Spindle design (Speed?)

[Degrom]

Does the speed of the Spindle matter a lot? (I would love to engrave on wood/plastic and aluminum)

Do I really need a spindle that runs at 20K rpm plus

or

can I design a spindle with a shaft that has two sets of bearings and then connects to a 500W drill motor with a pulley that runs at 3000rpm?

If the speed is really an issue will adding a small scale flywheel not remidy the problem? (This will add momentum...)

(I know a Dremel spins at 35k rpm but it's not very strong at only 130W)

Does the speed have an effect on how long the router bits will last?

Any info or opinions are welcome.
Thanks.

[totally_screwed]

Originally Posted by Degrom Does the speed of the Spindle matter a lot? (I would love to engrave on wood/plastic and aluminum) Do I really need a spindle that runs at 20K rpm plus or can I design a spindle with a shaft that has two sets of bearings and then connects to a 500W drill motor with a pulley that runs at 3000rpm? If the speed is really an issue will adding a small scale flywheel not remidy the problem? (This will add momentum...) (I know a Dremel spins at 35k rpm but it's not very strong at only 130W) Does the speed have an effect on how long the router bits will last? Any info or opinions are welcome. Thanks.

I read about this on cnczone today!

I'd like to take the credit for this, but I'd be lying!

This explains the difference between Power and Torque.
Feed rates & etc.

Whether you actually require such a high speed depends upon what you are intending to do. Engraving with small diameter cutters necessitates high RPMs.

If you want your cutters [even Tungsten Carbide or diamond] to last for more than a few seconds or minutes, you really should consider coolant.

I suggest a misting coolant [needs compressor] You could look at the following [there may be others] Noga minicool, Trico DL spray system, Kool Mist or Amflo Mist Coolant Unit. They all look very similar. These will work with water-emulsion coolants.

Using coolants will also enable you to achieve much better finishes with plastics which will otherwise certainly melt and fuse onto your cutter. Cutting dry will result in a clogged cutter and poor finish.

As I understand things, obtaining high speed bearings is not cheap,and using them isn't easy or straightforward either. You are much better off using one of these relatively inexpensive but well-engineered spindles. That's what I am going to do! Oh, btw, those ultra-high speed spindles like I think you were thinking of have an operating life of 1500 hours or so.

