Messages

241

General Mach Discussion / Re: Huge Threading Problem Help

« on: October 23, 2010, 11:58:21 PM »

Thanks. Yeah over the years I've done some crazy stuff with my lathe, but it all works out in the end.

BTW Giants GOING TO THE WORLD SERIES>>>>>> SAWEEET...I'm in SF if you didn't know.

242

General Mach Discussion / Re: Huge Threading Problem Help

« on: October 23, 2010, 07:31:50 PM »

OK great, now I just have to setup my motor plate so I can pulleys. Thanks a lot.

243

General Mach Discussion / Re: Huge Threading Problem Help

« on: October 23, 2010, 07:28:45 PM »

turning diameter, may be small but I've made some very complex precision parts over the years.

244

General Mach Discussion / Re: Huge Threading Problem Help

« on: October 23, 2010, 07:26:03 PM »

OK, so I know there is an exact stop and CV mode in general settings, but are you saying I should change it in Gcode?

245

General Mach Discussion / Re: Huge Threading Problem Help

« on: October 23, 2010, 07:20:00 PM »

OK, I upgraded to the 3.042.040 version and everything is the same. I already had Spindle Speed Averaging on.

So the only thing I need to know do I keep exact stop on while doing regular lathe stuff?

246

General Mach Discussion / Re: Huge Threading Problem Help

« on: October 23, 2010, 06:56:40 PM »

Where do I enable spindle speed averaging?

247

General Mach Discussion / Re: Huge Threading Problem Help

« on: October 23, 2010, 06:53:32 PM »

Thanks a lot for the help!!!

I'll look at the program and pages you scanned now.

@Hood, I went ahead and threaded at 200 RPM 16 TPI with 8 passes and it came out fine, thanks. The only thing is the last 2 or 3 passes vibrated the machine a ton. I guess it could be one of two things, either my bit is not exactly on center or that's when it's topping the thread. I persisted and reran the program and it did fine. Still a tiny bit of vibration at the end of the run, mind you I do 6 spring passes to clean it up so it's probably just rubbing.

Two important questions, will upgrading to the newer Mach mess up any settings, macros or VB buttons I run? Also what will exact stop do for regular lathe work when not threading, do I keep exact stop on all the time? Thanks again.

248

General Mach Discussion / Re: Huge Threading Problem Help

« on: October 23, 2010, 05:57:28 PM »

Thanks Hood.

I use carbide insert tooling and have both full profile and partial profile bits, but when doing 16 or 32 I tend to use the full profile.

WOW that's very few passes, I'll go try it and see what I come up with.

249

General Mach Discussion / Re: Huge Threading Problem Help

« on: October 23, 2010, 05:39:20 PM »

@Ray, I used a different pulley and was able to thread at 200 RPM and I only lost 1 RPM, pretty good.

@Hood, what I ended up doing was ordering an actual Adjustable Motor Base which will allow me to easily change pulleys and belts without too much of a hassle. So by the time I'm dong i should be able to switch them out pretty easy without having to sacrifice when threading.

What I'm threading is some Sch.80 304 Stainless Pipe to 16 TPI. What does everyone suggest as a good cut depth for this material running at 200 RPM. I've tried .002 and .003 cut depth per pass, as you know that's total. So from 4" next cut would be 3.997" and so on. The only reason I'm asking is toward the end of the run, the last 7 or so passes it starts to get crunchy sounding and leaves little burrs. Then I have to rerun the cycle to clean it up. So I'm wondering if that's a factor of TOO little cut depth so it's scrapping instead of shearing? or too fast or little speed? Suggestions?

250

General Mach Discussion / Re: Huge Threading Problem Help

« on: October 23, 2010, 03:06:30 PM »

Rich, thanks for the help.
Using Version 3.042.020
Using CV
can't really tell about how much RPM loss but looks like about 30 RPM
Using VFD
Single Index
Don't know what spindle speed averaging checked is, can guess what it is but don't know where to find that option or if it should be used.

As far as the taper. Let's say I'm making .002 depth of cut per pass so it doesn't bog down the motor, I think Mach may set it's own depth of cut anyway even though this is what I have it set for in the threading wizards setting page, because it doesn't take that long to thread as it sounds with a .002" depth of cut per pass. Anyway, let's say I'm making 16 TPI threads on 4" stock. First pass will be 3.996", next pass will be 3.992, then 3.988, by this time (with the old motor) it will start to loose RPMs and instead of the next pass being at a depth of 3.984", it will start at 3.984" and go down to something like 3.9645" tapering down the run and continue if I let it. I can't really tell what the exact end depth is on X as I'm just looking at the DRO on Mach and it's moving counting down as it moves. The beginning of the thread is larger in diameter and the back end is smaller. It happens after it makes a normal pass where it starts to loose RPMs, then the next pass is tapered and it continues.

@ Himy, I can't go slower even geared down motor with a VFD if I go to 100 RPM the motor will be very weak. I assume Himy, that you have a CNC lathe that you can actually gear down to 100 RPM? I usually don't have a problem at 500-700 RPM. I was trying 1000 RPM because my motor lowered to 500 RPM was losing RPMS during threading, but last night I changed to my 2 HP motor with gearing so the highest RPM I can get is 742 rpm, so that will give me full HP at that RPM.

@ Hood, thanks also, I'll try lower speed with the motor, with the old motor back in, if it continues to work I'll put a different pulley on it to make it's top speed 350 RPM or so.