Frequently Asked Question

Database design to avoid repetative tap testing.
Last Updated 3 months ago

MAL receives significant number of questions about the tap testing and modal parameter identification of the machine. We prepared the following information for our users.

Accurate prediction of sweet spots or stability lobes of the machine requires

1- Cutting conditions (radial engagement of the cutter): This is trivial and entered by the user. CUTPRO allows changing cutting conditions along the cut, has many options for the user. Shop-Pro allows up, down or face milling configurations.

2-Geometric model of the cutter (cutting edge geometry, helix, rake, run-out, variation of tool geometry from one tooth to next, pitch angles, approach angle,..) CUTPRO has the most sophisticated but easy to use cutter geometry entry. You can pretty much enter any cutter geometry you want, ranging from simple helical end mills, to variable pitch-variable helix, serrated, indexed, arbitrarily distributed inserts or user defined complex cutters.

3- Work material properties during machining, cutting coefficients We provide more than 250 work materials in the database via material selection wizard. It checks the database and offers you the most accurate and up to date cutting coefficient for that material. Extensively used materials in Aerospace industry, such as AL6061, 7050, 7075 and titanium, Inconel, Wasp Alloy are prepared by our research laboratory and they are most accurate worldwide. Both CUTPRO and Shop-Pro share the same material database.

4- Frequency Response of the Machine and maybe workpiece as well if it is flexible. This is the most challenging task for most users, since it is time consuming and not easy to measure if the tool is long with small diameter. A flexible tool technique was developed by us as explained in the previous message.

We went further with our MALTF module. The tap testing is automated with human voice feedback. You either hear it from the speaker of the laptop, or headphones and get in the machine and tap test it without having to push buttons at each hit. The fuzzy logic based expert system automatically rejects-accepts the measurements, and tells you how it is progressing with a human sound. It also displays reliable measurement frequency range by checking the signatures of the data mathematically. MALTF has multiple measurement channels in CUTPRO, and single input/single output in Shop-Pro.

Also, we designed a three-level database design for our users. You can identify the spindles, and store them in a database. You can define the holder geometry, and cutter stick out and diameter by providing basic dimensions. MALTF will automatically predict FRF at the tool tip without having to do tap test. Alternatively, you can identify the spindle and tool holder assembly, and store it in the data base, and add only tool diameter and tool. MALTF will recommend you the proper tool length so that you can have a sweet spot (stability pocket) at a desired speed.

These will not be as accurate as direct tap testing on each tool, but our tests showed that the results are amazingly practical enough with shrink fit tools. All the algorithms are based on UBC’s five yearlong investigation on receptance coupling research which was supported by Mitsubishi Materials, Sandvik Coromant and Boeing. The tool optimization is also based on UBC’s chatter theory and optimization algorithm.

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