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Old 10-28-2012, 06:46 PM   #1
Dousi
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Default 4-Axis CNC or 3-Axis CNC and lathe?

Hi guys,

I'm planing to build some model engines and want to build a CNC mill for doing so. My question is now, if its ok to build a 4-axis CNC or if I must have a lathe?

I plan to do crankshafts and eventually the camshafts with the 4-axis CNC.

hoping for answers.
Florian

Florian

PS: sorry for my english, as I'm from switzerland...



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Old 10-28-2012, 07:30 PM   #2
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Hi Florian,

First of all, your English is very good.

This is my opinion, but I feel the three axis CNC and a lathe would be the better combination. I think you will find many jobs will be easier to do on the lathe. You can always add a 4th axis to your mill by putting a stepper on a small rotary table, such as a Sherline table or similar.

My experience comes from a Taig 3 axis CNC mill and a Sherline 4 inch rotary table with a stepper motor on it. My control was built from the beginning with 4 stepper drivers. I have a manual lathe and also another manual mill in the shop.

Good luck and please keep us informed as you build your CNC mill.

Best regards,

Chuck Kuhn



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Old 10-28-2012, 07:51 PM   #3
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I agree, the 4 axis mill may not give the finish on the crank to fit the bearings. Not that it can't be done but a lot can be done with the lathe and a cnc mill.

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Old 10-28-2012, 08:06 PM   #4
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Florian :
1st of all welcome to the forum. Please post an introductions in the welcome area. if you please sir.
2nd may I ask why a warp jump to cnc is that what you are used to ? college or tech school maybe. We recommend manual machining first.

While it is completely possible to build an engine with just a mill a lathe is considered king of the shop. and the most essential machine tool.

you are talking crankshafts and camshafts so sounds like you are planning on multiple cylinder Internal combustion engines. not an easy task but doable.
IMHO you need a lathe for the task.

To build a 3 axis cnc or 4 axis is just a matter of an extra stepper motor and a rotary table and maybe a center support. building a fourth axis is easy programming it to make cams and crank shafts could be a challenge but again doable.
Comparing a 4 axis cnc mill to a lathe is like comparing an apple and an orange.
Tin

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Old 10-29-2012, 06:50 PM   #5
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Thanks to all for your answers!

I know that its easy to step ud from 3 to 4-axis cnc, but I don't know if I should spend the money for the lathe or not. I will go CNC because its more fascinating to me, and I'm an Automotive Engineering Student, so I have acces to all the programs needed to draw and programm the machine. I also have the knowledge to build and operate the cnc, and I can operate an manual mill and lathe too, learned it in my apprenticeship.

Quote:
you are talking crankshafts and camshafts so sounds like you are planning on multiple cylinder Internal combustion engines. not an easy task but doable.
IMHO you need a lathe for the task.
I wasn't thinking about a special engine when I wrote this, I just meant the camshafts and crankshafts for all those engines that I'm gonna build.

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Good luck and please keep us informed as you build your CNC mill.
I will, as I'm gonna build it from ground up, not based on a commercially available machine.

is it only the quality of the surface wich bothers you, the 4-axis couldn't handle? I think this should be doable with the mill, when proper machined?

greetings
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Old 10-29-2012, 07:36 PM   #6
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commercial cams and crankshafts are usually ground. If you make a grinder for cams and cranks machining to 2 to 5 thousands oversize then finish grinding could give the best results. or mill to size then hand polish.
sounds like you have a good foundation and a good grasp of what you are doing.
I guess the next question is what size/scale engines are you planning and what size machines are you building.

I put together a small cnc lathe for IIRC $350 US It uses the same computer and controller as the mill.

I see nothing wrong with using commercial machines or parts as a foundation for your project will likely save time and possibly money. but this is your journey your choices.
I put together a getting started in cnc thread in the cnc area you may find it helpful. I am US based so suppliers are US based.
Tin

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Old 10-30-2012, 03:23 AM   #7
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Quote:
Originally Posted by Dousi View Post
Thanks to all for your answers!

I will, as I'm gonna build it from ground up, not based on a commercially available machine.

Florian, what size mill are you planning to build?

When you speak of a 4th axis, I think of a stepper driven rotary table or indexing device. Are you perhaps considering something like a motor driven lathe headstock and spindle mounted on the mill table? Something like that might take the place of a lathe.

Regards,

Chuck Kuhn
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Old 10-30-2012, 02:35 PM   #8
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A lathe is a requirement in my mind. So many parts are cylindrical and would be much more difficult to produce on a mill. Many engines have been built on a lathe alone, but I've seen very few with just a mill. I just added a 4th axis to my small CNC mill, and hope to take my projects to the next level, but it can all be done without a CNC 4th axis.

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Old 10-30-2012, 06:05 PM   #9
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That depends on your 4th axis. If it is fast enough, you don't need a lathe. Fast means 2000 RPM. But that would mean a hybrid or dual drive for your axis.

Something like this (minus wife's comments):



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Old 10-30-2012, 06:51 PM   #10
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Quote:
Originally Posted by Tin Falcon View Post
commercial cams and crankshafts are usually ground. If you make a grinder for cams and cranks machining to 2 to 5 thousands oversize then finish grinding could give the best results. or mill to size then hand polish.
thats a good idea, I think it's the way I will go. Handpolishing at beginning, eventually building a grinder later.

Quote:
Originally Posted by Tin Falcon View Post
sounds like you have a good foundation and a good grasp of what you are doing.
I guess the next question is what size/scale engines are you planning and what size machines are you building.
Thanks, I'm planing to build engines about 1/4 scale V8


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Originally Posted by Tin Falcon View Post
I put together a small cnc lathe for IIRC $350 US It uses the same computer and controller as the mill.
sorry, but what's IIRC?

Quote:
Originally Posted by Tin Falcon View Post
I see nothing wrong with using commercial machines or parts as a foundation for your project will likely save time and possibly money. but this is your journey your choices.
I put together a getting started in cnc thread in the cnc area you may find it helpful. I am US based so suppliers are US based.
Tin
I will base my CNC design on the momus design seen here. but I will make it bigger than the momus design, because I want do other works with it too. it wil be about X:1200mm, Y:650mm Z:300mm

Quote:
When you speak of a 4th axis, I think of a stepper driven rotary table or indexing device. Are you perhaps considering something like a motor driven lathe headstock and spindle mounted on the mill table? Something like that might take the place of a lathe.
I was thinking of a stepper driven rotary table, but considered a combination both, so that I'm able to work as a Lathe, and a indexed axis, something like muellernick just posted.

This would be the killer machine in my opinion, if it would be possible to work in lathe mode, but with the (running) milling cutter as a lathe tool. is this doable?

Florian


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