10HP motor + rigid ram BP CNC, crazy idea

[rsr911]

So I've got this unused inverter duty 10HP AC motor and drive and I've got a CNC BP Boss 5 with the reeves drive and a max speed of around 4000rpm. My crazy thought is to get rid of the reeves drive and install the large motor figuring it would still put out enough torque even at low rpm so I could control the speed with Mach 3 when I get my new controllers wired up. Well this got me thinking crazy thoughts, like what if I where to increase the spindle rpm? Will the bearings take it? Could I install better bearings etc.? I know the spindle is pressure lubed but not continuosly, I'd like to DOUBLE the rpm for use with 1/4" endmills in aluminum. I know I'm insane, just wondering to what degree LOL

[rsr911]

I was browsing mcmaster's website, particularily the bearings section for ABEC-7 and these are listed as machine tool spindle bearings. All the ABEC-7 bearings are listed at least 17000 RPM. I wonder if my machine has ABEC-7 and if they can handle these loads. Is there a reference for the bearing part numbers that came from the factory?

[JRouche]

I'd like to DOUBLE the rpm for use with 1/4" endmills in aluminum.

Spindle speeder....

Will you lose back gear? JRouche

[rsr911]

I don't use back gear much as the majority of my work is done with 1/2" or smaller endmills. I see no reason I can't keep it in the system though, it's 8.3:1. I'm thinking replace the reeves drive with a cogged belt and pulleys but instead of 1:1 go 2:1 or even 2.5:1. I need 8-10,000 rpm to maximize carbide 1/4" endmills. With this I could push the feedrate up where it should be, get the parts done faster and hopefully improve the finish at the same time.

Like I said it's probably a crazy idea but I still would like to remove the reeves drive and install cog belts with a larger motor so I can control spindle rpm through software. This way I could increase the speed for finish passes automatically as well as change speeds in software for tool changes etc.

I've been a long time in planning the mill conversion and this has sort of been on my mind the whole time. Sure I can just set the reeves at max rpm and control the existing motors speed with a VFD tied to software but then it will have little torque at low rpm and this 10HP motor is a freebie that's brand new. I suppose worst case is I'd have to replace the spindle bearings and intall auxillary oiling but for me it would be worth it. My main question is whether or not the existing bearings can take 8-10,000 rpm.

Right now I'm stuck between carbide and HSS, HSS is too slow while I don't have the RPM for even uncoated carbide so I run max RPM and drop the feed slightly. If I had 10k I could run coated carbide and increase feeds by about 40 percent. RPM is the stuff for Al machining IMHO.

[JRouche]

Ok, sounds like you have been mulling over this for some time. Cool, then I wont have too

I have a Bridgeport Boss 5 and would love to see the conversion and performance.

Keep a good log and take lots of photos please. JRouche

[John Stevenson]

Christian,
I personally think it's a bad idea and that the spindle just isn't built for this type of work.

I have two CNC mills, a Bridgy MDI with a fixed head, variable speed and a QC30 spindle limited to 3,000 rpm
The other is a Beaver mill, INT40 taper and a top speed of 4,000.

Both are too slow for small cutters, I managed to get a couple of speed increasers off Ebay. One is a INT45 [ yes weird ] with a DIN collet chuck built in and it's 6:1 ratio.
I was going to machine the taper down to a 40 and fit it to the beaver but then a INT40 speed came up on Ebay with a Clarkson chuck at 4:1 which fitted straight on.

I aim to make a new shank for the 6:1 head to fit the Bridgy and then both machines will have roughly the same top speed.
I paid آ£135 for the 6:1 head in like new condition and آ£45 for the 4:1 in reasonable condition.

So far i have only used the 4:1 head but it's been very good and certainly speeded the jobs up.

.

[rsr911]

Christian,
I personally think it's a bad idea and that the spindle just isn't built for this type of work....
.....So far i have only used the 4:1 head but it's been very good and certainly speeded the jobs up.

.

In your opinion why is it a bad idea? If it's bearings that should be easy enough to address or is it spindle balance? Lubrication could also be addressed. I am looking for reasons both for or against the idea but I need to know those reasons. Perhaps there is an issue I'm totally overlooking. My problem with an increaser is the lack of torque I'll have if I eliminate or lock the reeves drive and control speed with a VFD, this would be exaggerated with an increaser. I'm not limited to using the 10hp motor I have, there is room in the budget for a smaller motor if you think it's too much hp for the spindle. My next step is to contact spindle reconditioners for there professional advice. My thing is the mill is in fantastic shape with perfect ways and a flawless table, now if I could get an enclosed VMC in similar mechanical condition with at least a 20x20 XY work envelop on the cheap then this machine would be for sale in a heartbeat. Since those type machines usually command more money than I'm willing to spend I figure it's cheaper to modify what I have. My spindle runs dead smooth at it's 4200rpm max.

