Options For High Speed Milling

countryguy said:
I have the Dewalt 611 trim router and think it is grand! I also have the same air powered pencil spindle noted above as Jim and the guys here helped me get my high speed engraving spindle basics nailed down. The only item I have a comment on is related to Carbide small end mills on high speeds. I tried that. Broke most everyone of them (with CNC being used for engraving). So brittle and delicate. Of course, I am also very new and learning but did fare much better with HSS in those really small sizes. I now also love Cobalt. I'm just curious what type of material you would use these Carbides and higher speeds upon? When I used my setup for engraving on Brass- the carbide would just not last long when cnc driven. I also ran them on Steel and Stainless. In the end I needed a mount w/ a spring spindle and HSS. Thought I would toss in my newb feedback on really really small carbide EMs
Click to expand...

My choice of materials is aluminum and mild steel. I'm considering carbide because the high speed spindles and router motors I've looked at are rated 10,000 RPM on the low end. 10,000 RPM is too fast for a 1/8" HSS end mill in mild steel. My mill's top speed is 1,970 so I have a gap to fill between 2,000 and 10,000 RPM.

I've been in the machining industry my entire career (45+ years) so I understand feeds, speeds, chip load, chip evacuation, etc. but I don't have any experience running end mills smaller that 1/8" so I appreciate your feedback on using small diameter carbide end mills. Always something new to learn.

Tom S
 
Gunrunner you need to order a set of these for the Z axis hand crank. Bill did you just spit coffee on your monitor? :rofl:

View attachment 253356
 
TomS said:
My mill's top speed is 1,970 so I have a gap to fill between 2,000 and 10,000 RPM.
Click to expand...

That is going to be your problem Tom. It doesn't appear to me that you will be able to cover your desired range with a single option.

I took a look at the PM932 brochure at it appears that this essentially the same as the Grizzly G0755 which I have some experience with. If you are considering changing the motor, how well will your spindle bearings hold up running at six times the rated spindle speed and how well balanced is your spindle? Tormach goes so far as to cut a second keyway on their R8 collet for the TTS system. Finally, how would the gear train hold up to the increased speed?

For what it is worth, the Tormach 770 uses a 1 hp. (1.5 hp peak) 3 phase vfd controlled spindle motor coupled with a dual pulley system, low range 175 -3250 rpm, high range 525 - 10200 rpm. The motor maxes out at just under 7,000 rpm. It is fairly anemic at the low end of the speed range, however. Based on your gear train, that still wouldn't get you to 10K.

Regarding the speed increaser approach, here is a link to a German company: http://www.henningerkg.de/produkte/...lauf-frasspindeln-mit-ubersetzung-16/?lang=en. I suspect that the price will make the Tormach solution look like a bargain though.

Here is a wild idea. Rather than using a gear train to achieve the speed increase, how about a hydraulic system. A relatively high volume hydraulic pump driving a low volume turbine. The advantage would be the mechanical isolation between the input and output. With the right drive coupling, any spindle runout would not be of consequence.. The output drive would be a turbine on a shaft with high speed bearings and something like an ER20 collet chuck. Hmmm......:rolleyes:

Bob
 
Somewhere I saw a pretty cool setup on a mill, it may have been on HM but I don't remember. It had a high speed spindle that was held in the mill spindle in a collet. It was driven with a timing belt powered by a router motor mounted to the side. This would allow a speed reduction from the router spindle. A 2:1 reduction would put you in the speed range that you are looking for with a 2:1 increase in torque.
 
Tom
I am quite impressed with with the unit I purchased and how well it works, If I had it to do over though I would have purchased the
2.2 to get the larger collet size. ( I can only use up to 7mm ) I have never wired my vfd to my controller I manually turn it on and off because I also use it on my Sherline mill for making really small parts and 4 axis engraving.
One thing that I do notice and try to stay ahead of is the micro fine chips coming off of the cutter. I keep a guard as close as possible to the work and place a
rag over the table drain to catch everything I can. They are so fine they will float on the coolant and get into everything including your fingers it is like your playing
with a cactus. When I use it I vacuum everything to keep it out of the ways. when doing steel placing a magnet by the drain may even be a good idea.
Steve
 
RJSakowski said:
That is going to be your problem Tom. It doesn't appear to me that you will be able to cover your desired range with a single option.

