Motor Tuning questions from a newbie

[edclayton1]

I just recently got my table built and got the wiring to a new blade runner all hooked up. I have 3:1 ratio gearboxes on my x an y axis and a direct drive motor on my Velox z axis. Everything seems to be running pretty quickly with the 620 oz. motors I got with the new bladerunner ethercut 4. My question is: Is it really necessary to do the motor tuning as suggested by Artsoft and CandCNC? If so why does a guy need to do it?

Is it needed so the DRO's understand travel distances?

I did try to setup soft limits and noticed that even though I specified a table size of 48" * 48" the x axis seemed to ignore my limits while the y axis seemed to understand the soft limit?

[acourtjester]

It is very important to do the motor tuning if you want your cuttings to be correct. Go here and check the 6th post down on how to do it
easily. you don't want circles to look like eggs do you?? http://www.plasmaspider.com/viewtopic.php?f=52&t=18000

[tcaudle]

Motor "tuning" is also motor "calibration". The default steps per unit are set at 2000. That is close for a 3:1 belt reduction and 1" pinion but not exact. For every step you are off on the calibration you will be moving several thousands over or under the actual size. If you are off the same amount on all the axis it willcut round holes and what you draw....it will just be to big or too small. Keep in mind the effect is cumulative. If you are off .010 in one inch you will be off .1 inch in 10 and a full inch in 100! Use the "tape measure" method in the manual and measure the error at 24 to 36" and get it close to zero at that distance and it will be dead on in one inch. Velocity just sets the MAX speed the axis canmove at. More important is Acceleration. If its too low it will cause the toolpath to "skid" and round off corners and sharp turns. The thinner the materialhe faster you have to cut. The faster you have to cut the higher you need the acceleration to be. You have to tune for the THINNEST material and highe3st speeds you will ever cut.

Soft limits are only usefull if you have the Axis homed and zeroed. The number is just relaitive (what is displayed in the DRO) so if you zero and start in the middle of the table and run 48" you are well past the edges. If you don't have homes on X and Y or you forget to homeand zero the axis in a corner soft limits are useless

[edclayton1]

It is very important to do the motor tuning if you want your cuttings to be correct. Go here and check the 6th post down on how to do it
easily. you don't want circles to look like eggs do you?? http://www.plasmaspider.com/viewtopic.php?f=52&t=18000

Thanks I will check that out. Its different than the way my manual explains how to do it but I will give it a whirl. After all this time I've been working on building this machine and waiting for the money to come in so I could get it done, now that I'm almost there I am just so anxious to start cutting metal I guess I was just hoping to take a few short cuts. I have watched several you tube tutorial videos about this topic and read my manual concerning this area but its just not completely sinking in.
I'm in about place trying to understand the homing and zeroing techniques.

[edclayton1]

Motor "tuning" is also motor "calibration". The default steps per unit are set at 2000. That is close for a 3:1 belt reduction and 1" pinion but not exact. For every step you are off on the calibration you will be moving several thousands over or under the actual size. If you are off the same amount on all the axis it willcut round holes and what you draw....it will just be to big or too small. Keep in mind the effect is cumulative. If you are off .010 in one inch you will be off .1 inch in 10 and a full inch in 100! Use the "tape measure" method in the manual and measure the error at 24 to 36" and get it close to zero at that distance and it will be dead on in one inch. Velocity just sets the MAX speed the axis canmove at. More important is Acceleration. If its too low it will cause the toolpath to "skid" and round off corners and sharp turns. The thinner the materialhe faster you have to cut. The faster you have to cut the higher you need the acceleration to be. You have to tune for the THINNEST material and highe3st speeds you will ever cut.

Soft limits are only usefull if you have the Axis homed and zeroed. The number is just relaitive (what is displayed in the DRO) so if you zero and start in the middle of the table and run 48" you are well past the edges. If you don't have homes on X and Y or you forget to homeand zero the axis in a corner soft limits are useless

Thanks for writing me and explaining the importance of this step. I will just have to roll up my sleeves and try a little harder to figure it out. I have the data for the math I was just being to impatient and did not want to go through the process if it wasn't really very important anyway. And yes I will be wanting to cut pretty thin metal as I only have a HT powermax 45 I'm kind of thickness limited.

