"Chinese" spindle minimum speed

[Hirudin]

I've been wanting to buy one of those Chinese spindles for quite some time now. I'd like to use one to replace the spindle on my Taig.

One thing that is holding me back is I'm unsure of the minimum speed I can make the spindle spin. The auction descriptions usually say 6000 or 8000 up to 24000. Since the VFDs can output 3 phase power between 0 and 400 Hz I know 400 Hz = 24,000 RPM. I am guessing 100Hz = 6000 RPM. What happens at frequencies lower than 100 Hz?

Through reading the VFD thread it looks like the VFD's default frequency is 50Hz. People who have run their air-cooled spindles at that frequency have burned them up as the cooling fan doesn't come on until 100Hz or greater. Is there anything stopping the water cooled spindles from working at 50 Hz?

If 6000 RPM is the minimum speed does that mean these spindles are mostly unsuitable for drilling? If fly cutting also out of the question? How about milling steel or using larger end mills?

Thanks!

[ger21]

Typically, spindles for woodworking are not designed for heavy axial loads, like drilling. You shouldn't have trouble with large diameter tools, but cutting steel may put more force on the bearings than they are designed for. I have no experience with the chinese spindles, but these are recommendations for more expensive spindles, like HSD's and Columbo's. They recommend not even plunging into wood, but ramping into the cut.

I think you may find that at slower rpm's, the spindles have much less power. I don't think it'll hurt the water cooled ones to run them slower, as long as it has enough power to do the job. I know it's not quite the same, but I've used a 6" diameter raised panel cutterhead on an HSD 10HP (22K rpm, electric fan cooled) spindle at around 7K rpm.

Just realized that you want to run at 3K rpm? Not sure about that at all. ???

This .pdf might give you some info, although it's for Columbo spindles.
http://pdscolombo.com/pdf/PDS%20Spindle%20Care%2007.pdf

[Hirudin]

Oh no... I was hoping someone would come here and say "I run mine all the time at 1000 RPM without any trouble". Instead I find out that maybe it isn't a good idea to plunge straight down? My CAM program (RhinoCAM) will ramp in for the first contact with the material, but as far as I've seen, every subsequent drop in Z is straight down.

Off topic for a second...
ger21, you created the "Aqua" screen for Mach3 right? I haven't actually used it yet, but it looks very nice and well thought out. Thanks a million for sharing it!

[ger21]

Originally Posted by Hirudin Instead I find out that maybe it isn't a good idea to plunge straight down?

Depending on the tooling you're using and what you're cutting,as well as feedrate, plunging forces can vary considerably. When we first got our machine at work 10 years ago, we always just plunged straight down, as we didn't know any better. We plunged fast, too, with probably a few hundred pounds of force. Never did any damage. What we did see, was a lot of burning at the tool tip and a lot of tool wear from it.


And yes, I did the Aqua screen. I think it's pretty cool, too. Hope you like it. Thanks.

[rognets]

I recently found your (Ger21) Aqua screen and find it great to use..

I am just setting up a 2.2 Kw spindle with Mach3. As you probably would know the VFD unit has a frequency and current output via serial communications back to the DRO's. Using the Huanyang VFD plugin.

How would I display these on the Aqua screen?


Thanks Steve

[ger21]

Honestly, I have no idea, as I don't have one.

A guess would say they are sending data to UserDRO's, which you'd need to add to the screen using a screen designer. The plugin creator should be able to give you more info on how to do it.

[isakl]

Hi Hirudin,
Sorry for the late response.
I've just received my new 2.2KW water cooled spindle.
Before purchasing I had exactly the same dilemma, as many times when machining steel, or even aluminum with large diameter HSS tools you need rather low RPM.
Now I have this spindle, and a Hitachi X200 inverter.
The very first tests that I did was seeing at what lowest RPM I can run it.
To my amazement, it was no problem at all running even it as low as 200RPM.
At first it had very little torque at this speed. After playing with some parameters of the inverter, I managed to throw the full 10Amps while turning 200RPM.
Of coarse it will start to heat up rather quickly, but this is the advantage of water cooling. If you have sufficient pump and radiator, there is no problem.
I have about 1 liter water reservoir, and a small radiator with a fan.
I can run it at 200RPM, 10Amps for more than half an hour. It becomes pretty warm to touch, and the reservoir temperature climbs to about 45 centigrade, but that's the hottest it gets. I can continue to run it, and it won't get any hotter. I think that putting a bigger radiator would reduce the temperature even further.

I tried to mill steel (low carbon) with 3/8 carbide endmill, 0.1mm DOC at 800RPM. It ate it without any difficulty.
Aluminum is even better.

[Hirudin]

Wow! That's great. Thanks for the response isakl, I really appreciate it.

[stk2008]

Hey why not get the spindle then run it via a gearbox that way ya have the gearing doing the low RPM stuff and less loss in torque.

All so this way you wont be putting any load on the spindle bearing.

There was a link some where to a gear box that came with an ER collet set up......

[isakl]

I think that's the whole Idea of an "integrated spindle", that is that you don't need a spindle and a motor. If you add a gearbox, you effectively use the spindle as a motor, and then the gearbox acts as a spindle.
I don't think that driving the spindle at low RPM will put extra load on the bearings. As I see it, the axial force on the spindle is a function of the chip load (but i might be wrong).
It will cause it to produce more heat, so you'll need a decent radiator, and it probably won't work with air cooled spindles.
Also make sure that your inverter have this "torque boost" feature (and that it is working).

[jeffrey001]

Originally Posted by isakl The very first tests that I did was seeing at what lowest RPM I can run it. To my amazement, it was no problem at all running even it as low as 200RPM. At first it had very little torque at this speed. After playing with some parameters of the inverter, I managed to throw the full 10Amps while turning 200RPM.

Hi, would it be possible to post what parameters you have changed to the VFD.

Thanks, Jeff

[isakl]

Hi,
It took some time, I was busy on writing a program to connect to the VFD via the rs485.
Eventually I would like to control the VFD via the emc2 program.

Here are some of my parameters (i hope i don't miss some of the important ones)

A003: 400
A004: 400
A041: 0
A042: 8.5 (Manual torque boost value)
A043: 1.5 (Manual torque boost frequency adjustment)
A044: 0
A045: 100
A061: 0
A062: 0
A085: 1 (Operation mode selection), not sure if that's necessary.
A086: 70 not sure if that's necessary.
B082: 5
B083: 3.0
B086: 60.0
B092: 2
C149: 100.0 (relay turn off delay) Used for coolant pump activation.
H003: 7 (2.2KW motor)
H004: 2 (poles)