Starting a DIY-mini-lathe

Hi all,

... as Sebastien pointed out, i'll show here the building of a mini-lathe-/CNC-lathe with alternative methods.

First the combination of a 4-jaws-chuck and a collet chuck mounting plate - i can change the chuck between an 1kW-servo-motor used as direct-drive lathe, or a 7Nm-microstepper atached to my CNC-mill as 'CNC-lathe'.

I'll post more pics, when going on ...

Viktor

That looks really good. Do mention what kind of tooling method your going to employ. My first thought is, steppers for cnc lathing would make great contact free machining but couldn't hold up in a traditional lathe setup. Although thats depending on motors and materials.

The idea of using stepper motors occurred to me before ~ for making things like a Ball Chain drive wheel / gear.

However I decided that the Stepper would be hard to maintain and drive enough power into to cut materials like steel bar without stalling.

So I went and bought a Chinese low cost Lathe.

So I am very interested in this project.

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Bodge It [reprap.org]
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BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
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My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

... more than a year ago i made first tests with an extreme simple stepper-driven CNC-lathe-axis ... but had some problems with resonancy with my standard halfstep-drivers and the Nema34-200-steps-per-rev. stepper with 1.5Nm power, so stopped this and went on optimizing the CNC-mill ... atached are some images of my first stepper-lathe-axis and a roughing test.

Recently i've got some Precitec-steppers with drivers capable of 200 to 50000 steps per rev. and 7Nm torque, so i decided to make a second attempt with a 'realistic' setup

... and the last image is another sample of a small CNC-lathe-kombi ...

Viktor

If there is interest or as it develops, I'll give this subject its own forum.

There's a wiki page here for notes and links and suchlike:
[objects.reprap.org]

Great Victor Im now even more interested !

If I can get away with a smaller stepper on Big Bertha for the Z axis and use the two smaller 2.2NM steppers shown here for X and Y I will have a 3.5Nm stepper as a spare to try out on a lathe.. sort of in beteen the sizes you are using.

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Bodge It [reprap.org]
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BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

Hi Sebastien,

... i'll fill in the wiki when going further -- but this can take a wile, as i can only make progress some hours as weekends and at nights, if i'll avoid any noise ...

@Bodge It: - motors are strong enoug when over 1.5Nm, maybe even with 1Nm

The limiting range is the force of the mill-bit cutting in the material.

So when only using mill-bits smaller than 3mm diameter and avoiding fast rotation of the lathe-axis (best turn a step with the turning axis, then move the XZ-toolpath) you won't have much forces, even in hard materials ...

Viktor

Nice! It's a very interesting approach. I'd love to follow follow your progress. It also really fits well in the RepLab.org concept!

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Regards,

Erik de Bruijn
[Ultimaker.com] - [blog.erikdebruijn.nl]

Hi Eric,

... i'm awaiting a bigger/stronger stepper so the max. dimension will change and i have to redesign the motor-holder and the support.

So when i have the final metrics i'll mill oll the holders and assemble the CNC-turning axis first, this is much more promising than a 'simple' lathe

I'll feed the progress in ...

Viktor

One question I forgot to ask.

Will all the parts to build the Min Lathe be RepRapable where ever its posible?

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Bodge It [reprap.org]
=======================================

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BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

Another option would be to start with printed parts and bootstrap a stronger lathe. I'm just shamelessly repeating what cathal garvey just said in an email. My first thought on that is that with feedback you might not need a lot of stiffness to machine to tight tolerances.

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Regards,

Erik de Bruijn
[Ultimaker.com] - [blog.erikdebruijn.nl]

... interesting question ... which stability is possible with plastic-chucks

The motors aren't reprappable yet, but all the holders and fixatures are - i remember a post or blog where someone made some lathe-supports out from sandfilled epoxy or plastic and embedded some berings for a steady rest (? - german "Lünette").

When fabbing moulds for metal-casting you can build your own chucks and tools, so it's not 100%-reprappability what's interesting, but more the methods and toolchains for DIY ...

Viktor

If you want to know what it takes to build a mini-lathe start with this set of books.

[www.lindsaybks.com]

You also get to play with fire and molten metal.....
You all be real careful when doing this.

Bob Teeter

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Bob Teeter
"What Box?"

VDX Wrote:
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> ... interesting question ... which stability is
> possible with plastic-chucks

Well, I jump on some parts here that have barely 20%
hexagonal infill and they will not break.
If they can build Car-parts from ABS the it should
be strong enough to hold some wood, plastic of
leightweight metal object centered.

