New to CNC - Please can i have some Help?

[Chiapaprikos]

Hi All,
Sorry for the long post but I really need some help to the followings in order to work my machine:

1. Chip load is according to tool or type of wood?
2. My motor tuning is setup for 400mm per min (Can I put it as much I want?)

I have found a table with chip loads and my calculations as follow:

Soft Plywood 0.021-0.023.
My bit: 16mm 2 flute straight bit.

Spindle Speed Chip Load Num of flutes Feed Rate
10000 0.021 2 420
10000 0.022 2 440
10000 0.023 2 460
9500 0.021 2 399
9500 0.022 2 418
9500 0.023 2 437
9000 0.021 2 378
9000 0.022 2 396
9000 0.023 2 414

Just for safety, I used the red selection from above, in order to stay under my range of 400mm per min.

So when I created a pocket in VcarvePro, I put those details in tool database, but in the tool path txt file I have export, I found that the feed rate was 60 times bigger than 378 (22680).

I simulate the toolpath in Mach3, and while running, I found that my velocity was way above that 400mm per min.

See attached file for details…..

I run the program with my bit on, but I got a very rough cut, do you think is because my machine can move only 400mm per min and I got much more?

Can you explain how the procedure is to get at least a better finish, and be safe?

[awerby]

Hi All,
Sorry for the long post but I really need some help to the followings in order to work my machine:

1. Chip load is according to tool or type of wood?

[Both need to be considered, but the tool is most important.]

2. My motor tuning is setup for 400mm per min (Can I put it as much I want?)

[You want that velocity setting to be about as fast as your machine can run reliably. 400mm/min is pretty slow, especially for wood. 4000 would be better, if your machine can handle it.]

I have found a table with chip loads and my calculations as follow:

Soft Plywood 0.021-0.023.
My bit: 16mm 2 flute straight bit.

Spindle Speed Chip Load Num of flutes Feed Rate
10000 0.021 2 420
10000 0.022 2 440
10000 0.023 2 460
9500 0.021 2 399
9500 0.022 2 418
9500 0.023 2 437
9000 0.021 2 378
9000 0.022 2 396
9000 0.023 2 414

Just for safety, I used the red selection from above, in order to stay under my range of 400mm per min.

[The feed rates in that chart are probably in mm per second, not per minute.]

So when I created a pocket in VcarvePro, I put those details in tool database, but in the tool path txt file I have export, I found that the feed rate was 60 times bigger than 378 (22680).

[Right; sixty times bigger.]

I simulate the toolpath in Mach3, and while running, I found that my velocity was way above that 400mm per min.

See attached file for details…..

[It looks like Mach3 might have been set up in inches, but you're running it in mm.]

I run the program with my bit on, but I got a very rough cut, do you think is because my machine can move only 400mm per min and I got much more?

Can you explain how the procedure is to get at least a better finish, and be safe?

[How deep are you cutting per pass? You'd probably have best results by dropping the tool about 8mm at a time, and feeding a lot faster. Wood tends to burn if you try to cut it too slowly; the tool is rubbing more than cutting. Look at the chips you're making - they should be rather coarse, not fine dust. To get a better finish, you might go with a rough cut to remove the bulk of the material followed up with a finish cut to smooth the edges. ]

[Chiapaprikos]

I am cutting 1mm per pass, because i need to pocket only 3mm. I am trying to flatten my table. How can i calculate best feed and speed? So there is no problem that my machine is set up to 400mm per min and getting more than that?

I will try try to go deeper (3mm) at once to see what will happen, and i will let you know.

Thank you very much.

[bhurts]

400mm per minute is generally very slow for anything but metal working. Is the machine capable of going faster then this? You should set the max feedrates in motor tuning to as fast as you can go without losing steps. Then back off 30-50%.

Ben

[Chiapaprikos]

I have set my stepper motors to 1/2, how can i check how fast it can go?

Shall i leave it to 1/2 and just increasing the tuning until i start loosing steps and then go back us you said?
If i start loosing steps to a not good tuning, what do you suggest?

i.e If i start loosing steps to 1000 mm per min, go back 30% to 700 steps per min, is it good or have to change hardware?

Thanks

[bhurts]

For now just speed things up in motor tuning. When you start losing steps back off 30-50%. Then let us know how fast it can go.

Ben

[Chiapaprikos]

Hi,

I tested it on weekend, it can go without loosing steps 1200mm with driver set to 1/2. (Leadshine 542)

Microstep------Steps/Rev------sw5-----sw6-----sw7-----sw8
2 ------ 400 -------off ------on-------on------on

My lead screws just for info are normal 10mm screws

[Chiapaprikos]

Hi,

Any advise yet?

Thanks