mike everman's tech corner

Video of third place winning shot

Mon, 12 Dec 2011 09:29:56 -0800

IMG_0538.MOV Watch on Posterous

Permalink | Leave a comment »

Final swish seals up third place

Sun, 11 Dec 2011 06:30:33 -0800

...and a photo of our team, Masha, Greg, Robbie, Jocelyn, Jay and Davey. A great time had by all!

Permalink | Leave a comment »

Playoff round

Sat, 10 Dec 2011 19:35:02 -0800

IMG_0537.MOV Watch on Posterous

Rules for the playoff were:
90 seconds to set up and fire one shot into a reduced size hole
60 points for a swish
50 points for hitting the edge and in
30 points for bouncing off the top

We tried to adjust backward for a swish by looking at the videos of the first run. Unfortunately, I should have videoed it from the side. We didn't know it would be important later! One team swished, another lipped and in, we bounced off. So first and second were set.
Jocelyn accosted the director to make sure there would be a runoff for third against the two other teams that bounced the top.

Permalink | Leave a comment »

JPL Challenge Finals

Sat, 10 Dec 2011 19:15:06 -0800

IMG_0536.MOV Watch on Posterous

Our team want on Friday To JPL for the finals. Here's video our first round, three successful shots putting us in a five way tie for first out of thirty teams!

Permalink | Leave a comment »

JPL Invention Challenge, our team going to the finals!

Tue, 22 Nov 2011 14:11:33 -0800

We competed at Manual Arts High School against 54 other teams last Saturday. Not a great showing compared to all of our practice sessions, sinking one and two off the lip for a score of 110. Held on to second place through the first 16 or so teams. Went to lunch at Fillipe's for some amazing French dip sammiches, then came back to find we were out of the trophy race, but found out later that we were going to the finals anyway. Between the two venues, there were only 6 teams with scores higher than us, but several like us at 110 points.

In practice before our time slot, we hit 8 for 8, then moved to the competition area, which was sloped in two directions! I do not think that was the killer, though. Our trigger mechanism, if you can call pulling a loop off of a hook a mechanism, has a bit of sensitivity to technique. That's something we will fix this weekend for the finals on the 9th of December.

My team is great! Hats off to the gang and our fearless physics teacher leader, Jarrod Bradley!

See the full gallery on Posterous

IMG_0518.MOV Watch on Posterous

Permalink | Leave a comment »

JPL challenge update

Sun, 23 Oct 2011 23:02:34 -0700

image.mov Watch on Posterous

> >

Permalink | Leave a comment »

San Marcos Engineering Team JPL Challenge first test

Fri, 23 Sep 2011 06:25:26 -0700

jpl challenge bump 300fps.m4v Watch on Posterous

A small group at San Marcos High is doing the JPL challenge; a machine that kicks a football into a trashcan 5m away, over a 2m barrier. I am enjoying advising the students on the project!

I find it very helpful to do little tests like this, so that if we were to calculate the metrics of this motion, we will have a real life verification of our math model, or point out where it is deficient.

This was a good shot, maybe a little low, but just about dead on the 5m distance. Students can make measurements from this video for angle of inclination (look to the bookshelf in the background for a vertical line reference), and determine acceleration of the ball and the velocity of Mr. Bradley's fist at impact. The video is shot at 300 frames per second, so check what frame rate your computer is playing, divide 300 by the frame rate to get the time factor.

Permalink | Leave a comment »

POLAR MINI CNC

Thu, 11 Aug 2011 16:38:13 -0700

The polar CNC is getting closer to full production ready. Our customer is making their own enclosures and HMI panel, so we have that to create that as well for our metal cutting version. I think that before I put this out there as a full cnc, I'll want to have a solid spindle and some sort of tool changer available. Lots to do, so it's good to be a subsystem for now.
Mike

IMG_0411.MOV Watch on Posterous

Sent from my iPad

Permalink | Leave a comment »

ServoBelt goes Semicon (again)

Wed, 13 Apr 2011 05:52:00 -0700

semicon stacked SBL, burn in with test mass.MOV Watch on Posterous

This is a set of ServoBelt stages stacked to be an XY for a semiconductor application. This video is just a burn-in move. The critical move of 12mm can be done in 180msec, settled to 5um. Payload is 34 lb. Motors are Teknic NEMA34 4-stack on the bottom and NEMA23 4-stack on the top, with Teknic Eclipse 350R amplifiers, and Renishaw RGH41 linear encoders.

