How difficult is cnc mini lathe to learn? How useful?

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Hi
I have the opportunity to purchase a 7x12 mini lathe that's been converted to CNC, it comes with stepper motors installed and I think a box with stepper motor controllers mounted inside it doesn't have a break out board controller.

anyone have an idea of how much it would cost to get this up and running? I have a computer to dedicate to its operation.

How useful would such a lathe be? I plan on doing lots of modelling
 

RonGinger

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As home shop CNC goes, its about 90% mill and 10% lathe. I have beenusing a CNC mill for several years, and I have a lathe "almost'" working for about 6 years now and never quite get around to finishing it. I did get it to make a few parts once.

If you have the stepper drivers, then all thats needed is a breakout board and maybe a motion board- like a smoothstepper for mach or a Mesa card for linux. Linux is free, but you need to be pretty good at computers to use it. Mach3 is $175, The new Mach4 is $200. If you are just starting I would look at Mach4, but its lathe support is not ready yet.

Besides getting the hardware up you will need to use a CAD package and a CAM package. There are MANY choices in this area, way more than I can list here. Start reading, the web has it all, and google knows all!
 

rcfreak177

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Hi,

If the lathe has stepper motors mounted and stepper drives already there is no reason the machine can be functional on a very cheap buget.
There are many types of breakout boards available. I have found that the HY 5 axis board to be very stable and also cheap. Obviously you will only need 2 axis, The other 3 could be used for input/outputs.

http://www.ebay.com.au/itm/5-Axis-CNC-Breakout-Board-Interface-Adapter-F-Stepper-Motor-Driver-DB25-Cable-/321152019128?pt=AU_B_I_Electrical_Test_Equipment&hash=item4ac626eab8

A cnc lathe can be very useful, particularly when machining complex shapes or bulk lots of a specific component. Also the machine can be running on its own while you are doing other things,

One thing to remember though is generally by the time the cnc late is set up, program written and tested and cutting, you may have been able to make the part on a manual machine.

If you set a budget of $100 I think the machine could be ready to run providing there are steppers,stepper drivers, you have a computer handy and the rest of the machine is functional.

Mach 3 software will set you back another $175 or so, If you decide to go with it.

Happy machining.

Baz.
 

canadianhorsepower

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Hi
I have the opportunity to purchase a 7x12 mini lathe that's been converted to CNC, it comes with stepper motors installed and I think a box with stepper motor controllers mounted inside it doesn't have a break out board controller.

anyone have an idea of how much it would cost to get this up and running? I have a computer to dedicate to its operation.

How useful would such a lathe be? I plan on doing lots of modelling
Hi I don't know the price and what comes with it. But some instalation can be very bad. If you can still use it manualy and if the price is good I would think about it.
You can have one of those lathe for $450.00 brand new and another$350.00 to have it fully functional as a CNC and to your standard of work.
Programing a lathe Gcode is not realy a walk to the park if you don't have a CAM program and those dont come buy cheap.

I have 3 lathe,12x36 a 7x10 and a Taig 2 of them are manual ( two first one)one is CNC the Taig . every time I use may Taig I have to dust it off, it's not use to often!!!!!!!!!!!! do I love it YES
Hope it did help
 
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As home shop CNC goes, its about 90% mill and 10% lathe.

If you have the stepper drivers, then all thats needed is a breakout board and maybe a motion board- like a smooth stepper for mach or a Mesa card for linux. Linux is free, but you need to be pretty good at computers to use it. Mach3 is $175, The new Mach4 is $200. If you are just starting I would look at Mach4, but its lathe support is not ready yet.

Besides getting the hardware up you will need to use a CAD package and a CAM package. There are MANY choices in this area, way more than I can list here. Start reading, the web has it all, and google knows all!
Thanks Baz, its sounds like its worth the effort just to learn... then if I later decide I dont like the cnc lathe I can use equip to convert my CT129 mill
 
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Hi I don't know the price and what comes with it. But some instalation can be very bad. If you can still use it manualy and if the price is good I would think about it.
You can have one of those lathe for $450.00 brand new and another$350.00 to have it fully functional as a CNC and to your standard of work.
Programing a lathe Gcode is not realy a walk to the park if you don't have a CAM program and those dont come buy cheap.

I have 3 lathe,12x36 a 7x10 and a Taig 2 of them are manual ( two first one)one is CNC the Taig . every time I use may Taig I have to dust it off, it's not use to often!!!!!!!!!!!! do I love it YES
Hope it did help
Thanks for the feedback Luc. I fiure that for the price I'm getting the conversion hardware for free. The person who did the conversion made a CNC router and a huge CNC plasma cutter so I think he's likely done good work on the conversion install.

I'll be making tons of wheel sets for model trolleys, and power poles for electric transmission lines, so I can see a real benefit.
 

kvom

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Getting the lathe running is the first step, but then you need to program the toolpaths. This likely means learning a CAM package that support turning. Or else manually programming the g-codes yourself, which can be quite tedious and error prone.
 
