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Up too late milling

posted Feb 8, 2017, 8:41 PM by Daniel Taylor

You know it's a good day when you end up with a bucket of chips.

Doing the impossible... almost

posted Feb 7, 2017, 6:09 PM by Daniel Taylor

It turns out I made one last mistake on my design: You can't assemble it. I don't feel like explaining it, but basically you just can't get at all of the screws you need to at the times you'd need to to assemble everything. With a little cheating (ie, grinding down some material so I could slide the leadscrew in after securing one of the support blocks), I managed to get it mostly assembled. "Mostly" meaning that everything is there, but the rails are missing 2 screws each. I could (and probably should) fix that by drilling some holes through the moving part so I can feed the screws in while it's attached, but... eh. Maybe once I get a drill press and/or discover that it's a problem.

Anyway, pictures:

For reference, here's what it used to look like:

And what it originally looked like:

It sure looks better now! Unfortunately I don't have enough time tonight to finish milling the lid for the laptop, but so it goes. Much better that I get enough sleep tonight- all of this shop time is tiring!

So close... one last(?) mistake

posted Feb 6, 2017, 6:38 PM by Daniel Taylor   [ updated Feb 6, 2017, 6:48 PM ]

I once again spent far too long in the shop today (if there is such a thing), trying to get my new Z axis all put together. I had to fit the bearing blocks (both to the Z axis backbone and to one of the bearings I neglected to account for differing in size from the other), drill holes to attach the stepper mount, and as it turns out, the M6 screw holes on the linear bearings are SLIGHTLY undersized for standard M6 screws, so I had to turn the heads down on the lathe.

All that out of the way, here's what I got:

Here's the part that moves up and down. -Z is pointing away from the camera. The grooves in the right image are for mounting the spindle clamps in.

Same thing, but with the fixed piece of the axis. You can see where the X axis leadscrew attaches, as well as the stepper mount.

Comparison to the old back plate... it's a little thicker.

Parts mounted on the Z axis fixed plate. This had to be disassembled, since you can't actually get it attached to the machine if you assemble it in this order, but everything fit together nicely

Same thing, but without the rails.

The fit is REALLY nice between the two pieces- the rails don't bind, and there's clearance between the various pieces.

...And then we get to here:

(This is the X axis ballnut and the new Z axis plate you're seeing- you can see one of the X axis rails and part of a bearing block at the top of the image)

Apparently the previous Z axis plate was like this as well- not sure how I didn't notice or break something. Anyway, there isn't enough of a relief in the plate for the X axis ballnut. So it's back to the mill tomorrow to deepen it and THEN I should be able to put this on the machine and be back in business.

Is it done yet?

posted Feb 2, 2017, 4:55 PM by Daniel Taylor

Per Betteridge's Law, no.

As it turns out I've been extremely delinquent in posting updates here, so this will have to include some background, as well as what I initially intended to post.

The background: I tried to machine some parts for my laptop case. In doing so, I observed that the Z axis wobbled. A lot. Turns out the bushings in the Z axis are pretty terrible under load. My previous assertion that the Z axis couldn't be all of the error is clearly false- with a single finger I can deflect the tool FAR more than I should be able to (I don't recall the exact numbers).

So now the lid of my laptop is clamped down to the table, and I don't want to un-clamp it and lose my zero. So... time to upgrade the Z axis.

I got that all CAD'd up (big bricks of aluminum for the supporting structures, linear rails to facilitate travel- I should have a picture, but don't want to fire up CAD), ordered bearings/screws, and now I just need to machine the parts.

Which brings me to the update I set out to make here- progress on that front. The Z axis is 6 machined parts: A mounting plate, a carriage, a stepper mount, 2 ballscrew mounting blocks, and a ballnut mounting block. The latter four pieces are complete-ish (sans tapping):

Stepper mount, ballscrew support, ballnut mount, and another ballscrew support.

The mounting plate I haven't started yet, and the carriage (or whatever you want to call the part the spindle clamps to) is... half? done. Everything that can be done from one side has been done, at any rate. So I just need to tap a bunch of holes and finish 1.5 parts... I REALLY want to get that done by the weekend, so tomorrow may be a half day of vacation==shop time...

Makin' chips

posted Jan 4, 2017, 7:33 PM by Daniel Taylor

Pocket test

So it turns out I can feed a lot faster than I had been. That's ~94 IPM (2400 mm/min), and I think there's room for more. Pretty cool to see those chips flying.

The final dimensions of the piece (and another test I didn't catch on video) aren't quite right, so I'm trying to figure out where that error is. I feel like the machine should be able to hold a LOT better than 13 mil. Currently it looks like most of the error is in the Z axis, though that doesn't seem to account for all of it. Grr...

Because nothing says "Merry Christmas" like a flat chunk of metal

posted Dec 24, 2016, 9:53 PM by Daniel Taylor

Lots of stuff going on... I made a new sub-table to mount my t-slot table to, since of course the arbitrarily-pitched hole pattern I drilled on the previous one was completely incompatible with the table. Serves me right, I'm sure.

