A site dedicated to CNC of Mini lathes - the 7x10, 7x12, 7x14, and 7x16

Welcome to 7xCNC!

A site dedicated to computer numeric control (CNC) of Mini lathes - the 7x10, 7x12, 7x14, and 7x16

The chinese made mini lathes are cheap, widely available, and capable (with a little work). They are made in a number of factories and rebadged under many names including Sieg, LMS, Micromark, Harbour Freight, Grizzly, and Homier. The basic design is common to all but details and finish do vary.

Have a look at my conversion, or see what other conversions people have done.

I've just put up an article on a spindle encoder that allows software speed sensing and CNC threading.

I'm working on some software guides (mainly for linuxcnc, as that's what I use).

Posted by  7xCNC  June 21, 2014

This guide will show you how to set up a probing routine for use on the mill/router. It finds the corner of your work (or vice). It uses an NGCGUI subroutine which has configurable settings. This is 95% based on great work from Rick G at LinuxCNC forums.

Explanation:
This Subroutine finds a corner (front (lower) left) and sets it to X0 Y0, it then probes Z at a set point and sets Z0
You need to jog the machine so your probe is near to the front of your work piece.

Sequence:
 - Fast probe Y+, retract, then slow probe Y+ to find Y0
 - Retracts, then moves along in X- direction by "Y Search increment"
 - At each increment it does a fast probe in Y+ until encounters material, then retracts and moves along next increment
 - If no material is encountered when moving Y+ within "Dist to Probe" it begans to probe in X+ direction
 - When it encounters material, it retracts in X-, then does a slow probe X+ to find X0
 - "Y Search Max" sets a maximum distance it will try to probe along X- to find the corner, if the corner is not found within this distance it will stop and error
 - Uses G92 to set X and Y axis at probe position minus radius of probe plus correction
 - Once X0Y0 is set, retracts Z up to "Z Safe" then travels to "X Coord" then "Y Coord" to perform a Z probe to set Z0
 - Finally moves to final coordinates "Z Safe" first, then "X Final Pos""Y Final Pos", then "Z Final Pos"
 

Warning: This code has been tested in simulation primarily. You need to test it yourself, on your machine, to make sure the world does not explode. I take no responsibility for what happens when you run this code. Pay particular attention to the tool change / Z offsets.


This code is intentionally quite slow. It uses G38.3 (probe) for all nearly all moves. It could be sped up significantly by using G0 (rapid) for the retracts etc.

Posted by  7xCNC  June 20, 2014

Probing is one of the great basic functions of a CNC setup. Easily find the top, edges of you work piece, or even find the centre of a hole.

LinuxCNC is very customisable in this area, like most others, but unfortunately you need some probing code. Never fear, I've collected a few useful bits of code and some subroutines to make probing easy!

Have a look at my guide on a Z Touch Off Plate for LinuxCNC. This is very useful for routers and other machines that have no way of a repeatable Z height for each tool. With a router, each time you change tools you end up with a different tool length sticking out. With this simple code you just place your plate under the tool and hit a button.

Next up we'll get a bit more complex with a NGCGUI subroutine for finding the corner of a workpiece and the Z height (this one needs a probe rather than a touch plate). It's configurable with probing speeds, distances, safe heights, and final position.

Posted by  7xCNC  February 19, 2014

bladehunter over at CNCZone has come up with an interesting approach to fitting a ballscrew to the X axis of a mini lathe.

There is hardly any room, and it's quite difficult to do. Various solutions have been used including:

1. Tiny ballscrews - hard to find, expensive

2. Screw off to the side of the cross slide - fiddly, exposed screw, not ideal but workable.

Posted by  7xCNC  December 18, 2013

Probing is one of the great basic functions of a CNC setup. Easily find the top, edges of you work piece, or even find the centre of a hole.

I'll explain here how to set up a Z axis Auto Touch Off plate for a router.

Hardware:

This is very simple. For a G540, or any BOB that uses inputs shorted to ground: I use a piece of blank PCB wired to pin 13 on my breakout board. I then have a wire from ground to an alligator clip on my spindle. When the tool touches down on the plate, a circuit is completed from ground to pin 13.

