Gemmasta Encoder Mod Thread

[daw1zard]

Cool idea, I will need to look at getting the fine adjustment upgrade first. Thanks for that.

Troy

[Gem Ranger]

Looks great! Is anyone selling the completed units for a Gemmasta ... if so who and how much?

GR

[Lefty]

You're well and truly an engineering-minded bloke Andrew

Ever considered building your own machine from scratch?

[Orange Pirate]

a US Digital E2 encoder, 1250cpr,5000ppr gives me 0.072 degree steps. The encoder also has an index so the unit recalibrate every time the hand piece is lift above roughly 95degrees. I got it for about $50 of ebay,

Thanks for that. You've certainly got the old brain box thinking.

An instructions thread would be a great idea. Tips, photo's, tutorials, code, etc..

Cheers
OP

I'd love a 5000cpr, 20000ppr encoder 0.018degree steps  one day, easy to swap over.  I might start putting some info into a word document over the next week or so.

I'll probably stick with your proven first. Then complicate things later - can't even find the smiley thingo on here. I'll be using a PICxx microcontroller.

So if there is anybody who wonders how writing software for Arduino's is even possible - like me. There is a god. It's called Flowcode - http://www.matrixtsl.com/flowcode/info/v6_licence_info.php
I think the free license will work for this. All you need to buy is the components and a PIC programmer ($40). I've even found a basic code example that (in theory) should do this job. I shall post an image once internet starts working properly.

Question------. Dismantling that shaft with the big nut. Is there anything I should be aware of. Like a unique rare spring that shoots out, fly's across the room and get sucked up by the vacuum cleaner rendering the Gemasta to the scrap pile? Or a preload that has to be nano newtons perfect? I can rebuild an engine but that makes me nervous.

Cheers
OP

[MakkyBrown]

Ever considered building your own machine from scratch?

I was thinking about doing that Lefty after I decided we couldn't afford a new machine, but then I got myself a nicely priced lightly used Gemmasta for $1000 with some new laps , plus about $120 in bits for the encoder setup. Very happy with my machine atm.

Looks great! Is anyone selling the completed units for a Gemmasta ... if so who and how much?

GR

No, these are just do it yourself projects atm based on the designs in Tom Herbst's faceting book.

[Rusted]

Orange Pirate.
I am going to dismantle my Gemmasta head tomorrow and put the new hollow shaft that I manufactured in. I will take photos as I do it and post them here. MakkyBrown made a replica of the original shaft and drilled it. I made a few minor mods which I hope will make it better.
There's nothing in there that should scare someone who is a bit mechanically minded, its probably worth dismantling and cleaning and regreasing anyway, when I first looked at mine the grease had dried and gone hard so yeah its worth doing.

Paul

[MakkyBrown]

Leah(thanks ) has created  a"Faceting Machine Modifications" folder upload all pics and documents to that folder.  Found in galleries.
http://aussielapidaryforum.com/forum/index.php?action=gallery;cat=86
For reference maybe add part of your username before each photo. ie "Rust-Gemmasta mod pic1" etc and supporting doc. I'll put together a parts list with ebay links etc of what I used and a bit on selecting an encoder. I will see if I can upload a zip of the arduino program code I used.  The hardest bit for this build is making the new shaft. It has to be close to perfect so the movement can be transfered into the smaller shaft without a flex point. If you can make the shaft I am happy to help with the rest of the build, machining the shaft is the trickiest bit imo. 
Cheers
Andrew

[Orange Pirate]

Orange Pirate.
I am going to dismantle my Gemmasta head tomorrow and put the new hollow shaft that I manufactured in. I will take photos as I do it and post them here. MakkyBrown made a replica of the original shaft and drilled it. I made a few minor mods which I hope will make it better.
There's nothing in there that should scare someone who is a bit mechanically minded, its probably worth dismantling and cleaning and regreasing anyway, when I first looked at mine the grease had dried and gone hard so yeah its worth doing.

Paul

Thanks Paul. Didn't think it would be too hard but better to be prepared.

Cheers
OP

[Rusted]

I have just uploaded some pictures of the build so far, at this location----http://aussielapidaryforum.com/forum/index.php?action=gallery;cat=86

As Makky Brown mentioned, the shaft is a really precise bit of engineering, both of us took quite a few hours to accurately machine a replacement shaft. It would be possible to drill a small hole down the centre of the existing shaft but both of us were concerned at the likelyhood of breaking a small hardened drill in it and having no wiggle room left at all. This is not a job that you can do with your trusty Black and Decker cordless drill or even a decent drill press, it has to be done in a lathe, very carefully.

