Axiom CNC, 1/2 Straight flute, MDF/Birch Screaming? Help with Feed/speed please.

[CustomSP]

I have an Axiom Elite CNC (modified with 'servo steppers') and I have been running the following as a roughing strategy:

Material: Baltic Birch Plywood; 3/4" laminated to 3" overall height
Bit: 1/2" amana 2-flute straight cut brazed carbide bit (45424); 4.25" overall length, chucked to 3.2" exposed tool
Feed: 3500 mm/min (137 in/,min)
Speed: 10,000 RPM
Depth of cut: 4mm (full engagement for a 'profile' pass)

The issue is the noise; ear bleeding screams and squalls. Of course loud = bad for tool and machine life. What am I doing wrong? I have played with speed, up to 18k rpm, and feed, up to 4000 mm/min (157 in/min).

I spoke with a Vortex rep yesterday and he said that 1/2" is a bit too big for my spindle and recommended going down to 3/8" bit and let it eat. I have already ordered the recommended tools, but I would like to hear from the group if I can run the 1/2" on my machine with success.

For some reason, I am scared to push the feedrate to the 500 in/min, 1/2" depth of cut that I read about in previous forum posts, it just seems counterintuitive to my engineering mind.

Any and all advice is greatly appreciated.
-B

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[MillAlien]

I have an Axiom Elite CNC (modified with 'servo steppers') and I have been running the following as a roughing strategy:

Material: Baltic Birch Plywood; 3/4" laminated to 3" overall height
Bit: 1/2" amana 2-flute straight cut brazed carbide bit (45424); 4.25" overall length, chucked to 3.2" exposed tool
Feed: 3500 mm/min (137 in/,min)
Speed: 10,000 RPM
Depth of cut: 4mm (full engagement for a 'profile' pass)

The issue is the noise; ear bleeding screams and squalls. Of course loud = bad for tool and machine life. What am I doing wrong? I have played with speed, up to 18k rpm, and feed, up to 4000 mm/min (157 in/min).

I spoke with a Vortex rep yesterday and he said that 1/2" is a bit too big for my spindle and recommended going down to 3/8" bit and let it eat. I have already ordered the recommended tools, but I would like to hear from the group if I can run the 1/2" on my machine with success.

For some reason, I am scared to push the feedrate to the 500 in/min, 1/2" depth of cut that I read about in previous forum posts, it just seems counterintuitive to my engineering mind.

Any and all advice is greatly appreciated.
-B

I think you might be pushing in the wrong direction - my math is that for plywood, your chip-load target is in the 0.025 - 0.027" range. Assuming a 2-flute 1/2 bit and 137/minute feed rate, I'd run the RPM down to ~2,635, not 10k. At that RPM, the feed-rate math is 520/minute. Looks to me like your machine is recommended to max at 320/minute feed-rate, which would be 6,154 RPM at that chip-load.

I don't think your pass depth (4mm) is the problem.

I don't know why Vortex told your Axiom Elite can't run a 1/2" bit - that machine ships with a 1/2" ER20 collet.

[CustomSP]

I appreciate the feedback! Your math checks out and I'll test it and let you know the results. Though, i'm worried that it will be chomping at that setting...? And also, the spindle motor wouldn't have as much available torque at such a low speed.

I did find another 'sweet spot' at 22k rpm and 3500mm/min. Chips were fine, not dust, and noise was greatly reduced.

[CustomSP]

Tried it. Stalled my spindle out.