Well, I finally got back to the micRo stand. Undoubtedly this is because the parts are starting to be cut out at Lumen Lab (http://www.lumenlab.com/). If you haven't been there lately you really should check it out. There are great things happening, not only where it started in DIY video projectors, but DIY robotics and CNC machines!!

I found out the dimensions of the electronics needed to run micRo:

(1) Parallel Cable break-out board= 1"x2-13/16"
(1) Power Supply= 1-1/2"x3-3/4"x5-1/8"
(4) Driver Board= ~1-7/8"x~3/4"

And all the electronics will fit under the micRo stand in a plywood tray I am going to build. As I have said before, I try to use things I have laying around instead of buying stuff. I had some nice 3/4" ply sitting left over from making the top of the stand. I cut out a piece the size of the skirt on the stand. I wanted to make it fit up inside the skirt so I used this tool which I hardly ever find use for to measure the angle of the skirt taper. Here is the tool. It is a Universal Angle Level. It's not too terribly old, but I think it"s cool.

And here it is measuring the angle. That is a spirit level in the middle.

Ten degrees. So I set the bandsaw to cut a 10 degree angle.

And beveled the edges of the board I will use for the tray.



I cut the two back corners to allow cables to go in and out once the tray is mounted up inside the skirt.

I decided to use a couple of angle brackets to hold the rear of the tray. I'll mount them with pop-rivets.

Nothing too critical here.... Drill a couple of holes and mount the brackets.

Here is one showing the cable access hole in the corner. and one of the installed angle brackets.

I put an anchor into the front of the tray to hold it. I probably didn't need to use an anchor, but I did anyway.

The finished tray. Installed in the skirt.

As far as I can intuit, this will keep the electronic components sheltered from the stuff topside, and yet be relatively accessible. The two brackets are in the back and the single screw holds the front. This should work well because I don't expect much weight.

Next I will install my BIG RED BUTTON!

Making the Thing That Varies the Speed

I must tell you at this point (because you will soon guess it any way) that I usually tend to use things that I have instead of things I can buy.

Well I have a drawing that I think will work. I will transfer it to a piece of hardboard. Recognize this?

Not many people see carbon paper any more. I will use it to transfer the drawing of the cam.

I then cut this out on the bandsaw.

and drill a 1/4" hole where I plan to put the pivot.

I have a bunch of bolts, washers and nuts.

Can you tell my Dad used to smoke cigars?

In all this there are no bolts the right size. I need to cut off a piece of 1/4 - 20 allthread.

That's it in the vice on my rotary hacksaw. I don't have a large number of tools, but this one really saves a lot of hard work.

You can see my collection of aluminum cans in the bucket under the saw. I have this fantasy that I can sell it back to the place where I buy scrap aluminum and reduce my costs that way. We'll see...

Next I need to drill a 1/4" hole in the post that holds the motor.

It is high enough to allow the flexable shaft to hang almost straight when it is mounted in the micRo CNC machine. I have mentioned this before, but it bares repeating, micRo is a kit which is being designed and manufactured at Lumenlab (http://www.luminlab.com/)

What's cool is you get to kind of observe as the head guy, "Brainchild", goes through the different design decisions, watching the successes as well as the changes in direction as the machine slowly takes shape. It is actually going into the manufacturing phase now. This is very exciting to the people who have been checking in on the progress for any length of time. I've been watching for about 5 months now. The tension and anticipation is high. I needed to do something, so I started preparing for the kit's arrival. That's why we're here.

So next I see that my bracket needs a little 1/8" shim to keep the controler unit held firmly in place. Oddly enough, a Benjamin More paint stirer is exactly that thickness.


You can probably see that I save time consuming precision for places where it will count. This speed controler will probably be just fine with ballpark cuts and fitment.

Here you can see the cam mounted on the allthread squeezed betweem a couple of washers and nuts. I am mounting the controler bracket just below the cam so that when it turns, it will gradually depress the plunger. I cut the shape of the cam so that the radius went from just touching the plunger then increased until it was 5/16" greater. This increase is within 120 degrees (1/3rd of a turn). I felt that 120 degrees would be a good amount for the handle to turn in order to control the motor from a stopped condition up to full speed.

