An element of design layout sometimes overlooked by planners of robotic work cells is control panel door opening space requirements. “NEC Table 110.26(A)(1) Working Spaces”, summarized below, shows the depth of working space required in front of electrical control panels. Typically, control panels are located outside the protective barrier of the robot cell. Additional clear space as described below is required in front of each panel. The effect of this is typically to increase the overall footprint of the robot cell.
Minimum Clear Distance
| Nominal Voltage to Ground |
Condition 1 |
Condition 2 |
Condition 3 |
|
0–150 |
914 mm (3 ft) |
914 mm (3 ft) |
914 mm (3 ft) |
|
151–600 |
914 mm (3 ft) |
1.07 m (3½ ft) |
1.22 m (4 ft) |
- Condition 1 – Exposed live parts on one side of the working space and no live or grounded parts on the other side of the working space, or exposed live parts on both sides of the working space that are effectively guarded by insulating materials.
- Condition 2 – Exposed live parts on one side of the working space and grounded parts on the other side of the working space. Concrete, brick, or tile walls shall be considered as grounded.
- Condition 3 – Exposed live parts on both sides of the working space. (not guarded as provided in Condition 1) with the operator between.
Note: Where the conditions are as follows:
A couple of things can be done to reduce the impact of this specification. Sometimes the control panels, including robot controller, can be recessed into the robot cell so that the control cabinet access door is flush with the safety barrier. This will shrink the floor space depth required by the depth of the control panel.
Another means to lessen the impact of the control panel access requirements is to relocate the panel to a location where there dead floor space already exists. The caution here is that relocating a control panel away from the robotic work cell will usually result in higher installation cost.
Motor control panels are usually going to require 240VAC or higher; so greater space requirements are going to be in effect in most instances. (3’6” to 4’ versus 3’ clear). Conveyor control panels in most cases can be limited to 110VAC, so only 3″ will be required in front of an open panel. It may be of benefit to keep motor controls separate from low voltage control panels (150VAC and lower) specifically for this reason.
Other options to give the robot cell designer flexibility in floor space design requirements include breaking larger multi door control enclosures into multiple single door enclosures, (or vice versa) and using motor driven roller conveyors that reduce or eliminate the need for motor control enclosures, instead mounting the conveyor drives on the conveyor frame. Also, different robot control enclosure styles that are available may give relief where floor space is restricted.
Contact Motion Controls Robotics, Inc., your FANUC Level IV Certified Servicing Integrator for picking, packing and palletizing applications at 419.334.5886 for more information on control panel layout considerations for your robotic work cell.
