Versa-Fab Inc., New Kensington, Pa., is a busy fabrication, machining and finishing business. The company serves a variety of customers while emphasizing the manufacture of sheet and stainless steel cabinets for the power products and distribution industry.
Vice President James Cullen said the business may appear simple, but “we put through 700 different part numbers and manufacture and ship more than 20,000 parts in a month.” As a result, the company is constantly looking at where it can employ flexible automation to generate efficiency.
Courtesy of Versa-Fab
Versa-Fab combined bar-fed lathe operations and vertical milling to machine this 1 "-long, 316 stainless steel gas hose seal in a cost-competitive way.
Versa-Fab’s machine shop supports the company’s fabrication operations and makes parts for external customers. “We are a very robust job shop,” said Matt Aubele, machine shop manager. Successfully bidding on outside jobs requires the shop to be cost-competitive. Aubele said one job symbolizes the company’s efforts to automate whenever possible. That part is a 17⁄8 "-long, 316 stainless steel gas hose seal. It has a maximum diameter of 23⁄8 ", a 1-14 UNS thread, two grooves for O-ring seals and connects a gas hose to a tank.
Although the part would be well-suited for a live-tooling machine with a Y-axis and C-axis, the shop did not have that kind of equipment when bidding the job. “We had to figure out a way to be competitive,” Aubele said.
They did. Versa Fab efficiently processed the part by combining a bar-fed SL20 Haas lathe with a Haas VF3 vertical machining center.
Working with a part print, Aubele programmed the job in Mastercam. Versa-Fab machines the seal from 2 3⁄8 "-dia. bar stock, which is sawed into 3 ' lengths and loaded into the SL20’s bar feeder. The first operation is turning the bar’s diameter to 2.142 ", then stepping in to turn the 1 " major diameter of the thread, using Iscar CNMG-432 inserts run with flood coolant at a 600-sfm cutting speed and a 0.008-ipr feed rate.
To machine the 0.088 "-deep × 0.051 "-wide O-ring groove on the front of the part, the shop chose an Iscar Picco 0.030 "-wide, solid-carbide face-grooving tool. The shop only runs the tool at 200 to 300 sfm and 0.001 ipr. “We’ve always run it very conservatively because it is on a bar-fed machine and there is no one standing there,” Aubele said. “When I started in this business as a programmer, I always wanted to push a tool as hard as it would go. I have learned it’s not always the best to push it so hard. Slow and steady isn’t hurting anything because the machine is just running by itself.”
Next, the 1-14 UNS thread is cut with six passes of a Vardex single-point threading tool. After that, a 12.7mm-dia. Guhring P/M drill run at 340 sfm and 0.0065 ipr drills a 1 "-deep hole in the center of the seal. When the seal is parted off with an Iscar 0.118 "-wide, TAG-style cutoff tool, a 0.256 "-wide flange remains on the back of the part.
A 3 '-long section of bar stock produces 32 parts. To run unattended, the shop uses redundant tooling in the machine turret and programs tool changes according to part volume. “Tool 1 is our roughing tool, and we also have tool 10 loaded as a roughing tool. We know we get two bars out of roughing tool, so when it goes to the third bar it automatically switches to tool 10,” Aubele said.
Aubele said 316 stainless can be “pretty nasty to cut. It’s gummy, it likes to stick to the tools and snap inserts off. We have it dialed in pretty good, though.” Flood coolant is essential, he added.
Efficiently fixturing the parts in the VMC was another challenge. “The best way we found was to use Kurt Double Lock vises fitted with custom soft jaws,” Aubele said. “Four of the vises are mounted on the machine table and each set of soft jaws holds four parts, enabling 16 parts to be processed at a time.”
The completed side of the part with the thread is loaded pointing down into vise. The VMC then machines a 0.360 "-deep × 0.148 "-wide O-ring groove on the back of the part with a Niagara 1⁄8 "-dia. solid-carbide endmill run at 200 sfm and 5 ipm.
Aubele said: “We took advantage of the ramping capabilities of Mastercam. Instead of just dropping an endmill into 316SS and trying to plow around there, we ramped that O-ring groove. The endmill comes down to Z zero, and, as it interpolates around the part, it ramps in at 1° or 0.050 " every time it goes around. At the bottom of the groove it stops ramping. It does one side of the groove and then the other side, and one endmill usually lasts long enough for a run of 250 parts.”
Four holes are then drilled in the part flange with a Guhring 0.300 "-dia., through-coolant carbide drill run at 400 sfm and 0.008 ipm. The operations on the mill “go through pretty quick,” Aubele said, “and we found the operator couldn’t keep up with the machine. He would still be deburring parts while the machine sat idle, waiting for him to change the parts.” As a result, the shop added a 45° solid-carbide chamfering tool, run at 400 sfm and 20 ipm, followed by a 1 "-dia. carbide brush.
