[ToolChatter]

Hey folks,

I'm having an issue with my BP Series II with Centroid M40 Servo system. When I run a program, any time it goes to Z home (for tool change, for example) I get either a Z-position error or a Z-stall error. I can jog the knee all day without issue, but I do get a shudder (2-4" from the bottom of travel) when I rapid the knee down. It seems to be worse if I start at the top of travel than if I start mid-travel. This machine has an air support for the knee. The installation manual for the Series II says it should be run at 40 psi. I wonder if something is wrong with this system. I have a relieving regulator supplying the air, and it doesn't seem to spike the pressure or anything. Are the shudder and servo error likely related, or separate issues? Any thoughts?

Thanks everyone!
Tom

[ToolChatter]

Some more info: One of the reasons I suspect the air support is that the shudder seems to coincide with hearing air escape. While traveling down, when it gets near the bottom there will be a hiss of escaping air and a shudder. It does this even if I completely disconnect the air supply and leave the line to the pedestal open. Occasionally it will stall around this point, and after servo power is cut the knee will creep *UP*. Does anyone know how the air is supposed to be released from the system when traveling down?

[brian257]

How do you have the air going to your air cylinders? Is it fed into the cylinder direct from a compressor with a check valve or no air tank? I have a BP conversion and it has two cylinders about 2.5" diameter and they connect to a Harbor Freight air tank that I pump up to about 100 PSI. I thought it might be an issue with increased pressure with the knee down, but then I ran the numbers with the volume of air in the cylinders plus the volume in the tank it it only varied one or two PSI with the knee fully up or down. If you have no air tank and just the volume of air in the cylinders and the air line going to a tankless compressor you will have a big increase in pressure as the knee goes down.

[ToolChatter]

I have the air coming from a pancake compressor (regulated at 85 psi) to a regulator on the machine set to 40 psi. It is a relieving regulator, but I suspect it isn't relieving very well. By completely disconnecting the air line from the pedestal, I seem to have made the issues go away.

Looking at the pedestal drawing in a pdf of the maintenance manual, it looks like there is supposed to be a vent/breather at the top of the air cylinder. The only port there on mine is connected to the lubrication system. It's possible that the previous owner hooked the lube system up to the vent port and tee'd in a vent/breather at the inlet port. Has anyone heard of this being done?