Mini Mill Spindle?

I'm going to be obtaining a Mini Mill within the next couple months (6"x4"x4"), and I need to find a spindle for it. I know most people use routers, but I have 2 issues with this approach:

1) Size: I think a router would be a bit large for this machine.
2) Noise: Routers are extremely loud from my experience, and I'd like to keep the noise down if I could.

So I'm not sure what this leaves me with. I've looked at some Drywall Routers, which are quite a bit smaller. The one I'm looking at is adjustable between 15k and 30k RPM. Would this be too fast? I plan on routing PCBs mostly, but will do some Plastic and Aluminum as well.

I'm open to any suggestions, but please try to keep the cost down. I'd be okay with fabricating something myself if anybody has any ideas.

Thanks,


- Jesse

dremel tool?

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Originally Posted by Teyber12

dremel tool?

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I'm under the impression from my reading that Dremel tools have excessive amounts of run-out. I'm not sure if this is true, but if it is, it'd make manufacturing PCBs quite hit or miss, imo.


- Jesse

Jesse,

Keling sells a 24,000 rpm spindle for $329.00

http://www.kelinginc.net/CNCSpindleandController.html

Jeff...

Quote:

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Originally Posted by jalessi

Jesse,

Keling sells a 24,000 rpm spindle for $329.00

http://www.kelinginc.net/CNCSpindleandController.html

Jeff...

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Thanks. That's a bit more than I initially wanted to spend, but I will seriously consider it.

Just curious, so that if I run across something I can decided whether or not it suits my needs, what kind of RPMs should I look for for the following things:

PCB Boards
Plastics (Delrin, HDPE, etc.)
Aluminum

Thanks,


- Jesse

I've seen this use for PCB milling in a homebuilt PCBmill; http://www.foredom.com/foundations/s...=H.25&tab=docs

There are collets up to 1/4 inch I think. You would still need a flex shaft and motor but these things are really long lasting, much tougher than a Dremel.

cary

Quote:

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Originally Posted by packrat

I've seen this use for PCB milling in a homebuilt PCBmill; http://www.foredom.com/foundations/s...=H.25&tab=docs

There are collets up to 1/4 inch I think. You would still need a flex shaft and motor but these things are really long lasting, much tougher than a Dremel.

cary

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I've also seen similar pieces used (same company actually, just a different model), so maybe I'll look into that. The one problem with that is that I just have no clue what kind of specs the motor needs. Maybe somebody can help out :)

Thanks,


- Jesse

The web site lists a few different motors and flex shaft styles. There are different brands also.

The good thing that I see about them is, with the motor hanging from above, there will be a minimum weight on the z axis.

I've got one that was my grandpa's and he used it hard. It still works good, got to be over 30 years old. I use it when I don't want to fire-up my air compressor to just run my air die grinder for a few minutes.

cary

For a temporary solution, would something like the following work?

http://www.instructables.com/image/F...-and-motor.jpg

Thanks,


- Jesse

Well after looking at a few projects, I think that I'm going to make my own spindle. If I source all my parts properly, it shouldn't cost me too much at all. I have a Dremel that I'll use temporarily until this is done, but that should get my by just fine. All I figure I'll need is access to a Lathe, and I'll be in business (and I'm pretty sure I know somebody who has one).

I found 3 projects in particular that all have aspects of what I would like to achieve with my spindle.

http://www.mycncuk.com/forums/showth...e-design/page2
http://www.cnconabudget.com/PaulJonesPCBSpindle.html
http://babelfish.yahoo.com/translate...l.php&lp=de_en

I do have a few questions, however.

1) What size collet should I go for? I was looking at an ER-16 Collet for 1/4" Bits. That sound good?
2) Would a simple shank such as THIS work for what I'm wanting to do? If not, any recommendations?
3) Where can I purchase bearings for this project for as inexpensive as possible. They'll need to be handle fairly high speeds (20k-30k rpm).
4) Where can I purchase inexpensive pulleys/belts for the motor as well as the shank?

Thanks,


- Jesse

http://www.vxb.com/

http://www.sdp-si.com/estore/CoverPg/pulleys.htm

About 20 years ago I built a manual pantograph mill and used one of these for the spindle;http://www.parlec.com/pages/straight..._collet_chucks

It makes building the spindle super easy. The collet part is already made, just add bearings and a housing. If you look around you can find them used.

cary

Quote:

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Originally Posted by jalessi

http://www.vxb.com/
http://www.sdp-si.com/estore/CoverPg/pulleys.htm

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Quote:

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Originally Posted by packrat

About 20 years ago I built a manual pantograph mill and used one of these for the spindle;http://www.parlec.com/pages/straight..._collet_chucks

It makes building the spindle super easy. The collet part is already made, just add bearings and a housing. If you look around you can find them used.

cary

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Awesome, thanks a lot guys.


