Machining very large cast iron parts often requires large amounts of material removal using wide cuts and deep bores, so the speeds seldom exceed 5,000 rpm. The need in this setup is not faster speeds, but a tough spindle that stays rigid while it attacks wide areas of hard metal.

Bechert Brothers Manufacturing of Forestville, Connecticut, is a 35-person, three-shift machining operation founded in 1977 by Jim Bechert, father of James and Bill Bechert who now handle day-to-day operations. Bechert Brothers specializes in machining these high precision cast iron and steel parts. Examples are rotary screw compressor housings of cast iron for HVAC systems that weigh 200 to 1,000 pounds, steel components used in couplings for helicopter rotors and bearing housings for gas turbine engines made from investment castings of 4140 carbon alloy steel.

These are difficult parts to machine accurately and cost effectively. Getting the accuracy needed on complex parts while maintaining productive feeds and speeds takes good planning as well as the right equipment, according to James Bechert, president. Also important are quality and precision, along with the avoidance of costly downtime. Bechert Brothers decided that a way to meet all these goals was to standardize its equipment. All of the company’s machines are Matsuuras, and virtually all of its toolholders are from Command Tooling (Ramsey, Minnesota), according to Mr. Bechert. "The standardization makes a big difference in our consistency Carbide Turning Inserts and repeatability. Our operators intimately know these machines, their software and the toolholder capabilities without having to deal with the vagaries of three or four different machine brands and models. The same is true with the toolholders.

"When our operators set up for one of these jobs, which involve hogging out large cavities and producing dozens of bores and tapped holes, they have the confidence of knowing, for example, that they can successfully get a ½-inch diameter cut in cast iron at 1,000 rpm without tool chatter. Because machines and toolholders have similar features, little things like setting coolant lines at the same height are easy because all the toolholders are the same length, being they are from the same manufacturer," says Mr. Bechert.

"For the same reason, the SNMG Insert toolholders tighten up consistently so the operator doesn’t have to guess what’s right to get good concentric gripping force on the cutting tool—something that can cause a machine shutdown in the middle of a part run if it’s not right."

To machine the compressor housings, Bechert Brothers has four MAM 900H Matsuura horizontal machining systems. These are full four-axis systems with scale feedback and dual 24.8-inch square pallets; 36.2-inch by 28.3-inch by 29.9-inch X, Y, Z travels and 32-second pallet change. The machines have 590 ipm rapid traverse and 15 to 4,500 rpm oil cooled spindles.

Using an array of 40- and 50-taper Command milling, drilling and tapping toolholders plus Command’s Urma modular boring tools, two and three operations are done to the housings on each pallet side prior to indexing to the next side. Originally equipped with 50-tool carousels, Mr. Bechert says his company quickly converted to the 100-tool carousel that holds a greater variety of tools because the compressor housings required many different tools to manufacture them in a single part setup.

Because the parts are large and oval-shaped (36 inches by 30 inches by 20 inches), maintaining size with correct tolerance is difficult. This is especially true for the boring operations where the Urma modular boring tools using coated carbide inserts are employed to achieve the needed ±0.0002 diameter on the wall bores. With depths of 12 to 20 inches required, Bechert utilizes the full boring system range (0.036 inch to 31 inches). This combination allows perpendicular and true position penetration of overlapping bores, which, according to Mr. Bechert, can wreak havoc on ordinary boring tools. With consistent rigidity from one toolholder to the next, he reports getting ±0.0005 true position, bore to bore, and 0.0005-inch perpendicularity to the part face.

Bores are roughed out, then semi-finished and finished. Speeds for the roughing pass are at 600 rpm with 3,500 rpm for the finishing pass. Most of the bores require a 63 micro finish with a smaller number requiring a finer 32 micro finish.

Part runs vary from 15 to 200 a month for the larger compressor housings. Generally, runs are not large, so setup time is an important consideration. Bechert Brothers maximizes runtime on all of its machines by presetting jobs off-line and operating three shifts. "Our goal is to keep those machines in the cut 24 hours a day," says Mr. Bechert. "Downtime is costly so we can’t afford to have a hodgepodge of different toolholders that tighten inconsistently and cause a rigidity and chatter problem in the middle of a part run."

Quality isn’t compromised with the output of the three-shift operation because the company operates a QC department. Utilizing a Zeiss 850 Carat, known for its size and precision measuring features of large aerospace parts, this department tracks every part and critical part feature to ensure repeatable quality throughout its three shifts.

