What is tap testing in CNC machining?

Tap testing, also known as impact testing, identifies structural dynamics by impacting a structure and measuring its response, in other words, tap testing tells us how flexible a machine tool assembly is. In CNC milling, the tip of the milling tool is excited with a hammer to induce vibrations while collecting the measurement with an accelerometer. The relationship between the force (input) and acceleration data (output) is the transfer function of the structure which is also called Frequency Response Function (FRF). FRF represents the dynamic stiffness of the structure across the frequency spectrum and is used as an input for spindle speed Optimizer to calculate recommended spindle speed and depth of cut.

Tap Testing Champion

Angela Hill, the Partnership Engagement Coordinator at University of Sheffield Advanced Manufacturing Research Centre (AMRC), holds the current record for the fastest tap test time of 11 seconds. Despite not being a frequent tap tester, her time defies expectations in terms of how long it should take to complete a successful tap test.

How to perform a tap test?

Productive Machines offers a TapStarter kit that includes tap testing hardware, standalone software, access to Essential Optimization web apps and tap test training. We have also partnered with Research Centres to provide tap test services or on-site/remote training for companies unfamiliar with the tap testing method.

Machining 4.0 Technology

Our partners at National Manufacturing Institute Scotland (NMIS) demonstrate how tap testing is used to determine the stable cutting parameters for the tool and the incredible benefits for the quality of the part and the efficiency of the manufacturing process.

What do we do with FRF data?

DigiTap, our tap test standalone software, calculates the FRF data from the tap test. FRF data includes natural frequencies, stiffness and damping ratios of the machine tool assembly.

FRF data feeds into the Spindle Speed Optimizer to generate a stability lobe diagram. The user then knows to select a stable spindle speed and depth of cut under the stability boundary.

Tap Testing enables Chatter-free Optimization

Tap testing combined with Productive Machines technology, brings precision and efficiency to manufacturing. It empowers operators to optimize machine tool performance against chatter vibrations reducing waste and enhancing product quality.

Spindle Speeds Optimizer

Find optimal Spindle Speeds for your individual machine with Productive Machines’ web application. The Spindle Speed Optimizer helps engineers select the right set of parameters for profiling, providing spindle speed and depth of cut combinations to achieve stable milling processes. Frequency Respond Function (FRF) data, obtained through tap testing, is used by the app as an input.

TapStarter - Launch Bundle

Get one year free Essential Optimization and tap test training when
you buy DigiTap standalone software and our tap test hardware kit.