Bp Series 1 Cnc - Z Axis Problems

[unterhaus]

Wow, somebody saw my "work" log. I'm not sure that the bp cnc's were as common in europe as they were here in the states. There are a ton of them here, and it's so much easier to fix them up as a good cnc than converting. I agree, in the States its a bad idea to convert a manual since it's so easy to buy a cnc that needs work.
Having said that, there was a recent discussion about converting a series 1 to cnc on cad/cam/dro yahoo group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/ There's also a guy that is selling plans to cnc a series I for $35US, certainly worth it rather than trying to measure the bolt patterns and come up with a quill drive design. Sorry, no link for that.

Many of the bp cnc did use the knee as the z axis. I saw a knee ballscrew recently on ebay. Mine has a ballscrew built into the quill, so the knee is just an acme screw.
You must compensate for the weight of the knee which is generally done by supporting the knee with air springs. The mills like mine came with an air assist on the knee which I don't understand. Feeding air into mine just lets more air out into the atmosphere. Hate to have too much air in the atmosphere. Sure didn't make the knee any easier to push around, it's a monster, the knee, saddle and table weigh more than a series 1. I would like to motorize my knee, since it is a pain to move, but maybe I'll just counterbalance the thing.

[machintek]

All the BPTs that had series 2 iron had an air assist in the pedestal for the knee. The regulator was set at 50 PSI for an empty table. For each additional 100 pounds you put on the table, the regulator needs to be increased by 5 PSI. Too much air is not good either. The old NC2s had a stepping motor and ball screw on the knee. I was called in because the knee would not go down. Sure enough the air assist regualator was set at 90 PSI. There was an upward force of 800 pounds which the stepping motor could not overcome.
It is inportant to maintain oil in the air oiler because there is a leather cup in these. It is normal to see small bubbles of air leaking past the seal but no more than that.

George W.

[unterhaus]

Originally Posted by machintek All the BPTs that had series 2 iron had an air assist in the pedestal for the knee. George W.

I guess my seal is leaking. Is the air assist a cylinder inside the screw? How did it work?

[machintek]

If you give me your email address, the next time I go to the office, I can scan an exploded/cross sectional view with BPT part numbers of the air assist built into a series 2 pedestal. I can email it to you as an attachment. It will be in PDF format.

George W.