Messages

71

General Mach Discussion / Re: Taig Mill Questions

« on: February 28, 2018, 01:10:40 PM »

The only way a bigger motor would actually run slower is if it has a much higher inductance than the smaller motor.  The bigger motor will have more torque at the higher speeds unless the the inductance causes it to fall off very fast.  My 860 in/oz steppers turn 1500 rpm reliably without missing steps. They are low inductance and I have a 68 volt power supply.

72

General Mach Discussion / Re: 3rd Machine Control Revamp!!!I'm Stumped!!! Please Help!!!

« on: February 27, 2018, 06:54:24 PM »

Jug,
Some paragraphs would be nice. Streams of thought are very difficult to follow except when they are in my own head.

73

General Mach Discussion / Re: Taig Mill Questions

« on: February 27, 2018, 06:50:01 PM »

If your 48vdc power supply is a switcher, they have very high inrush current on startup, so a slow blow fuse would be appropriate to fix that problem.

74

Third party software and hardware support forums. / Re: z axis stepping inaccurately

« on: February 26, 2018, 10:29:53 AM »

I would try something else first before motor tuning. Use the rapid rate override slider and slow down the rapid rate only. Rapids at full speed are when motor torque falls way off and steps can get missed. As you lower the rapid rate the motor torque increases and that may solve your problem. My machine never misses steps, but the other day it did while cutting stainless. Part shape was perfect but location was wrong. I finally realized that I was using the slow speed spindle with a large motor that is much heavier so it missed some steps during a rapid to a new location.

75

General Mach Discussion / Re: Spindle orientation on a Bridgeport...

« on: February 21, 2018, 08:52:17 PM »

Another thought about this issue. Things like this work much better when they are designed to be extremely tolerant of misalignment rather than being very accurately made.  So I htink a better approach here is to have the tool gripper mounted to be spring loaded upward.  You press it against the spindle and if the dogs are not lined up the compressing of the spring triggers a limit switch that causes the spindle to rotate until the dogs drop into the slot and the limit switch then indicates that the alignment has been achieved, fasten the tool and  retract the gripper.  No spindle switch needed.

76

General Mach Discussion / Re: Spindle orientation on a Bridgeport...

« on: February 21, 2018, 05:11:52 PM »

I don’t think this problem is a big as you think with sensorless vector VFD, I once built a pump with that kind of VFD and it ran reliably down to 18 rpm with a load, or 1/100 of base speed. My machines also had to stop and line up with rails that plugged in. Taper your drive dogs as much as you can too, so you don’t need to be perfect. Run the motor at the lowest possible speed and tell it to stop on the sensor. Worse that will happen is that it will overshoot a bit. As long as the overshoot is reliably consistent you can adjust sensor position to accomodate.

77

Building or Buying a Wood routing table.. Beginnners guide.. / Re: Motor Sound and Motor Temperature

« on: February 21, 2018, 04:58:12 PM »

My motors are 980 in/oz nema 34 size and also low inductance. However steppers are constant power motors, they use the same amount of power whether loaded or not. So I wonder if the low inductance means less of the energy lost as heat.

78

General Mach Discussion / Re: MDI stops working - cannot enter input

« on: February 20, 2018, 09:06:57 PM »

A warning here.  Using the shift key to get high speed jog can be deadly!  Mach 3 has a known bug where the axis you are jogging just takes off and goes and nothing will stop it.  Scared the heck out my grandson when I was trying to teach him to run the machine and it ran away breaking off a tool!  This bug has been discussed and reported by others.  It happens on machines using the parallel port, on the motion board I have and also with the smoothstepper.  It has happened to me often enough I don't use the shift jog funvtion anymore.  The only reason it has not damaged my machine is because being the trusting person that I am NOT, my limit switches kill all power to drives directly, not through software.  I can home by holding in the reset button until the homing finishes.

79

Building or Buying a Wood routing table.. Beginnners guide.. / Re: Motor Sound and Motor Temperature

« on: February 20, 2018, 08:57:17 PM »

I am always surprised about reports of motors running hot.  My steppers barely get warm and they are running from a 68 volt power supply.  However I have Leadshine digital drivers so maybe they do a better job of controlling the motor current.  I do have them set for half current when idle but sometimes a program runs continuously for several hours and the motors never get at all hot.

80

General Mach Discussion / Re: Mach3 slowing around corners

« on: February 16, 2018, 12:58:05 PM »

What causes this is the acceleration rate your machine is capable of which you indicated to Mach 3 with motor tuning. To avoid losing steps or position Mach has to keep the acceleration and decelleration below the value you indicated. So machines with big motors capable of high accelerations corner much faster, but every single one slows down on sharper curves unless the feed speed you selected needs an acceleration less than the motor can do.