It was Makky Browns idea to use the same 1/4" National Fine thread on both ends of the shaft, the big brass front nut and the lock nut underneath it just fit straight back on.
Behind the protractor is the spacer, this is machined from 40mm bearing Nylon and has a 1/4"NF thread to match the new shaft, this replaces the original 1/4"Whitworth brass nut that was on the old shaft, it also is machined out inside to 20mm to house the flexible coupling, three countersunk 3.5mm allen head bolts hold the encoder to the spacer.
The nifty charcoal hammered metal paint look of the spacer is how it came, the nylon has Graphite or Moly or something in it to help it be a slippery bearing and thats how it looks.

I am still contemplating how I attach the thin encoder shaft to the facet head.

So far all this has been achieved without drilling screwing or putting globs of Silicon anywhere near my facet machine.

Paul

[MakkyBrown]

Looks good Rusted. I used dextone metal epoxy(that I've been dopping with) to stick the riser alloy bit to the front and to bed the shaft into the end piece. I first glued the riser in place with cross over piece attached and aligned with the 2.5m shaft loosely in it. I used a tempory brass sleeve to centre the shaft(drilled a 3mm lip into the replacement shaft and had some brass tube) in the recess hole filled with dextone in the front piece. I first filed some gouges/flats on the end of the 2.5mm shaft. I then dextoned it in two steps.  First with a small amount into the front bit. The front bit had about a 2.6mm hole furthest in and flared out 7mm cup. After the shaft was set in place I pulled it out(remove the two screws holding the riser to the cross over bit) and filled the cup around the shaft. It is a very solid connection. The only thing I'd do differently is have more of a surface area where the riser glued onto the round alloy face on the faceting machine. I decent bang could remove it but both alloy surfaces were light sanded and perfectly clean so it might be stronger than I think.
I just realized after typing all that it's going to be trickier for you as you need a removable connection/clamp due to your setup on the other side.  NO, or a small hole through your mount to get at the grub screw on your coupling to let the 2.5mm shaft come free . You have probably already thought of that.
Cheers
Andrew

[Rusted]

If this is beyond your capabilities then at least consider upgrading your machine to an electric Depth of Cut meter. For very few dollars you can put together an analogue meter, (with a needle) a battery holder, a linear potentiometer, (variable resistance to adjust the needle deflection) and some wire.
In the Gallery for this thread you can see my meter in the photo of the completed encoder mounting.
I fancied mine up with a couple of banana plugs to make it easier to dismantle when I am cleaning around the machine and a switch,( if you use the original Gemmasta buzzer plug hole underneath the head then park your head in the upright position it can touch the frame and drain your battery.)





Edited by admin to add the photo.

[Rusted]

Attaching the lever to the encoder shaft should be easy, just a small grub screw will do that, and to anchor the end to the head, something thin underneath the screw that holds the angle cheater on, or maybe not.
I would like it to be reasonably easy to dismantle for machine maintenance, greasing bearings etc. perhaps the best way would be to drill and tap a small hole so I can bolt an encoder shaft operating lever of some description to the facet head.

Paul

[agemcutr]

I tried to upload my PDF on machine tuning to the gallery.but it seems to be picture or video only.
When are you going to make a step by step with photos so we can all have one of these.

[Aussie Sapphire]

I tried to upload my PDF on machine tuning to the gallery.but it seems to be picture or video only.
When are you going to make a step by step with photos so we can all have one of these.

You can email the pdf to me Tony and I will upload it to downloads section with link to this thread if you like.

I may also be able to modify the gallery to accept pdf files but will have to check later on that (off to tennis shortly).

cheers
Leah

[MakkyBrown]

I tried to upload my PDF on machine tuning to the gallery.but it seems to be picture or video only.
When are you going to make a step by step with photos so we can all have one of these.

I haven't tried uploading documents yet, could you check that Leah?
The tricky bit is the idea of the design has come from a book and anyone building it should buy the book. Tom Herbst(who wrote the book) has his code freely available on his webpage http://www.facetingbook.com  so I don't think it would be an issue uploading my modified code I used but his wiring etc. Although I changed it a bit(but not much as I tried to keep it as similar as possible), the idea is still his and in his book. I can see other tutorials using encoders/lcd etc but to do a full blown tutorial to build it without the need to buy the book is probably not right imo. That said I'm more than happy to help anyone that buys the book and can provide a parts list of exactly what I used so it all works, even happy to modify the program for others. There are a lot of possibilities to develop a heaps better unit, a bigger screen and an ability to read/display cutting steps from gemcad files(probably off a SD card) etc.. I've already started thinking about an upgrade .
I might send Tom an email to see what he is happy with being made available in a tutorial
Cheers
Andrew