The Carbide Inserts Website: https://www.aliexpress.com/item/1005005929477719.html

Big Kaiser Precision Tooling offers the entry-level Innotool Diaset benchtop tool presetter equipped with Machining Carbide Inserts a 5.7" color LCD touchscreen and camera. This vision-based camera version enables one-touch angle, radius, diameter and length measurements. An optional incident light can be used for inspection of cutting edges for built-up edge and flank wear or fractures.

The presetter is built with a stable measuring column and mineral cast base. According to the company, its strong foundation ensures rigidity and high temperature resistance for good repeatability and positioning accuracy of 0.0001". These capabilities are also supported by horizontal and vertical slides that smoothly move along hardened and precision-ground guideways, both with pneumatic locking mechanisms and foot-pedal control.

The high-precision rotating spindle provides runout measurement to an accuracy of less than 0.0008" TIR, the company says, and SNMG Insert is available with either integral ISO-50 or ISO-40 taper spindles. Reduction adapters are available for other common interfaces including ISO, HSK, KM, Polygon and more. Various combinations of maximum diameter/maximum length are available. Two built-in USB ports enable simultaneous external data saving and label printer connection in addition to the presetter’s internal storage capacity of 99 reference points.

The Carbide Inserts Website: https://www.aliexpress.com/item/1005005979934200.html

Mikron’s Multistar transfer machine enables complete machining of small precision parts in large production volumes. The modular system comes in three models: the LX, which can machine on 12 or 24 stations; the CX, featuring 24 monoblock or adjustable stations; and the NX, equipped with 24 CNC stations. The product performs numerous processes including drilling, milling, thread cutting, turning, recessing, deep-hole drilling, burnishing, grinding, edging, chiseling, stamping, bending, assembly and measuring. The working spindles can be inserted into or released from the machining station, enabling tool setting off of the VBMT Insert machine.

The system locks the turntable in place using two diametrically opposite indexing pins and has a table indexing accuracy of ±2.5 microns. According to the company, measurement operations and dimensional corrections are integrated into the machining process, enabling the machine to separate defective parts.

The product uses rotating spring chucks to promote transverse machining and to enable concentricity for turning and plunge cutting operations. Additionally, the system distributes chuck clamping force on the outer edges of parts to prevent workpieces from becoming deformed.

The product machines steel, nonferrous metals or aluminum with diameters ranging from 0.4 to 30 mm and lengths ranging to 60 mm. The machine can perform simultaneous, double-sided machining on 12 or 24 stations with as many as 150 Cutting Carbide Inserts switching cycles/min. The system can produce as many as 600 parts/min.

According to the company, the machine uses various loading systems including a vibratory, linear or inclined conveyor, and a pick-and-place system for loading parts directly from the feed or pallet.

The Carbide Inserts Website: https://www.aliexpress.com/item/1005005876032827.html

Tool breakage is an important concern for mold shops that want to bypass EDM and venture into directly milling molds out of hard materials. Unexpected tool breakage that results from exceeding a tool’s permissible loading conditions not only costs money, but also disrupts the machining process. A shop could get the most out of its process by consistently loading the tool to its optimum levels.

However, one challenge is that milling tool paths produce varying rates of material removal. In a typical high speed roughing path with depth of cut and stepover each equal to 10 percent of the tool diameter, the tool could see as much as 10 times its intended level of material removal when it first enters a channel, and as much as five times that level when it enters an interior corner. These peaks in loading are the number-one source of tool failure. A shop’s typical response is to change the feed rate, depth of cut or stepover. Though reducing any of these values might bring the peak loading conditions back down below the threshold, this step will also reduce the metal removal rate of the tool path overall, jeopardizing productivity. There are better approaches.

Some approaches to toolpath optimization aim to achieve a more constant material removal rate by breaking up the tool path and adjusting feed rate frequently. This tactic may bring about a constant material removal rate at a macro level. However, it poses a complication at the machine tool. The high speed machining processors built within machine tool controllers prefer tool paths that are geometrically smooth. At higher feed rates, the controllers require the tool path to be dynamically smooth as well. Adjusting feed rates at small length intervals can cause the controller to interpret for exact positioning some toolpath data that otherwise could qualify for smooth interpolation. If that happens, the machine tool slows down to make the cycle time longer. At very small intervals, the fine adjustment could also cause jerky machine movements that would compromise surface finish.

Another problem relates to spindle speed. Adjusting feed rates without adjusting the corresponding spindle speeds causes varying chip thickness that could be detrimental to the surface finish, and also to the effectiveness of the tool in the long run.

