|A nine-pallet system, special tombstones, and a Mori Seiki NH4000 give Straitline Components the flexibility to switch quickly from machining one mountain bike component to the next. |
Straitline Components is “obsessed” with doing everything itself, and from day one the shop’s operators vowed not to ship any production offshore. That’s quite an uphill course to take, considering that it manufactures aftermarket mountain bike components — a market niche that sees virtually all of its part production performed offshore.
Surprisingly though, Straitline Components not only competes successfully in that segment but continues to grow and gain considerable marketshare. The shop sells worldwide, and its name is well known and well respected, especially in the competitive downhill mountain biking world.
Products from Straitline Components (a subsidiary of Straightline Precision Industries) rival those produced for the aerospace industry, in terms of quality, precision and dependability. The shop operators should know: They have a strong background in machining aerospace and medical components and continue to do such job-shop work, as well. The problem was that outside suppliers continually failed to meet the shop’s high standards.
Straitline Components employs seven people, four of whom work the shop floor machining about 100 different parts for the company’s aftermarket product line. Some of Straitline’s more notable products include hydraulic disc hand brake levers, pedals, handle bar stems, and chain guide devices, all of which are available in various anodized colors.
Pedals are probably the shop’s most in-demand item. Pedal bodies are made from aluminum blanks milled and bored to accommodate the axle assembly.
Instead of ball bearings and threaded nuts, the system uses wear-resistant polymer bushings and high-strength alloy axles with dual retention clips to secure pedals in place and prevent them from being knocked off by obstacles on the trail. The system also allows riders to rebuild pedals in the field within minutes and with minimal tools.
Straitline Components machines its pedals, custom disc brake levers and handle bar stems on a Mori Seiki NH 4000 horizontal machining center. Initially, the machine was purchased for producing aftermarket off-road motorcycle components, but for the past three years it has been the heart of the shop’s mountain bike component production.
Originally, the machine was a two-pallet standalone system, and Straitline ran brake levers in batches of 50 to 100 on two 8-station vice columns. But, there were problems keeping up with production demands.
“We were constantly changing over jobs and setups. Then as demand increased, we needed to produce higher volumes. Plus, we were worried about being able to accommodate new products,” explained D.J. Paulson, who, along with his brother Dennis Paulson and father Mike Paulson, owns Straitline Components.
|High demand drives mountain bike pedal production at Straitline Components. |
The brothers found it difficult to keep the machine working because they seemed to be in a constant “set up” mode. Plus, the machine had to be continuously manned for part loading and unloading.
Straitline Components didn’t have a lot of skilled labor at the time, and in a pinch the brothers would have their sister run the machine in the evenings. But, if a cutter broke or some other problem arose, someone had to come in to fix it.
Paulson said the shop was getting perhaps 12 hours per day of actual run time, and still required someone to man the machine constantly to load and unload parts. After about two years of this, they added a 9-pallet system to the NH-4000.
The coincidentally named straight-line-configured pallet system from Mori Seiki (), installed by Ellison Technologies () of Kent, Wash., boosted actual machining time to between 20 and 24 hours per day and reduced necessary manned time.
Straitline Components had custom tombstones, from Tombstone City, made for its new pallet system. These workholding tombstones, along with in-house designed fixturing, allow the shop to use every square inch of the machining center’s travel and fixture parts as densely as possible on the pallets.
For example, the shop machines its brake levers in pairs nested together and runs 56 of these pairs at a time on one pallet, and can run as many as three such loaded pallets if needed. Typically, fixturing for the levers is split between two pallets, with remaining tombstone space of each pallet reserved for other parts. For instance, the shop will have about 48 handle bar stems fixtured and ready to run on the unused faces of the tombstone.
The goal is always to fixture as many parts as possible, and to perform as many operations on them as possible, to minimize handling.
“We minimize the amount of time the machine needs to be manned by putting as many first-op cycles on a pallet or in the general pallet zone as we can. We run those over night, then all the second ops during the day when someone is available to man the machine. This gives us an added 16 hours of production time overnight,” said Paulson.
|Straitline Components completes its mountain bike pedal axles in one setup and eliminates a grinding operation using a Mori Seiki NL2000 SY 500 with its tool turret often loaded to the hilt. |
For first ops, part cycle times might run from three and half minutes to as much as 11 minutes. To reduce cycle times, the shop maps out the machine’s programmed production in a way that limits the amount of tool changes required.
Once a pallet loads into the machine, the program calls up a particular tool and machines as many of the different parts loaded on that pallet as possible before changing to the next required tool. For example, though there might be 72 handle bar stems loaded, the machine might change tools only seven times versus changing every required tool 72 times. As a result, part cycle times dropped dramatically, most by half.
Initially, Straitline programmed the machine to complete one full part, then go on to the next. But, soon they realized that most of the machine’s non-cut time was changing tools. Indexing pallets took a fraction of the time that tool changes did, and the machine’s positioning accuracy made it possible to work from one part to the next and back again to minimize tool changes.
For pedals, the NH4000 maintains perpendicularity for boring axle holes. These holes are bored from one end, then from the other end, meeting in the middle. The machine holds these bore tolerances to within 0.0003 in. and eliminates the need for an external tumble finishing operation because an edge-breaking pass is run while pedals are still fixtured on the machine.
To machine pedal axles, Straitline Components uses a second Mori Seiki machine, an NL2000 SY 500 single-turret, twin-spindle turn/mill turning center. All 12 stations of its turret have live-tooling capability, and the shop doubles up these stations to pack the turret with about 35 tools total.
Previously, the shop ran pedal axles on a CNC Swiss-type screw machine, followed by a grinding operation. However, the level of straightness and required tolerances were not being achieved, mainly because the axles taxed the capabilities of the Swiss-type machine.
Paulson acknowledged they were overworking the machine. In addition, he said that previous manufacturing methods involved four to five separate operations with multiple setups, which also contributed to the inability to hold straightness and tolerances.
Now, pedal axles are completed in one setup, and the grinding operation has been eliminated because of the NL2000 SY 500’s rigidity and its ability to hold such close tolerances and straightness. The machine also reduced the scrap rate for axle production down to practically zero.
Production scheduling is a bit tricky at Straitline Components, mainly because products are available in various color choices. This makes it tough to build an inventory of finished products. The most the shop can do is stock parts that have been machined, but have not yet been anodized to a particular color.
However, reduced part lead times thanks to the horizontal machining center and pallet system, give Straitline the flexibility to operate closer to JIT production. The shop can interrupt production and quickly set up and machine 200 “hot” parts, for example, then go back to what was running.
In the past, Straitline would have had to keep thousands of parts in stock to meet current production needs. But, Paulson said that they no longer have to do huge part runs to make the pallet system cost effective.