Potential stack and stitch rig

[ChrisR]

I bought this.
I assume it was intended as a frame for a 3D printer.
Do those with experience think it's substantial enough and suitable to carry a dslr, for a stack and stitch setup?

The main beams are 20mm x 40mm extrusions.
The leadscrews are all 8mm diameter and pitch, and motors 1.8°. (42mm sq x 49mm).
I see X and Y are anti-backlash nuts, but the verical one (Z) isn't.

I would expect to swap the 8mm pich for 1mm pitch thread for Z. I'm assuming that's some standard

Z height is about 28cm.











The motors just have 4 way flying sockets.

Any/all suggestions welcome!
The intention is to get it going with an RPi (or Arduino)

[ray_parkhurst]

Looks well-built to me. Anti-backlash nuts, dual pillow blocks on each guide and well-spaced guides.

I love the knobs on the dual-shaft motors. Wish I could find a source for such knobs.

It looks like it would be very easy to add an idler rail to the lower side of the Z-rail to give more stability and load capacity.

[Lou Jost]

Looks like a beautiful piece of equipment! Congratulations on finding something like that.

[ray_parkhurst]

I would expect to swap the 8mm pich for 1mm pitch thread for Z. I'm assuming that's some standard

I think the smallest standard pitch for T8 is 2mm / 1-Lead

[mawyatt]

Chris,

Jolly good find Chap

That should make an excellent S&S stage. The Z axis screw might need to be finer, and a 0.9 degree stepper would help. Also, might want to use the Off-Axis Loading concept to load the Z axis downward.

42mm sounds like a NEMA 17 size motor, so you have plenty of options available for replacing these with 0.9 degree motors.

For starters though, I would go with what you have while waiting on the finer thread screws and motors. If it has 4 wire (2 coil) motors, then you should be able to control them with most adaptable controllers, including the ones we've developed here on PM.

Best,

[ChrisR]

Thanks guys.
Unless I'm misinterpreting, ebay 352575728985 has T8 x 1mm , 200mm long with a nut, for $3.89.

And 272767923336 is a T8mm x 1mm anti backlash, though I'm thinking that gravity would make it redundant?

Not sure where an idler might best go. It's not much like the Wemacro stand. A and B centers are 42mm apart.
I could put longer rods in (red) and put a pillow blocks at green?

A diagonal strut could be good to stop the main frame vertical member bending forwards as the camera is lowered & the moment increases.

[ray_parkhurst]

Thanks guys.
Unless I'm misinterpreting, ebay 352575728985 has T8 x 1mm , 200mm long with a nut, for $3.89.

And 272767923336 is a T8mm x 1mm anti backlash, though I'm thinking that gravity would make it redundant?

Hmm, that would seem to be the case. It's not the first time I've been wrong...

Not sure where an idler might best go. It's not much like the Wemacro stand. A and B centers are 42mm apart.
I could put longer rods in (red) and put a pillow blocks at green?

I can make a drawing for you, but describing in words...

I'd suggest mounting a linear rail carriage on the crossbar just above the red/green rectangles shown in your pic. The rail would then mount on the underside of the long attach plate, just left of the red/green rectangles. The optimum rail length would be about the same as the unsupported area of the long attach plate. I believe this would give full support without compromising any vertical range.

This arrangement would only stabilize the Z-stage. It is TBD how much motion you will get from play in the pillow blocks from the X-stage, or from flexure of the whole X/Z stage. The X-stage pillow blocks have a wide spacing, so it may be unnecessary, but I can suggest a slightly more complex system which would give further stabilization (and increase of resonant frequency/decrease of recovery time) of the X and Z together.

Either the Z alone, or X/Z stabilizers would be pretty simple to implement.

[ChrisR]

I'd be interested to hear what you think Ray - perhaps you have something on another rig you could photo?

There's 6mm in there at the moment - less at the black nut in the middle. not much room for another slide:

[ray_parkhurst]

I'd be interested to hear what you think Ray - perhaps you have something on another rig you could photo?

There's 6mm in there at the moment - less at the black nut in the middle. not much room for another slide:

Your pic shows exactly where I was referring. You may need to add shims/washers/spacers between the large plate and the carriage to get enough room to insert a linear rail.

You almost always need to do some shimming on these idlers to ensure the rail and stage axes are parallel.

