How Its Made – Machining and Rollerskis

Kevin BrookerDecember 12, 2008

Before getting to the ski gear (I promise you its here), there’s a touch more background to cover. Just as IM can be found in almost every piece of gear we use, CNC machining is used throughout the industry and one of the reasons equipment has become light, reliable and fast.

Most of the machine work for the ski industry is not used on the actual gear itself. The vast majority of lathe, milling and grinding operations are used to make molds. These molds are everywhere, and represent a large portion of the costs associated with the production of gear.

Computer Numerically Controlled machines, or CNC for short, have proven to be the most accurate and repeatable methods of turning raw stock into finely crafted parts. Designs are produced and laid out with some form of CAD program. CAD is the catchall acronym for Computer Aided Drafting software. AutoCAD is a brand created by AutoDesk and has the distinction of being the ubiquitous term for any CAD work. Not every brand of tissue is a Kleenex.

Figure 2 CNC machined parts by Piorier

The actual cutting process is entirely automatic with almost no human interaction. But the set-up requires experienced human machinists. The machine starts out with a known, 3-axis zero point and the G-code describes the finished shape of the part. The machinist must program the dimensions of the cutting tool (depth, length and diameter) to enable the computer to alter the path of the tool to achieve the correctly sized parts. Any time a change is made to a tool (i.e. its sharpened), the machinist must tell the computer if there are any changes in size.

Let’s say we want a finished part that is 1” square. If the CNC machine is told the cutting tool is 1” in diameter, the track of the mill will place the edge of the cutter to leave the finished piece 1” square. If we install a ½” diameter cutter and do not inform the CNC machine of the change, the track will remain the same but our part will now be too big.

The operator inspects the finished parts to be sure they meet the design specifications. The precision and repeatability of CNC machining is important to having a well made rollerski. The wheel hubs on the classic ski are round and cylindrical to within one-ten thousandth of an inch. These close tolerances keep the bearing and clutch races running true after they are pressed into the hubs, a process which takes place at Jenex after the rubber tires are molded onto the hubs. To give the rubber tires something to grab onto and keep from slipping off the hub, square grooves are cut into the hub in a herringbone pattern.

Figure 4 Riverside produced parts

Just as Poly-Ject utilizes energy efficient machinery, the 40,000 pound Amada punch press uses only $1.00 worth of power every hour to cut and form sheetmetal ranging in thickness from ten thousandths to ¼” thick. The punch press is also CNC and has the ability to figure the most efficient manner to cut parts from the flat stock.

Figure 6 Bending operations (not Jenex part in photo)

For parts where the required bend will not have enough material for the brake to properly shape, the tabs are cut oversized and cut after bending. This post-bend cutting is accomplished at the CNC laser station. This 2,000 watt laser is capable of cutting ½” plate steel at a rate of 36 inches per minute. On the thinner material used in rollerskis, the cut requires only a few seconds from placement to removal. Sitting next to the laser station are tanks of liquid nitrogen which is boiled off and blown out in a high pressure thin stream just behind the beam. This helps keep the parts cool (temper or annealing is generally not needed post cut) and removes the slag or molten material. The laser does such a good job concentrating the heat and is so fast the parts can be picked up with bare hands almost immediately after cutting.

Figure 8 Frame and fork ready for TIG welding

Eventually, all of the parts find their way to Jenex for final assembly. Bearings and clutches are pressed, split rim wheels are assembled, decals applied to the frames and final inspection is made of the completed rollerski.

After all of the automated and machine controlled production, the final assembly of the rollerskis is all done by hand. Bearings and clutches are pressed into the hubs with a hand controlled (arm-strong motor) arbor press. Any metallic inserts are also pressed into position by a human. Nuts and bolts are snugged down with motorized drivers and the final tightening is done with a wrench.

Figure 10 Racks of finished rollerskis

This piece is the end of the background information pertinent to most all of the gear we use. From now on, the How It’s Made series will have much more ski gear filling the pages. If anyone has questions regarding some aspect of making gear, please leave a comment and I’ll see what I can do to find an answer.

Kevin Brooker

Kevin is 42 years old, married with two children and living in Post Mills, Vermont. He began racing bicycles at sixteen and continued pursuing individual sports. After a six-year layoff, Kevin has returned to athletics racing in biathlon events. He has written numerous articles for FasterSkier, including a series on his return to racing and his current "How It's Made" series.

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