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Project Logs / Re: Building a New Lathe
« Last post by vtsteam on Today at 06:20:23 PM »
Well, I used to feel that way re. pop-tech more than I do now. I don't mind, as long as somebody doesn't tell me that's the only way to do things. In fact I owe apologies for negative sentiments I  expressed a few years ago re. 3D printers. Not that I want one, but why shouldn't other people be happy? I just figure, now, that people should do what they're interested in. Including cultivating personal fame if that''s what they want. Me, I like metal, and traditional basic things, and old ideas losing currency now. That's fun for me. I don't like plastic, so I'll probably never make stuff out of it unless there is no viable alternative for something I really want to do.

End of structural politics...... anybody want to get back to making this lathe? And messing with zinc? Okay, then.

Today, I took this organic substance called scrap wood and sawed it into a desirable, to me, shape. This is one of the earliest materials used by man, and it is possible to make it conform to your mental ideas of shape fairly easily with shaped tools and zero programming. It took at most 10 minutes to rip out enough stock for 16 of these patterns, though I didn't need that many -- I just wanted to have enough in case of goof-ups.

It had to have clearance around a Tee nut so it could slide, but enough overhang to hold without breaking, plus clearance to the top surface plus machining allowance. Ordinarily in pattern casting you'd also need draft and shrink allowances, but not in the way I intended to cast this today.

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Composites & Plastics / Re: Glass fibre mould from the slender plug
« Last post by PekkaNF on Today at 04:42:44 PM »
And it was partly translucent!

That got some attention, some were thinking that it could not be "legal" but when they held it, they concluded that it was pretty light to be dangerous and most just could not get over with the glass fibre part.

It shows some wear, specially gold painted parts, but my daughter thinks that it shows some real character and looks more like weathered.

Most importantly it held 8 hours of constant handling.

Pekka
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Project Logs / Re: DIY tablet computer, maybe.
« Last post by S. Heslop on Today at 03:11:09 PM »
Boy howdy it's hot. I've been taking it easy and daydreaming about portables some more. I think the ideal device is probably the slider style phones they were coming out with before the stupid iphone ruined it and every manufacturer turned towards big solid cheap to manufacture touchscreen slabs.

Here's a doodle of a really bad idea for a chunky handheld games console.



Not a great idea at all really. I'll need to re-think it a bit. But something i've been hung up on for years is how... nice DSLR cameras feel. I think something with a similar form factor that's better than what I came up with might make a neat novelty device, if a goofy one. I believe those dirt cheap Rapberry Pi's are capable of playing the only game that matters - Doom (1993). Or more specifically the custom levels for Doom and its sourceports that people have been making for the last 25 years, refining their art. So it could be relatively cheap to slap together something silly some day.
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Well no point in putting it off - remove board - replace capacitors - return board to it's rightful  place and switch on keeping fingers crossed.

It all went ok - capacitors replaced and now I can jog X & Z, I can send the X & Z axis to their reference points, and I can jog the spindle. What I can't do at the moment is initialise the Tool Turret - it's asking me to do it but the format of the command is eluding me at the moment.

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Project Logs / Re: Building a New Lathe
« Last post by S. Heslop on Today at 12:32:55 PM »
Of course, I do enjoy running against conventional wisdom. So far: welded steel lathe beds will warp, firebrick can't be used for melting iron, plaster of Paris won't make a suitable foundry furnace lining, and zinc alloys in a lathe will turn to powder.

Outside of this forum I've been told hundreds of times I can't do things I've managed to achieve, so I guess it's just a normal situation for me. I don't mind, just hope people widen their knowledge base. My firm belief is generalizations are true, except when it comes to specific cases. And even that belief has exceptions!  :lol:

I think it's important to run against conventional wisdom at least a little bit, especially to make up for differing tooling. I can't see myself ever melting cast iron but I can manage aluminium and presumedly zamak too. The thought of which is rekindling a few project ideas i've had.

I think going against conventional wisdom it's also important for the sake of a community. On the internet especially I feel everything ranges from either a Community - or a Cult of Personality. And where a community innovates and shares ideas, a cult of personality copies ideas and waits for the great masters to bestow more wisdom upon them. Which you can really see in the hacker maker world, not to disparage them too much because there are cool people involved, but the vast majority have a hard time imagining anything outside of the capability of a 3d printer or laser cutter since they're surrounded by media personalities with sponsors and partnerships trying to sell them more.
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Project Logs / Re: Building a New Lathe
« Last post by vtsteam on Today at 11:57:32 AM »
Good point WR.

I don't melt anything with lead in it (for health and safety reasons), use a separate graphite-clay crucible for Zamak melting only, and use stamped pure known zinc and Zamak-2 ingots, from the same supplier.

