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yadu
15-01-2011, 10:44 PM
I want to build a CNC lathe for my shed at home. I am a production engineer and have full access to CNC lathes mills, grinding m/c and heat treatment. I have lots of Ideas mechanically but I am a little lost when it comes to the electronics, and software to drive the machine. I want the machine to programmable in G code, because its what im used to, also I have Cad/Cam software I use at work which posts in G code.

Im not in a rush to build this machine and I want to do a nice job. I want to build a slant bed with a box section base. A little bit like the Haas SL30 machines. with a indexable turret. Again quoting Haas again they use a servo motor to index the turret.

The X and Z axis will run on Linear guide rails as well as the tail stock.

Also I think I will need a encoder for the spindle rpm

The questions I would like to ask are:-

*which software would be best suited for my requirements

*I need a controller that takes care of the stepper motors and the spindle speed.
I have a computer with parallel port and usb. which is best.

*do I need a special motor for the spindle, that is controlled by a spindle controller.

*Will the CNC control software, and control boards take care of coolant on and off, spindle on/off ect

*Most machine bases are made of cast Iron, that isn't an option for a one off m/c tool, If I make it from mild steel and weld it into box section and fill it with concrete will this help?

thanks Keith

i2i
16-01-2011, 01:44 AM
I want to build a CNC lathe for my shed at home. I am a production engineer and have full access to CNC lathes mills, grinding m/c and heat treatment. I have lots of Ideas mechanically but I am a little lost when it comes to the electronics, and software to drive the machine. I want the machine to programmable in G code, because its what im used to, also I have Cad/Cam software I use at work which posts in G code.

Im not in a rush to build this machine and I want to do a nice job. I want to build a slant bed with a box section base. A little bit like the Haas SL30 machines. with a indexable turret. Again quoting Haas again they use a servo motor to index the turret.

The X and Z axis will run on Linear guide rails as well as the tail stock.

Also I think I will need a encoder for the spindle rpm

The questions I would like to ask are:-

*which software would be best suited for my requirements

*I need a controller that takes care of the stepper motors and the spindle speed.
I have a computer with parallel port and usb. which is best.

*do I need a special motor for the spindle, that is controlled by a spindle controller.

*Will the CNC control software, and control boards take care of coolant on and off, spindle on/off ect

*Most machine bases are made of cast Iron, that isn't an option for a one off m/c tool, If I make it from mild steel and weld it into box section and fill it with concrete will this help?

thanks KeithYou could use a cast iron surface table for the base, that would give you a nice solid base to work off for the linear rails.

djc
16-01-2011, 10:02 AM
...I am a little lost when it comes to the electronics, and software to drive the machine.

Have confidence. Ask lots of specific questions. I would say that detailed electronics knowledge per se is not required, just a logical approach; an ability to think systematically. Draw lots of diagrams.

If you go for lots of off the shelf parts it is as easy as connecting the input of the first device to a 13A lead, its output to the input of the second in line and just keeping going.


I want the machine to programmable in G code, because it's what I'm used to, also I have Cad/Cam software I use at work which posts in G code.

I don't think there are many paths you can take that will not achieve this.


I want to build a slant bed with a box section base.

I don't know if it's frowned upon to mention it here, but do have a look over on CNCZone as there is a huge amount of information there.

http://www.cnczone.com/forums/vertical_mill_lathe_project_log/51688-slant_bed_cnc_lathe_scratch.html


Also I think I will need a encoder for the spindle rpm

If you wish to do threading or CSS or have feedback on the spindle speed, yes. This can be as simple as a disk with a single slot in it that interrupts a light beam. Depending on which control program you choose, more than this might not be needed.


which software would be best suited for my requirements

There are three main ones: Mach3, EMC2 and TurboCNC. Mach is windows-based and is very simple to set up and use. In its native state it is easier for a beginner to set up for a mill than a lathe. EMC2 is Linux-based, and has a steep learning curve. TurboCNC is DOS based and was originally designed for a lathe. You could run it on minimal computing hardware.

Download the documentation for all of them and see what rings your bell.


I need a controller that takes care of the stepper motors and the spindle speed. I have a computer with parallel port and usb. which is best.

For your first machine, I would buy a second parallel port card and install in in the PC. This will give you enough control lines for now. It is possible to use a single parallel port, but it limits the scope you have for controlling the machine.

Any kind of USB solution requires an add-on board.

