[er-mtl]

Hi,

I just bought a recent second hand CNC that came with a MT1090-100-ER32 HSD spindle.
It really makes a very loud noise and I wonder if someone uses a similar spindle
and if that noise level is normal or not.

It's difficult to describe noise, but it sounds like a bunch of screaming shopvacs.
It's by far the noisiest tool I have and people from other shops in the building have
been asking questions. it's annoying even with earmuffs.
I tested it without the coaxial fan, and it makes very little noise (quite similar to
a water cooled spindle), there are no abnormal bearing noises.
I also noticed the coaxial fan was quite wobbly, contacted HSD USA, and they
sent me a new one. However, it was just as wobbly, and just as noisy.

HSD offered to inspect it, but i have to ship it to the US and back (I'm in Canada),
so before I do that, I'd like to know what you think ...

Thanks

[ger21]

It's probably the cooling fan. They can be very loud on spindles with shaft driven fans. I've heard a Teknomotor spindle with a shaft driven fan, and it was very loud as well.

[er-mtl]

Yes, it's the cooling fan. I also have a smaller, 2.2Kw Chinese shaft driven fan spindle GDZ80-2.2, and the noise is much lower.
I expected a real HSD spindle to be a nice upgrade, quite disappointed with what looks like a not so good design.

Is anyone using a similar spindle and how loud is it ?

[ger21]

I expected a real HSD spindle to be a nice upgrade, quite disappointed with what looks like a not so good design.

I suspect that the HSD moves considerably more air than the quieter chinese version.
The tradeoff for more noise is a cooler running spindle, that should last much longer.
I too have a chinese air cooled spindle, and it's very quiet. But it moves very little air.

One option would be to pull the shaft driven fan, and mount an electric fan to the top of the spindle. Should be a lot quieter.

I've used some large HSD spindles in the past, with electric cooling fans, and they were quite loud as well. But it was a more tolerable noise than the screaming that you are probably hearing. There's no real good way to move a lot of air through a spindle quietly.

[er-mtl]

as you say, it's moving a lot of air. I'm going to try using an electric fan. From what I've seen, a 3A 12V 120mm server fan should do the trick.

I've designed a shroud that convert from the spindle top part to a standard fan, I have to print it and check if it does a powerful enough cooling ...

Attachment 408276

[adam_m]

as you say, it's moving a lot of air. I'm going to try using an electric fan. From what I've seen, a 3A 12V 120mm server fan should do the trick.

I've designed a shroud that convert from the spindle top part to a standard fan, I have to print it and check if it does a powerful enough cooling ...

Attachment 408276

I was thinking of doing the same and would be interested in the outcome of your experiment and your drawing if your sharing after its success.

From what I can tell there is very little air movement form the built in impeller for cooling.

So is it more effective to draw air from the bottom to the top or vice versa?

Adam,

[ger21]

From what I can tell there is very little air movement form the built in impeller for cooling.

Chinese spindles typically don't move nearly as much air through them as an HSD like the OP has.

Air should always blow from the top, and exhaust out the bottom, to keep chips and dust from being sucked into the cooling passages.

[er-mtl]

So, I made one and tested it.

Results are a mixed bag. I printed it (PETG, first try with ABS warped badly) It works, the shape increases the pressure, but the air flow is much lower than with the shaft fan. As a result, temperature gets much higher even in steady state, so when doing hard cuts, it will shorten the bearings life.

my spindle is rated 4.5Kw / 5.4Kw S6, and it's about the same size as a regular 2.2Kw. HSD also makes an electric fan cooled version, and it's limited to 2.5Kw. it looks like the very high noise is the tradeoff to get such high power from such a small / lightweight spindle.

So, despite the ugly noise, I went back to the default fan for now.

However, my fan is a Scythe computer case fan that only draws 0.6A 12V, I will try again with a 1.6A fan, but I don't expect a miracle. the 3.3Amps fans sold for bitcoin miners have flat blades and already incorporate counter blades (same as my shroud). as a result, they move a lot of air, but the pressure is low, so that's not good (and they would not work well with my shroud).

If the airflow is decent with the 1.6A fan, I will slightly lower the spindle voltage and make it dynamic in the VFD. that way, the spindle will be useable as a lower power unit, still retaining the ability to get short power bursts. It would be like a 2.2Kw continuous with 5.4Kw S6 ...


Attachment 408740

I also include the FreeCad model (a bit messy, but it works).

http://dox.mailpeers.net/HSDFan.FCStd

[ger21]

HSD electric fans are not exactly quiet either.

[er-mtl]

Then maybe water cooling is a slightly more complicated but superior solution.

I'm now thinking about selling the HSD and it's VFD to get a water cooled Chinese ATC like this one. it's about the same power, but 24000 RPM with a lower torque. What do you think ?

[skrubol]

Hard to answer those questions for you. Is ATC important to you? How much important is it that it's quiet?

As far as using an electric fan, some fans do give a pressure rating, may be that it is as important as the flow rating. Also, the stator fins in your shroud look awful aggressive to me. Probably doesn't matter much, but how did you design them (I'm not an expert in aeronautics so they may be ideal, just don't look right to me.)