Open Discussion Pertaining To Inexpensive But Accurate Spindles For Drilling PCBs

idbruce

Hello Everyone

Here is another topic that I am sure will have a wide variety of views pertaining to the topic.

As many of you already know, I am in the process of building CNC PCB Drilling Machine. I am at a phase in this project where I will have to start making some serious additional design decisions and purchase missing materials. One of these decisions and missing items pertains to the drilling apparatus, and to simply the discussion, I will simply refer to this as the spindle. I am getting ready to purchase a spindle very soon, but before I do, since I value all of your input and opinions, I want to hear what you guys have to say.

Here is my criteria for the spindle:

• The spindle must be accurate.
• The spindle must be inexpensive.
• The spindle must have a 1/8" collet.
• The spindle must be lightweight (added).
• The spindle speed must be variable, with a minimum speed of around 15,000 RPM.
• And preferably (not absolutely necessary), the shaft should indexable for locking the shaft for changing bits.
• And preferably (not absolutely necessary), I would like the body to be round (cylindrical) for easy adaptation to the machine.

Custom DC Motor Assemblies

I personally have no objections to a custom dc motor assembly, providing the motor is capable of achieving approximately 15,000 RPM. However, I do believe that an appropriate motor would require a lot of start and running amperage, and it may be difficult to finding an appropriate power supply and a means of adapting a 1/8" collet. And yes, I know that I can purchase Dremel collet kits, but their threads are proprietary.

Readily Available AC Rotary Tools

There is always the Dremel rotary tools and other similar rotary tools, but in my opinion, the ergonomic plastic shells would make it hard to adapt to the machine and make it sturdy. This option would be much more appealing if someone was out there providing ready made clamps to adapt to machinery.

Pneumatic Micro Grinder

This is probably the route I will take, due to the cylindrical body and variable speed. However, I do not like the idea of requiring air pressure, especially when AC power is much more readily available. However, if you are interested in seeing my most likely future purchase, you can see it here, and a photo of the kit has been attached below: http://www.harborfreight.com/1-8-eighth-inch-air-micro-die-grinder-47869.html

I am open to all valid suggestions.

Bruce

W9GFO

This meets all but one of your requirements;

http://www.wolfgangengineering.com/Spindles.php

idbruce

@W9GFO

During my internet travels, I came across that page once before, and needless to say that they are nice, however just a bit too expensive for my blood.

If I was going to be milling PCBs, instead of just drilling them, that would probably be my first choice.

Thanks for your input.

Bruce

T Chap

I built a cnc machine once using a hand held Dewalt router with 1/8" collet. It worked really well and was precise and sturdy. The plastic body had a section that was like a straight tube sufficient to mount 2 clamps around it, I designed the clamps out of aluminum and milled them in sections. The rear section mounted to the gantry and the front sections allowed for very quick removal of the router. These routers are cheap, 60-80ish, the come in various fixed speeds and variable. If you were to post something on cnczone.com you would likely find plenty of guys that have already designed sturdy aluminum mounts for various routers, someone may be already have a design for a model that suits your needs and they can build the aluminum mounts. An alternate to aluminum mounts is Delrin, 1/2" thick material would be very solid if you had an upper and lower mount. I wired the AC in to an SSR triggered by the software. The problem with these high speed routers is the noise, I hate using them for any length of time and ear plugs are almost mandatory. OTOH, a motor that is separate from the spindle and belt driven will sometimes be a lot quieter and you can gear a slower motor up. for pcb drills you are not talking about a whole lot of torque required, so gearing up is an option. I have used a Taig spindle set for years and love it. You can get a lot of collets in a kit, starting at 1/8" and it is nice to have options for collets in case other needs pop up. You may want to call them and see if they have an option that works at the speeds you want.

Leon

Die grinders are popular for PCB drilling. Typical speed is 25,000 rpm.

idbruce

T Chap

I guess I should have mentioned one other item of criteria, and that is it must be lightweight. The linear actuators that I will be using are going to be light duty. OTOH, now that I think about it, it will be the Z axis with no radial load. HMMMM.... I have a nice Milwaukee router, and I probably have an 1/8" collet for it. I know I have several collets, just unsure what they are.

However, as you mentioned, router motors are very noisy and pretty large in diameter. The motor will almost be as large as the PCBs that I intend to be drilling LOL.

Bruce

T Chap

The noise of a system must be considered. Certain routers even with ear plugs or headphones will leave you completely frazzled after even minute of use. The weight of the hand held routers are insignificant. For the Taig, I use a 1/5"HP motor that runs 10k and it does not wear me out so bad and I do not wear ear plugs with it. Wearing ear plugs or headphones have their own fatigue and annoyance factors.

potatohead

I second the die grinder suggestion.

Ttailspin

A machine for your perusal...
Dewalt Heavy Duty Cut Out Tool.

This seems to encompass most of your design criteria..
And, they are tough machines...


-Tommy

hover1

idbruce wrote: »

Hello Everyone



Pneumatic Micro Grinder

This is probably the route I will take, due to the cylindrical body and variable speed. However, I do not like the idea of requiring air pressure, especially when AC power is much more readily available. However, if you are interested in seeing my most likely future purchase, you can see it here, and a photo of the kit has been attached below: http://www.harborfreight.com/1-8-eighth-inch-air-micro-die-grinder-47869.html

I am open to all valid suggestions.