- Jesse

Alright, been throwing together a rough design (not bothering going into any detail until I get something usable, so I know the CAD sucks), and I have a few questions. I got the rough dimensions of the Shank, as well as some bearings (rated for 15k rpm and cheap!), and the 550W motor I'll be using (I know it's small, but it's very powerful and very efficient).

http://i36.photobucket.com/albums/e1...th_Spindle.png

Anyways, I have 2 questions as of now.

1.) Is there anything that I need to put on the shank, such as a clamping collar or something, to keep it from falling out of the bearings? How do I go about doing this, etc.?

2.) What is the top of the shank like, for connecting either pulleys or just a coupler?

Thanks,


- Jesse

http://i36.photobucket.com/albums/e1...h_Spindle2.png

That's pretty much what I'm planning to go with (rough design, will be refined one I decide on a few more things). Total footprint is about 6"x4"x3"; not bad for a 0.5kW spindle, imo :)

Still need to figure out the 2 questions listed in the previous post, but I've got pretty much every part picked out otherwise.


- Jesse

EDIT: Bit better layout and whatnot. Everything fits nicely, even the speed control.

http://i36.photobucket.com/albums/e1...h_Spindle3.png

HerbertKabi has provided information here on how to make highly accurate, highly reliable High-speed spindles.
http://www.cnczone.com/forums/showth...t=12184&page=5

I am building a low quality lower speed lower reliability spindle here.
http://cnczone.com/forums/showthread.php?t=103610

Quote:

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Originally Posted by RotarySMP

HerbertKabi has provided information here on how to make highly accurate, highly reliable High-speed spindles.
http://www.cnczone.com/forums/showth...t=12184&page=5

I am building a low quality lower speed lower reliability spindle here.
http://cnczone.com/forums/showthread.php?t=103610

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Thanks for the links. The first one has lots of information, but that seems like absolute overkill for what I need. I will not be running my machine daily, it will just be a "whenever-I-need-it" type machine. I'm liking your thread, as well as the build on /www.metallmodellbau.de. My design is actually highly influenced by his build.

One question however. Refer to the below linked picture.
http://www.metallmodellbau.de/pictur...SPINDEL-11.jpg

What are those brass-looking rings, and what are their purposes?

Thanks,


- Jesse

Those are nuts. He threaded the inside of his spindle housing, and then made these nuts to retain the bearing.

Quote:

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Originally Posted by RotarySMP

Those are nuts. He threaded the inside of his spindle housing, and then made these nuts to retain the bearing.

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Ah alright :D I just wasn't sure if they were some special vital piece or whatnot. Thanks for clearing that up.


- Jesse

Well I found some CAD files for the pulleys, so I got those. I did a few little revisions, got something I'm fairly happy with.
http://i36.photobucket.com/albums/e1...h_Spindle4.png
I also thought that I may be able to use the pulley to retain the shank? See image below.
http://i36.photobucket.com/albums/e1...nkAssembly.png
Would I be able to do this? I'd be able to shim it or whatever it takes to remove and linear play. Just an idea since those pulleys have clamping hubs.

Thanks,


- Jesse

Alright, found the rest of the parts I need. I figure this should be pretty much it. Can't make a final mock-up in CAD until I have all the parts I need, but this is fairly close :) Found some new bearings that are good up to 48k RPM, way more than I'll ever approach. Top of the spindle assembly will screw off, just to make it look a bit nicer than an open top. Using pulleys so that I can adjust the ratio for different speeds and whatnot. Anyways, here it is.

http://i36.photobucket.com/albums/e1...h_Spindle5.png

Lemme know what you think.


- Jesse

Any reason the spindle can't be a block instead of a cylinder? Just for my edification.

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Originally Posted by jjobezo

Any reason the spindle can't be a block instead of a cylinder? Just for my edification.

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None whatsoever. I just decided to model it up using a cylinder.

Another question, more based on the control of the spindle.

The method I'm going with requires a ~5v PWM signal to determine the speed of the spindle. Can this signal be output from the software via a pin on the Parallel port, or would I have to write a small application that did it otherwise? Also, would I be able to connect an encoder and have it display the RPM in the software?

I'm also considering just making a small control box containing a microcontroller to take care of all this. I'd have some form of input method to change the RPM, and LCD to display all the necessary info, and the MCU could take care of the PWM.

Which would be preferable?

Thanks,


- Jesse

Mach 3 can output a 5V pwm signal (assuming your parallel port is 5V, many newer ones are only 3.3V).

