Speeds and Feeds

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marklazarz
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Speeds and Feeds

Post by marklazarz »

When I began using my CNC router, I needed a starting place for determining speeds and feeds.  There are numerous Web resources with charts, calculators, and forums dealing with the subject.  All of this seemed way to complicated to me so I took a more pragmatic approach.  I had experience using routers so I had a "feel" for the way they sound when they are working properly.  If I smelled smoke, I was feeding to slow or my bit was dull.  If the cut was chipping or jagged, I was feeding to fast or in the wrong direction.  If I was pushing too hard, I was probably trying to take too deep of cut.

I decided to use my experience and observation to configure my tool parameters through experimentation.  Routers run at nearly 30K RPM flat out but I put a speed control on the CNC so I had to do some testing to get the same "feel" for how the machine cuts at various speeds.  I now have a fairly good idea of what works, at least for wood.

I'm curious how other people approached their "Speed-Feed" parameters if you care to comment.
DanL
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Re: Speeds and Feeds

Post by DanL »

for using a router I do it the same way plus what the chips look like, if it's dust speed is to fast or feed is to fast, for most wood types other than a hardwood it's all about the same just depth and feed needs changed by a %.
hardwoods I just go a bit slower and not as deep 25% less in feed and depth of cut.
in MDF 75% depth of cut, 75% to 100% width of cut at 21000 rpm 1250mm/min works good in V carve pro with a 1/2 inch, 1/4 is 50% depth 75% to 100% width of cut at 21000 rpm

MDF cutting with a file done in fusion 360 by mistake I have done 150% depth of cut 100% width, it was fine with a HSM tool path
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ArtF
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Re: Speeds and Feeds

Post by ArtF »

I look for the heat of the chips. Nice warm wood chips indicate a proper transfer of heat
to the chip, not the tool. Number one mistake made by most if too low a feed speed, not too high.
  Your method, Mark sounds good to me and is generally how I do it, a quick test sometimes
if I'm not familiar with a material, otherwise I try to take as fast a cut as I can, lowering
pass depth if I cant get up to what I think is a good speed.

Art



   
marklazarz
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Re: Speeds and Feeds

Post by marklazarz »

DanL wrote: for using a router I do it the same way plus what the chips look like, if it's dust speed is to fast or feed is to fast, for most wood types other than a hardwood it's all about the same just depth and feed needs changed by a %.
hardwoods I just go a bit slower and not as deep 25% less in feed and depth of cut.
in MDF 75% depth of cut, 75% to 100% width of cut at 21000 rpm 1250mm/min works good in V carve pro with a 1/2 inch, 1/4 is 50% depth 75% to 100% width of cut at 21000 rpm

MDF cutting with a file done in fusion 360 by mistake I have done 150% depth of cut 100% width, it was fine with a HSM tool path
Interesting numbers DanL, my feeds and speeds are around 30-45 ipm @ 18K-20K RPM which are remarkably close to yours.  I usually peck drill at 8K - 10K RPM.  I have not yet cut plastic but when I do, I'll be back asking for advice on bit types, plastic types and cutting parameters.

Mark
DanL
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Re: Speeds and Feeds

Post by DanL »

when I last cut plastic with a 1/4 cutter I had to drop the rpm down to 18000 with a feed of 1250 mm/min 50% depth 75% width other wise it was it was getting hot at 21000. (chip load)

pvc pipe I cut full depth and full width 2000 mm / min on the A axis 1250 on X and Y.

chip load is the biggest thing to look for to much it gets hot to little it gets hot.

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