A brief plumbing diversion

Pulling out your Dremel during plumbing work is probably a mistake.  I should have pulled out the WD-40 first, but I didn't.  I probably could have gotten the faucet valve off without the Dremel, but I'll never know for sure. What I do know for sure is that no one makes those types of valves anymore.

It started so innocently.  I had some extra time between Christmas and New Years, and my bathroom sink faucet was dripping.  It seemed like a good time to fix the sink, rather than the beginning of a journey down a dead end tree in plumbing's evolutionary past.  A view into an alternative reality that sucks.  I knew that the sink was old --- probably 90 years old --- but I hadn't thought through what that meant.

When my wife told me it was a Crane sink, I didn't give it a second's thought, because I'd never heard of Crane.  There is a reason you've never heard of Crane sinks --- they're so badly designed for maintenance that it boggles the mind and most people simply junk them.  I've been writing software for 31 years, and I've never seen anything in the software world this bad.  Except for FIX order state management.

The first problem, which we'd noticed when we looked at the house, was that the stopper didn't work, and hadn't worked since I first touched a computer.  Every now and then someone unfamiliar with the house would push it down, and then I'd have to get a knife out to lift it back in place.  Forcing repeat pusher downers to get their own knives prevented repeat occurrences.  The stopper couldn't be fixed because the pole for the stopper is in the ceramic box on the right.  Unlike modern, surviving sink designs, you cannot get to the stopper pull. 

You also cannot get to underneath the faucet, because it is blocked by the same ceramic box that keeps you away from the stopper pull.  Instead, the faucet is held against the sink with a butterfly-like anchor that you insert through the hole on the bottom and then screw up. The top hole is for the water supply.  Being the first person to view the wing nut in 90 years gave me the same queasy feeling I get when I look at gcc's codebase, and wonder, "Does this really work? But the {tests pass}/{water comes out}." It also turns out that no one --- and I mean no one still alive --- makes plumbing fixtures designed to fit this sink.  At one point Mary Anne said "Oh, so it is a four hole sink." No, no it is not. And Mary Anne claims to have realized that, too.

Once I took the faucet off, I was able to pull the whole assembly out:

It looks like something from an Alien movie.  The pipe on the right is the supply, and the long hooked rod is what (in some alternate world) moves the stopper up and down.

My offer to buy a 3D printer and print out a new faucet assembly was summarily rejected by Mary Anne.

A new pedestal sink is in our future.  90 years isn't a bad run.

Bits have width...

I'm working on generating custom gcode to carve topless boxes. The intent is to use them for a dresser I'm building for my daughter.

For my first test I did a bottom and a side; the side is the top piece.

The code for the boxes is up at https://github.com/razeh/gcode-boxes; unlike a lot of other box generators it generates straight gcode, without any intermediate vector representations.

It has two problems: it isn't take the width of the bit into account when it carves the indents, and it doesn't create an tabs for the sides.  I hadn't realized how important tabs are until the bottom piece dropped out from the plywood while the router was still moving.
  

Expanded z axis, new spindle

Over the last weekend, I upgraded my Z-axis.

I replaced the stock spindle with a more powerful DeWalt DW660, which included replacing the stock mounts with DW 660 mounts. I'd bought the DeWalt spindle and the mounts a while back; if I had to buy again today I'd buy a quiet cut spindle, so that I could control the spindle's speed from software.  

While I was at it, I also replaced the stock 200mm Makerslide with one of the 500mm sections from my original Shapeoko 2 kit.  I don't need the extra height now, but when I upgrade the X axis I will.

Both upgrades are working fine, but I'm still having problems with the cutting depth. When I try to carve a circle 1/2 an inch deep I only get a circle about 3/8 of an inch deep.  If I reduce the depth per pass from .028 inches per pass to .014 inches per pass it goes a bit deeper.  If I support the table under the spindle it goes even deeper.

I think there is too much flexibility in the current setup.  Right now there are two big sources of the flexibility.  