If you are trying to drive an RC ESC, then the PWM signal is timed into a narrow band at the start of each interval. None of the CNC programs has native support for that protocol (afaik), but there is a pretty simple circuit floating around the internet to translate Machs signal.

Quote:

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Originally Posted by RotarySMP

Mach 3 can output a 5V pwm signal (assuming your parallel port is 5V, many newer ones are only 3.3V).

If you are trying to drive an RC ESC, then the PWM signal is timed into a narrow band at the start of each interval. None of the CNC programs has native support for that protocol (afaik), but there is a pretty simple circuit floating around the internet to translate Machs signal.

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Alright, thanks. Know any of those circuits off-hand?

There was a link in the thread which Herbert posted into:

http://www.epanorama.net/documents/motor/rcservos.html

Ah, thanks. :) I have an idea for a circuit that I'm gonna go ahead and design, and I'll decide between the two at a later date.


- Jesse

http://i36.photobucket.com/albums/e1...h_Spindle6.png

That specific gearing would put it around 30k rpm at top speed. Should be able to get it going a fair bit slower as well just fine :)

Quote:

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Originally Posted by Jesse B

http://i36.photobucket.com/albums/e1...h_Spindle6.png

That specific gearing would put it around 30k rpm at top speed. Should be able to get it going a fair bit slower as well just fine :)

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At what sort of speeds should a spindle be using direct drive rather than being belt driven? Looks like commercial spindles don't use belt drives much past 10krpm, and I'm assuming they have good reason to given the convenience of having a separate motor when it comes to manufacture and servicing the thing.

I'm assuming its a bearing life issue, primarily, but I'm only guessing here.

Quote:

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Originally Posted by serriadh

At what sort of speeds should a spindle be using direct drive rather than being belt driven? Looks like commercial spindles don't use belt drives much past 10krpm, and I'm assuming they have good reason to given the convenience of having a separate motor when it comes to manufacture and servicing the thing.

I'm assuming its a bearing life issue, primarily, but I'm only guessing here.

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I never considered that yet; maybe somebody can chime in and let me know whether or not belts are fine at this speed. The reason I wanted to go with this setup is due to the fact that this motor will only be able to hit about 19k rpm with the power supply I was planning on using. I may be able to do a direct gear drive however. I don't know, I'll figure something out :p

As for the bearings, the manufacturer claims that they're good up to 48,000rpm, so I'm not too worried about that.

Quote:

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Originally Posted by Jesse B

As for the bearings, the manufacturer claims that they're good up to 48,000rpm, so I'm not too worried about that.

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Bearing ratings don't tell the whole story, unfortunately. You'll have to derate that a good deal when you preload them, for example. The faster your spindle goes, the more the bearings will suffer from runout and imperfect alignment, causing them to wear out faster. Spindle engineering gets dramatically more complex when you go above speeds of 7-10krpm. Apologies if you already know this stuff!

You described Herbert Kabi spindles as overkill; I'm going to have to disagree with you there. Winding your own motors; yeah, that probably isn't for everyone ;-) but the rest of the engineering is pretty much what is necessary for the speed and power requirements he's working within. You may end up being disappointed with either the runout or lifetime (or both!) of your spindle if you don't follow broadly similar design constraints.

Quote:

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Originally Posted by serriadh

Bearing ratings don't tell the whole story, unfortunately. You'll have to derate that a good deal when you preload them, for example. The faster your spindle goes, the more the bearings will suffer from runout and imperfect alignment, causing them to wear out faster. Spindle engineering gets dramatically more complex when you go above speeds of 7-10krpm. Apologies if you already know this stuff!

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No worries, always nice being reminded :)

Quote:

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Originally Posted by serriadh

You described Herbert Kabi spindles as overkill; I'm going to have to disagree with you there. Winding your own motors; yeah, that probably isn't for everyone ;-) but the rest of the engineering is pretty much what is necessary for the speed and power requirements he's working within. You may end up being disappointed with either the runout or lifetime (or both!) of your spindle if you don't follow broadly similar design constraints.

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Alright, I'll look into making my design a bit more robust. I've got lots of time so I'm in no real rush.

Thanks for the input,


- Jesse

I've just read a thread on the HSM forums covering a relatively simple high speed spindle design, which was belt driven to >30krpm. The author goes into more detail about his problems with machining his own collets (which he eventually gave up on) than into making the spindle itself, but its good to see this sort of spindle design working nicely!

See here for the whole thread. The final working design with ER11 collets is on the last page.

That's a pretty nice looking spindle. I'm fairly confident in my design. Worst case scenario, it doesn't work :)