# Cutting a Groove -- Power Requirement

1. Nov 15, 2016

### George Zucas

Hello,

I am designing a machine that will make grooves on round objects. Not a perfect groove actually, think of a sheave, so round profile. I have the attached formula for cutting power taken from below website:

http://www.iscar.com/Products.aspx/countryID/1/ProductID/32

In my case, W=80mm, f=0.1mm/s. Vc=375m/min, efficiency I assumed as 0.8.

If I take Kc as around 2000 (steel is St52), I get power as 98kW! Obviously it is not possible to use such a motor-gearbox couple in my paltry device.

The possible problems:

- Groove width of 80 is too big: but this is what I need.
- Vc is too big: the round object is 800 mm in diameter, so even at average RPMs the velocity at the contact point becomes big.
-Kc is too big: Actual Kc in my case will be much lower because I will preheat the material. HOwever I can't find specific cutting force vs. temperature chart.

What can I do to find a reasonable power requirement? I have seen such a device with very small dimensions, so I know it is possible. I have limited experience with machining though.

#### Attached Files:

• ###### GrooveForce.JPG
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2. Nov 15, 2016

### Nidum

Use a narrower tool and traverse to get required width of cut .

Alternatively use a milling process .

Why do you need to design anything anyway ? Standard machine tools will do this task easily .

You should really learn at least the rudimentary basics of engineering before tackling a project like this .

Last edited: Nov 15, 2016
3. Nov 15, 2016

### bsheikho

I see some mm then m/min. I didnt read the background, but that could be a reason.

Edit: NVM, m/min is your RPM

4. Nov 15, 2016

### George Zucas

I am designing a new one for a couple of reasons:

- The workpieces for this project are rather big, with diameters of 800 mm - 1500 milimeters. Out of capacity of the lathes we use because of the size.

- The pieces will be heated, I tried to do some research and it seems pieces are heated to about 800-900 degrees Celsius. I don't know the exact reason but since the depth of cut is quite big I assume it is to decrease the specific cutting resistance of the material so that machining will go faster. We need quite a bit of modifying to make heating possible on existing devices. The lathes are also quite busy so this machine will only be doing this.

- I already designed the entire system, I need to select two motors; one for rotation of the workpiece, and one for the blade movement. I am trying to calculate power requirements. I know how to calculate it for machining by turning, but in those cases blade also moves sideways. This one I have never seen or calculated before.

For the tool suggestion, there is a specific cutting tool for this to make the needed cut profile. When you reach the desired depth, the shape is created by itself.

5. Nov 16, 2016

### Nidum

I would like to help you but there is just not enough information given for me to understand what is going on with this machining process .

6. Nov 16, 2016

### George Zucas

I'll try to explain everything. I watched a perfect video for this a few weeks ago, but I can't find it now for the life of me. It would have been much easier. I'll still try to find it though.

What I am trying to manufacture with this machine is basically this (it is just the groove part I am interested in):

I will start with a straight round plate, 50-100 mm thick, with a diameter of around 1000mm let's say. It will have a hole in the middle and using a shaft on the hole, I will rotate this piece. The machining tool will be on a small assembly on rails. There will be two motors, one for rotating the workpiece, one for the tool movement.

My undecided parameters are ( pretty much everything since they are all dependent on each other):

Rotational speed of the workpiece,
Speed of the tool (feed),
Specific cutting power needed for the workpiece at elevated temperatures (they are easily available for room temperatures but not for high temperatures).

If I find these, then selecting motors will be easy. Though the formula I linked above may be wrong, as you can see I not well versed in machining.

Even though the shape of the cut on the part is different I assumed it as a groove for easier calculation, feel free to prove me wrong if it is not the case.

As you can see with the shape of the groove, traversing with the tool is not really possible. It will be go in - go out.