Did you know that manufacturers deal with up to 800 hours of downtime a year? Just think of all that lost revenue! Much of this can be prevented by having a good monitoring and maintenance program in place. This is especially true for vacuum work holding systems.
Many shops use vacuum chucks to hold aluminum and plastic parts for milling or turning. These systems typically include a vacuum source or pump, vacuum chuck, connecting hoses, valves and controls. To keep the system working efficiently and effectively, these components should be monitored and maintained regularly. Here are some tips to do so:
1) Take Care of the Heart
The heart of a vacuum work holding system is the vacuum source. This may be a stand-alone vacuum pump at the machine, or supplied by a central vacuum system. Typically, each machine will have its own pump. There are many types of vacuum pumps available, including venturi, electric dry, electric oil lubricated and liquid ring. The type of vacuum pump should be selected based upon the type of chuck being used.
Carefully follow the suggested maintenance schedule for your vacuum pump. This may include changing filters, lubricating oil and other cleaning steps for trouble free operation. Most vacuum pumps run continuously, so it is critical that they are not neglected. A TEFC motor running continuously can become quite hot, so make sure the fan blades are clean and not blocked from providing a sufficient amount of cooling air across the pump motor frame. A pump failure in the middle of a critical part run can ruin your day.
2) Measurements Count
You should also monitor the voltage and current consumed by the vacuum pump motor. That can be a great indicator of overall pump condition. If the pump motor is drawing higher than expected current, compared to the motor plate rating, there is probably a mechanical problem developing. Better to know in advance and take corrective action before a costly shutdown occurs.
Many shops that use a ton of vacuum chucks will typically have a large central vacuum pump and reservoir system. Vacuum is delivered by pipe to each station. While this is more cost effective, the need for monitoring and maintenance is significantly higher. Simply put: a failure will shut down the whole shop, not just one machine. Ouch!
3) Eliminate the Weaknesses
We all know that a chain is only as strong as its weakest link. In this case - the potential weak links are your connections. Take a look at how the vacuum is connected to the chuck. This usually includes hoses, or pipes, valves and perhaps liquid filters. Like all fluid systems, it is critical to have a leak-free system. Vacuum leaks will reduce your part holding force. Vacuum leaks can not easily be seen. With a pressurized fluid system (like your garden hose) leaks are very easy to spot. If it leaks, water sprays everywhere. Vacuum is invisible. So, make sure all the vacuum connections are tight and use thread sealant or PTFE tape on all threaded connections.
4) Keep an Eye on those Hoses
Check all connecting hoses. Make sure solid hoses are not kinked or cracked. If you use push-to-connect fittings, make sure they are tight and not broken. For flexible hoses, make sure they are wire reinforced (to prevent collapsing) and all hose clamps are the proper diameter and tight.
5) Don’t Let the System Drink the Coolant!
Most aluminum parts are machined using flood coolant. It is very difficult to prevent coolant from being sucked into the vacuum system, either by vacuum leaks or just normal operations. Vacuum pumps do not like to ingest any fluids. This can cause considerable damage to the pump components. So, filters or liquid separators are used to catch the coolant before it gets to the pump. This may be a small filter, similar to a filter-regulator, or there are also larger systems that use stainless steel mesh and a storage tank. The coolant filters should be checked and drained often, either manually or by an automatic valve.
6) Keep Your Valves in Check
And, speaking of valves, just be aware that valves used for vacuum are not the same as standard pneumatic valves. Valves designed for vacuum, either hand operated manual or electric solenoid valves, include venting. When the valve is turned off, fresh air is provided to the vacuum chuck in place of the vacuum. Otherwise, your part would not come off the chuck!
7) Use Seals of Approval
Lastly, most vacuum chucks use some type of sealing gasket material to provide the seal between the part and the chuck. It may look like an O-Ring material, or be supplied in an extruded circular cord form. The gasket cord is pressed into a slot machined into the vacuum chuck. The material should be firm enough to provide a good seal. It must also compress slightly to allow the part to locate against the chuck surface. If the material is too stiff, under vacuum, it can lift the part above the chuck surface and affect part accuracy. If too soft, it will not provide a good enough seal.
Changing parts will expose the gasket material to coolant, chips and air blow cleaning. Make sure the gasket sealing material is clean and undamaged. You should change it when necessary. If the seal does not last very long, and consider trying a different diameter or material.
In the end, a good vacuum system has a well maintained pump, nice, tight connections and hoses, a good coolant separator and the correct size and type of sealing gasket. Neglecting any one of these components can jeopardize your production and affect your shop’s efficiency. This causes delays, customer anguish, and loss of profits. So, it makes sense to routinely investigate and maintain your vacuum system and prevent costly failures and shop downtime