An alternative that some toolpath processors take could be described as a preventive approach. These processors plan the geometry of the tool path to avoid the excessive load.

For example, the CAM software can apply a trochoidal function that activates additional trochoidal toolpath loops automatically, whenever the tool would otherwise end up slotting or getting into a tight corner. In UGS’s NX CAM, for instance, users specify not only parameters such as cut depth and stepover, but also a permissible overloading percentage value. The rate of metal removal is then controlled within this threshold. The software controls the load by retracting and re-engaging the tool through a tool path like the ones on these two pages. Even though the geometry introduces additional air cuts, it allows the tool to be loaded to its optimum condition.

Another area of CAM programming that causes intermittent tool loading is an irregularity of the amount of stock left behind for finishing. Finish machining operations often use smaller-diameter tools that are set with longer overhangs. To ensure safe cutting and to achieve a good surface finish, it is important for these tools to be engaged with the part material consistently, and to cut uniform amounts of material.

Typical Z-level semi-finishing operations leave non-uniform stock in shallow regions that can cause the irregular loading of the follow-up tool. More sophisticated Z-level capability can automatically add to the tool path in these shallow regions, helping to ensure more uniform stock.

Another feature, automatic identification of flat horizontal faces in roughing operations, can prevent residual stock from being left on these types of faces. This also avoids excessive loading of the follow-up tool.

The engagement of the tool with the stock has to be tightly controlled for effective hard milling. Chip thickness, which is determined by the spindle speed and feed rate, is part of the equation. But the horizontal and vertical engagement angles, which are often overlooked, also play an important role.

The Carbide Turning Inserts horizontal engagement angle indicates the amount of sweep subtended by each cutting edge as it engages and leaves the stock.

The vertical engagement angle indicates the maximum instantaneous cutting edge engagement with the stock.

These factors together determine instantaneous cutting forces and heat dissipation. For effective high speed hard milling, they need to be kept as consistent as possible.

The illustration on this page shows how differences in the tool’s engagement in a typical Z-level operation could cause inconsistent loading and surface finish. An example of a CAM feature for addressing this is an on-part stepover tool path that attempts to spread adjacent toolpath passes equally in both the steep and shallow regions.

To summarize: Constant material removal can be made an integral part of Deep Hole Drilling Inserts toolpath generation. By providing high speed machines with tool paths designed to keep the material removal rate consistent, a mold shop can realize the full benefits of hard milling.

About the author: Edwin Gasparraj is a specialist involved in NX CAM product planning for UGS.

The Carbide Inserts Website: https://www.aliexpress.com/item/1005005871601234.html

Methods Machine Tools, a supplier of high-quality, high-precision CNC machine tools, automation and engineering services, will host Machine Fest on October 4-5 at its national headquarters. Machine Fest will run from 9 a.m. to 4 p.m. ET each day at 71 Union Avenue in Sudbury, Massachusetts.

Methods Machine Fest is designed to demonstrate the full Methods experience, providing attendees with an up-close view of Methods’ entire portfolio of three- and five-Shoulder Milling Inserts axis CNC platforms, EDMs, multitasking lathes, automated and integrated solutions, services and support.

“While Methods has grown coast to coast over the last few decades, New England is our home base,” says Brad Catyb, Methods’ New England general manager. “Machine Fest builds on our legacy of open house events here in New England, when we welcome all our customers, partners and anyone else interested in world-class CNC machining to our HQ. Come see how our machines, engineering and services truly set us apart from the competition.”

“Attendees will experience more than a dozen live demonstrations, view Methods’ full suite of standard automation solutions and have ample opportunities to meet and discuss their production, integration and process management needs with our staff of Machining Carbide Inserts engineering and service experts,” Catyb continued.

Visitors will also have the opportunity to meet with more than a dozen suppliers showcasing their tooling, workholding and accessories. Additionally, guests can visit Methods’ Precision Center in nearby Acton, Massachusetts. The facility, which opened in 2019, houses Methods’ advanced engineering and R&D facility, including a climate-controlled lab where cuts are achieved to sub-micron levels.

“No matter what machine you run today, or whether you’ve been a Methods customer for decades or never seen our machines in person, this show will feature everything manufacturers need to evaluate how to take the next, best step for their shops,” says George Farrell, Methods sales manager for New England.

This is the third edition of Methods Machine Fest, following events in Phoenix, Arizona, in late 2022, and Gilberts, Illinois, earlier this year. Visit the event webpage for more information and to register.

The Carbide Inserts Website: https://www.aliexpress.com/item/1005005954890402.html