“Because stainless is gummy and likes to roll burrs over, we come back in with the carbide brush and clean the O-ring groove and the entire face of the part after chamfering the holes,” Aubele said. Now, when the parts come out of the VMC, the operator performs any further deburring that may be required, cleans the parts and packages them for shipping. Aubele said the current blanket order for the part is about 2,500 pieces, usually machined in lots of 150 to 200.
Aubele considers the bar-fed machine to be the largest contributor to the process’s efficiency. “The bar feeder makes us competitive. It runs lights out. That is, in essence, free labor.” Automating and consolidating processes whenever possible, he said, “is the way this company is going. We are thinking toward the future.” CTE
For more information about Versa-Fab Inc., visit www.versafab.com or call (724) 889-0137. About the Author: Bill Kennedy, based in Latrobe, Pa., is a contributing editor for CTE. He has an extensive background as a technical writer. Contact him at (724) 537-6182 or at email@example.com.
Related Glossary Terms
Machining a bevel on a workpiece or tool; improves a tool’s entrance into the cut.
- chamfering tool
Cutter or wheel that creates a beveled edge on a tool or workpiece.
Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.
Step that prepares a slug, blank or other workpiece for machining or other processing by separating it from the original stock. Performed on lathes, chucking machines, automatic screw machines and other turning machines. Also performed on milling machines, machining centers with slitting saws and sawing machines with cold (circular) saws, hacksaws, bandsaws or abrasive cutoff saws. See saw, sawing machine; turning.
- cutting speed
Tangential velocity on the surface of the tool or workpiece at the cutting interface. The formula for cutting speed (sfm) is tool diameter 5 0.26 5 spindle speed (rpm). The formula for feed per tooth (fpt) is table feed (ipm)/number of flutes/spindle speed (rpm). The formula for spindle speed (rpm) is cutting speed (sfm) 5 3.82/tool diameter. The formula for table feed (ipm) is feed per tooth (ftp) 5 number of tool flutes 5 spindle speed (rpm).
Milling cutter held by its shank that cuts on its periphery and, if so configured, on its free end. Takes a variety of shapes (single- and double-end, roughing, ballnose and cup-end) and sizes (stub, medium, long and extra-long). Also comes with differing numbers of flutes.
Rate of change of position of the tool as a whole, relative to the workpiece while cutting.
- gang cutting ( milling)
gang cutting ( milling)
Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.
- inches per minute ( ipm)
inches per minute ( ipm)
Value that refers to how far the workpiece or cutter advances linearly in 1 minute, defined as: ipm = ipt 5 number of effective teeth 5 rpm. Also known as the table feed or machine feed.
Turning machine capable of sawing, milling, grinding, gear-cutting, drilling, reaming, boring, threading, facing, chamfering, grooving, knurling, spinning, parting, necking, taper-cutting, and cam- and eccentric-cutting, as well as step- and straight-turning. Comes in a variety of forms, ranging from manual to semiautomatic to fully automatic, with major types being engine lathes, turning and contouring lathes, turret lathes and numerical-control lathes. The engine lathe consists of a headstock and spindle, tailstock, bed, carriage (complete with apron) and cross slides. Features include gear- (speed) and feed-selector levers, toolpost, compound rest, lead screw and reversing lead screw, threading dial and rapid-traverse lever. Special lathe types include through-the-spindle, camshaft and crankshaft, brake drum and rotor, spinning and gun-barrel machines. Toolroom and bench lathes are used for precision work; the former for tool-and-die work and similar tasks, the latter for small workpieces (instruments, watches), normally without a power feed. Models are typically designated according to their “swing,” or the largest-diameter workpiece that can be rotated; bed length, or the distance between centers; and horsepower generated. See turning machine.
- machining center
CNC machine tool capable of drilling, reaming, tapping, milling and boring. Normally comes with an automatic toolchanger. See automatic toolchanger.
Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.
- milling machine ( mill)
milling machine ( mill)
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.
Process of both external (e.g., thread milling) and internal (e.g., tapping, thread milling) cutting, turning and rolling of threads into particular material. Standardized specifications are available to determine the desired results of the threading process. Numerous thread-series designations are written for specific applications. Threading often is performed on a lathe. Specifications such as thread height are critical in determining the strength of the threads. The material used is taken into consideration in determining the expected results of any particular application for that threaded piece. In external threading, a calculated depth is required as well as a particular angle to the cut. To perform internal threading, the exact diameter to bore the hole is critical before threading. The threads are distinguished from one another by the amount of tolerance and/or allowance that is specified. See turning.
Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.