Messages

261

General Mach Discussion / Re: Backlash...

« on: November 01, 2016, 10:20:27 AM »

I have an interesting experiment for you to try. I'll bet your Z axis is no problem with backlash, because it is gravity preloaded againt the screw and bearings in one direction. So try the same thing on the X&Y. Get a gas spring with a force greater than the cutter thrust and preload the axis in one direction. An initial experiment could be done with enough bungee cords to provide the force required and tie the ends to the wall, another piece of immovable equipment.
I bring this up because I once owned a Spindle Wizard knee mill conversion that had double nuts with bellville spring washers loading a second nut against the first so it stated against one side of the screw. That machine was not fast, 20 ipm cutting speeds, but would hold tenths with no problem, and round holes were like they were were bored!

262

General Mach Discussion / Re: Mach 3 Lathe questions

« on: October 12, 2016, 08:37:01 PM »

Rich,
I have a large stepper driven by a 68 volt supply and a 3.6:1 timing belt reduction, and I get 1000 rpm at the spindle using 32 microsteps with no problem. It is likely not as good as a vfd or servo drive, but it will allow me to turn and machine a part without refixturing it.  I can turn a part now as long as I simply program enough turns to match the X travel, but then it unwinds to get back to zero.

263

General Mach Discussion / Mach 3 Lathe questions

« on: October 11, 2016, 07:10:07 PM »

In Mach 3 Mill I can't find a way to drive a stepper motor as a spindle using a Xulifeng 4 axis motion card.  I can't program the fourth axis that way.  I was wondering if Mach 3 Lathe can operate a stepper motor driven spindle using this card. I'd have to be able to set up the spindle as an axis drive I believe.  The reason for doing this is I have a stepper driven 7x12 lathe that I use as a fourth axis just fine.  However I would also like to run it as a spindle with the toolpost mounted to the mill head.  That part is done, I can spin it a hundred turns, position but I just can't make it turn continuously.

Can Mach 4 do this?

Thanks,

264

General Mach Discussion / Re: G41 G42 Automatic tool diameter measurement and input?

« on: September 26, 2016, 07:32:39 PM »

Unless the tool bit is a router bit with no spiral you or your fork is very wide you are likely to get different results on either side. Also one of the reasons for using diameter comp is to correct for tool runout and even deflection. Then there are 3 flute tools that you can't measure with a micrometer. So now you in the realm of non-contact measurements made with say a profile measurement laser and selecting the max measurement at the proper location along the length of a tool. So it gets difficult faster than it gets easy!

265

General Mach Discussion / Re: Cutting smaller

« on: September 22, 2016, 06:20:13 PM »

Tool diameter set correctly?  Is the tool not the size you think?

266

Building or Buying a Wood routing table.. Beginnners guide.. / Re: Problem with upgrade nema 23 to nema 34

« on: September 21, 2016, 05:44:41 PM »

You don't mention the inductance rating for the Nema 34 vs the Nema 23. If the Nema 34 are high inductance compared to the 23s the torque will fall off faster. I drive low inductance Nema 34 with 68 volts and get over 1500 rpm with no problems.

267

General Mach Discussion / Re: Help needed v carve to mach3

« on: September 17, 2016, 06:38:55 PM »

The answer is right in the g-code. Is the code it producing the same size as the part you drew? Have you put a tool diameter in v-carve and are you cutting inside or outside of a profile?

268

General Mach Discussion / Re: AIRCRAFT PROPELLER

« on: September 17, 2016, 06:34:50 PM »

An aircraft propeller is about as complex a curve as you can get since it has an airfoil cross section combined with twist to  to change the angle of attack for the velocity change from the center to the tip. So unless you have a program that parametricly generates the shape this is a really tough part to do even in high end cad and cam programs.

269

General Mach Discussion / Re: Offsets :)

« on: September 15, 2016, 06:50:45 PM »

It's all relative!

270

General Mach Discussion / Re: Code wrong?? Broken tool :(

« on: September 09, 2016, 02:22:40 PM »

On other CNCs the H word called tool length offset, not to T word. I see an H word after the XY moves. Just grasping here.