Originally published June 2006

The WEHMER Dual Wheel Model Trimmer has been a standard for orthodontic model trimming applications for almost 50 years. Though there have been periodic upgrades to individual parts, the basic trimmer has remained pretty much unchanged, making parts availability and refurbishment a simple matter. We routinely recondition machines that are 25 years old or more, giving them additional years of productive life. On the other hand, we also see machines that are less than 10 years old that are ready for the junk pile. What’s the difference? Maintenance and care. Here are a few guidelines on specific issues we see in our repair department:

Damage due to improper drainage.

Flooding of the machine is a very common occurrence, particularly when using a diamond wheel. Diamond wheels generate a lot more plaster slurry at a much faster rate and have a tendency to clog the machine unless adequate water flow is maintained to the wheel. Unfortunately, more water flow means more mess, and the operator may be inclined to turn down the flow to stay dry, resulting in the plaster slurry becoming almost paste-like. When the drain cavity and/or drain opening get clogged, the water begins to rise inside the trimmer housings. This will cause damage to the motor and bearings, as well as to the drive belts and hubs. If the wheels are sloshing in water while you are trimming, it’s time to find the drain obstruction, otherwise, the life of the machine will be considerably shortened. Besides routine cleaning of the drain cavity and drain hose, a simple solution to this problem has been the #1126 Drain Tray (shown in the above picture). This raises the machine off the counter (about 1-7/8”) and allows running the machine with the front drain plug removed. Two drain openings pretty much guarantee no clogs, and if the hose becomes obstructed, the back-up is in the tray, not in your trimmer.

Trimming with dull wheels.

In spite of the amazing benefits and long life of diamond abrasive trimming wheels, many of our customers still use carborundum (silicon carbide) abrasive wheels. These are an economical alternative, however, when they start to get dull they can cost you money in terms of increased trimming time and extra wear-and-tear on your trimmer. Carborundum wheels are two-sided, so they can be flipped over before replacing them. We recommend flipping every six months, and changing annually. Just like your smoke-alarm battery change, wheel changes should be on your routine yearly maintenance schedule. Grinding with dull wheels puts excessive strain on the motor and creates heat that shortens motor life. Worn wheels also have a tendency not to wear flat, so you’ll notice that it is harder and harder to maintain a flat surface or correct model angles. Excessive grinding pressure can also cause the wheel to spin slower than the hub that supports it, causing damage to the hub - an expensive part to replace. We stock a complete selection of carborundum and diamond wheels for Wehmer trimmers, so call us to keep your grinding efficiency up and your problems down.