CNC processing speeds, which is the correct relationship...

[Newton]

To all who have worked with you're machines ;

Doing really intricate pocketing and cutting matching designs to inlay using a really small bit like 0,3 -0,5mm, which processing speeds do we need and which spindle speeds do we need? The movement of the CNC is not limited to much (Max working speed is 20000mm/min), but is for instance 18000 Rpm on the mill enough? Milling that small, should you use high movement speeds and slow mill speed or is it slow movement and 100 000 RPMs on the mill which is the best ? In other words, the more RPMs the better?

I would think the last, but I remember I read some time here that the heat of the small drill bit was the largest danger of having it to break, so high processing speed/movement was important. Would then 18000Rpm on a HSD spindle be sufficient ?

Any experts which could please give me a feedback?

N

 

[Chris Byrne]

Look up precisebits.com they have info on finding the correct cutting speed and rpm on their site. Chris.

 

[billiardbum]

To all who have worked with you're machines ;

Doing really intricate pocketing and cutting matching designs to inlay using a really small bit like 0,3 -0,5mm, which processing speeds do we need and which spindle speeds do we need? The movement of the CNC is not limited to much (Max working speed is 20000mm/min), but is for instance 18000 Rpm on the mill enough? Milling that small, should you use high movement speeds and slow mill speed or is it slow movement and 100 000 RPMs on the mill which is the best ? In other words, the more RPMs the better?

I would think the last, but I remember I read some time here that the heat of the small drill bit was the largest danger of having it to break, so high processing speed/movement was important. Would then 18000Rpm on a HSD spindle be sufficient ?

Any experts which could please give me a feedback?

N

The range of bit speed IMO should be at least 25K and no more than 60k. If you are running .010 cutters you would run 60k rpm. I run .031 cutters at 30k and have no issues in material. Hope this helps.

 

[cuebuilder]

There are several sites on the net that you can find "feed and speed" charts. When I'm running a .010 cutter in most woods, I run 60,000 RPM at around 4 inches per minute With a .015 cutter, the same RPM at around 6 or 7 inches per minute.

 

[Newton]

Look up precisebits.com they have info on finding the correct cutting speed and rpm on their site. Chris.

Hmmm.

It sounds like a 18-25K Rpm spindle is then to slow even if it's a industrial spindle
I have no option of getting a higher RPM machine at the moment so I guess I can compensate using pressured air from air tool compressor then to cool the mill ?

I had a look at the web page and the example shows a 30K Rpm speed.. 60K is for sure a really fast flying spindle ...

Thank's all, I'll do another search on the web to have some more sources.

Regards

Newton

 

[rhncue]

Hmmm.

It sounds like a 18-25K Rpm spindle is then to slow even if it's a industrial spindle
I have no option of getting a higher RPM machine at the moment so I guess I can compensate using pressured air from air tool compressor then to cool the mill ?

I had a look at the web page and the example shows a 30K Rpm speed.. 60K is for sure a really fast flying spindle ...

Thank's all, I'll do another search on the web to have some more sources.

Regards

Newton

The smaller the bit equals - the more rpms and the slower feed-rate and the less run-out and the shallower the depth of cut that you need to help eliminate cutter breakage. I looked into an air cutter with a rate of 300,000 rpm once for running very fine cutters.

Dick

 

[Newton]

I had a email correspondence with another CNC user (not building poolcues) and he had the problem that the spindle was to fast, over heating the material he was milling. Cutting in plastic with drill bit speeds > 8K and the maximum movement speed he had was not enough. He claimed that he either needed a mill running slower then 8K or a faster movement of the Gantry. Since he had stock screw axis (no real ball screws for higher movement) he was stuck in frying his plastic parts.

I think I would try for a 18K Rpm spindle, small depths and then using compressed air to cool the end mill blowing away any small chips/mist.

Hopefully it would work out... Or is this a waist of time, money and drill bits?

K

 

[rhncue]

I had a email correspondence with another CNC user (not building poolcues) and he had the problem that the spindle was to fast, over heating the material he was milling. Cutting in plastic with drill bit speeds > 8K and the maximum movement speed he had was not enough. He claimed that he either needed a mill running slower then 8K or a faster movement of the Gantry. Since he had stock screw axis (no real ball screws for higher movement) he was stuck in frying his plastic parts.

I think I would try for a 18K Rpm spindle, small depths and then using compressed air to cool the end mill blowing away any small chips/mist.

Hopefully it would work out... Or is this a waist of time, money and drill bits?

K

Cutting in plastic or soft aluminum can cause problems but why would you want to use either? I tried once to cut some small spear heads out of aluminum to mount ivory into to go in the top of some custom joint protectors. I tried feed rates down to 3 inch per minute and taking cuts of .003 in depth and broke about a 100.00 worth of .031 end mills before giving up and using sterling instead. I would have saved about 95.00 if I would have used the sterling to start with. As soon as the cutter touched the aluminum it would get hot and weld itself to the end mill stopping the cutting action and breaking off. I run directed air to my cutters but it doesn't have a very efficient cooling affect like a liquid coolant would.

With .031 cutters I run .060 - .080 on depth at a feed rate of 40 inch per minute with rpms of 35,000 - 38,000. When engraving in MP butt caps, which are a soft plastic, I use an engraving bit and run at .015 depth at around 2,000 rpm. In this way the cutter acts more like a non-rotating engraver than an end mill.

Dick

 

[RocketQ]

Dick something that might work submerge the whole part down in oil for aluminum and stick that down to the table and mill. Shouldn't melt the al to the bit.

 

[Newton]

Cutting in plastic or soft aluminum can cause problems but why would you want to use either? I tried once to cut some small spear heads out of aluminum to mount ivory into to go in the top of some custom joint protectors. I tried feed rates down to 3 inch per minute and taking cuts of .003 in depth and broke about a 100.00 worth of .031 end mills before giving up and using sterling instead. I would have saved about 95.00 if I would have used the sterling to start with. As soon as the cutter touched the aluminum it would get hot and weld itself to the end mill stopping the cutting action and breaking off. I run directed air to my cutters but it doesn't have a very efficient cooling affect like a liquid coolant would.

With .031 cutters I run .060 - .080 on depth at a feed rate of 40 inch per minute with rpms of 35,000 - 38,000. When engraving in MP butt caps, which are a soft plastic, I use an engraving bit and run at .015 depth at around 2,000 rpm. In this way the cutter acts more like a non-rotating engraver than an end mill.

Dick

Dick,

Well, I did not say I was planning to mil with that small bit's in Aluminum. Doing milling in Alu would be to make custom machine parts when I build other equipment. For this I have/buy a mist cooling system.

The point I was trying to make in my last post was ; could you over do it with respect to speed (Rpm) on wood and actually burn the wood (or make it brown). Is it possible to compensate by moving the Gantry quicker with less depth pr cut with a slower spindle Rpm as I got the impression of during my emailing with this sign maker?

K

 

[brianna187]

contact ron reed at precise bits he is the man

 

[Newton]

contact ron reed at precise bits he is the man

Thank you Lee. I have dropped a email on the support email address and hope to hear from him.

N