I knew right away I was going to like the relationship. The movement of the table, spindle and toolchanger, combined with the processing power of the controller, was enticing. I wanted to learn more.

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James A. Harvey is a machinist and moldmaker who has worked in shops across the U.S. for nearly 40 years. Harvey’s Shop Operations column for Cutting Tool Engineering magazine is adapted from information in his book “CNC Trade Secrets: A Guide to CNC Machine Shop Practices,” published by Industrial Press Inc., South Norwalk, Conn. The publisher can be reached by calling (888) 528-7852 or visiting www.industrialpress.com. By indicating the code CTE20OFF when ordering, CTE readers will receive a 20 percent discount off the book’s list price of $29.95.

Not everything about operating a CNC machine is uncomplicated, though. For example, one time when our shop got some new machines, our lead man got stuck on the step that involves pressing the power-on button, waiting for the controller to boot up and then pressing the power-up/restart button. He didn’t know he had to press the power-up/restart button after pressing power on. Therefore, he couldn’t get the machine to do anything. The sad thing is, because of his initial disappointment or lack of ambition, he never touched the machine again.

Designers and manufacturers also seek this functionality when optimizing the chip transport characteristics of high-performance machine tools, because the rate at which chips are removed from the cutting face has a major bearing on the tool’s cutting speed and efficiency.

NUM contends that the level of control flexibility provided by NUMRoto’s new update for creating flutes will be a key enabling factor for manufacturers seeking to develop the next generations of machine tools.

Pressing the ATC FWD button in MDI cycles the automatic toolchanger forward. In turn, pressing the ATC REV button cycles the ATC backward. You don’t need any toolholders in the machine to use these features. Cycle the tool change a few times, until you get used to the action and noise. Always keep your hands out of the machine when cycling the toolchanger.

NUMRoto’s new profile insert function simplifies the programming of the new types of ultra high-efficiency CNC tool grinding machines now coming into service. After selecting the profile insert form cutter, users are presented with an easy-to-understand menu from which to specify whether the part to be ground is held in a fixed or adjustable collet, or by clamping plates.

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For example, to help prevent vibration, each of a tool’s cutting edges is twisted at a different angle – and with differential helix designs, the twist angle of each individual cutting edge also changes along the length of its body, from the tip of the tool to the shaft. Furthermore, the width of the flute area of these tools can vary considerably, demanding precise positioning of the grinding wheel to ensure that the land width on the back of the tooth is correct.

Working with several tool manufacturers and tool sharpening companies, NUM has developed NUMRoto's form cutter function to simplify insert grinding significantly. Users can define a form cutter as a rotary tool or as a standalone profile insert. Holders with soldered or cemented inserts can still be defined as rotary tools, and the position of each insert can be probed individually, allowing any mounting inaccuracies to be detected and compensated for automatically during the grinding process.

Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.

One of the first programs I concocted was for drilling on that machine. Once the program was running and started drilling holes, I thought, “We have a winner here! If nothing else, this machine is a drilling maniac.” I was surprised at how easy it was to change feeds and speeds, as well as how quickly the machine components moved to different locations.

Until relatively recently, the inserts were soldered or cemented to the holder prior to being ground, which sometimes made it very difficult or impossible to produce or maintain such tools on a CNC tool grinding machine – due to their size and complexity. Another disadvantage of this approach is that it requires the manufacturer to define the complete assembly as a rotary tool in the CNC program, demanding time-consuming and expensive programming.

The software supports different mounting plate arrangements to allow the insert to be oriented in any of three planes, and provides a simple method for specifying parameters such as transverse and longitudinal offset values.

By harnessing the speed and computational capabilities of state-of-the-art PCs, the new version of NUMRoto is able to handle the extremely complex path calculations necessary to create these sophisticated flutes. Users can define the core path geometry of flutes on end mills easily and accurately.

The expanding challenges of grinding and servicing new generations of complex-geometry drills and end mills are resolved in a new release, according to the developers of a tool grinding software package. Version 3.8 of NUM's NUMRoto software automates multi-helical and variable flute grinding, and introduces a form cutter function for profile inserts. It is available to existing NUMRoto users as an update.

When inserting a toolholder in the spindle manually, it’s important to line up the spindle lugs with the slots in the toolholder as you press the tool release/engage button on the side of the spindle housing.

Currently, the cutting edges of most machine tools are ground from tungsten carbide. Small rotary tools are usually manufactured from a single piece of carbide, whereas larger rotary tools and the majority of non-rotary tools feature individual cutting blades in the form of carbide inserts, which are retained in a holder made from a less expensive material.