The difference between the two is that with a parallel solution, the timing is done inside the PC; with a USB solution, the timing is done on a dedicated processor on the board.


do I need a special motor for the spindle, that is controlled by a spindle controller.

If you want variable speed, you will need either a DC motor (and controller) or a three phase AC motor (and VFD). None of the software packages above will control the speed directly - you will require another add-on board that goes between the VFD and the computer. What the board does is to convert the signals coming out of the PC into signals the VFD understands.


Will the CNC control software, and control boards take care of coolant on and off, spindle on/off

Yes. The only control board you need here is a simple relay board. The PC can only give out 5v at small current, but that's enough to switch a relay.


If I make it from mild steel and weld it into box section and fill it with concrete will this help?

Your idea is correct; the material is (technically) incorrect. Have a search in CNCZone for 'epoxy granite'. Filling any hollow sections will always increase their stiffness and mass. Concrete made of Portland cement (stuff you build walls with) is not good as it is not dimensionally stable over time - it creeps. Hence, instead of usng cement as the binder for your aggregate, you use epoxy resin. For the coarse aggregate, use the most dense material you can find - granite, lead shot, iron pellets, barytes aggregate. Again, the denser the fine aggregate, the better.

Ask again if you have any further questions. I'm not far from your location and would be happy to help or show you what I've done.

djc
16-01-2011, 10:07 AM
...I am a little lost when it comes to the electronics, and software to drive the machine.

Have confidence. Ask lots of specific questions. I would say that detailed electronics knowledge per se is not required, just a logical approach; an ability to think systematically. Draw lots of diagrams.

If you go for lots of off the shelf parts it is as easy as connecting the input of the first device to a 13A lead, its output to the input of the second in line and just keeping going.


I want the machine to programmable in G code, because it's what I'm used to, also I have Cad/Cam software I use at work which posts in G code.

I don't think there are many paths you can take that will not achieve this.


I want to build a slant bed with a box section base.

I don't know if it's frowned upon to mention it here, but do have a look over on CNCZone as there is a huge amount of information there.

http://www.cnczone.com/forums/vertical_mill_lathe_project_log/51688-slant_bed_cnc_lathe_scratch.html


Also I think I will need a encoder for the spindle rpm

If you wish to do threading or CSS or have feedback on the spindle speed, yes. This can be as simple as a disk with a single slot in it that interrupts a light beam. Depending on which control program you choose, more than this might not be needed.


which software would be best suited for my requirements

There are three main ones: Mach3, EMC2 and TurboCNC. Mach is windows-based and is very simple to set up and use. In its native state it is easier for a beginner to set up for a mill than a lathe. EMC2 is Linux-based, and has a steep learning curve. TurboCNC is DOS based and was originally designed for a lathe. You could run it on minimal computing hardware.

Download the documentation for all of them and see what rings your bell.


I need a controller that takes care of the stepper motors and the spindle speed. I have a computer with parallel port and usb. which is best.

For your first machine, I would buy a second parallel port card and install in in the PC. This will give you enough control lines for now. It is possible to use a single parallel port, but it limits the scope you have for controlling the machine.

Any kind of USB solution requires an add-on board.

The difference between the two is that with a parallel solution, the timing is done inside the PC; with a USB solution, the timing is done on a dedicated processor on the board.


do I need a special motor for the spindle, that is controlled by a spindle controller.

If you want variable speed, you will need either a DC motor (and controller) or a three phase AC motor (and VFD). None of the software packages above will control the speed directly - you will require another add-on board that goes between the VFD and the computer. What the board does is to convert the signals coming out of the PC into signals the VFD understands.


Will the CNC control software, and control boards take care of coolant on and off, spindle on/off

Yes. The only control board you need here is a simple relay board. The PC can only give out 5v at small current, but that's enough to switch a relay.


If I make it from mild steel and weld it into box section and fill it with concrete will this help?

Your idea is correct; the material is (technically) incorrect. Have a search in CNCZone for 'epoxy granite'. Filling any hollow sections will always increase their stiffness and mass. Concrete made of Portland cement (stuff you build walls with) is not good as it is not dimensionally stable over time - it creeps. Hence, instead of usng cement as the binder for your aggregate, you use epoxy resin. For the coarse aggregate, use the most dense material you can find - granite, lead shot, iron pellets, barytes aggregate. Again, the denser the fine aggregate, the better.

Ask any further questions you may have. I'm not far from your location and would be glad to help or you can look at what I've done.