Archives for posts tagged ‘sketching’

the importance of sketching

I’ve often talked to students, young designers, and colleagues about the importance of sketching as a part of the design process, whatever flavor of design that might be. I like to think that I practice what I preach, but sometimes I forget.

I have been struggling with the design of an enclosure for my CNC mill that would allow me to use flood coolant and contain the mess of metal and plastic chips this machine can create. I had a rough idea in my head, and looked around at existing enclosures, so I immediately jumped into CAD to sort out the design. For days I iterated on-screen, unhappy with the results but trudging through each new concept until I hit a wall.


So last night as I sat on the couch I opened up my laptop to give it another go, only to find technical issues that kept me from launching my CAD software. Frustrated, I shut the laptop and pulled out my sketchbook. Within minutes I was teasing out the solutions that were so elusive on screen, and by the time I shut off the lights I had my design roughed out.

So, one more time, especially so I remember: Never underestimate the importance of sketching. CAD is an invaluable tool, as are rendering packages and Illustrator and Photoshop, etc. But for quick ideation, brainstorming, breaking through a mental block, or simply communicating with your fellow designer/engineer/marketing person, nothing beats sketching.

Thanks for humoring me. And stay tuned for my next rant, titled mock it up before you fock it up

CNC mill oiling system – concepts

As I’m preparing to dismantle the milling machine for its major ball screw overhaul, I’m thinking about what else I want to do while it’s apart. One thing that most commercial machines have is a semi-automated way of oiling the sliding parts of the machine. Like most of the awesome mods that can be done to this particular mill, Hoss has already figured it out, so I’ll base much of what I do on his existing work.

The biggest component of this project involves modifying the saddle in such a way that it can deliver oil to each of the four X and Y-axis ways. A series of tubes (shown in blue below) deliver oil into holes drilled into the saddle (shown in red), which in turn come up in the middle of each way. The surface of the ways are then milled with a shallow “S” curve groove to distribute the oil across the surface. Additionally, the saddle holds the ball nut mounts so it can conveniently distribute a squirt of oil to each of the ball screws as well.

The Z axis ways will be oiled from the head, so it will have its own plumbing. But the two assemblies will have to meet on the column via some flexible tubing, then connect to the oil pump and reservoir.

I have some thoughts on implementing my oiling system in a more compact way than Hoss. There are a lot of tight spaces in which this will operate, and other things I may want to integrate into the same real estate like limit switches, way covers, scales, etc. Furthermore I feel that clear plastic tubes are useful for seeing that oil is present in the system but they seem a little too flexible for my taste, probably requiring that they be tacked down periodically to prevent them getting in the way. I’m thinking about using rigid copper or aluminum tubes that are bent into position, which seems to be the way most commercial machines do it.

I took a look at McMaster’s selection of fittings and decided they are too bulky for my application, and probably way overkill for the relatively low pressures my system will see (up to 7 psi). I started thinking about how small a fitting could get, and figured that soldered connections are about the best you can do. The trouble with fully soldering all the connections is that the plumbing becomes permanent to the machine, which is probably bad. So then I thought maybe the plumbing could all be soldered into a semi-flexible assembly that is then pressed onto fittings in the saddle (see the above sketch).
These fittings were starting to look a little fussy to machine, and in a high vibration environment like a milling machine I don’t like the idea of friction alone making a pressure connection (albeit a low-pressure one).


So next I thought about a hollow screw solution that would also serve to attach the fitting to the saddle. There would need to be a nice soft seal (like an o-ring) that could compress enough to allow aligning the hole in the screw (shown in green) to the hole in the sleeve (medium blue). Then I realized that if the screw had a shoulder that reasonably sealed to the inside of the sleeve, it could also serve as a flow control valve– useful for getting the flow consistent between the varying oiling points. The idea can also be adapted to a tee configuration, where there is free flow past the junction:

So I was feeling pretty good about myself when a coworker pointed out that I had basically re-invented a banjo fitting, which is a low-profile, high-pressure connection commonly used in brake lines. A banjo fitting has a donut-shaped reservoir around the bolt, designed to provide free flow at any orientation. So my design provides the flow adjustment that a banjo fitting intentionally avoids, which is a useful feature in my low-pressure system.

Oh well. I realized a long time ago that coming up with something that has already been invented is just means you’re on the right track.

CNC mill to-do list

Making progress (finally) on the mill upgrades, including full enclosure, flood coolant, oiling system, and ball screw conversion. Stay tuned!

CNC mill oiling system – plumbing

This is it… Grizzly Miller is in several large pieces on my bench, and the major upgrades have begun. First up, oiling system.

I made some refinements to the original concept and even built a tube-bending tool for the small brass tube I’ll be using.

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First step was machining the X and Y axis ways on the mill’s cross slide. I used a simple ‘S’ curve, programmed point-by-point into an old ProtoTRAK-converted Bridgeport. On the same machine I pocketed out some clearance for the X-axis ball nut.

Beyond these sketches, most of the design work happened on-the-fly. This is unusual for me, but I don’t have CAD data of the original milling machine parts, and tube fabrication turns out to be more sculpture than engineering anyway. I also bought a silver solder kit specifically meant for joining copper alloys, and tried a small test piece from some scrap material.

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I then fabricated the main brass manifold and mounted it to the cross slide. From there it was a matter of drilling end points in the cross slide and connecting the dots with brass tubing. Each of the four ways are connected with my modified banjo fitting, which allows for flow control adjustments. The two ball nut mounts were modified to accept an oiling tube, which will simply splash each ball screw with oil. The manifold will be fed by a flexible tube, which will attach to the little stub coming off the manifold.

The soldering process is messy and dangerous, but once the parts are cleaned up they’re really quite beautiful.

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The finished cross-slide assembly:

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The Z-axis got a similar treatment:

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More to come, stay tuned!


My First Robot, part 1

Isabell is ready for robots!

Isabell is ready for robots!

Several months ago I backed a Kickstarter campaign for Primo, a simple Arduino-based teaching tool for introducing programming logic to kids age 4-7. My oldest daughter was just 3, but my pledge got me plans and code only, and I figured the way projects go around here it just might be done by the time she’s 4. The Primo experience involves a cute (albeit simple) little robot named “Cubetto”, and right off the bat I figured I would modify some things to make him more… well, awesome. Little did I know of the rabbit hole I was about to tumble into.

As usual I started off with some sketches, thinking about what the robot could do aside from the Primo stuff. A suite of sensors would enable all sorts of behaviors, from simple (light seeking, line following) to more complex (play catch, drawbot). I would definitely enable a simple “radio control” mode, but I’m much more interested in autonomous (or semi-autonomous) behaviors. Isabell is obsessed with the Curiosity Mars rover, so it should definitely have some of that DNA. I also believe the rover should have some personality, so I’m looking into some simple dot-matrix display “eyes” that can communicate artificial emotion, and a simple speaker to give it a voice.




I’m focusing on a tracked design for now, so it can navigate a moderately challenging indoor environment. I love the idea of solar charging, or at least autonomously finding its own charging station. Of course it needs a camera so I’m drawn to the Raspberry Pi as a brain, which might also make remote control from an iPad relatively easy. I imagine the Rasp Pi might talk to one or more Arduinos, which can handle low-level functions like battery monitoring or distance sensors. I already have some small full-rotation servos, which will make the drivetrain simpler (vs. motor controllers, gearboxes, etc.).

My main guiding principle here will be flexibility/modularity, so features can be added or changed as we try things, get bored with them, imagine new uses, learn stuff, etc. Next step, start building the platform.