You might also notice that I am using an OSH thing. This was a great deal. This little driver was on sale for $15. Great deal.

The plunger is shown here with the shim, mounted just under the cam in the back of the post.

As I mount the control lever on the front of the post you can see the internal star washers I've added to keep the handle from turning relative to the cam. So far the cam has not needed this.

Here's the cam at the back. I have marked the "off" point and the "full on" point on the cam with an arrow in the direction of the turn.

I cut off the excess allthread infront.

Touch it with a file to clean up the roughness and we're there.

All done! and it works great! I may put a little silicone grease on the cam where it touches the plunger. I may put a plate under the pointer to make some kind of indication of the speed. But other than that it will, as it sits, hold the voltage to the motor steady. Now, this is not a constant speed controler. It will not compensate for varying loads on the motor as the tool grinds its way through different matrials, but it may serve well enough. We'll see.

Next I am going to install the "BIG RED BUTTON". That thing all machines need to stop them when everything is going wrong.

How to vary the speed

Since I am going to use this flex shaft grinder for something it was not intended to do, namely be the spindle for a CNC Milling Machine at this great site Lumenlab (http://www.lumenlab.com/forums/index.php?showtopic=25411), I would like the ability to vary the speed of the tool to suit different situations . Different materials different cutting tools, etc. The unit is supplied with a foot control for varying the speed, but I don't want to be strapped to that thing for the duration of some machine operation which could take hours, overnite, ??

So I decided to take apart the controler. This is what I found

I unscrewed the four philips head screws shown in the photo and took out the little plunger unit




This is a variable resistor activated by the foot pedal top which I removed. The resistance varies from 0 to over 2MOhm (the limit of my meter). There is quite a taper to the resistance meaning at one end of the plunger travel there is very little change and at the other it is quite dramatic. However when depressed by the foot pedal or even by hand it is possible to control the speed quite well. I think that there is a way to depress the plunger with a cam arangement so that the speed can be set at some value. This probably won't hold as the tool is working, but could be useful.





I bent a little bracket to hold the variable resistor behind .





I then used this tool which General Tool calls a "Multi Use Rule & Gauge". I love that name. I actually like the tool too. I just don't find that much use for it in daily life.





Cute, isn't it? Anyway I scratched a prelimenary drawing of the cam and tried to imagine it working.




I could have used Sketchup or another drawing program, but I like to use a pencil sometimes. I think I made the radius a little large. I will cut it in half maybe then cut it out of hardboard to control the speed. I bent an "L" bracket to hold the variable resistor on the backside of the post above the working surface where I could reach it.

Maybe I'll get the hardboard cut out tomorrow.

Those dang cheap bearings

The cost of the Grizzly handpiece unit was right (about 64$ with shipping). It turns with a speed of 15,000 rpm, if you believe the product specs. I haven't measured it myself yet. It has a little chuck which will take up to a 5/32" shaft. This will be usefull for a lot of my projects, but in the future I plan to either modify the stock handpiece or get a replacement which uses a collet to take up to 1/4" tools.

I have to tell you that I am trying to spend as little as I can to get this machine up and running. Not only do I not have a lot of disposable cash, but I'm not sure if this will be a lasting interest of mine, so I don't want to have invested a lot. I gotta say it has been hugely interesting so far and I learn stuff everyday about machining and tools, so that alone is really worth it.

When took the handpiece out and gave the chuck a spin it would only turn about one revolution before stopping. It turned easily, but I could feel a rough spot in the rotation of the bearings. Because of this I decided to try and upgrade the bearings.

The handpiece looks like this.

You can see the cute little chuck, the supplied key and a spare set of brushes for the 1/4 hp motor. I thought the brushes were a nice touch to include. The rear of the handpiece unscrews and this is what you have

The nut is 12mm. I inserted the key into the chuck. It kept the shaft from turning and when I turned the nut the chuck very easily disengaged from it's taper mounting. This apears to be a Jacobs "0" taper. The chuck has JT0 etched into it. Here is the chuck removed.