Just read it!
Regards and good luck,
totally_screwed

Originally Posted by whelen I wrote up a post "High Speed Spindle for SIEG X2 - Getting Technical", well I found the spindle. Looking for an affordable high speed spindle for your SIEG X1, X2, or X3 - or for any bench milling machine? I've been looking for one for over a year, and finally found one at KDN Tool. I first looked at the NSK Astro-E 250, which sells for over $2,000. I can buy 18 of the KDN Tool high speed spindles for the price of one NSK Astro-E 250. The solutions I found on ebay, the internet, and in the discussions on Yahoo CAD-CAM-EDM-DRO group, DIY-CNC group, hf47158toCNC group, Irk-torquemax group, X-Series-Mills group, and CNCzone came close, but not quite close enough in price, power, number of collet sizes, reliable collet chuck design for small end mill shanks, air cooling, variable spindle speed, commercial designed spindle nose bearings, low spindle run out, quiet running, and a fairly good duty cycle for long jobs. I've got it on order - 5,000 to 20,000 rpm with six collets 1/32" to 1/8" - for $170, which includes the mounting bracket for the SIEG X2. You will find it on www.kdntool.com Finding the KDN Tool spindle has been quite an adventure. When I first got into CNC, I determined that I would not be primarily making conventional machine parts, but would be engraving, and sculpting plastic, aluminum, and brass. I was surprised to learn that I would need a high speed spindle, for the same reason that PWB drilling, and engraving applications demand. The very small diameter end mills require the high speed. My stock SIEG X2 at 2,500 rpm needed to be stretched up to 20,000 rpm. No way. I looked at high speed routers (collet limited to one size), air driven spindle motors (too noisy), hand pieces for manual grinding, engraving, sculpting (not enough power or too expensive), and die grinders (one speed). The breakthrough for me was when I found an article by Paul Frederickson and David Grimes of The Precise Corporation, “Increasing Torque For A High Speed Spindle”, in MMS Online. They published a formula to determine the cutting torque required, and a Power equation. The cutting torque equation is: Torque (N-m)= Depth of cut (mm) x Width of cut (mm) x Feed rate ( mm per tooth ) x Number of teeth per revolution x Machinability Torque Factor Machinability Torque Factor – aluminum (0.145), brass (0.29), and steel (0.435). I wrote Paul Frederickson and he graciously told me the process for determining the Feed rate ( mm per tooth ), and told me the factor for brass. He said that, “a good rule of thumb to start with is 1% of tool diameter per tooth”. So a 1/32” ( 0.794 mm ) dia end mill, 0.4 mm deep cut, 0.008 mm feed rate per tooth, and 2 teeth results in Torque ( N-m ) of 0.0007 aluminum, 0.0015 brass, and 0.0022 steel. The power in watts for the KDN Tool spindle at 20,000 rpm is 1.5 aluminum, 3.0 brass, and 4.6 steel. The KDN Tool spindle has a 100 watt capability. So it will cut through these speed and feeds like butter. If you've never seen such high rpms before, it's because it involves the breakthroughs from High Speed Machining technology. Engraving machines have been running at those rpms for decades, and so have PWB drills. Small end mills / drills, small chip loads, and high rpm. For a 1/8” ( 3.175 mm ) dia end mill, 1.6 mm deep cut, 0.032 mm feed rate per tooth, and 2 teeth results in Torque (N-m) of 0.046 aluminum, 0.093 brass, and 0.139 steel. The power in watts for the KDN Tool spindle at 20,000 rpm is 97.2 aluminum, 194.4 brass, and 291.6 steel. So for brass and steel either the depth of cut needs to be reduced, or the speed needs to be decreased to 10,289 rpm for brass, and 6,859 rpm for steel. Power ( kw ) = ( Torque (N-m) x rpm ) / 9,550 When I tried to adapt some of the other solutions to my SIEG X2 I was stunned to find out that it is a major production to remove the “Spindle box” casting part # 49 from the “Spindle box seat” casting part # 63, which rides the column Z axis vee way. Part #49 is bolted through the back of part # 63, and you can’t see the bolt heads, because the are covered by the Z axis column vee way. Aggghhh! Wait till you see KDN Tool’s solution. It’s just right for me, I don’t need all of the X axis travel. When you get to the web site scroll down past "It's Alive", and past "Just Born" to "Our Latest Innovations" - "High Speed Spindle Attachment For The X2 Mini Mill", click on CLICK HERE for more information. If you don't own a CNC Mill and want to get one for small hobby work or jewelry making take a look at "Just Born" - full CNC conversion of the Proxxon MF70 micro mill, with stepping motors and full electronics, and it comes with a Proxxon high speed spindle. If you are looking at the SIEG X2 then you may want to look at "It's Alive" XJ-95 alternative to the SIEG X2 - with Y axis travel of 6.3" vs SIEG X2 3.94". I sometimes wish I had the extra 2.3", oh well it wasn't around when I was looking. With the KDN Tool, SIEG X2 High Speed Spindle and adapter, I'll be able to finally start me sculpting, and engraving. God bless you all. Bill Perun

[Degrom]

Originally Posted by totally_screwed I read about this on cnczone today! I'd like to take the credit for this, but I'd be lying! This explains the difference between Power and Torque. Feed rates & etc. Whether you actually require such a high speed depends upon what you are intending to do. Engraving with small diameter cutters necessitates high RPMs. If you want your cutters [even Tungsten Carbide or diamond] to last for more than a few seconds or minutes, you really should consider coolant. I suggest a misting coolant [needs compressor] You could look at the following [there may be others] Noga minicool, Trico DL spray system, Kool Mist or Amflo Mist Coolant Unit. They all look very similar. These will work with water-emulsion coolants. Using coolants will also enable you to achieve much better finishes with plastics which will otherwise certainly melt and fuse onto your cutter. Cutting dry will result in a clogged cutter and poor finish. As I understand things, obtaining high speed bearings is not cheap,and using them isn't easy or straightforward either. You are much better off using one of these relatively inexpensive but well-engineered spindles. That's what I am going to do! Oh, btw, those ultra-high speed spindles like I think you were thinking of have an operating life of 1500 hours or so. Just read it! Regards and good luck, totally_screwed

Now what can I say!!! You answered my question and about 3 more I was thinking of!!! Thanks for that!!