Typically, knee-type milling machines have heads which rotate about the X and Y axes. This flexibility allows these machines to cut workpieces at various angles when needed. Unfortunately, even though the milling head can be tightened down, it can work its way out of the original position, thus becoming "out of tram." A milling head is put "into tram" by attaching a test indicator to the spindle and rotating it while tapping the head into position until the dial reads zero all the way around. During this process, machining setups may need to be disturbed or completely torn down. This operation can take 30 minutes or more to perform, and if several machinists use the same machine, the tram verification time adds up significantly.
Riverwest Engineering & Design Company (Milwaukee, Wisconsin) has introduced a quality control device to solve the problem of workpieces being scrapped due to a milling head going out of tram. This device, called the Tram Monitor, continuously detects and reports the slightest movement of a milling machine head during the machining process.
Established in 1993, Riverwest began designing and building big mechanical testing devices for a local medical college and expanded to include plastic injection mold design, repair and manufacturing services, such as CNC machining and EDM. The company is now involved in many facets of design, machining, manufacturing and product development. Ed Malczewski, owner and founder, had a bad experience with a costly project scrapped because a milling machine was out of tram. He became determined to solve the problem.
In the conceptual design phase, Mr. Malczewski envisioned many ideas and criteria for his new invention. The device would be an affordable solution for any size company. It would drastically reduce the time-consuming procedure of tramming and allow the operator to return to the tram position without removing a setup. The tram monitor would provide constant feedback of the milling head tram status without inconveniencing the operator. And the device would be designed to mount on virtually all knee-type milling machines, including CNC retrofit mills.
The company began by gathering measurements from a wide variety of domestic and imported milling machines, including the width of the motor housings, the distance of the eyebolt hole to the motor, and the height of the milling head off the ram. Another design issue was accommodating the brackets of digital readouts or CNC retrofit controllers.
With these critical measurements, Mr. Malczewski began the virtual prototyping phase using CADKEY from Baystate Technologies (Marlborough, Massachusetts), a PC-based mechanical CAD system. Each component was modeled as a 3D solid, with fasteners and other components generated in solids using DRAFT-PAK, Baystate Technologies' add-on mechanical productivity package.
To speed up the "art to part" process, the 2D top and front views of a needed machining fixture were downloaded from the Reid Tool Supply web site and imported into the CAD system. By using the 2D profiles, 3D solid extrusions were created. The Intersection and Union functions in CADKEY finished the solid modeling of the digital fixture. Using the 3D-model-to-drawing associativity feature, detailed drawings and assemblies were completed in Layout Mode. Shaded renderings and hidden line drawings were also generated for marketing materials.
The Tram Monitor (retail price: $249.99) mounts on the back of milling machines through the eyebolt hole and remains on the machine. The mechanism uses two standard 1-inch travel dial indicators, that are positioned in the shortest position possible, to make contact with the back of the motor housing and one side of the milling head. After "tramming" in the head, the dials are zeroed out on the two indicators. The device is then ready to monitor the position or "tram" of machine's spindle. If the milling head should move while machining, the operator repositions the head until the dials read 0, indicating that the spindle is properly reset to its original location.