I placed the back end of the handpiece over a hole so the shaft would have someplace to go, then I tapped the spindle using a little piece of wood so as not to damage it. The shaft came right out. I could read the number on the bearing and saw that it was 608.

People familiar with bearings for inline skate wheels or skateboard wheels will recognize this size bearing. Since there are so many of these produces the price for new ones, (even high quality ones) is quite reasonble. I went to eBay and saw an auction ending in 18 minutes for 16 of the ABEC 9 versions of the 608 bearing which is used in the handpiece. They are made by ARSENAL. I got the set for $9.95 + $6.50 shipping which comes out to about $1.03 per bearing. That seemed like a good deal.

The ABEC number indicates the quality. I don't know what the stock bearing was but the number must have been low. As far as I know, 9 is the highest number, so these ABEC-9 bearings should be quite an improvement. Here is what I got.

When I took the Grizz handpiece apart there was one bearing which stayed on the spindle shaft(The other stayed in the handpiece tube.) Here it is next to my shipment of bearings. With 16 there is plenty of spares in case I get into this and start wearing them out.

I was surprised at this point to find that when I turned the shaft while holding the bearing I could actually feel it "catch" in one spot in the rotation. I put the spindle shaft in the vice, and unscrewed the 12mm nut.

I was able to pull the old bearing off with my hand.

Here is a close-up of the old bearing on the left and the new precision one.

I could not quite push the new bearing on by hand as can be seen by the 1/16" gap between the bearing and the shoulder on the shaft.

I needed to put the nut back on and seat the bearing by tightening the nut. It went on easily. The second bearing was too far down in the handpiece to reach, so I chose a bolt with a 1/2" head which was large enough to cover the inner race to use to push the old bearing out.

This I was also able to do by hand.

In seating the new bearing in the handpiece I thought I would be more carefull so that it didn't get cocked one way or the other on it's way in, so I chose a 5/8" deep-walled socket to push it into place with the drill press.

I used the drill press with the chuck closed to push on the socket and seat the bearing in the tube. I could probably have just pushed the socket with my hand it went in so easy. In order to seat this new bearing on the shaft, I set the handpiece on the socket to support the bearing inside the tube and chucked up the bolt. I then pressed the shaft and bearing in with the drill press.

It was all pretty uneventfull and totally worth doing. After the handpiece was assembled again

I found that if I gave the chuck a spin by hand it would spin for about 5 seconds as opposed to one turn. This was very gratifying. And it gave me something to focus on while I was waiting for the development of micRo at Lumenlab.

My micRo Journey Begins

As I describe what I'm doing with this little machine, there is a lot I just can't explain in detail because there is so much. I would sugest a trip to http://lumenlab.com/ to catch up on the way this machine works. The short of it is, I decided that I would get one.


I needed a place to put it. So I carved out a small space (about 7'x9') behind my house and started preparing. I had to do something. Brainchild would tease me and tease me with pics and videos of his progress and then ... Well, reality came in and the wait would be longer. I was going nuts! The subject matter was so intriguing. I had to keep watching the posts. and I had to do something with my hands.


Last month, Brainchild made the decision to have a flex shaft spindle. The Grizzly knock off of a Foredom unit was chosen and my plans for a small niche on my small bench went south because I would need additional height above the micRo. So I needed to make a stand. I couldn't stand it any longer! I had a friend with a rusty trash heap next to his driveway. He had thrown away his Craftsman contractor saw and stand when the motor died. I rescued the stand and with a little paint and MDF for a top I had my micRo stand.





I made some leveling feet.



I ordered the Grizz.



I imagined that the best mounting would have the cable as straight as possible. It seems the only way to do that would have the motor suspended above micRo and move up and down with the Z axis. I haven't figured out the movement yet because I don't want to put a pull down load on the Z motor, but I have a suspension for now. and kind of looks like micRo will be getting some wierd type of transfusion with that motor hanging there.

In the picture you can see the old cast off computer which is just fine for runing the LINUX software which will control the stepper motors in micRo. The motor hook clears my limited ceiling height by 3 inches.

"

I will also need to re-rout my compressed air line (shown on the left), it looks like, so that the motor can swing freely from side to side.

Next post I will talk about upgrading I had to do to the bearings in the handpiece.