Novamill - maximum spindle speed?

[JohnHaine]

In the two machine manuals that I have, there is no mention of the maximum spindle speed! Does anyone have this information please?

Thanks, John.

[Steve]

I believe it is 5000RPM (that is what is set in the VR Milling 5 Software.

[JohnHaine]

Thanks Steve. I have a feeling that may be the maximum motor speed, but not sure what the pulley ratio is. When I wind mine up to maximum speed it doesn't "feel" like it's running at 5000, but I don't have a tacho to check it (yet - another project!).

John.

[Denford Admin]

That should be running at 5000 on the spindle, not the motor

[flyingmike]

I measured my max spindle speed at ~5000rpm. I think the motor and spindle pulleys are 1:1 if I remember correctly.

[angel-tech]

5000 is the norm.

[JohnHaine]

OK, thanks everyone, 5000 seems to be the number! I have now measured mine (approximately) and discovered initially it was limited to 3000 but this turned out to be due to a setting of the output voltage pot in my KBWM240 motor controller which was limiting the voltahe to ~100v. Tweaked it up to 180 v (rated output) and my approximate rpm measurement went up to 4800 which is more like it!

[JohnHaine]

I just wanted to resurrect this thread. I'm happily using my Novamill for 4 years odd now, but finding that the maximum spindle speed is a limitation. I'm usually cutting aluminium, sometimes brass, running the spindle flat out. I did a nameplate engraving job over Christmas using a 1mm cutter running at 5000 rpm, and had to limit the feed rate to avoid breaking the cutter, so the job tool about 4 hours for a 30 x 90 mm plate! That was 8 hours total machine minding time...

Really I'd like to at least double the maximum speed, which probably involves a new motor,but I'm wondering what the maximum speed rating of the bearings is as well. Please: (a) could anyone say what the bearing spec is; and (b) does anyomne have any suggestions for motor type? I'm not even sure how large the standard Baldor motor is as I can't find a type number that mateches their catalogue.

Thanks in anticipation!

John.

[Steve]

The bearings fitted will be the limitation on the speed. Without re engineering the head and fitting a matched pair of bearings I dont think you will go any faster.

When engraving I would use say a 2mm ball end cutter and only go 0.1mm deep. This gives a nice finish with a stronger tool and you could probably get away with 600mm / Min in brass.

As you only cut 0.1 deep the line thickness is not too thick. This relies on the work piece being flat.

[JohnHaine]

Hmm... Well I was quite happily running a 1 mm endmill at 5000 rpm and taking 0.5mm cut in brass at a maximum feed rate of ~80 mm/min. I didn't break any cutters in 8 hours odd running. I needed to clear out 1.5 mm of material, and needed a 1mm cutter for the required detail. If I took 0.1mm cuts it would extend the cutting time by 5 except that I could increase the feed rate by say the same factor. But as the tool is happily cutting 0.5 mm out and the recommended speed is at least 10,000 rpm, I'd prefer to increase the speed, though as you say I'd maybe need to look at new bearings - hence my question.

[TomJennings]

Hi,
I replaced the original Sprint Electric 400 card with a new Sprint Electric 340i unit. it has a speed x2 switch.
My spindle can now run quite happily at 12000 rpm for 1/2 an Hour without getting even hot.
I cut P C Boards with a 0.2mm engraving cutter at this speed for 1/2 an hour or more quite often.
Perhaps I'm lucky!

[JohnHaine]

Tom, that's really interesting! That must mean that the drive is doubling the drive voltage at its output - I assume this is on a 230 V mains supply? I think if I could run at double speed it would meet most of my needs.