This article explains four methods for evaluating workstation utilization for the purpose of closely estimating the savings achievable with on-demand Ecogate systems.
What is Workstation Utilization?
First, we’d like to share how we define workstation utilization. To be more specific we'll use the term Workstation Active Utilization, which might do a better job at signifying what we're trying to evaluate here.
We know an operator may be working at a workstation an entire shift, however, this doesn’t mean the workstation utilization accounts for the entire shift. Workstation utilization only factors the time when the machine is producing particles for extraction, and not the time when the operator is loading/unloading material, programming CNC, cleaning, maintenance, etc. This is also the perspective management cares about, as this is the only time when the machine is producing.
The smart Ecogate control units (greenBOX NXT & greenBOX MASTER) send data to our cloud servers every 10 seconds. The data is used to send daily emails to maintenance personnel (with air volumes, air velocities, fan & filter pressure, and more) and monthly emails to management (with workstations & plant utilization, energy use, and savings). The workstation's active utilization is an important part of the data.
Options to Evaluate Workstation Active Utilization
Before installing an Ecogate system you evaluate the workstation active utilization. This allows you to calculate the exact savings that can be achieved. To do this, there are several options.
Some factories use a system that measures and records the number of products (parts or operations) a particular workstation produces per shift day and per month. This lets them know the maximal capacity of each workstation. By dividing the actual production number by the maximal capacity of the workstation (recorded in percent), we arrive at a good average working utilization for this workstation.
If option 1 is not available, you can try a different method. You can measure utilization by using a stopwatch and observing the full production cycle - the average utilization will be the cutting cycle time divided by the complete cycle time (recorded in percent).
If the first two options are not viable, then we can resort to a simple snapshot method to measure the utilization of the entire factory. Start with a full list of workstations and walk from machine to machine to record which ones are cutting material and which are not. After this, you calculate the percentage of active workstations. This method is not the most accurate because it is based on a snapshot. Surprisingly, however, it is pretty close to carefully measured numbers. You can conduct snapshots several times per shift(s) to improve the overall accuracy.
If you need the most accurate utilization numbers then you can install sensors (data loggers) on motors that are driving cutting tools of workstations. This is covered in more detail in the following sections.
Using Onset Data Loggers
As we mentioned earlier, the time when the machine is producing (therefore needing dust/mist/fume collection) is what needs to be recorded in our measurements. To do this we need data loggers that will record the time/date of when the motor of the cutting tool is active and the time/date of when it is inactive.
Note: Data loggers should only be placed on motors that are driving cutting tools, otherwise you will have incorrect data. For example, if you add a data logger to the vacuum pump of a CNC machine, that pump may be running the entire shift, which does not represent the active utilization of this CNC machine.
Simplified Step by Step Instructions
Here's a condensed list of steps that covers how to properly add data logger sensors to your workstations. Below this list, we go into more detail and include pictures!
Mount the data logger sensors on the workstations’ motors that are driving cutting tools, and fix them properly in place (must withstand all vibrations for 2 weeks).
Start the CUTTING motor of the workstation.
Press the right CALIBRATE button and HOLD it until the calibration sequence starts.
When the calibration is finished, you can test the sensor by starting and stopping the CUTTING motor. Proper status should be indicated on the sensor LCD screen.
If the motor sensing is working properly, you can deploy the sensor by pushing the left START button and HOLD until the sensor starts logging. The sensor is set to display the percentage of logging time (it will show 100% if the motor keeps running, and it will drop as the motor stops).
Leave sensors installed for a minimum of two full weeks (to capture one full week, and one full weekend).
After two weeks of deployment, use the STOP button and HOLD to stop data logging. You may now collect all the sensors.
Onset HOBO UX90 Motor On/Off Data Loggers
We are using the new and improved generation of Onset HOBO UX90 Motor On/Off data loggers. These data loggers are not connected to the motor, instead, they are powered by a battery and can sense the magnetic field of an active motor. They can be attached to the motor using magnets and/or cable ties can be used to secure it further.
The magnetic field of the motor is sensed by two little coils, and the sensitivity can be properly adjusted by using the Calibration button. A nice LCD display will help you understand if the calibration was successful. To start logging simply press the Start button.
Collect data for at least two weeks. After this period, press the Stop button to stop collecting data and collect all sensors. Use a Micro USB cable to download the data onto a computer and use the HOBOWare software to evaluate the average utilization.
Since we are only interested in the utilization during the shift time, we can use the HOBOware software filter to display motor utilization:
The final result of the evaluation could be a table where we can see workstation active utilization day by day and weekday averages:
Before you deploy the sensor, you need to prepare it by using the HOBOware Launch option. Recommended settings are:
Internal (sensor): “State”
State Description: "Motor Off/Motor On"
LCD: For State and Runtime sensors, show: "%"
Start Logging: "Push Button"
Stop Logging: "When Memory Fills"
Check the "Push Button" box
Click “Button Start”.
Author, Ales Litomisky