The first is that the 25mm by 50mm extrusions that make up the table have too much flex in them, given that they span 1800mm.  I'm going to deal with this by using some of the 25mm by 50mm extrusions as supports under the table instead of as the table surface. I'm also going to start using 25mm by 75mm extrusions for the table surface.  The 25mm by 75mm extrusions are a lot stiffer in 75mm axis (with a moment of inertia of 37cm⁴ vs 12cm⁴), and a bunch stiffer in the 25mm axis (3.1cm⁴ vs 4.5cm⁴) as well.  They also manage to be a little bit cheaper per surface area than the 25mm by 50mm extrusions because you don't need as much hardware to hook them up to the table.

Scythe

I managed to make a scythe for Peter, who wants to be the grim reaper for Halloween.  Along the way I realized I've somehow got things mirrored.

Other things that went wrong: I need bigger holes for the string, and I'm skipping steps on the Z-axis, or some kind of scale is not set properly.
The project is available online at Inventables.

Video for Jens

Here, at reader request, is a video of the mill in action:

More aluminum lessons

Today I managed to make a couple of circular cuts all the way through, but then the bit fell through the hole it had just cut.  The dimple is from a previous attempt.  Some of them are a bit off circular.

Lessons:

• The bit tends to creep up, so put it as far in as you can from the start.
• Clamp the metal down on both sides
• If things start making loud vibration noises, stop everything and see what is loose.
• I tried lowering the feed rate from recommended 500mm/second to 400mm/second to reduce some of the noise, but I'm not sure if that made much of a difference, or if I just should have tightened things down.

Lessons learned from milling aluminum

• No manual steps for the g-code generation.  The workflow that I came up with for the top brackets is:
  •   Draw in Inkscape
  •   Export to SVG
  •   SVG into makercad
  •   Manually adjust the vertical position for the SVG
  •   Add profile operations
  •   Export g-code
  The problem is that the manual positioning made the process impossible to reproduce.  In my case, I wanted to change the feed rates in the middle of the first run, but have it mill the same workpiece. 
• If the piece around the spindle's collet starts to shake, stop things before it falls off.
• The settings from Inventables for milling aluminum work.
• Mill in the center if you want to avoid getting aluminum dust on the y-axis rails and carriage. 

Drawing the top bracket mounts

To mount my 80/20 25-5010 extrusion to my two Makerslides, I need to mill some brackets for the top.  Doing the design has been a bit harder than I thought it would be.
My first thought was to use Easel, but it doesn't let you specify locations in absolute terms with numeric input. Since the top bracket has to line up with the T-slots in the three extrusions, that rules out Easel, at least for the design.
Since the top bracket is a simple milling it seemed like it would be worthwhile to dive into generating the SVG for it by hand, and then import the SVG into Easel.
The first complication was spending a lot of time looking at the SVG arc, which seems to lack a clear explanation, although there is this excellent demo.  Having had some difficulty working with SVG's arc, I decided to use a Bezier curve instead.  You don't have to figure out the style for the curve on your own; there is a nice page right here that lets you dynamically adjust things.
Or, I could just edit things in Inkscape, which turns out to be much easier.  The only complication is that I have to specify the drill locations for the holes via bounding box, instead of center point.  This is painful when you want to adjust the hole's diameter.
But here are the calculations for the top bracket.
An extrusion bracket for Makerslide is 14mm wide, which means we want to have 3mm of clearance from the Makerslide's v portion, meaning we'll want the section of our bracket over the Makerslide to be 17mm.  The 25-5010 extrusion takes up another 50mm, and then the other Makerslide takes up another 17mm, for a total of 50mm + (17mm*2) = 84mm.
The T-slots for the Makerslide are centered, but our bracket section isn't, which means that the holes need to be centered 7mm from the edges of our bracket.  The 25-5010's T-slots for the  25-5010 are 12.5mm in from the edge of the 25-5010.  That would give us drill holes centered at Y=7mm, 29.5mm, 54.5mm, 77mm.
But Inkscape won't let us put in center coordinates.  If our drill holes are to be 6mm in diameter, we need to subtract 3mm from each Y position, for 3mm, 26.5mm, 51.5mm, and 74mm.

Ready to bootstrap

After a bunch of work to stiffen everything , it is ready to start cutting aluminum to attach my makerslides to my 50mm by 100mm extrusion for the x-axis. 

Next purchase list

This is what I'm going to need to stiffen the X axis, plus a few parts to broaden out the table.