Edited to add: you could also add a block to the bottom of the rail to allow it to recess a bit, and possibly even add some level of adjustability. Indeed this seems the best approach.

[elf]

Thanks guys.
Unless I'm misinterpreting, ebay 352575728985 has T8 x 1mm , 200mm long with a nut, for $3.89.

And 272767923336 is a T8mm x 1mm anti backlash, though I'm thinking that gravity would make it redundant?

Not sure where an idler might best go. It's not much like the Wemacro stand. A and B centers are 42mm apart.
I could put longer rods in (red) and put a pillow blocks at green?

A diagonal strut could be good to stop the main frame vertical member bending forwards as the camera is lowered & the moment increases.

How much vertical travel do you need?

p.s. I have a T8x1mm leadscrew but didn't have the anti-backlash nut. The T8 leadscrews I have have an equal to or better finish than the precision acme leadscrews from McMaster-Carr.

[ChrisR]

How much vertical travel do you need?

Not all that much.
The screw is under 200mm long.
Does anyone use more than 25mm or so of actual focus range on a table top rig?? I don't think I have - I'd use a tripod. Assuming an Arca compatible rail/clamp, I can shift the height.

I'll have to search the forum for telecentric options at lowish magnifications. A Canon 100 macro may do but the WD is too long.

[mawyatt]

Chris,

Agree, 25mm is good for most high magnification things since DoF is ~180um at 2X I believe, which would give you ~200 images at 0.7*DoF. I also use a long ARCA plate/clamp for coarse adjustments on most of my setups, very handy and easy to work with....and cheap!!

Best,

[ChrisR]

While in confab with Mike, it dawned that if the base leadscrew were fine too, then I could it as a horizontal rig as well.

[Chris S.]

ChrisR, nice piece of kit! It might also be handy for building a CNC router or mill.

Looking at it, I don't see the need for additional stiffening via an idler. What am I missing? That aluminum plate should be thick enough not to bend, and the existing assembly looks very stable for that axis. Could the long aluminum plate be omitted, or moved higher so that it is centered on the carriage?

I love the knobs on the dual-shaft motors. Wish I could find a source for such knobs.

Ray, have you looked at an "Inertial damper for stepper motor"? I see that at least a couple of outfits make them, though I don't see any with knurling such as those in ChrisR's acquisition. Some of the surplus stepper-driven hardware I've bought has these dampers.

Also, Velmex offers some knobs for stepper motors, though mostly with handles included.

--Chris S.

[ray_parkhurst]

ChrisR, nice piece of kit! It might also be handy for building a CNC router or mill.

Looking at it, I don't see the need for additional stiffening via an idler. What am I missing? That aluminum plate should be thick enough not to bend, and the existing assembly looks very stable for that axis. Could the long aluminum plate be omitted, or moved higher so that it is centered on the carriage?

I love the knobs on the dual-shaft motors. Wish I could find a source for such knobs.

Ray, have you looked at an "Inertial damper for stepper motor"? I see that at least a couple of outfits make them, though I don't see any with knurling such as those in ChrisR's acquisition. Some of the surplus stepper-driven hardware I've bought has these dampers.

Also, Velmex offers some knobs for stepper motors, though mostly with handles included.

--Chris S.

Chris...I have been using the Vexta "clean dampers" for a few years now, having been unsuccessful at sourcing knobs. The dampers indeed serve a dual purpose so I am happy with them, but sometimes simple knobs are preferred. I'd like to find some which are smaller than the ones shown by Chris R (which appear to be same size as the dampers). Still looking.

Regarding the need for idler, I've found that it's difficult to predict how stiff and stable some of these rails can be with visual inspection. Even the KR rails I use, which are very stiff, benefit greatly from an idler. That said, the spacing between pillow blocks is indeed quite wide, so it may be that there is sufficient stiffness as you say, but pillow blocks are notorious for having significant play. They are nowhere near as stiff as a preloaded linear rail carriage. In general they are probably fine for the relatively coarse movements this system was designed for, but I would expect a linear rail idler will be required if the system is asked to perform 8x better than it was designed for.

edited to add: it may also be that an idler could help with any play introduced by the X-stage. This would involve a bit more complexity but might be worth it. I would still offer to sketch this if interested.

second edit: I missed the link to Velmex on first read. Those look interesting! I'll need to see if they offer 5mm shaft mount. Lots of knobs out there with 1/4 shafts, but metric seems to be a bottleneck.