The cast parts have shown no deterioration in extreme humidity changes in an unheated shop over 2 years. So-all-in-all I think my lathe is safe from the lead contamination problem (zinc pest).
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Back from entertaining relatives at the Pub, and straight back to the workshop to chase that fault. Lucky I was the driver, so my head is quite clear on only Soda and Lime !

Chasing now I know where the relays are, it turns out that CR10's contact is working, but CR20 - either the relay or the wiring is duff. I have temporarily wired round it, and guess what - things started happening.


She's ALIVE


I could jog the Z axis up and down as I wished. Initially the X axis moved a fraction then something tripped - repeatable problem - I thought that perhaps it was on the limit switches, and wanted to remove the cover from the servo motor / ball screw drive to wind it by hand, but it was in an inaccessible place too close to the tail stock. But - hey - I can JOG Z where I want it. So the saddle was trundled down the ways giving access to the belt cover.

Cover off revealed the expected drive belt and pulleys and what I had forgotten - the X axis brake unit. As the X axis is tilted up at a step angle, without a brake, and with low friction ball screws, it will descend under it's own weight. I checked the current though the brake coil (0.6 amps) with my clamp on ammeter - no way can I turn the pulleys, and I dare not remove the brake or the X axis will plunge.

Well it looked a bit grotty with surface rust - perhaps the plates are rusted together. A few gentle taps with a plastic mallet, and guess what - X now moves as it should. As you jog it's slightly disconcerting hearing the loud 'click' as the brake comes off, and on again when motion ceases. (Brake is spring loaded ON with no power)

SO - I was able to move X & Z to their home / reference positions to make the controller happy, and was just starting initialising the Tool Turret when there was an almighty   :zap: BANG  :zap: and the workshop filled with acrid smoke - it still stinks as I type this .

I leapt to the main switch to kill the power - smoke was pouring out from below the KTK Mentor main spindle drive. Closer inspection (holding my breath) showed that in fact it was coming from the Field Coil Controller which is mounted below the Spindle Drive, and the culprit was one of those 0.1 uF  500 volt AC RFI suppressor capacitors, identical to the ones I replaced on the Mentor drive. Luckily I still have some left over.

Oh boy it made a loud bang and a huge volume of smoke - fortunately due to the hot weather I had my roller shutter door open and fans blowing. Knowing how hard it was to clean the mess off the Mentor board, I quickly set to with some IPA to try and clean the mess off the grey trunking - no way was it shifting, and I can see globules of molten solder have embedded themselves in various places.

However I am a happy bunny - this is a major milestone passed. OK I need to bottom the CR20 relay problem, I still need to replace that I/O card, and no doubt there will be a few more 'issues' along the way. I've not yet got the Main Spindle turning under power, nor the drive for Powered Tooling.

. . . but satisfying . . .  :ddb:
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Project Logs / Re: Building a New Lathe
« Last post by WeldingRod on Today at 11:20:50 AM »
I think y'all are worrying about zinc pest:
https://en.m.wikipedia.org/wiki/Zinc_pest
Modern lead free alloys don't suffer from this.
Fascinating reading!

Sent from my SAMSUNG-SM-G891A using Tapatalk

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Project Logs / Re: Building a New Lathe
« Last post by vtsteam on Today at 11:16:06 AM »
So what are the implications of the above? Well yes, cast parts can be cheapened by a manufacturer, because it is so strong, you can design a part to use very little material, by forcing it into webs and hollow shapes. They feel cheap, too because they are relatively light in weight. And they are brittle because the thin webs have ironically, the tremendous yield strength of the material.

Now suppose you don't want to cheapen a part. But are looking to endow a lathe (for example) with high strength and stiffness. So you build parts with equivalent thickness in ZA-12  to cast iron or steel. In this case the yield strength of the part will be enormous. Greater than any other metal you could cast.

The parts won't be brittle in any practical sense, because the application can never come close to generating yield  forces. The strength of the part will exceed most everything you could build out of except hardened tool steel. The mass will be substantial, because Zamak weighs almost as much as iron. It won't feel or seem cheap or insubstantial. When painted, one casting looks the same as another.Iron is also painted for resistance to rust.  Zamak does have the advantage of bearing slipperiness, so it will be better than steel for slides, and stronger there than cast iron, which is also a good bearing.

In other words, for me, it was the material of choice.
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Project Logs / Re: Building a New Lathe
« Last post by vtsteam on Today at 10:39:46 AM »
Okay, off the jokes, here's some simple data re. casting.

Zamak 2 Ultimate tensile strength is 52,000 PSI (apologies to metric folks, but just for relative comparison)
Zamak 12 is 58,000 PSI
SAE1008 steel is 42,000-52,000 PSI
Named aluminum casting alloys ~ 45,000 PSI

For yield strength:

Zamak 2 = 41,000 PSI
Zamak 12 = 46,000 PSI
SAE1008 steel = 20,000-40,000 PSI
Named aluminum casting alloys ~ 22,000 PSI
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