Bridgeport SX OR DX

[innovator]

I'm looking to buy a used Bridgeport series 1 with EZ Trak control. Some have an SX controller and some DX controller. Can some one tell me the difference? I'm assuming one has more bells and whistles. Is there a place to research these controls?

[machintek]

In theory an SX was originally built with NO hard drive and with a 286 or 386 processor.
It had no space in the cabinet for a hard drive and no space to upgrade to a third axis.
The DX had a hard drive, a 486 or better and could be upgraded to full 3 axis.
Later DX machines had control made by Cutler Hammer, Computer Express, and BPT. The last ones had the option of a color LCD screen. Last version of software could accept DXF files with limitations, and could do engraving.

George

[MKST]

I just bought an ez trak sx and it doesent seem to be cutting round holes in side or outside.Im runnung a 3 phase static converter. Itried to run the command to tune the survos but the screan with the differant opps doesent come up all i get is c:\ .
is there a diagnostics disk that i need could anyone please help.

thank you Mark

[machintek]

You have to determine if your problem is mechanical or control related.
The SX machines came out in the later half of 1992. Thus there could be a lot of hours on the ways and ball screws and associated bearings and belts.
The SX machines were not lasered for pitch error compensation and the original versions of software thus did not support Pitch error compensation.
But all versions supported backlash comp. Have you checked for lost motion? For "dishing"of the ways? Do you have the maintenance manual to set the gibs?
Drive tuning is done in PFM.EXE which is one of the DOS files that exist in your software. You will need a full size keyboard and be DOS literate. Backlash comp can be set there as well or by homing the machine and at the main screen press the "*" key, a small window will ask for the code which is "11235" follwerd by "enter" twice!
Now you can see your travel limits and backlash comp values.
I find it easier to make the comp values bigger by a few thousandths, mill a circle with a light finish cut and sweep the circle with a dial indicator. Make sure your knee is locked! I cannot tell you how many people forget to do this and complain of inaccuracy. At the points of the compass you can measure the step which is the amount you are overcomped. Subtract this value from the axis it is relative to and you should be spot on and you have done this in a dynamic state which is more accurate than a static state test. Note that on a older machine the backlash can be greater in the center of travel because of wear in the ballscrew.

George

[MKST]

Thanks so much for your help George,
I typed pfm at the c promt and the screan came up for the tuning command and they look pretty equial . as far as lost motion i dont understand what you mean could you explain a little more about it. i notice that where the vise has been loccated in the center of the x and y axis the table seems to travel
freely but out too the farther ends of the x axis there seems to be more resistance is that what you mean as dishing.

thanks agan George

Mark

[machintek]

Typically there is more wear at the center of travel. The previous owner could have tightened the gibs there for more accuracy (tighter table). But this is fudging the real problem. In theory the tightness should be consistant along the entire travel. Now you have a table and possibly a saddle that cannot achieve position as well on longer parts. There are more forces working against the motors, belts, bearings, etc to overcome the additional friction.
Backlash comp is the lost mechanical motion in each axis. If it is set to zero, then you will see how far the motor must move when the direction is reversed to achieve motion of the table or saddle. But a dial indicator in the spindle against the side of the vise. move in one direction and set the dial to zero and the display to zero. Using the jog knob or step, reverse direction and see how far the display moves before the table moves. This is your lost mechanical motion or backlash comp.
I have never seen more than .0035 inches in a healthy machine.

George