Aluminum

See here

and here

Geez, Igor, you really need to start surfing the wiki! It is ALL in there. See

down a couple pages, there is all sorts of great stuff that has been posted. Specifically, what you are looking for is this one uses a DAC to control a VFD, but I know somebody has set up code to control the varispeed drive. Basically, you compare measured speed with commanded speed, and if the speed is too high, operate the lower valve, if too low, operate the raise valve, if within some tolerance, do nothing.

Jon

You're all set then. That start hi ,start lo, is a good idea as you should only range shift right when the motor begins to turn. If you could get tricky and have the motor just barely turn during range shift your machine would last longer. Unless you like ground up gears

Karl

I just turn the spindle by hand. I could add jog also.

i

You could use another EMC2 output to control the speed select input on your VFD, to allow EMC2 to select an alternate frequency set to something really slow like 10Hz on the VFD then actuate the high/low gear change signal to allow a gentle gear change. I know your VFD supports a couple speed select inputs to select from several frequencies preprogrammed in the VFDs memory.

Typically one lets the modual provide a 0-10volt analog signal and uses the RS485 port simply for programming or for remote monitoring. The chances of the port going bad is slim, but the distance between the puter and the port can be an issue along with a host of other issues, such as lightning in the neighborhood and so forth. Relays, which are historically reliable are used to control Run Forwards/Stop/Run Reverse.

A typical command of M03S2500 causes the module to output a 6 volt signal AND close the M03 relay, (for example) which is a double safety feature and one that can be controlled locally...and overridden at the VFD. Which is not always the case when controlling via a RS232 or 485 port. Worst come to worst..one opens the drive cab door and pulls out the M03 relay. Or kills the power..which often will crash the machine and bust the tooling and other Stuff.

RS485 is ok...when controlling remote fans in a large building..but for local "hands on" machines....cringe...

Gunner

"A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9

I tend to agree with Karl..you could very easily let the VFD control the speed rather than the vari drive.

HOWEVER...when going below or above the base freq..you start losing power transmitted to the tool. That vari-drive does a very good job of maintaining proper torque at the tool. But on the other hand..I doubt if you would notice the power difference in anything smaller than a 7/8" shank took with heavy cuts.

On the gripping hand..if the vari-drive Stuff does go bad..you can simply lock the drive in the center of its travel and use the VFD to control speed. Thats what VFDs were designed for.

Gunner

"A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9

I never suggested using serial control for spindle start/stop, only for VFD frequency / speed setting.

True indeed. But when one starts the serial control issue...its a quick fast work around that some people select. Iggy may never have an issue with it. Seriously. Stuff has gotten far more reliable over the years.

But if an issue DOES come up...that certainly limits ones choices of stopping things. And on some VFDs..there is no "emergency stop" input..so one has to be very careful about what sorts of VFDs to use.

Ive seen a few VFDs that once Serial was selected as communications mode...local controls were simply...turned off.

Which may not be a good thing if something turns to poo.

Gunner

"A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9

Yes, I could do it, it would be a jog function.

i

Using vari-drive is far preferable to using VFD for speed control. VFD is a very cheap and poor way to control speed.

i

Yes and no. VFD costs you up to 15% of actual motor hp rating when far below or far above rated RPM. Which is why many devices use a vfd and motor thats a hp or two above actual needed ratings, because they may be run at low hertz. Or high hertz.

Its a very good way to control speed when the machine you just built or modded doesnt have a reeves drive. And its one of the best ways for rapid or varied speed changes during run-time.

They work very well, with few issues.

A perfect example is my Gorton J-22 Mastermill. Its a step pully mill with a 3hp motor running the spindle. My 5hp VFD will run it from about

10 RPM to over 10,000 (spindle is rated for 5k)

Its also running from Single Phase elec. and powering a 3ph motor.

With no issues after 5 yrs of operation, plus instant breaking and instant reverse makes tapping easy and of no issue.

Gunner

"A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9

Yep, and pretty much none of the commercial CNC machines of any remotely recent vintage use any sort of variable pitch drive. At most they have a high/low gear range and the rest of the speed control is done with the spindle servo.

I just wonder; the older designers didn't have or know about VFDs. So those motors are not "inverter duty". I'm always a little worried about the insulation resistance of the older motors. It would be a mother- bitch to retro-fit a series I with a newer motor.

On my R2E4, I simply use the VFD to drive the motor at its rated speed, and to reverse and brake it, by routing the spindle contactor excitation controls to the VFD (with some conditioning).

I let the vari-speed drive do the rest of the work. I have not yet EMCd my machine, so the spindle speed is not CNC-controlled.

It was a simple, quick mod that permits the machine to run from single- phase with no problems.

LLoyd

All I have heard suggests that any 440v rated motor is probably safe for a VFD.

People use VFDs and massively oversized motors these days, because it is cheaper than varidrives and maybe easier to maintain. But it is not necessarily better. Since I already have a varidrive, I should use it.

This way I could tap 1/2" holes at low speed, etc.

i

I think people make a bit too big a deal over the "inverter duty" rating. While there may be some insulation differences, I think the bulk of it really relates to the ability to drive above the normal 60Hz without blowing up the motor. I've been running my old 1J Bridgeport on a VFD for quite a while now with no issues, and I routinely operate

*below* 60Hz, but I do not operate *above* 60Hz.

Ayup..since the late 70s at the least.

Gunner

"A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9

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Well ... the Bridgeport BOSS-3 lathes had (in some cases, but not in mine) a pneumatic motor cranking the variable speed dial -- but as far as I know, it just went N turns from a full stop at one end of travel. (Only a LSI-11 CPU, with only 64K of RAM, so not much smart that it could do.

If you had fixed pulleys, it would be easy to have the computer output an analog voltage to the VFD to command a specific speed. You would need a spare axis to output the proper command voltage to the VFD.

If you told it that you would always have your variable speed pulleys set to a specific speed, it could do a pretty good job of selecting a speed.

But -- it would have no way of telling if you had reset the variable speed pulleys, in which case the mapping of voltage to speed would be all wrong -- unless you could use the projected encoder to provide speed feedback. Note that if you had that, and the variable speed pulleys were cranked to a low speed position, you would have problems if you needed a high speed -- perhaps running the VFD to a frequency which could damage the motor. (What is the nameplate RPM of the motor? If 1800 RPM or a bit less, you could push things to 120 Hz safely enough. if near 3600 RPM -- that would risk running the motor so fast that the rotor would self-disassemble.

Perhaps the best would be to have a combination of the VFD speed control and pneumatic or other motors to change the variable speed pulley. This way, if you needed a very low speed, it could crank down to the lowest pulley speed, and then run the VFD down to complete the speed setting.

Hmm ... ideally, you would want a switch to tell the CNC when the back gear was engaged -- for two reasons:

1) This would affect the speeds which you could reasonable achieve, and it would be nice of the computer could prompt you to switch the back gear in or out. 2) You also need the computer to know whether the back gear is engaged because it makes the spindle run backwards -- and you need to have the CNC know this to command reverse when you want forward or vice versa.

Enjoy, DoN.