Permalink | Leave a comment »

First push on the Inverted Pendulum

Sun, 28 Nov 2010 20:51:43 -0800

CIMG3491.MOV Watch on Posterous

A little closer view from the first push. Still need to take data, but I've got to travel for a bit. On close inspection, I see I need to dress the critical surfaces a bit for smoothest contact, so I'll take a quick data set, then clean it up. I may take it from .003" to .001" flexures while I'm at it.

Permalink | Leave a comment »

Inverted Cycloid Pendulum photos

Wed, 24 Nov 2010 10:28:46 -0800

Here are some photos of the build-up of the Inverted Pendulum.

See the full gallery on Posterous

Permalink | Leave a comment »

Inverted Cycloid Pendulum

Wed, 24 Nov 2010 10:27:25 -0800

inverted cycloid pendulum, vid and photos.wmv Watch on Posterous

As I progress toward building a unique clock, it occurred to me that the "rodless" cycloid pendulum I had previously built could have supports of virtually any length. What has come of it is a very interesting inverted pendulum which I will be testing over the Thanksgiving holiday to see how isochronous it is. The bob still follows a cycloid path, and will have a (roughly) 1.2sec period. The supports however, require a different treatment to make them isochronous at that period, considered alone, without the bob. That is an upcoming experiment.

This hardware is simple breadboard stuff, using segments of a 6.75" diameter bearing race, which will eventually all be replaced by jewel shoes among other exotic materials. I plan to build 6 clocks, one for each of the artisans that contribute to the case, the faces and the machine work. I will plan on 2-3 to sell at some point. This whole project will be years in the making, as I will be designing a completely mechanical movement that I hope will be as unique as the pendulum itself.

This is a very satisfying engineering exercise!

Permalink | Leave a comment »

Some alignment photos of Mini Polar CNC

Mon, 04 Oct 2010 09:28:52 -0700

Just some random photos of the Polar CNC going together, and a video of the spindle coolant and air feed lines simply managed.

See the full gallery on Posterous

coolant and air lines.MPG Watch on Posterous

Permalink | Leave a comment »

Mini CNC first coordinated moves and circle interpolation

Sat, 02 Oct 2010 17:01:08 -0700

Polar CNC first pattern.wmv Watch on Posterous

The boys at Delta Tau have gotten the bugs out of the coordinate system. Looking wonderful so far! I'll post up some more pics of the mechanics soon.

Permalink | Leave a comment »

Mini CNC Progress

Tue, 07 Sep 2010 08:30:24 -0700

The mini CNC is coming along very nicely. Friday was first light, and over the coming weeks, the forward and inverse kinematics will be fine tuned. Our goal is to be taking XYZ moves coming in, and process into the ABZ polar coordinate system. The spindles shown are not the final ones, however, as these have been discontinued by NSK. The search continues for an inexpensive air driven spindle of greater than 150krpm.

CIMG3323.MOV Watch on Posterous

Permalink | Leave a comment »

Very Nice ServoBelt gantry bridge during burn in

Thu, 20 May 2010 19:41:03 -0700

This ServoBelt is a variant that has the bearing rails attached on adjacent faces of the Bosch extrusion. It is adjusted to track a straight line in the Y-axis to within +/-.0002" when up on edge, used as the bridge in a gantry setup. Since we are operating within the dimensional limits of an extruded beam, this bearing mounting allows us to tune in one axis perfectly, so in this case, the customer needed dead straight in Y axis (along this beam), and the Z axis then is limited, but still, amazingly within .002". Sealed encoders are used as this is a laser cutting gantry.

