Sindrian Arts

I figured it out!

As is often the case, after stepping away from the problem for a bit I came up with a simple solution:

First, secure one side of the gantry to the table (or have a friend hold it).  Next, apply power to the machine, but engage an e-stop.  Now take a long square (I used a drywall T-square) and place the short side flush against the side of the gantry that is secured so the long side is pointing across the table to the unsecured side.  Make sure that one edge of the long side is lined up with some landmark that appears on both sides of the gantry (I used the vertical edge shown in the above pic).  Finally, go over to the unsecured side of the gantry, manually deflect it until the same landmark is lined up with the appropriate edge of the square, and then release the e-stop switch to apply power, thus locking it in.

Granted, this is not a super-precise method, but given that you’ll probably get your deflection down to less than an eighth of an inch over the entire width of your table, it should be close enough for most work.

Ok, back to making Kickstarter rewards!

The new couplers are doing great!

Mostly.  I think.

Since I’m done traveling for the next few months, I finally got to spend some time working on the Kikori last week. I wanted to mill out one of my tablet stands, but to make sure everything was staying nice and accurate, I did a test first.  I decided to drill a hole at a known location, do an air-cut of the hole pattern, and then have the machine return to the hole location to see if it had gotten off at all.

It had.  Only about 1/16th of an inch in X, sometimes in Y (I tested it multiple times), but it had.

The two most likely culprits are set screws working themselves loose and couplers slipping.  I applied loctite to the set screws before I left, so today they should be set.  I’ll make registration marks on the couplers to check on slippage there.  Wish me luck!

Remember the coupler issues I was having?  Fixed ‘em!

While I was in Oakland I did a fair bit of research on what my options were, and finally decided on these “light duty” couplers from McMaster-Carr (Part no. 6115K18).  As you can see, not only are they aluminum (instead of plastic (nylon?) like the last ones), they are HUGE.  You can see the size difference here.  I actually had to dremel out the x-axis motor mount to get it to fit, but thankfully it didn’t need much.

After slapping those puppies in and tightening up some things (I really need to remember to put loctite on those set screws), I milled out a couple new test pieces.

Beautiful.  Not only did they have wonderfully smooth edges, free of steps and ripples, but they also fit together snugly!  This means that they are likely within 0.01″ of their intended dimensions.  I’ll have a better sense of it’s accuracy once I mill a harder material like masonite.

Of course, now that my machine is finally working well I’ve got to go to Chicago for my nephew’s bris, but once I get back on Monday, I’LL FINALLY GET TO MAKE STUFF!!!

I’m very excited.

The Kikori is now at MakeIt Labs!

Granted, right now it’s little more than a pile of MDF and various bits of gantry, but it shouldn’t take long to put back together.

My biggest concern right now is the torsion box.  Unfortunately, very few of the ribs survived the move intact; most of them are in two if not three pieces.  Thankfully, I have all the pieces and it’s clear which pieces go together. This means that while I can reassemble the torsion box, but I’m not sure how strong it will be.

My current plan is to put it back together as-is and immediately use it to make a new set of ribs out of 3/4″ MDF instead of 1/2″.  This means I would have to use the reverse side of the skins since these new ribs would no longer fit into the slots the original ribs fit into, but given that the slots were too tight to begin with, this might actually be a good thing.  Another option is to make them out of 1/2″ MDF again, and simply make them taller this time, increasing their strength that way.  I could sand out the slots to make them looser.

Of course, if the reassembled torsion box seems fairly strong even with the broken ribs I might just use it as-is. After all, having a perfectly flat milling plane is only super-important if you’re doing 3D carving; it doesn’t matter as much for simple profiles.  Besides, I’m itching to start prototyping the launcher!

Last night I finally finished assembly of the kikori!  After taking a break for a good maniacal laugh, I got started on testing by putting a sharpie in the router and having it draw ‘EMC2 AXIS’.  Not surprisingly, I ran into issues right off the bat.  Thankfully, tackling them was fairly straight-forward.

The issue was that there was some slop in the X and Y axes.  The source of this slop was the set-screws in the drive sprockets; if the screws aren’t tightened down all the way onto the flats I machined into the drive shafts, the sprocket will rock back and forth when the gantry changes direction.  On the Y axis this was fairly easy to fix; since the gantry is comparatively light, I was able to rock it back and forth while tightening the screw until it was solid.  However, on the X axis the weight of the gantry meant that this approach would cause me to strip the little screw before it would tighten all the way.  Therefor, this afternoon I implemented the fix I used on the blackfoot I built in Boston.

I replaced the small set screw with a socket-head screw.  This allowed me to use a larger allen wrench which in turn allowed me to apply more torque in tightening it.  The only downside was that I then had to grind a flat on the head of the screw so it wouldn’t rub against the roller-chain.

After all that I ran another test and found that while things were much better, there was still some play in the X axis.  This turned out to be from the Lovejoy couplers I was using to connect the motor to the two drive shafts.  I’ve used these couplers before, and they had no perceptible backlash, but these had enough to translate to about a eighth of an inch of travel.  Luckily for me, I know a local guy who bought a blackfoot kit that he has yet to assemble, and he lent me the ridged couplings from it.  Once those were slapped in, it ran like a dream.  There was still a tiny bit of wobble, but I’m fairly certain that that was the sharpie not being solidly mounted in the router.