[sdeering]

Question for you fellas with the old Bridgeport CNCs.

Bridgeport boss5 converted with origonal steppers on 70v DC wired in series.

1020 steel

1" rough end mill 1.5 doc
250 rpm 2ipm feed
1/8"+- cut
Circular cut 2.5" with about a .3 dia leedin/out. the hole is pre plasma cut just 1/8ish cleanup pass.

I had problems with the steppers not holding/feeding while finishing thehole with this feed. Endmill would grab and move the table. Removing about 1/8" of material.

I am haveing success at .5 doc 3 passes.

Does anyone know if in pushing the old girl too far with the above cut or do I need to wire the steppers in parralel and go to full step instead of microstepping?
I read microstepping loses 30% tork?
I don't want to make the old girl do what it wasn't intended to do.
Any insight would be appreciated.

Thanks
Stephen

[sdeering]

I just had a look in my origonal programing book and it says 1.5cubic inches/min. in mild steel. I guess I will have to do some math.

[machintek]

ALSO: stepping motors get weaker with time as the magnetic fields inside the motors diminish. Secondly, the machine drives may needs to be tuned. IE, current set, etc.

George

[sdeering]

Im using Larken cobra drives 9amp Im rumming 70v DC to them.
Yep the motors are old could be a little demagnitized.
I will have to find a way of calculating side load and figure what the motors are capable of I guess.
What were they 800in/lbs?

[keebler303]

I have a BOSS5 with original stepper drives and mach3 control. I don't remember the RPM but I once put a 1" rougher into 1" thick A36 full width at 60 ipm and it didn't break anything. It lost some steps but I was able to hit the red button before anything let go. I would say it would have handled half that speed with no problem. Mind boggling how fast those roughers will rip up steel.

1.5 cubic inches/min at 1.5" DOC and 2 IPM is 0.5" WOC. Seems like it should handle it assuming all your machine parts are up to snuff.

Also you should be using a conventional cut so your cutting edges aren't slamming into the hard slag on the plasma cut edge.

Matt

[sdeering]

Yep conventional milling is the way to go.

Thanks
Stephen