Just wondering how the 2412 handles a power failure when in operation. Noticed that Haas has a power fail option listed. As to what it does, I have no idea.
Haas used to have a nitrogen counterbalance system. They have I believe discontinued that and just let the servo carry the load. If power fails, there is nothing to stop the Z axis from falling a bit, thus gouging your part.
I believe the Sharp is exactly the same as when at rest, you can look at the axis loads on the load monitor screen and see that the Z axis is about 35% or so.
Same as my Haas...
The Haas (at least the VF3SSYT at the shop) will drop ~.25" during a power loss.
Since about 2001 Haas machines have not used a counterbalance on the head; the weight of the head is supported by the Z axis servo drawing power. On these machines if you look at the Z servo load it stays anywhere between 25% to 60% and this is just to hold up the head weight.
Naturally when the servo does not have any power the ballscrew is going to freewheel so to stop this there is an electromagnetic brake on the motor. The brake is locked on by permanent magnets and released when it receives power.
When the power goes down, either by a main power failure, or by hitting E-stop both the servo power and the brake power go off; the servo stops holding the weight and the brake locks on. On the small machines like the MiniMills and the machines with low pitch ballscrews the brake locks before anything moves. On the bigger machines , especially the ones with the high pitch ballscrews, the ballscrew can rotate a small amount, and the head drops a small distance before the brake locks.
The power failure detection module prevents this drop. It senses the loss of power and shuts off the power to the brake before the servo power goes off. This means the brake locks before the servo stops carrying the weight and no head movement occurs
An open mind is a virtue...so long as all the common sense has not leaked out.
Geof, thank you for the explanation regarding the Haas.
Thanks for the feedback so far. I'm in an area with alot of power fluctuation esp. during the summer months with the storms. It's bad enough being down for a few hours waiting for power to be restored, but I'd like to avoid losing parts & tooling as a result of a PF.
I am not sure of the mechanics on the 2412 but I can tell you that mine stopped on two different occasions, both time it was tapping a 10-24 hole and never broke the tap. I love my 2412...