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Getting the lathe running is the first step, but then you need to program the toolpaths. This likely means learning a CAM package that support turning. Or else manually programming the g-codes yourself, which can be quite tedious and error prone.
Thanks, so I need to find a decent yet inexpensive CAM package... then see if the price is justifiable.
 

xpylonracer

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Hi, If you get the lathe running in cnc mode for little cost you may be able to spend some time teaching yourself some G & M codes, download the Mach 3 trial version, you can run up to 500 lines of code which for manually entering code is a huge program and would be quite time consuming.
If you are able to either remember 10 or so G code commands and 2 or 3 M codes you are well on your way to test running your cnc lathe.
You don't even need to remember them as you can print the full list of codes that can be used in Mach 3.
Also there are "Wizards" available to use, these are programs in which you just add the dimensions you need to machine, they work out the code for you and you can save to a file for downloading to the lathe when needed.
If cnc lathe work suits you can download DXF files to the cam program in Mach and it will do the program coding for you.
Software to generate DXF files is available FOC at several places so spend a fortune later rather than in the first instance.
There are some lathe operations you may not be able to achieve easily without using cad/cam but you will be able to do most of the hobby type machining jobs.
Even without cnc control the lathe will still function in Mach as a manually operated machine, instead of turning handles you press a keyboard button to traverse the tool around.
You can vary the feedrate at the touch of a button and traverse in X&Z simultaneously at a pre-set feedrate.
Hope this helps !!!
Emgee
 

kvom

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It can be extremely tedious to program lathe G-code for any complicated shapes unless the controller supports canned procedures. For a mini-lathe that's pretty unlikely. One way to think of it is that you need to run a series of roughing passes with increasing DOC to get near the profile, and then a finishing pass that follows the profile.

I use CamBam for milling, and it does have a fairly simple facility for generating turning toolpaths. You can download it for an extended trial period.
 
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Also there are "Wizards" available to use, these are programs in which you just add the dimensions you need to machine, they work out the code for you and you can save to a file for downloading to the lathe when needed.
If cnc lathe work suits you can download DXF files to the cam program in Mach and it will do the program coding for you.
Software to generate DXF files is available FOC at several places so spend a fortune later rather than in the first instance.
There are some lathe operations you may not be able to achieve easily without using cad/cam but you will be able to do most of the hobby type machining jobs.
Even without cnc control the lathe will still function in Mach as a manually operated machine, instead of turning handles you press a keyboard button to traverse the tool around.
You can vary the feedrate at the touch of a button and traverse in X&Z simultaneously at a pre-set feedrate.
Hope this helps !!!
Emgee
Thanks for the very detailed response!

I am sure I can learn simple coding to create things like train set wheels. Its good to know I can use programming wizards to suit many of my needs, that allows me to try it out at a low cost.
I have several CAD programs that output dxf files, so that's a bonus.

I also didn't know I could use a cnc lathe manually by simply inputting commands rather than turning feed handles. That alone makes it worth while since I have arthritis type condition.
 
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It can be extremely tedious to program lathe G-code for any complicated shapes unless the controller supports canned procedures. For a mini-lathe that's pretty unlikely. One way to think of it is that you need to run a series of roughing passes with increasing DOC to get near the profile, and then a finishing pass that follows the profile.

I use CamBam for milling, and it does have a fairly simple facility for generating turning toolpaths. You can download it for an extended trial period.
Thanks!

I checked out cambam... 40 evaluation sessions then reverts to 500 line of code evaluation version... purchase price with Mach3 is only $315 US, seems like a good deal to me!
 

RonGinger

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Have a look at the Mach3 wizard called NFSturn. This has a screen for each common lathe operation, like turn, face, bore, thread, etc. On each screen you simply fill in the blanks for things like your starting dimension, finish dimension, etc. Then there are two buttons, one labeled Do It which causes that operation to run, or Add to File, which, as the name says, adds that operation to a file so you can build up a complex program. You can easily use this wizard to build programs for things like bushings, bolts, etc.

I think NFSturn is a brilliant program, but then, I wrote it, so I am not really an unbiased observer :D

I wrote a wizard to profile railroad wheels, making the standard form of tapers, flange and filets. I have not released this wizard, its used at the Boothbay Railway Village to turn wheel sets for 24" and standard gauge railroad wheels.
 
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I wrote a wizard to profile railroad wheels, making the standard form of tapers, flange and filets. I have not released this wizard, its used at the Boothbay Railway Village to turn wheel sets for 24" and standard gauge railroad wheels.
Brilliant... if I get this cnc lathe is there any way to obtain a copy of the wizard profile to turn train wheels? I'm a member of the Ontario Electric Railway Historical Association and want to model many of the pieces from their collection...
 

hanermo3

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You may not like this, but..
First, almost all minilathe cnc conversions are pretty weak to near-useless, most especially if machining in steel.