Next time, I think we will pitch the customer on Renishaw magnetic encoders. It will be far less expensive than the Heidenhain sealed glass scales, which were selected solely for the environment.

CIMG2297.MOV Watch on Posterous

CIMG2298.MOV Watch on Posterous

Permalink | Leave a comment »

ServoNut Lowboy Granite Base CNC

Wed, 19 May 2010 07:45:00 -0700

Permalink | Leave a comment »

My new lathe/mill

Mon, 05 Apr 2010 21:42:31 -0700

It was a childhood dream of mine to have the mythical German U-boat multi-tool that could make anything. Well, this one's a passable Chinese. It's 7 years old with little use, and is far better than reviews I've read of more recent ones. I had to sell my other lathe to make room for it which went to a friend.

I've taken it all apart for cleaning and lube, and I've now made my first mill cut at home! Loving it. Nice dovetail ways on it with a good amount of surface area. The mill is a bit anemic; I might throw a dedicated 1 hp motor up there, but for now, it's got everything I need in my little space. Just need a decent vise for milling and a quick change tool holder for the lathe.

It's got the old school tool holder that makes you shim the cutters to height, so I'm going to make some brass wedges to make that a breeze.

I was going to buy a bunch of tooling for it, but now think I'll make it an NC, since I have most of the stuff; motors, amps and a DeskCNC card. I'll see how it goes. If that one is no good, I've got a few others to try.

At the office, the NC choice is Extratech. I've got a ServoBelt gantry with that control going on soon, but need a Z axis for the spindle, which I may just make at home as as warm-up for the CNC conversion here.

Cool!

Permalink | Leave a comment »

Stupid high inertia mismatch test with ServoBelt

Thu, 25 Mar 2010 21:55:00 -0700

sb232P 200 to 1 inertia mismatch.MPG Watch on Posterous

This is a ServoBelt test where the inertia mismatch between payload and motor was 200:1. For those that may not know, the normal rule of thumb is to keep this mismatch under 20:1 or so. It's a common rule that is no longer relevant with the advent of high resolution encoders, high servo update rates, and the fine current control of modern amps. The Teknic amp that is driving this brings some special additional mojo to it, too.

Upshot is that this move is settling in position within 2 encoder counts in 30msec with the smallest motor we'll put on these things. Hatcha cha! Cool stuff.

You can't do this with a conventional belt drive. Too springy. At least, not practically. Mode shaping at the control end could do it for a specific move.

Permalink | Leave a comment »

High and Low Inertia Pendulum Bob

Sun, 21 Mar 2010 22:37:57 -0700

This rig has two identical stainless bands for a suspension. It is like a belt speed reducer, with the bands running from large diameter at one end to small at the other. The two bobs are less than .0002" different in diameter and their faces are parallel to the same degree by kiss grinding. The thicknesses are such that each bob, though one is made of two disks on the ends of a tube and one a single piece in the middle of an equivalent tube, are the same weight, that is to less than .001 lb. which is the resolution of my scale.

This can be set up for two cases, one where the bob's apparent moment of inertia (about it's center) is roughly ten times what it would be if rigidly attached to a rod, if there were one. In the other, with the small suspension diameter above, the local inertia is one-tenth of rigidly attached.

What it does is allow me to verify my math model of variable inertia bobs. One interesting aspect of it is the high inertia case can be shorter than a normal pendulum for the same frequency. I'd say another neat thing is that it follows a perfectly circular path, until one considers centrifugal deflection of the bands, but that would I'm sure fail as a theory on close inspection. I predict that it will be no more determinate than a knife-edge, but maybe more than a conventional band suspension, where bend radii are not enforced.

I've just gotten the flexure bands made, and have not made the support clamps yet. There's no meaningful data to be gotten yet, since, as much as I love my hot glue gun, it fails as a rigid mount. Look closely at the high inertia case and you can see the upper hardware moving. Bad show, that!

CIMG2245.MOV Watch on Posterous

CIMG2240.MOV Watch on Posterous

See the full gallery on Posterous

Permalink | Leave a comment »