Newbie looking for basic settings for feed rate for bits

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RacerChris
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Newbie looking for basic settings for feed rate for bits

Post by RacerChris »

Its been a heck of a week getting to know my Shark HD CNC Machine! nice machine!

I am having a quality of cut issue with a .25" end mill through 3/4" MDF. Some cuts are clean, but others jagged and stepped. i want to make sure I am using the proper feed rate for MDF and Oak which is coming next.

I tried searching on line for feed rate for various types of lumber but not finding it... Any input would be helpful.

Thanks for the foothills of California!
Chris
Shark HD3 / vCarveDesktop 10.512 / CNC Shark Control Panel v2.1 Build 22

ger21
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Re: Newbie looking for basic settings for feed rate for bits

Post by ger21 »

What settings are you trying to use? Feedrate, rpm, depth of cut, type of bit?

Feedrates and depth of cut have a lot to do with the specific machine that you're using, as the machines rigidity effects how deep and fast you can cut.
Gerry - http://www.thecncwoodworker.com

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Rcnewcomb
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Re: Newbie looking for basic settings for feed rate for bits

Post by Rcnewcomb »

Chip load and feed rates are also affected by the brand of bit and its geometry.

Here is a link to the chipload data for an Onsrud bit and MDF: ->Onsrud MDF Chipload

If the chip load is 0.006, and the bit has 2 cutting edges, and the router is spinning at 12K RPM then the feed rate would be:
Feed Rate (ipm) = chipload X RPM X cutting edges
144 ipm = 0.006 X 12,000 X 2

That may be too fast for your particular machine. Start at half that speed (72 ipm) and work your way up until you get chatter, then back off the speed by 10%.
- Randall Newcomb
10 fingers in, 10 fingers out, another good day in the shop

RacerChris
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Re: Newbie looking for basic settings for feed rate for bits

Post by RacerChris »

Wow that was quick! thanks guys for trying to help :-)

yes, i should have provided specifics for my application:

-I have a brand new Shark HD3 CNC Machine
- cutting 3/4" MDF (for now as i work through the settings, will go to hardwood (oak) next.
- 1/4" End Mill Amana Bit 46102: http://www.amanatool.com/46102-solid-ca ... p-cut.html
- All cuts are profile cuts. I have the tool set at .125 pass depth, .10" stepover, 24000 rpm, 100 in/min, plunge rate at 30.

I took the following steps to clean up the cuts and they seem to have improved things:

1. Turned on last pass at 1/32" in reverse direction
2. Changed to Climb from conventional

Curiously, Amana does not specify the chip rate for their bits...

I am learning, but it seems hit or miss. Perhaps there is a reference i should have that will help me with the cutting end of things?

Also, one strange thing is the bit does not seem to cut through the entire board even though I have the right thickness and use hte touch plate for zero...
Chris
Shark HD3 / vCarveDesktop 10.512 / CNC Shark Control Panel v2.1 Build 22

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Rcnewcomb
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Re: Newbie looking for basic settings for feed rate for bits

Post by Rcnewcomb »

Slow the RPMs down if you are able. At 24000 RPM and 100 ipm it ends up making dust not chips.
- Randall Newcomb
10 fingers in, 10 fingers out, another good day in the shop

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FixitMike
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Re: Newbie looking for basic settings for feed rate for bits

Post by FixitMike »

"Also, one strange thing is the bit does not seem to cut through the entire board even though I have the right thickness and use hte touch plate for zero..."

Sometimes 3/4" material is actually 13/16". Plywood is usually undersize.

For me, single flute bits give me better results and are quieter.

When you feel like trying slower rpms than your router can be set to, check out the SuperPID drive.
Good judgement comes from experience.
Experience comes from bad judgement.

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