There are a myriad of errors and problems, usually because people want to do this this cheap.
Cheap usually makes it worthless, in this case.

The common problems, and why they occur:
First, a lathe is very, very rigid, and very very accurate, by its nature. Its is an absolute, totally required feature in any metal-working lathe, which a 7x may be.
Machining steel requires great rigidity, in about 1% of the use.

Things like boring the corners or ends of holes, in deep bores.
In doing the sharp ends of ouside turning, where the final cut is deep.
In accelerating out of a cut in turning, or threading, where you need a very, very fast pullout, as fast as possible.

To get good results, above all you need great rigidity (not a lot of power. Power is not really a problem.)
The loss of rigidity is small, only about 0.1 mm of flex, or 3-5 thousandths of an inch, but it totally spoils the ability to get good bores, good threads, or good results in general.
This error is further increased a lot by the semi-finished flexible nature of most minilathes.

The 7x series are not really too rigid, are underpowered, and there is a lot of slop in all components.
Each shortcoming is easily repaired with some work, and some few components of not much cost.

The cheap, nasty, poor cnc conversion have these shortcoming in general:

Direct couplers are used, of poor quality, resulting in flex.

Steppers are used, of low quality and low voltage. Even worse, they are direct couplled.
Resolution is low, and thus achieved results are very, very poor.

The breakout boards are very bad.
They dont have a good, clean stable pulse train.
The pulse train is mushy, leading to lack of speed and acceleration and reliability. As a result, they need to be run too slow.

Screws are not rigid. These exhibit wind-up (like rubber).
Screw mounts are not rigid. These exhibit flex (like rubber).
Screw mounts are badly made. This results in slop.

Voltages, when used with steppers, are too low. Thus you have low acceleration and low speed.

Stepper drivers are bad (due to using wrong, cheap, drives). Thus results in unreliability at high speed, so you need to run them at low speed.
Thus you have poor acceleration and low speed.

Each problem above is easily fixed by 10-50€ in bits and pieces, per issue. Some are fixed by 10-20€ pieces in less than half an hour.

This is what you should have:
1. Good drivers, at 48V DC, or higher. An example is the 542 series of drivers. 10 microsteps, bipolar parallel, individually disabled at need, no back emf, soft start, no noise (hirring), adjustable microsteps, 100 kHz top speed at least (when driven with suitable hw board).
An example is the 542 series of chinese microstep drivers. These are good and cheap, and have above characteristics. They also have differential signals.
2. If using steppers, belt drives at 1:3 or 1:2, using HTD 5m pulleys, or better (GT2 or GT3, or T5 metric pulleys. NOT XL, or L series, non-precise belts).
Alternately, thick large rigid couplers.
3. Good screw mounts that dont bend. Test with a DTI and hand pressure. Must not move more than about 0.01 mm with moderate force (10 kg or so).
4. Full-step resolution of about 0.005 mm. This means a belt drive or servos.
5. Rigid screws. Essentially, thicker is better. Go up 2 sizes or more from typical.
6. Ideally, ballscrews. Acme screws will work fine, but wear fast. They will have backlash, but this (mostly wont) may not matter.
7. An ethernet-based breakout board, able to do 300 kHz or better in speed.
At a pinch, 125 kHz like pokeys will do, especially for steppers. Its also cheap.
8. Good crisp signal for threading at wide range of speeds. The only one I know of is servo encoders indexes.
A mushy signal will make it impossible to track threading.
 

xpylonracer

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Hi Hanermo3
Guess you must have tested nearly all the 7X lathes to put them in the useless category.
What you claim may be right, I have never owned one but have seen some excellent working models that were built with 7X machines so they can't all be as bad you claim.

I agree rigidity is necessary but it's horses for courses, if you want to take off 6.00mm per pass from toolsteel then a 7X is not for you, however if your hobby is model engineering then you will match the DOC to the material and machine in use.

I believe the member asking the question was looking for constructive advice which is what most people have given, but I agree there are always two sides to a story and it seems you have had a bad experience with 7X lathes.

Emgee
 

goldstar31

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Thank you for the first real bit of practical advice. I lost a deal of money earlier- with what turned out to be a POS and with increasing loss of manual dexterity from old risked falling for the same old rubbish once again.

My thanks, Sir, for writing so advisedly.

I look forward to your next contribution 'tho my own lathe is not a Sieg or whatever.

Norman
 
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Thanks hanermo3

While I cant change the design of this particular cnc lathe, I wont be purchasing it unless I can can check and verify that the stepper motors are sufficient power, the acme screws are of a precision variety and sufficient size for the task.

I'll likely be rebuilding all the electronic components and intend to build quality since I'd be testing for doing cnc mill conversion.
 

kf2qd

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If you have an interest in CNC then it would be a place to begin. I have worked with lathes, mills and plasma cutters and i am comfortable (though out of practice) and I have been able to do many things without having software to generate code. It will get you up tp speed on your trig and algebra, but none of of is very hard.

Have you done any computer programming?
 

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