On my newer machines, I use a Mesanet 7i76. This has sinking inputs. They require +ve voltage connected to the input to trigger. This is a problem with my touch off plate, as the spindle is grounded, and connecting 12V to it via the touch off plate results in a short to ground. The solution is to have a pull up resistor. The wiring is: Ground connected to the tool. PCB plate connected to input of 7i76. A 2.2k resistor between the PCB plate and 12V. This 'pulls' the input high, then it goes low when the PCB and tool form a circuit to ground. In this setup, the pin is always high (triggered) except when the probe touches, so I invert the input in LinuxCNC.

Software:

A standard install of LinuxCNC has everything you need.

We are going to use G38.2 (probe toward workpiece, stop on contact, signal error if failure ) and G10 L20 P1 Z (Set Coordinate System to a calculated value that makes the current coordinates become the given value)

We are going to need to modify your .ini file, your .hal file, custompanel.xml, and custom_postgui.hal. We'll also need to create a file '100.ngc' and place that in the nc_files folder.

.hal first up:

Posted by  7xCNC  September 15, 2013

DSCN3914_zpse16145a4.jpg

Skyfire, located in China, have developed a great small CNC mill and is now beginning manufacture - no struggling with a conversion of a manual mill. They call the it SVM-0

Part One covered making the blanks for the casting moulds.

Part Two covered machining of the cast iron and initial parts fitting

Part Three covered painting, assembly and alignment

Skyfire now have their website open and are taking orders. At present they are offering the SVM-0 for $3700 plus freight, with a range of optional extras available!

They are also working on a range of larger machines, with extended capabilities such as automated tool changer (ATC), and looking at producing lathes.

This article covers the electronics and enclosure.

Posted by  7xCNC  September 12, 2013

ToolsandMods.com has some amazing improvements and modifications for the 7x lathes. They include how to improve the fit of various parts.

Posted by  7xCNC  September 11, 2013

TouchDRO.png

Not quite ready to do a CNC conversion? How about a cheap and fully featured DRO (digital read out).

Yuri, who writes the blog Yuri's Toys has created an Android App that does just that.

Using cheap chinese scales , an Arduino , a Bluetooth Module , and a few resistors you can have a DRO that interfaces with your Android tablet or phone.

Yuri's application is available from Google Play and has all the basic DRO functions, as well as hole patterns etc.

 

Posted by  7xCNC  September 8, 2013

DSCN3914_zpse16145a4.jpg

Skyfire, located in China, have developed a great small CNC mill and is now beginning manufacture - no struggling with a conversion of a manual mill. They call the it SVM-0

Part One covered making the blanks for the casting moulds.

Part Two covered machining of the cast iron and initial parts fitting

Part Four will cover the electronics.

Skyfire are presently working on their website - we'll be sure to post a link when they have it up and running.

They are also working on a range of larger machines, with extended capabilities such as automated tool changer (ATC), and looking at producing lathes.

This article covers painting, assembly and alignment

Posted by  7xCNC  September 1, 2013

DSCN3914_zpse16145a4.jpg

Skyfire, located in China, have developed a great small CNC mill and is now beginning manufacture - no struggling with a conversion of a manual mill. They call the it SVM-0

Part One covered making the blanks for the casting moulds.

Part Three will cover painting, assembly and alignment

Part Four will cover the electronics.

Skyfire are presently working on their website - we'll be sure to post a link when they have it up and running.

They are also working on a range of larger machines, with extended capabilities such as automated tool changer (ATC), and looking at producing lathes.

This article covers machining of the cast iron and initial parts fitting

Posted by  7xCNC  August 25, 2013

DSCN3914_zpse16145a4.jpg

Skyfire, located in China, have developed a great small CNC mill and is now beginning manufacture - no struggling with a conversion of a manual mill. They call the it SVM-0

Part One covers making the blanks for the casting moulds.

Part Two covers machining of the cast iron and initial parts fitting

Part Three covers painting, assembly and alignment

Part Four covers the electronics.

Skyfire are presently working on their website - we'll be sure to post a link when they have it up and running.

They are also working on a range of larger machines, with extended capabilities such as automated tool changer (ATC), and looking at producing lathes.

This article is about the core of the machine - the casting