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Author Topic: Spindle speed increaser for engraving...  (Read 9097 times)

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Spindle speed increaser for engraving...
« on: December 16, 2009, 06:43:59 AM »
After searching for a reasonably priced speed increaser (not to be found), I found this: http://www.hemingwaykits.com/acatalog/Speed_Increaser.html

I ordered the kit which is full and well documented with everything needed to make the spindle speed increaser. I did modify this one for a more robust geartrain - I added two more planet gears for a total of three (could even get four in there...). You also could change the gear ratio for more increase since .5 module gears are quite common.

This might strike a fancy for some like it did for me. It makes the engravers much more efficient at higher speeds. My spindle top speed is about 2600 so is now three times that.

Thanks.
Bill C.

Hemmingway Kits has some other interesting items too!

Online Tweakie.CNC

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Re: Spindle speed increaser for engraving...
« Reply #1 on: December 16, 2009, 09:46:52 AM »
Thanks for posting the link Bill that is an interesting little tool.
How deep is it, or should I say how much Z Axis does it take up please ?.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

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Re: Spindle speed increaser for engraving...
« Reply #2 on: December 16, 2009, 10:45:37 AM »
You have got me thinking about this now.

Early radio sets used a ‘slo mo’ drive on the tuning knob using the differential between two circumferential tracks bridged by ball bearings.

Standard ball bearing races are designed to have a differential circumference ratio between the inner and outer tracks of around 2.6 to 1 therefore by holding the outer ring and driving a modified cage, the inner ring would rotate at 2.6 times the driving speed.

I don’t know the driving torque requirements yet but the cutter loading for engraving tools is extremely small (never stalled one yet).

This may achieve similar results to the proprietary item but without gears.

More thought is needed, but I might just build one to see the result (after I have completed all the other outstanding projects of course).

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

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Re: Spindle speed increaser for engraving...
« Reply #3 on: December 16, 2009, 10:57:59 AM »
Interesting gadget. I do engraving at 18,000 to 60,000 rpm.  9000 seems slow but is surely better than 2600.
RICH
Re: Spindle speed increaser for engraving...
« Reply #4 on: December 16, 2009, 02:14:55 PM »
Thanks for posting the link Bill that is an interesting little tool.
How deep is it, or should I say how much Z Axis does it take up please ?.

Tweakie.


Tweakie

The total Z height of the increaser is 2.421 (61.5 mm) less a cutter and arbor. This one has an R-8 arbor for 3/8 shanks but shortened for dedicated use with this tool.

60,000 rpm! That must sound like a dental drill, yikes! But yes, great for engraving.

Bill C.

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Re: Spindle speed increaser for engraving...
« Reply #5 on: December 16, 2009, 05:22:19 PM »
Bill,
It's an air driven small die grinder and yes it makes plenty of noise. But i have never broken any of the small end mills
with it. The small ones like 0.020" are not cheap!
RICH
Re: Spindle speed increaser for engraving...
« Reply #6 on: December 16, 2009, 06:02:32 PM »
Rich,

Do you use the 'D' bit type? I have some that are tapered from 1/4" to a point - (guessing) close to .020 and carbide is so darned brittle. I've found that 2600rpm is so much too slow that the feed must be ridiculously slow to keep from breaking the tip of the tool off. That's a job that at spindle speed and feeds such as they need to be, ya walk away from pretty quick....boring! The smallest E.M. that I have is 1/32" and it's been perfectly safe because of this slow spindle speed. Somehow I wound up with a very slow three phase motor for this mill's VFD, so stepping it up with the belt steps still makes a very slow spindle...

Thanks,
Bill C.

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Re: Spindle speed increaser for engraving...
« Reply #7 on: December 16, 2009, 11:35:12 PM »
Bill,
The small end mills break in a heart beat especialy if you have any backlash. They are just plain end mills and most are HSS. I made adapter plates off the bottom of the quill and can mount a small high die grinder or drill from it. Don't use it much  because i buit a small engraving machine.
RICH
Re: Spindle speed increaser for engraving...
« Reply #8 on: December 17, 2009, 05:19:40 AM »
You have got me thinking about this now.

Early radio sets used a ‘slo mo’ drive on the tuning knob using the differential between two circumferential tracks bridged by ball bearings.

Standard ball bearing races are designed to have a differential circumference ratio between the inner and outer tracks of around 2.6 to 1 therefore by holding the outer ring and driving a modified cage, the inner ring would rotate at 2.6 times the driving speed.

I don’t know the driving torque requirements yet but the cutter loading for engraving tools is extremely small (never stalled one yet).

This may achieve similar results to the proprietary item but without gears.

More thought is needed, but I might just build one to see the result (after I have completed all the other outstanding projects of course).

Tweakie.


Tweakie,

Yes, you have the idea most correctly. This system holds the planet gears with the input internal gear spinning them at a ratio of 60:20 but since the planets are idlers, the output gear or sun gear is rotating opposite the input at 3:1 ratio. The kit calls for one planet which seemed too light duty so three planets were installed. The spacing was critical and uneven diametrically with spacing of 126 degrees, 126 degrees and 108 degrees. Four planets would be evenly spaced at 90 degrees.

The ball bearings may slip, as you mentioned. But they may work due to the number of them doing the work overcoming a load. A angular contact ball bearing could be preloaded maybe to overcome the slippage.

Bill C.