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Motion &
Manipulation
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Q: Can a motor drive be added to a rotary
feedthrough?
A: Yes, to a standard rotary feedthrough. The body of the feedthrough is different, however, so it is not possible to simply mount a motor onto an existing unit. The body of the feedthrough must be replaced so it will accept the motor of your choice.
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Q: How does a "Tunnel Access" feedthrough work?
A: The shaft of the feedthrough is hollow. Wires can be threaded through the shaft to the removable flange that is mounted to the nosepiece. The removable flange can be modified to accept the wires.
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Q: What is the difference between Quick-Access Doors with clearance holes and those with tapped holes?
A: The main difference is in the practicality of mounting the door. Functionally, the performance is the same.
If the port flange for the door is so close to the chamber than bolts cannot be inserted through the backside of the port flange, then it is necessary to fasten the door from the front. Usually, this would mean the port flange has tapped holes.
If the port flange has clearance holes, bolts would be inserted from the back side of the flange and secure a door with tapped holes. If a door with clearance holes is to be mounted to a flange with clearance holes, consult factory for bolt length requirements.
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Q: Why are some in-vacuum accessory screws non-vented?
A: Non-vented in-vacuum screws can be used only where the threaded hole goes all the way through its component.
It is essential to avoid trapping any air inside a chamber, which can then slowly leak back into the chamber when it is brought under vacuum. This appears to be a flaw in the chamber or in a vacuum seal and is therefore called a "virtual leak." Blind tapped holes are a prime source for a virtual leak.
In the case of blind tapped holes, either the screws must be vented or there must be a side vent to the threaded hole to provide a path for trapped air to escape. Use non-vented screws only where there is an escape route for air.
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Q: Why is a linear guide rod standard on some load-lock systems and not on others?
A: A linear guide rod is standard only on the rectangular entry systems where it is essential to move the substrate in a single position only. Guide rods are optional on circular entry systems where it may or may not be critical to keep a sample in a single rotational position.
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Q: How does a differentially pumped seal work?
A: A pumping port is placed between two O-ring seals and attached to a vacuum pump. Any air that manages to pass the first seal is evacuated before it can pass the second seal. There are three levels of pressure at work: atmosphere on one side and vacuum on the other, with a differential pressure in between.
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