Bruce

RE: Pneumatic Micro Grinder
I have one of these, (same thing sold through Lowe's, and the bearings are horrible after a month's worth of use. Will throw your accuracy out the window.

A small laminate router is built more robust. Die Grinders are better, but need air.

Leon

Electric die grinders are available.

Phil Pilgrim (PhiPi)

One of the challenges in adapting a hand-held tool for CNC use is constructing a stiff, precisely vertical mount for it. Plastic housings, especially, will be problematic in this regard.

-Phil

idbruce

There are options, but they can get expensive.

idbruce

For Those That May Be Interested

Here is an interesting link, which contains access to collets, chucks, and motors: http://www.blackalloy.com/collet.htm

Bruce

idbruce

And here is a link to several micro grinders: http://www.gison.com.tw/product/Air-Micro-Grinder.htm

pjv

Hi Bruce;

I favour the use of a good small but powerful standard BLDC motor available from many on-line hobby shops. You will need a 3 phase BLDC driver that they also sell. Total cost could be less than $ 100. or even less for lower powered units. I have also run mine at 60,000 RPM from a Prop driven switching array, but it would probably be much happier at half that speed. You can get motors of half a horse power that draw 50-ish amps, and the 3 phase variable speed switcher I bought is rated for 1000 amps.

One neat thing I managed to do with it was to build a very simple automatic tool changer. It is still all a work under development, so I am unable to sell any just yet.

Cheers,

Peter (pjv)

jrjr.

Peter,

Thanks for the push.

I had thought about trying the BLDC 3 phase/ESC solutions but hadn't gotten around to it yet.

I'd love to see what you've created for the tool changer, even the napkin print.

I've been using multiple quick change ARO pencil grinders for years and they hold up extremely
well even to side loads, and have a very low runout even at 6 months in constant service.

They get a shot of ATF down the air line when I feel guilty.

The automatic tool changer would be worth the extra work to fit in place.

I've gotta figure it uses air to release and spring pressure to recapture the bits.
That would seem to be the only method to overcome the friction needed to hold the runout low.

I guess it could be magnetic as well, but I'm betting air.

jack

pjv

Hi Jack;

Actually, it uses neither. But I'm not ready to reveal it until I get more work done on the total system, and have my bases are covered as I'm intending to have this as a product for sale. I also need to be sure of its qualty and validity of my design specs. I keep flipping back and forth between mechanics and electronics.... there just are not enough hours in a day.

Cheers,

Peter (pjv)

idbruce

Hello Everyone

As it turns out, I just found out yesterday that someone already purchased the micro grinder from Harbor Freight for my B-day, and I will be receiving it tomorrow. So my decision has been made for me

I guess I will start out with that, and if it fails, I will probably disassemble it to see if I can use some of the parts and improve upon the design.

So now that I know that it is predestined to become a pneumatic PCB driller, I will now have to find a suitable solenoid for on/off operation.

Bruce

idbruce

Hello Everyone

Well I received the micro grinder the other day and it appears that it may work out well. I am hoping that the existing air hose can be utilized without restricting Z axis movement, however I do not believe it will be a problem. Additionally it appears as though it should be quite easy to adapt this grinder to the Z axis. The body is just a little less that 5/8", so I will be milling the edges of a 5/8" spade bit to make (2) 0.614 split hole clamps. Sounds possible anyhow.

Over the last several days, I have been purchasing miscellaneous parts, such as: stepper motors, LCD, and various Parallax products. And at this point in time, I am considering my purchase of a solenoid to control the on/off operation of the micro grinder. During my investigation of various solenoids, I came across "Proportional Solenoid Valves", which basically control the flow of air, being dependant upon the amount of current applied to the coil. Amongst other things, these solenoids are used to control the speed of dental hand pieces. Considering that the max speed of the micro grinder is 56,000 RPM, I am thinking that one of these solenoids should enable me to have very fine automated drill speed control for different drill bits and hole sizes. Additionally, I am thinking of opening the air valve on the micro grinder to "fully open", and just control the speed of the grinder completely with the solenoid valve.

Any feedback?

Bruce

EDIT: Just in case anyone is interested, here is the link to "Proportional Solenoid Valves": http://content2.smcetech.com/pdf/PVQ.pdf

EDIT: The one I want, which is: Part Number: PVQ31-6G-16-01N-F, well that baby is expensive. A whopping $98 buckeroos. I think I will hold off a while and keep my eyes open at ebay.

Capt. Quirk

Try building your own version around something like this

idbruce

Capt. Quirk

I do fairly well for a backyard mechanic and machinist, but making collets is a bit beyond my qualifications. However, thanks for the input.

Bruce

idbruce

To Those That May Be Interested

Referring to Post #20....

Even though I will be modifying a spade bit for different reasons, I have decided to alter my clamping design for the grinder. For those people that may be contemplating the use of a micro grinder in a future application, I have decide to share my clamping design, which is attached and shown below. When referring to the attachment, although not indicated on the drawing, the "clamping spacers" are a couple thousands less than the diameter of the grinder body.

Bruce

Capt. Quirk

Here is the same shaft with a motor attached

1/2 HP
26,000 rpm

and cheap

except, you would need to buy a 1/8" collet