[vladoportos]

Hello all,
I'm experimenting with some wood cutting on CNC, and its taking forever I know this depends on huge lots of things, but lets look at one special case from today.

I did cut small picture frame which is about 180mm x 180mm


Roughing was done by 6mm end mill this was fairly quick 30 min and finishing by "Solid Carbide 2mm Dia Spiral 2 Flutes Ball Nose End Mill CNC Engraving Bit ( from ebay, china )" not so quick as this took 9 hours to finish :-/ is this normal ? ( I have no experience... ) My feed rate was 20% ( I know this doesn't tell you anything, see my note about feed rate bellow) but later I tried up to 35% and it went faster but any more and I think the bit will break




The feed rate: Well this is issue I had for some time, simple answer.. I don't know. I have Chinese CNC ( this one: https://goo.gl/RZMNgV ) and not sure how to tell what the percentage mean in terms of mm/min

Spindle RPM: another value I'm not sure about. The controller show the speed in Hz ( see picture:, this is max value I usually use like 80% of it) I would like to find out though...




CAM: I used Aspire from Vetric to generate the G-code. It took in account the roughing part when generated finishing path ( the finishing path was in one stroke, didn't have to move twice the same path. )


Bits: For the finish I used "Solid Carbide 2mm Dia Spiral 2 Flutes Ball Nose End Mill CNC Engraving Bit" ( from ebay, china )


Video in real time:
https://youtu.be/uK0gbepkt-k


I'm bit paranoid now, cause I broke so many bits ( not this one yet though, I have 5 more so I might try to push it )

I have very vague experience with CNC I know how to do lots of staff but probably not properly ( and nobody around to ask ... ) So I would be immensely happy for any advice.

[1875]

400 Hz is 24k RPM. Just multiply Hz by 60.

You can figure out your travel speed by programming a linear move, say 100mm, and time how long it takes. The longer the move, the more accurate you can measure. Then just divide mm/s. The cutting speed in the video looks OK to me. That is a long small bit. You might be able to do more roughing with the larger bit and then finish with the smaller bit at a higher feed rate if you are taking less material. You'll have to experiment with the cut quality at different speeds for different materials.

[vladoportos]

Thanks the RPM value is a huge help for me, I had no idea The bit in the video is the 2mm ball nose finisher, I always try to remove as much material before using it with larger one so it go in one pass... I'll try to figure out the travel speed tomorrow

[awerby]

Speed in wood machining depends on what you're trying to do. For a project like the one in the picture, 9 hours doesn't seem too far off, considering that you're using such a small tool and stepping over a small percentage of the diameter each time. The velocity you're commanding doesn't really control the speed of the finish pass, since there are so many tiny movements that it never actually gets up to speed before starting another move. Boosting the acceleration will help more, assuming that your machine won't fault out when you do that. It looks like your process is doing pretty well; you might just have to resign yourself to long machining times. But if you're breaking a lot of those 2mm bits, you might substitute tapered carving bits, which have a more robust geometry: Carbide 3 & 4 Flute Tapered 3D C arving Tools