Re: [Emc-users] manually setting "home" values (newb question)
Just issue a g92 x0 y0 z0 when the table is were you want it this sets it the axis to 0 -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of rtwas Sent: Sunday, March 16, 2008 7:30 PM To: Emc-users@lists.sourceforge.net Subject: [Emc-users] manually setting "home" values (newb question) Hello, I'm new to cnc. I've been doing a lot of reading and experimenting with emc2. I currently would like to know how to *manually* set the home position (as apposed to *going* to the *current* home position). I have looked and looked and can't figure it out. The best I can do now is move the table to the desired position and kill emc2 and restart it. Thanks. Robert W. - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] manually setting "home" values (newb question)
John Thornton wrote: > Robert, > > If you have the line HOME_SEARCH_VEL = n in your ini file EMC will home to > the > switches. > > If you wish to do an offset for the work piece just use the touch off button > after you > are in the desired position. > My mill is not set up with home switches yet so I set the corner of the vise as HOME. In the ini files the HOME_OFFSET=0 so I can home anywhere and for me that is the corner of the vise. If I have to have a workpiece zero in a different location I use touchoff to set my G54-G59 then can gome back to the original HOME with a G53G0X0Y0 then set G54 to that point again.Ed. - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] How do I calculate leadscrew push/pull forces?
And, Don't forget screw pitch, or lead. Pitch is also a big determinate of screw efficiency. Glenn -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of John Kasunich Sent: Sunday, March 16, 2008 7:57 PM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] How do I calculate leadscrew push/pull forces? Stephen Wille Padnos wrote: > The leadscrew diameter isn't important for the force calculation. > > The motor can output 200 ounces force at a one inch radius, as you > said. For one revolution, the 200 ounces of force is applied over > 2*pi inches of travel, but produces 0.2 inches of table motion. Just divide: > 200 * (2*pi*r) / (0.2) = force in ounces =2000*pi, or about 6280 > ounces force (close enough to 400 pounds). > > The units are ounces * (inches) / (inches), which is ounces since the > lengths cancel out. > Actually the diameter does matter, at least for acme screws. The calculation that Steven did is correct if you neglect friction. For ballscrews, with 90% or better efficiency, you can almost neglect friction. Not so for acme screws - the majority of the torque at the motor is from friction. Here is the counter-intuitive part - a smaller diameter screw of the same pitch will be MORE efficient. Assume you have 100 lbs pushing on the nut. Steven's formula above can be used in reverse to calculate the torque on the screw from the nut. For a 100 lb load, and a 0.200" screw pitch, that torque is 100 lbs = 1600 oz, times (0.2"/(2*pi)) = 50.95 oz*in (call it 51). But now you need to add the torque due to friction. The force is equal to the load times the friction coefficient, so it will depend on the material of the nut and screw. Google says the coefficient for a lubricated bronze nut on a steel screw is about 0.16. That means our 100 lb load will result in 16 pounds (256 ounces) of tangential friction force. That force is at the radius of the screw, where screw and nut meet. If the screw is 5/8 inch in diameter, its radius is 0.312 inches, and the friction needs 256oz * 0.312in = 80 oz-in of torque to overcome it. So you need 80 oz*in to overcome friction, and 51 oz*in to move the load for a total of 131 oz*in. (You'll want a motor that can deliver at LEAST twice that amount at your maximum desired speed, for insurance against lost steps.) Now switch to a 2" diameter screw. Now the 256 oz friction force acts at a radius of 1 inch, and you need 256 oz*in of torque to overcome it. Add the 51 oz*in that actually moves the load, and you get 307 oz*in. Now you see why we like ballscrews so much. Regards, John Kasunich - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] manually setting "home" values (newb question)
Robert, If you have the line HOME_SEARCH_VEL = n in your ini file EMC will home to the switches. If you wish to do an offset for the work piece just use the touch off button after you are in the desired position. John On 16 Mar 2008 at 18:39, [EMAIL PROTECTED] wrote: > Hello, > > I'm new to cnc. I've been doing a lot of reading and experimenting > with emc2. I currently would like to know how to *manually* set the > home position (as apposed to *going* to the *current* home position). > I have looked and looked and can't figure it out. The best I can do > now is move the table to the desired position and kill emc2 and > restart it. > > Thanks. > > Robert W. - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
