Mill Dro, Power Feeds and Glass Scales??

Mike8623

Registered
Registered
Joined
Dec 18, 2013
Messages
583
Got a question Guys now don't laugh at me. Can someone explain to me how the DRO communicates to the machine through the power feed and glass scales to move the tables whether it be x,y or z. I can see the power feed connects to the scale via a micro switch and the to the power outlet. Two power cords. The Dro connects to the power outlet and then to the scales via a cord. So just how does the whole thing work to move a table. How does the dro tell the power feed to move the table. Again don't laugh at me.
 
No laughing, we all were in the same boat at one time or another.

A DRO does only one thing and that is to communicate to you where the spindle is in relationship to the table and /or the work. A CNC machine moves the table/work relative to the spindle and displays its position on a DRO, usually a monitor screen.

As far as I am aware, power feed devices are totally independent of any readout devices. The microswitch you mention may be the limit switch which is used to prevent the table from moving into undesirable areas. It is adjustable and may be located in the same general area as the DRO scale which would contribute to your confusion.
 
To add to RJ's post: A mill with a DRO and one or more power feeds is still a completely manual machine. You use the DRO for information, then use the hand wheels and/or power feed to move the work into the cutter as desired. The power feed is just a simple variable speed motor that moves the axis with a control handle or switches. Automating the axes is called CNC.
 
Got a question Guys now don't laugh at me. Can someone explain to me how the DRO communicates to the machine through the power feed and glass scales to move the tables whether it be x,y or z. I can see the power feed connects to the scale via a micro switch and the to the power outlet. Two power cords. The Dro connects to the power outlet and then to the scales via a cord. So just how does the whole thing work to move a table. How does the dro tell the power feed to move the table. Again don't laugh at me.
Not adding anything here, just reiterating. No bad questions on this forum. As mentioned by RJ and Bob above, the DRO just tells you where the table is relative to the spindle. It's a WONDERFUL device on the milling machine as backlash in the hand wheels is no concern. I have a Jet 8" x 30" mill with a 4-axis DRO on it and power feed on the X-axis. Modern ones have nice features like holes on a line and holes on a circle. Just plug in the start/end points, say how many holes, and the trig is all done for you by the DRO.

The power feed is really nice for repetitive passes across stock, but it does not communicate with the DRO. For example, you can't tell the power feed to shut off when the X-axis is a 5.000" (for example). Applications for power feed is facing something or cleaning up an edge (among others). It keeps you from continually turning the hand wheels. Mine has adjustable stops on it and a switch that will automatically shut off the power feed. So I could start a pass, walk away, and not worry about crashing the mill.

I recently picked up a 2HP Bridgeport with a 2-axis CNC set up and made the demo cuts shown below. Took me a while to figure out the programming, but I've got it now. I can pretty easily program the table to act like an X-axis or Y-axis power feed. Can even dwell at the end of the pass to allow the table to be moved for cutting on the return pass. I can't imagine the time it would take to make the path shown below by hand. It would require a rotary table and some trig so you know how far to go on each leg. The CNC cut this ~6 inch path in about 35 seconds.

Bruce

20170917_161142.jpg
 
Thanks Guys. I did indeed think the whole DRO, power feed and scale thing was a cnc. So I've learned a lot here. I just could not see how the dro would tell the power feed to move. So I've got it now and I thank all who responded.

Is there a conversion that can be added to the whole system described above and make it a simple cnc operation without buying a lot of other equipment?
 
Is there a conversion that can be added to the whole system described above and make it a simple cnc operation without buying a lot of other equipment?
Not really, but I will let someone much more familiar with CNC explain the lower end CNC equipment. I am a "turn the handles" guy, and love it just like that. I put a power feed on my mill, and I do not think I have made a cut using it yet, just use it to quickly position the table. Old habits die hard...
 
Back
Top