Buying a new shaker? 10 Things to consider before you buy
When the time comes to purchase a new electrodynamic shaker there are many things to consider. The particular model you select is important, because it is true, size matters! But there are many other considerations than you may initially realize that need to be taken into account. Listed below are 10 things to consider when analyzing your vibration test system purchase. While this list doesn’t cover everything, it is a great place to start.
1. What are your test specs?
What is the required frequency range and amplitude of your test requirements? This is important to know as it helps determine a number of factors such as displacement capability.
2. What types of tests will you perform? Sine? Random? Shock?
What types of tests do you need to conduct (i.e. Sine, Random, Time History, SRS, Shock, etc)? This is important to define so as to ensure the final shaker selection is appropriate for the test types and profiles determined in item #1 above. It is also important to know so that a proper control system is offered with the shaker.
3. Important information about your test specimen is required.
What is the typical size, weight and center-of-gravity of your test sample AND fixture? This is extremely important to know so that the proper size shaker can be determined using this and the information in items #1 and #2. Keep in mind that you may have many different products and profiles that will be tested. The idea is to determine the worst-case scenario to not undersize your test system. It is also important to consider that when a high percentage of your usage will be on smaller loads that you consider outsourcing your larger test requirements. This consideration is often the tipping point for a company to invest in a new shaker, as often they conceptually want to do everything in-house, but then can’t afford the shaker system that is capable of ALL tests they ever may run. If this is your situation, consider a shaker that is appropriate for 90% of your needs and outsource the remaining 10% if this make more economical sense.
4. Horizontal - Vertical or Multi Axis
Which direction do you have to run your vibration tests? Many options are available from a simple vertical direction shaker to a combination system that incorporates a slip table where-in the shaker can rotate 90 degrees to run horizontal testing. Additionally there are multi-axis (3-dof and 6-dof) shakers that can provide more realistic test environments and shorten test time, but these systems do come at a significantly higher price but can provide great benefits in product development and reliability testing.
5. Will you combine with an environmental chamber?
Do you require combined environment of vibration with temperature and humidity conditioning? This is another important consideration in the planning process. Generally additional features are added to a shaker that is going to be used with an environmental chamber. Thermal isolation barriers and vapor barriers may be added to these systems.
6. Air Cooled or Water Cooled?
-If water cooled is preferred, does your facility have the proper cooling water available?
-If air cooled is preferred, where will you exhaust the air? If outdoors, do you have enough HVAC make-up air to handle this airflow? Special options may be available that draw air from outside and exhaust it back outside.
7. Facility Power Requirements
Does your facility have enough power available for your new shaker system? This is something that is determined based on the size of the shaker.
8. Facility Modifications Required
What facility modifications/preparations will be required?
- Power connections need to be near the amplifier location
- Water lines run for water cooled systems
- Venting pipe installed for air cooled systems
- Air lines (shop air) with filter to supply system for isolation airbags and load support inside shaker
- Floor preparation may be needed for larger systems so that a proper reaction mass exists for large system testing.
- If located near offices or other employees, consider sound abatement. Depending on the size of the shaker and test levels, they can be quite loud.
9. Test Personnel Considerations
Who will do the testing? Often companies know they need vibration test equipment but they may be ill prepared to competently do the testing. Be sure to get proper general vibration testing education and training prior to the implementation of your own equipment.
10. Plan for the Future
How do you plan for the future of your equipment? A shaker is a lot like your vehicle that you drive every day. Treat it well and it will last many years. Just like you don’t drive your car at “red-line” rpm levels, don’t run your shaker at 100% all the time. Typically a shaker is sized such that your tests (profile based on total moving mass and some safety factors) don’t exceed 80% of the capability of your system. Also, plan for a regular preventive maintenance budget. Just like your automobile has to have regular oil changes, brakes replaced, fluids changed, etc. your shaker needs attention. Being proactive in servicing your shaker will help prevent headaches later when you are in crunch time.