Lockdown turntable and lathe - a DIY project

[A1beats]

40.jpg
The lathe, with the 'coin exciter' head mounted on its transport mechanism. When the head is fully lowered on to the disc, the stylus is at a very slight trailing angle (2 - 4 degrees from vertical).
41.jpg
Close-up of head transport. The counterweight is a collection of 'penny washers' held in place by two 6mm collars.

This post brings the 'project report' up to date (7 May) - I'll document my work henceforth in subsequent posts to this thread. Thanks to KNOP and Grooveguy in particular for their careful documentation of their own projects, and for making their findings public!

David

Hi David, Could u share info where u got the motor and linear pulley's and belt?
Thanks

Arnold

[pentlandsound]

Hi Arnold,

Here's some places where you might find what you require:

Pulleys: https://www.motionco.co.uk/grooved-pulley-20mm-round-belt-p-458.html
Depending on the diameter of the shafts of your linear rail and motor, you may need either or both of these:
https://www.motionco.co.uk/bore-reducer-bore-10mm-long-p-427.html
https://www.motionco.co.uk/bore-reducer-bore-10mm-long-p-430.html

Belts: https://www.ebay.co.uk/itm/394808486184
Endless 'O-rings' seem to work best. I don't think this was the exact listing on eBay, but it's very similar. You need a belt to fit your pulleys (3 mm CS), with the ID/OD (inner/outer diameter) chosen depending on how far apart your linear rail and motor are. Hint: don't make the belt too tight.

Motor: I have a Jugetek stepper, model 14HY0007-20B. I chose a NEMA-14 motor because it's fairly compact and sits more or less flush with the V-Slot rail, but there's no real reason that you couldn't use a NEMA-17 one - they are more common and easier to find.

Hope this helps!

David

[Fattcamp]

Hey guys,

I'm putting my Digikey order together and have a question on the capacitor values from the hand-drawn diagram (https://github.com/dn784533/lathe_guide/blob/main/LR_controller_circuit.png). Are these pF or nF? I doubt they are uF! These are for the 390 & 330 values on the bottom of the diagram:

Arnold: Sorry for the late reply. Had to take a break from the project for some family stuff. Appreciate Dave providing the links. I ended up getting the motionco stuff linked above and went with these O-rings on e-bay:https://www.ebay.ca/itm/335088185273?var=544315519791

Thanks guys,
Dave

[pentlandsound]

Hi Dave,

The 330 and 390 capacitors on the hand-drawn diagram are indeed uF. I had read somewhere that a 100 uF or so cap may be placed between 5V and GND to smooth out the supply to an Arduino; the 330 and 390 uFs were just two spare caps I happened to have that were near enough. Depending on your power supply and stepper motor, you might not need the capacitors. If memory serves, the Arduino in my system was being reset by spikes in the supply every time the stepper motor started up, and the capacitors were an attempt to get around this. It worked!

David

[Fattcamp]

Hi David,

Thanks very much for the reply. I can't seem to find non-polarized & non-smd/smt 330uF caps through my standard sources (Digikey/Mouser). Are these polarized or is there something I'm missing here? I was just looking for standard film or ceramic axial or radial caps but maybe I'm looking for the wrong thing. There's lots of SMD/SMT but I'm just going to be working with standard stripboard as per your build.

Thanks again,

Dave

[grooveguy]

Hey, Dave, not that familiar with this project, but looking at the perf-board layout it would appear that both those caps are across the power supplies, so you do want normal-old polarized electrolytics. I, personally, would also put a 0.1uF ceramic cap across the same points, as big 'lytics don't do that good a job at really high frequencies. And I question the need for the oddball-value 390uF, I would think that another 330uF would do just fine, or put in a 470uF if you feel so inclined. Caps across the power supply are simply noise-absorbers and oscillation-preventers for the most part. As with most electrolytics, be sure that the DC working voltage is higher than what they'll sit across; 50V for both would be my choice.

[Fattcamp]

Thanks for the info & explanation! Much appreciated. Onwards with my orders!

[Fattcamp]

Hey guys,

I've got pretty much everything for this build now minus the embossing stylus and a high-torque TT solution but I'll have my hands full for awhile putting things together. I was curious about something asked earlier in this thread:

inspector77 printed the parts themselves and provided a link to the drive (https://drive.google.com/drive/folders/155ahObO2Uf4BSHs89NWolO17SiiT1Aut) with their STL files, which included a new file "CONO_4.stl". These cones replaced the aluminum cones in David's build which can be seen in the picture below and figured I'd give them a shot.

Does anyone know what sort of metal shaft would have been used here and where to source these super tiny shaft collars? I'm wondering if it's worth doing this or simply following the build instructions for the aluminum cones. I've been able to find shaft collars for the rest of the build but these would need to be even smaller and can't seem to find a source.

Thomas (farmersplow) suggested searching for "modellbau stellring 1mm" awhile back but I'm not having luck.

Thanks again Dave for this awesome build! I hope to make some good progress in the coming weeks.

Dave

[grooveguy]

These may still be too big for you; what is the ID of the part you need?
https://www.ebay.com/itm/133005240498
Seems like something you could make from 1/4"-or-whatever round aluminum rod; just whack it off to the length you need, chuck it up in the drill press and bring it down on your drill bit clamped in a vise. Bore a 2-56 or smaller setscrew hole in from the side, and voilá!

[Fattcamp]

ID of the cone bore is 6mm and outer lip looks like 8mm... so that ebay link could work if I open it up a tiny bit and still have a thin wall to hold the collar in place.

Also curious what they used for the actual shafts that connect from the collar to the torque tube, but I guess it could be pretty much anything. I wasn't sure if material mattered for that at all. I'm a newb but dove hard into this build and have amassed many parts, so I'm ready to start putting it together! Appreciate the help on this.

Dave

[Fattcamp]

I ended up going with 2.1mm shaft collars and 2mm steel rods from amazon and we'll see how she goes. I was initially trying to find 1mm collars but I guess they are few & far between compared to 2mm.

As it turns out, these sizes/items are used for RC plane landing gear and whatnot. If all else fails, I'll go with the aluminum cone method from the original build notes.

Dave

[farmersplow]

The smallest finished part I found has a diameter of 1.6mm (for 1.5mm rods). The outside is 6mm.
https://www.amazon.de/MB-Modellbau-Berthold-Stellringe-Messing-Vernickelt/dp/B06WP2Z14F?th=1

But the material is brass and therefore heavy. I think you can achieve better results if you take a 6mm aluminium rod and shorten it to the length 4.5mm or 5mm? Then smooth the surfaces with a file or sandpaper and drill a 1mm hole in the centre (or you drill the hole first and then shorten the length so that you can hold the rod better). If the hole is not 100% in the centre, it won't make much difference. Then clamp it in a small vice and drill a 2.4 mm hole in the side and cut an M3 thread into it with a tap. You can then attach a 1mm rod with a small M3 grub screw. It weighs much less and still holds well.

I don't know the details of the attachment and the 3D printed parts. How is the adjusting ring attached to the cone?

Thomas

[Fattcamp]

I ended up returning the 2.1mm collars & 2mm rods and picked up 1.6mm collars & 1.5mm rods. Thanks for letting me know about those sizes!

I also just sanded down the 6mm rods to fit the 626RS bearings and glued them to their respective parts so making progress. I should be able to make some more progress tonight as I have nearly all parts for the build now.

Thanks,
Dave