Anyway, I made that, mounted it, and machined it flat.

...And mounted the t-slot table on top of it:

And here everything is sitting in my shop... I got a new workbench to put things on, so it's a little less cluttered.

It was a bit of a trip getting here. I blew up my nice Geckodrives- really not sure how, but they tell me I totally fried basically everything, from a FET or two down through the entire 3V3 bus. On all of them. At the same time. I have no idea how that happened- best they can guess is a ground loop. So now I've joined the Beaglebone and the stepper PSU grounds. Haven't blown up the new drives yet!

The new drives are an all-in-one unit from Geckodrive- the G540. It even has a drive for a fourth axis! What's nice is that the pinout matches that of the Beaglebone almost exactly- I only had to remap one pin. No idea if that's intentional or not. It's ALSO good that I had the forethought to wire my steppers to DB9 connectors in the standard Geckodrive pinout, so they dropped right in with the new drives. It's like I KNEW I'd blow things up or something... mostly serendipity actually, though I'm not going to complain.

I ALSO blew up the Beaglebone. Again, not sure how. I was probing pins at the time (trying to get the new drives configured), so I probably shorted something out. Normally electronics don't straight up die from a brief short, but that's all I can figure. One of the 3V3 rails is trashed, and there's enough stuff on said rail that I didn't want to dig. Plus the regulator is a large-ish QFN in an inconvenient place, so I didn't want to replace it on the off chance it's the problem.

Anyway... ready to get back to breaking end mills! And to stop slacking on that laptop...

T-slot table!

posted Oct 6, 2016, 5:42 PM by Daniel Taylor

I got a t-slot table for the mill! It's not steel, but it's nice and flat. I'll need to drill holes to get it mounted, but it's still exciting.

No place like home

posted Jul 5, 2016, 7:39 PM by Daniel Taylor   [ updated Feb 7, 2017, 6:14 PM ]

Well, if there were a home on this machine. I got the control box wired up, though that doesn't include home or limit switches. As such, I've made it so "home" is specified in software for the moment. I'll definitely have to fix that (and the limit switches), but for doing some tests of how square things are, it's good enough. I DO have the ESTOP wired in, however.

Anyway, the pictures:

In the first image, you can see everything wired up. The steppers all have DB9 connectors on the, with the same pinout as the Gecko controllers use. Not that that's likely to become relevant (plot twist, it became highly relevant, added 2017/02/07), but it was as good a method of choosing pinout as any.

Anyway, you can also see the steppers mounted (left side of the right image), plus the heatsink on the outside of the box. I sanded the coating off both the inside and outside, then added thermal paste to all interfaces in an effort to get a good thermal connection. The sanding was a pain, but that's the way it goes.

The only other thing to point out is the mess of cables. In theory things will get a little cleaner when I get around to ordering the right DB25 connector- I got the wrong gender this time around. In practice... it works, so it'll probably stay like this a while.

Not pictured is the table, which finally has all of the holes tapped (I got a nice blister doing that). At least all the holes that are drilled- there are still a few more that need drilling, though if/when that happens again remains to be seen.

It's probably time to get some help moving this to the 240Vac outlet so I can do some test cuts... Well, after I drill out the final 3 holes for each of the Y axis rails. Those aren't quite aligned, so I'll just drill them out and put nuts on the back. No big deal.

Some assembly completed

posted Jun 25, 2016, 7:54 PM by Daniel Taylor   [ updated Feb 7, 2017, 6:15 PM ]

I assembled things enough to check squareness... and it looks pretty good. At least as far as I can tell without actually machining some hard material.

That said, I may or may not have broken one of my stepper drivers. Due to a wiring issue, I blew up one of the current-sense resistors (it's 0.056 ohms, so I don't know what else it would be). On the up side, I can replace that pretty easily (and DigiKey will get parts here in a couple days for a reasonable fee). On the down side, it's one more thing to do.

Next step is probably trying to wire up a 240Vac outlet. I don't have one of those here, and definitely need one before I can cut anything.

So... mechanical good, electrical still needs work. And actually the mechanical does as well (adding in two more bracing pieces on the bottom, tapping the holes in the table, putting all the screws in the Y axis rails, etc.), but it's enough to try cutting things.

Some assembly required

posted Jun 22, 2016, 8:38 PM by Daniel Taylor   [ updated Feb 7, 2017, 6:17 PM ]

I think that's the last of the parts that need to be made. A few still need some more or less minor fitting/rework, but overall it's just assembly at this point. Plus pesky details like electronics and limit switches...

Anyway, the pictures:

The back piece needs the hole for the coupling enlarged so the clamping screw doesn't catch on it, but otherwise seems to fit well. The corner supports look good.

The table also fits well somehow- I'm still amazed when that happens, despite CAD and building things via CNC. The holes/countersinks line up perfectly for the ballnut mount and linear bearings. It just needs the edges cleaned up (not technically required, except for maybe the edge by the stepper), several holes drilled (all those black X marks), and every single bloody hole tapped. Preferably actually perpendicular to the plane, unlike most of my tapping jobs...

In short: I'm super excited! So close...

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