I took a look at the PM932 brochure at it appears that this essentially the same as the Grizzly G0755 which I have some experience with. If you are considering changing the motor, how well will your spindle bearings hold up running at six times the rated spindle speed and how well balanced is your spindle? Tormach goes so far as to cut a second keyway on their R8 collet for the TTS system. Finally, how would the gear train hold up to the increased speed?

For what it is worth, the Tormach 770 uses a 1 hp. (1.5 hp peak) 3 phase vfd controlled spindle motor coupled with a dual pulley system, low range 175 -3250 rpm, high range 525 - 10200 rpm. The motor maxes out at just under 7,000 rpm. It is fairly anemic at the low end of the speed range, however. Based on your gear train, that still wouldn't get you to 10K.

Regarding the speed increaser approach, here is a link to a German company: http://www.henningerkg.de/produkte/...lauf-frasspindeln-mit-ubersetzung-16/?lang=en. I suspect that the price will make the Tormach solution look like a bargain though.

Here is a wild idea. Rather than using a gear train to achieve the speed increase, how about a hydraulic system. A relatively high volume hydraulic pump driving a low volume turbine. The advantage would be the mechanical isolation between the input and output. With the right drive coupling, any spindle runout would not be of consequence.. The output drive would be a turbine on a shaft with high speed bearings and something like an ER20 collet chuck. Hmmm......:rolleyes:

Bob
Click to expand...

Bob - I have to agree with you that the spindle bearings, even if I upgrade to high quality, probably max out at about 6,000 RPM. The gear train less than that. The three phase VFD conversions I've seen have a top speed around 6,000. Speed increasers tend to be expensive but I'm still looking.

Tom S
 
jumps4 said:
Tom
I am quite impressed with with the unit I purchased and how well it works, If I had it to do over though I would have purchased the
2.2 to get the larger collet size. ( I can only use up to 7mm ) I have never wired my vfd to my controller I manually turn it on and off because I also use it on my Sherline mill for making really small parts and 4 axis engraving.
One thing that I do notice and try to stay ahead of is the micro fine chips coming off of the cutter. I keep a guard as close as possible to the work and place a
rag over the table drain to catch everything I can. They are so fine they will float on the coolant and get into everything including your fingers it is like your playing
with a cactus. When I use it I vacuum everything to keep it out of the ways. when doing steel placing a magnet by the drain may even be a good idea.
Steve
Click to expand...

Steve - thanks for the info. At this point I'm not sure which direction I'm going. Still searching and looking at what's out there.

Tom S
 
JimDawson said:
Somewhere I saw a pretty cool setup on a mill, it may have been on HM but I don't remember. It had a high speed spindle that was held in the mill spindle in a collet. It was driven with a timing belt powered by a router motor mounted to the side. This would allow a speed reduction from the router spindle. A 2:1 reduction would put you in the speed range that you are looking for with a 2:1 increase in torque.
Click to expand...

Thanks for turning the light on. I now remember an article in either HSM or MWS magazines a year or so ago. I'll have to dig through me magazine stack and find it.

Tom S
 
When I did the research on a spindle for the CNC router we built for the high school robotics team I spoke with many suppliers, manufactures and end users ranging from the hobby level to industrial. Our requirement was to cut aluminum from sheet to 1/2" with high precision. My conclusions were that the wood routers and low end Chinese spindles would not hold up based on our indented usage. The bearings are not up tot he task and they are not designed to plunge repeatedly (drilling). We settled on an industrial 3hp spindle made in Italy specifically configured for our application with the correct radial and axial bearings. The Spindle and Drive were $2800.

I think you can get away with a lot from low end spindles cutting just aluminum on a hobby level but steel is a whole other animal.

Also consider the feed rate limitation of your mill. The faster you turn the cutter the faster feed rate you may need to maintain the recommended chip load. I am finding my little CNC router cannot move fast enough to properly use some cutters even at the min spindle rpm of 8K.
 
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