One 25-5010, 1800mm long.
Four 25-2575 1830mm long
eight 25-4113 4-hole corner inside brackets to join the 25-2550s.
thirty-two bolt assemblies (75-3404 m6 x 10mm w economy t-nut) to tie in the 25-4113

To stiffen the vertical legs, which are wobbling a bit when we move the table around we'll add joiner plates on the middle legs to see if it helps.
2 25-4165 8-hole joining plates
sixteen bolt assemblies (75-3404 m6 x 10mm w economy t-nut)

six 25-4132 2 hole inside gusset corner brackets (2 for the midspan and 4 for the corners)
twelve bolt assemblies (75-3404 m6 x 10mm w economy t-nut)

When we switch out to larger motor mount plates, we'll also need screws that are .15 inches (4mm) longer (because the motor mount will be .25 inches thick, not 12 gauge.  That works out to:
four M5 x 34mm Button Head Cap Screws
eight M5 x 24mm Button Head Cap Screws

We'll also need to extend the carriage for the Y-axis, but this is enough for one night.

How's that for stupid?

Last night I got most of the new motors hooked up:

Naturally, the next thing I did was to hook up my gShield to verify that the motors would turn when commanded to do so.

But it didn't!  Even though all of the wiring looked good for the Y axis motor.  There was a brief sound every time I clicked, but no motion.  I double checked on the inventables website that I could drive my motors with the gShield, and sure enough I could.

This evening I took a look at it again.

I'd switched axis in my head.  The brief sound I'd heard was the other axis's motor.

Sigh.

It made buying a terminal block at Radio Shack, where you have to wrap the wires around the screws rather than sandwiching them between plates, look relatively minor.

Stiffening the X axis

Stiffening the Y-axis on a shapeoko 2 is easy; add more midspan supports.

Stiffening the X-axis is a bit harder.  I'd done some calculations before hand that showed there would be some flex with the maker slide given the rather large size I'm building out to.  For 1800mm, with an 44 newton load, a single maker slide would deflect over a millimeter.  Makerslide just isn't that stiff, and midpoint deflection goes as the cube of the length.

I've been looking at a couple of alternatives for stiffening things.

There are a couple of really cool projects that stiffen things up with steel.  Unfortunately, when I did the math, 1/8" of steel will not add much to the stiffness, and even a 25mm by 50mm extrusion doesn't add a lot of stiffness.  Stiffness goes as the cube of the height.

Another possibility would be to sandwich the maker slide around a custom cut steel piece.  It looks like there are places that will custom cut steel for you, but, again, after doing the math, it doesn't look like it would add that much stiffness --- steel's modulus of elasticity is about three times that of aluminum, but a solid square steel bar that would fit inside the maker slide (4cm by 2 cm) would have a moment of inertia of about  (( (4 cm)³ * 2 cm) /12) or 10 cm⁴

To get really stiff you need to move up to a taller extrusion, something like the 25-5010, with a moment of inertia of 132.  Of course, the motor mount plates won't fit anymore.  I'll have to design some custom ones.  From looking over the shapeoko forums, it looks like 6061 is the alloy of choice.

So, that makes the plan:

1. Design taller motor mount plates that can also fit nema-23 motors
2. Order 1/4" aluminum plates
3. Order longer screws for the motor mount 
4. Order longer screws for the X axis carriage
5. Order more spacers for the X axis carriage

Today's mistake

Today's mistake was putting the surface supports at a right to the y axis. Because there is no way the wheels are going to clear the surface. 

Beginning

I've been having some fun building out my Shapeoko 2, with Matthew, and it is about time that I started to document it, if only for my future self.
Today's learning experience involves bits.
On one of my initial runs I'd broken the bit that shipped with my Shapeoko 2.  Undeterred, I bought a few more 1/8" bits at the hardware store around the street corner.  I also, on a whim, bought a 1/8" Dremel router bit.
I wasn't very happy with the results.  My circles, were, well, mostly circular.   Probably because you could see the long 1/8" bits deflecting as they moved across the grain.
Today, after another 1/8' bit broke, I broke out the Dremel router bit.
Oh my.  What a difference a shorter, more solid shaft makes.  My circles are actually circles now.  It's even quieter.