Of cause even CNC-milled metal parts CAN in theory
be produced on a RepRap.
I just posted a Dremel milling-head for the RepMan
[www.thingiverse.com] yesterday.

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Hi Marcus,

... i know that you can build some really sturdy objects with plastic by embedding steel- or carbon-fibres - maybe some GFK/CFK-like material could be extruded?

Best method should be laminating with carbon-fabric and heat the surface to fuse the fabric with the plastic beneath ... then fab the next slice, and so on ...

Viktor

> Best method should be laminating with carbon-fabric and heat the surface to fuse the fabric with the plastic beneath ... then fab the next slice, and so on ...

But then the strength would be very directional. Especially perpendicular to the layers, the strength is lacking, and this will not aid it's strength much in that direction.

I do think additive processes and composite materials hold a lot of promise.

I'm thinking of vertical arrangement of fibers or other materials. I wonder if we could push in short rods of hot metal, perhaps in pre-fabbed shafts, and then fill those up with plastic. Or extrude a metal thread with molten plastic around it. I've actually experimented with this and it seems to be feasible. You can pull out a thread of metal (< 0.1 mm) and when you extrude while doing this, some plastic is extruded around it. I'm not sure, but possibly you can couple the extrusion with a metal/fiber feed.

I think the fiber, even with some plastic will not have the specific heat to weld with the object unless that's locally heated as well and there's a channel for more (newly extruded) plastic to fit in. Alternatively, a thermoset material could be used around the fiber, requiring no heat to cure.

Even without fibers, this could increase speed AND add strength, since you could use a larger orifice printhead for filling vertical shafts that were left in the model for this purpose.

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Regards,

Erik de Bruijn
[Ultimaker.com] - [blog.erikdebruijn.nl]

Hey Erik,

That sounds extremely similar to what we're trying to achieve right now!
[dev.forums.reprap.org]

Jacob

I edited the discussion page to include some ideas and findings from my trials. Discussion can proceed there since this thread is drifting off topic...

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Regards,

Erik de Bruijn
[Ultimaker.com] - [blog.erikdebruijn.nl]

Hi Eric,

... which discussion page?

Viktor

This one:
[poolHead" target="_blank" rel="nofollow">objects.reprap.org]
This is their project:
[objects.reprap.org]

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Regards,

Erik de Bruijn
[Ultimaker.com] - [blog.erikdebruijn.nl]

... the first link is broken ...

Viktor

I didn't realize it tried to create smilies out of this.

On this page:
[objects.reprap.org]
Click on "Discussion".

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Regards,

Erik de Bruijn
[Ultimaker.com] - [blog.erikdebruijn.nl]

Hi Eric,

... thanks, already found the discussion list and made a suggestion for fixing the wires along paths

Viktor

... update: - received the bigger stepper with 5:1-gearbox for the CNC-lathe ... have to order a collet for the 20mm-shaft first, then i can make a carrier with exchangeability for the stepper or servo.

The big stepper has the same parameters as the smaller, so i can use the same controller - it's only bigger, sturdier and with much more torque

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Viktor
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... update: - got another motor with 4Nm without gearbox, so i can use the 2Nm-motor with 5:1-gearbox for a finer turning-table and the 4Nm-motor with 10000 steps per rev. as CNC-lathe-drive.

Atached an image with first fitting-test in the CNC-mill - when all fixing and counterparts are ready, i'll exchange the Y-axis with the lathe-axis and can mill complex 3D-parts with a turning axis ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

what you are trying to do is called "rotary table" ("rundschalttisch" in german)
some time ago i worked for "Fibro" in Germany, they produce such rotary tables
it is'nt quite easy to make them.. and they are pretty expensive
its driven by a worm drive, take a look at this picture and you will know what i mean:


i do'nt think you can do such a thing in home environment - some really difficult 5-axis milling is involved...
best thing you could do: picking up such a manual rotary table and attatch a stepper motor to it


best

... oh, it's not for me - I have different rotary tables, revolvers, advanced microtech or other 'serious hardware' stuff at hand.

The idea was to show other methodes, that possible are better DIY-able or can be made by 'rearranging' available equipment.

A surely DIY-able approach is a rotary head with two big diameter ring-bearings and printed outside-pulley as shown in the image attached below - but with printed parts instad of the (pricey) milled parts.

For most applications in the DIY-area you can get away with a NEMA-23 motor and belt-drive ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]