Yes I do have home switches installed on this table and I have tested them and they are working just not necessarily how I expected them to. I assumed every time the switch was contacted no matter what they would stop the motors, but that turns out to not always be the case. I can jog right past them and crash into my hard stops. But when I follow your instructions in the manual to go to home they work perfectly as they should. So I conclude its operator error on my part.

[acourtjester]

I have 3 home/limit switches on my table (and the others I built). They are all wired in series normally closed. When Mach is telling the table to go to a home and it hits any switch it stops that motion. But because you said move to X home it is moving the X axis and there for it will hit the X home. Mach knows what motion it is doing and therefore acts on what happens. If you are moving to cut and it hits one of the switches it acts like a limit and stops the motion. When you do a ref home in plasma it will move the Y axis first then after it hits the Y home/limit switch it move back just off the switch. It then moves the X until the home/limit switch is hit and move back just off the switch.
It will zero the DROs then is you have that selected in home/limits menu. This works the same for a floating head switch you tell Mach to Z home (G28.1 Z0.02 g-code) when the torch touches the metal and trips the switch it Z zeros the Z DRO and back off the switch. If you have a feather touch it is wired to another pin and entered to the Probe input it uses the G31 command for G-code.

switch wiring AB.jpg

inputs.JPG

probe.jpg

[edclayton1]

I have 3 home/limit switches on my table (and the others I built). They are all wired in series normally closed. When Mach is telling the table to go to a home and it hits any switch it stops that motion. But because you said move to X home it is moving the X axis and there for it will hit the X home. Mach knows what motion it is doing and therefore acts on what happens. If you are moving to cut and it hits one of the switches it acts like a limit and stops the motion. When you do a ref home in plasma it will move the Y axis first then after it hits the Y home/limit switch it move back just off the switch. It then moves the X until the home/limit switch is hit and move back just off the switch.
It will zero the DROs then is you have that selected in home/limits menu. This works the same for a floating head switch you tell Mach to Z home (G28.1 Z0.02 g-code) when the torch touches the metal and trips the switch it Z zeros the Z DRO and back off the switch. If you have a feather touch it is wired to another pin and entered to the Probe input it uses the G31 command for G-code.

switch wiring AB.jpg

inputs.JPG

Thanks again for taking the time to comment here. I really appreciate all your help. Your wiring diagram is very interesting. Presently I have home switches hooked up but they are all separately going to the table I/O card in the blade runner as the manual instructs you to do. So my next plan was to mount and wire the limit switches all in series with each other like your diagram shows. I did ask a guy at CandCNC what he thought about the idea of using the same switches to do both functions, i.e. home and limit and he discouraged that idea. My thought was I could use the same switches on the common and the NC posts for the for the limit switch contacts and the common and the NO for the home switch contacts. Luke I believe it was advised me not to do it that way if I feel the need to use physical limit switches that they should be separate switches and in locations where there are both a limit switch and a home switch make them to where the mechanical stop would first actuate the home switch and it the motion were to pass by it then it would hit the limit switch to stop the machine before it hits the hard stops. So I figured that made good sense and after all they are the experts and I'm the hobbyist here so I better head there advise. It seemed like sound advice from a practical standpoint anyway after he explained it and I gave it some more thought. It just requires a couple more switches and a little more wiring than I was originally counting on. The good new is I do already have the extra parts and wire anyway so no big deal. Hopefully I made clear enough sense in all this that you were able to understand what I was trying to describe to you.
BTW I do have the floating h ead and I did purchase the feather touch but I have not even begun to install it or even read up on it until I get through the instructions in the main Bladerunner manual first. That is the approach they recommended in the manual so that Is what I plan on doing as I sure don't know what I'm doing otherwise.

[steel 35]

I made it past the dilemma your going through! To make it easier I basically tore the top half off your Attached diagram, and only did the Home switches but I don't see the Slaved motor switch on your Diagram you need if using one; On mine (A) Home switch and yes by now you have read don't need the Limits; You can't hurt the motors! I may have tested it once. Hit A Estop and it stops just as fast.
Good luck and Enjoy soon.

[acourtjester]

its the old horse and water deal.
Its your table mine works great built 5 tables the same way.

have fun
Tom