Robert Brooks has been a business-to-business reporter, writer, editor, and columnist for more than 20 years, specializing in the primary metal and basic manufacturing industries.

Many of the high-performance end mills now used for precision machining applications (e.g., producing aerospace and aircraft parts in specialty alloys or composites) are multi-helix tools designed for use at speeds up to 30,000 RPM. Producing these types of tools cost-effectively is demanding, requiring increasingly complex grinding capabilities.

Carriage or drum attached to a machining center that holds tools until needed; when a tool is needed, the toolchanger inserts the tool into the machine spindle. See automatic toolchanger.

Launched by NUM in 1987, NUMRoto has been updated frequently according to the many improvements and innovations in machine tool design. The software runs on NUM’s Flexium+ CNC system, which has some specific advantages, including the use of sub-nano interpolation to ensure high quality surfaces, with short cycle times to allow fast 5-axis movement – even if the part program contains a high density of ISO sequences.

Fifteen different manufacturers of CNC tool grinding machines now incorporate NUMRoto software in their products, and as a result it is used on more than 40 different types of machine.

Runs endmills and arbor-mounted milling cutters. Features include a head with a spindle that drives the cutters; a column, knee and table that provide motion in the three Cartesian axes; and a base that supports the components and houses the cutting-fluid pump and reservoir. The work is mounted on the table and fed into the rotating cutter or endmill to accomplish the milling steps; vertical milling machines also feed endmills into the work by means of a spindle-mounted quill. Models range from small manual machines to big bed-type and duplex mills. All take one of three basic forms: vertical, horizontal or convertible horizontal/vertical. Vertical machines may be knee-type (the table is mounted on a knee that can be elevated) or bed-type (the table is securely supported and only moves horizontally). In general, horizontal machines are bigger and more powerful, while vertical machines are lighter but more versatile and easier to set up and operate.

When you press the PROG button, a prompt will come up in the screen asking if you want to erase the program. Press Y (yes) to get rid of the code, but don’t worry about losing any vital information. MDI mode is used primarily as a scratchboard for small and temporary programs.

Type “T1” (or any tool number) with the controller keys. Then press either the ATC FWD or ATC REV button. The tool carousel will cycle T1 into position, and the actuating arm will install that tool in the spindle if it is in the carousel. The machine doesn’t know if a toolholder is in the carousel or not. If T1 is not in the carousel, you can manually install one.

When executing tool changes, MDI (manual data input) is the only mode that allows you to manually change tools. When you press the MDI button, the MDI screen appears. You don’t have to enter anything in this screen to make manual tool changes.

Many of the latest cutting tools employ user-replaceable profile inserts, which are ground as physically separate blades on a CNC grinding machine. Instead of being fixed to a holder during grinding, the insert is held in a production clamping system that has an optimized geometry for efficient grinding, with unobstructed working space for the grinding wheel.

By allowing the core path of each flute to be defined individually, NUMRoto makes it possible for tool designers to compensate for any potential imbalance caused by irregular helices or asymmetric cutting blades. Additionally, by enabling the entry point of the grinding wheel to follow the corner radius of the cutting edge, the software facilitates grinding of a defined rake angle on complex body forms and on cutting edges which pass from the body of the tool to its tip – a task that was previously extremely difficult to achieve.

Mechanism typically included in a machining center that, on the appropriate command, removes one cutting tool from the spindle nose and replaces it with another. The changer restores the used tool to the magazine and selects and withdraws the next desired tool from the storage magazine. The changer is controlled by a set of prerecorded/predetermined instructions associated with the part(s) to be produced.

NUMRoto also now supports 3-D models for the production clamping system, which means it can be visualized during 3-D simulation and monitored for collisions with the grinding wheel; the insert itself is displayed as a cube-shaped blank.

Flexium+ supports all the current standard safety functions of today’s high-performance CNC machines, and can be operated easily using the same type of ‘dual touch’ gestures that are employed with modern smartphones.

When you press the power-up/restart button, the machine will run through a short routine to calibrate itself. Once everything stops moving, you can proceed.

I was also surprised by how uncomplicated the machine was to set up. There are just a few things a machine needs to know before it can run a program, such as where the starting point, or origin, of the part is—just like on a conventional mill.

I started my CNC training changing tools on a new mill. That first step was important. Just the act of changing a tool let me interact with the machine and controller in a way that gave me confidence and let me know that the machine wasn’t out to get me. In a weird way, the machine didn’t seem to know or care that I was a rank beginner.

Secures a cutting tool during a machining operation. Basic types include block, cartridge, chuck, collet, fixed, modular, quick-change and rotating.

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