood cooling environments.
Please watch out for a upcoming article on how to set-up this Tool Setter with LinuxCNC from TheFeralEngineer
Thank you for reading and we hope you enjoyed the article.
Jonathan Gee
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