jscpm
Titanium
- Joined
- May 4, 2010
- Location
- Cambridge, MA
I thought the readers here might be interested in seeing a machining setup I constructed recently using a heavy duty optical baseplate. This kind of setup allows me to get a very good power to size ratio. In the configuration shown in the photo below we are grinding a precision bevel on die. Sure, you can do this with a big $30,000 surface grinder, but here I am accomplishing the same thing on a bench using equipment costing less than $3,000. Also, it is being done just using standard 120V power. This setup is flexible because we can reconfigure it to act as a lathe or as a horizontal milling machine all in the same small footprint. The bench or table used must be VERY strong and stable. In our setup we use heavy hardwood 2" tops with 6x 6" oak pedestals.
The key is the motor. We are using a Baldor CEM 3456, which is a true 3-phase, four pole 1 HP motor. This gives a lot of torque even at low RPMs. We get variable speed control by using a Leeson Speedmaster SM2 type 174605 motor controller. This both converts single phase 120V power to 3-phase 230V for the motor, and gives us the ability to control the RPMs.
The frame of the setup is constructed with thick walled aluminum cylinders and 5/8" aluminum plate, all precision machined for flatness. Everything is bolted to the base plate. Note that it is a "soft foot" motor, so a shim kit is needed to align the motor. Also, the arbor must be carefully aligned with the motor shaft, which requires a skilled process described in mechanical textbooks. The arbor bearing is provided by a simple babbit bearing and oil flask. Felt washers are clipped on to prevent oil from seeping out. For the grinding wheel arrangement we had to machine a custom arbor. Trying to find a commercially available arbor that fits what you are doing is a lost cause, so just plan on machining the arbors you need.
To position the work, here we are using a combination of small linear motion ball screw guide and a scissors Z-stage of the type used in optical work. This Z-stage allows us to control the up-down motion of the work very precisely.
To dress the wheel you can see we use an angle adjustable magnetic chuck. Obviously when using a grinding wheel you need to have a guard, here supplied by 3/8" plexiglass.
The key is the motor. We are using a Baldor CEM 3456, which is a true 3-phase, four pole 1 HP motor. This gives a lot of torque even at low RPMs. We get variable speed control by using a Leeson Speedmaster SM2 type 174605 motor controller. This both converts single phase 120V power to 3-phase 230V for the motor, and gives us the ability to control the RPMs.
The frame of the setup is constructed with thick walled aluminum cylinders and 5/8" aluminum plate, all precision machined for flatness. Everything is bolted to the base plate. Note that it is a "soft foot" motor, so a shim kit is needed to align the motor. Also, the arbor must be carefully aligned with the motor shaft, which requires a skilled process described in mechanical textbooks. The arbor bearing is provided by a simple babbit bearing and oil flask. Felt washers are clipped on to prevent oil from seeping out. For the grinding wheel arrangement we had to machine a custom arbor. Trying to find a commercially available arbor that fits what you are doing is a lost cause, so just plan on machining the arbors you need.
To position the work, here we are using a combination of small linear motion ball screw guide and a scissors Z-stage of the type used in optical work. This Z-stage allows us to control the up-down motion of the work very precisely.
To dress the wheel you can see we use an angle adjustable magnetic chuck. Obviously when using a grinding wheel you need to have a guard, here supplied by 3/8" plexiglass.