Things I'd change on the Boss 5 besides the controls update?
1) spindle speed
2) servos rather than steppers
3) larger XY
4) more rigidity
5) enclosed work area

I'm actually working on enclosing the work area and I think I have a pretty good design, now I just need to buy a sheet metal brake so I can build the enclosure. Of course everything I'd change could be found on a good Mazak if I had the money. My current temptation is to strip and repaint the mill, install the controls, update the spindle drive and eventually sell the machine if a good VMC comes along.

[Rich Carlstedt]

John is right, Its a bad idea, because your bearings will not hold up to the higher RPM.
You do not look at precision grade (ie 7) as a means of determining RPM.
In plain English, All bearings have a life. This life is DIRECTLY related to speed, no ifs, and,s or buts. The faster you turn, the shorter the life.
The bearing "ways" can only survive so many cycles. the faster, the shorter the life, but it is not linear !
The speed rating is based on surface feet per minite that the bearing can turn and is in many bearing handbooks.
The grade 7 bearings (2mm207DUL) in my CNC headstock are rated for 3,000 rpm,even though the mill can do 4,000. The 4,000 is in Red..signifying that this speed reduces my bearing life.
Lubrication makes heat.. when a bearing is going to run fast, you need to "lighten" the lubrication...believe it or not. High speed spindles are many times lubed with a oil spray mist. The grease in your bearing will overheat the bearing in short order if you try to run over the 3 or 4 k max.
Check the speed rating of your bearings before engaging in such a venture.
Or, do what John suggested as the easy way.

I find it interesting...Was just at the International Machine Tool Show in Chicago last week...among many things, I saw more "Spindle Rebuilders" there , then in my whole earlier life..you can imagine that all this is the result from the High Speed work that the new mills are doing.. adding to maintenace too!

There are high speed bearings out there.. but you just don't drop them in,
especially at the prices they charge.
Rich

[Rich Carlstedt]

I don't disagree with your thoughts on dumping the Reeves drive.
The mill will be much quieter with a direct drive, or poly V drive.
The 10 HP may be over kill since VFD's increase torque through a motor feedback mechanism that add power when the motor runs below a freqency setting. I think what you are saying is that you want to run a 3 to 1 increase in pulley size, but that would still give you the effective torque of a 3 HP motor at the spindle. don't forget the Reevs drive takes about 2 Hp away from the spindle now, so you gain that.
Rich

[rsr911]

Thanks Rich,

Like I said the 10hp is just a motor I have lying around that I could fit to the mill with some work. You did touch on what I figure the key problem is and that is heat. I also have assumed the existing bearings won't take the higher rpm but I won't know unless I get part numbers off of them or if someone here knows the part numbers. A polyvee or cog belt is definately in the plans as I don't much care for the guesswork of the reeves drive and I want to directly control spindle rpm with software a speed increase would just be a nice added bonus. I'm leary of adding an increaser in that I think it will put more lateral strain on the spindle as well as be less rigid, as it is I prefer to run most of my programs in the upper 2" of Z travel which is the quill on the bridgys. I know this is doable it's just a question of how much cost as at some point I'd have to ask myself if it wouldn't be better long term to just save for a mill with the features I want. For example I've got a rather specific wheel I'd like to reproduce in sizes never originally available like 17" and 18". The current mill makes this impossible unless I had a CNC rotary table so I could index into the work envelope.

My biggest problem is time as my shop is located at work and I have a family that wants me at home. I just finished a fixture for one of the items I make that makes 4 sets of parts rather than one, the run time is 3 hours so I can go home for dinner and come back later to cleanup. I'm also constantly coming up with other items that I can make and sell so faster cycle times would be great. Heck I've even considered another Boss 5 so I could double production but that requres more space which I won't have until I move the shop into the building next door to the current building and that's at least a year away.

[rsr911]

I heard back from a spindle reconditioner today, the bearings in my head are good for about 5000rpm. An upgrade to higher RPM capable bearings is possible and spindle precision balancing is recommended. According to the recondioner my head should have an ABEC-7 lower bearing on the bottom and a regular bearing up top. Both would need to be replaced with high RPM ABEC-7 bearings and oiling might need to be addressed. As expected the increased speed would bring increased wear.

I think I'll pursue this a little farther before giving up. As I'll need to disassemble the head to ditch the reeve's drive anyaway I figure I can check bearing availability at that time.

Now to get all these parts done so I can tear the mill apart.......

[Timleech]

I have a VFD on my Boss Series I, it'll go to about 25% above normal top speed, after that the spindle gets warm pretty fast.

Tim

[Bruce Griffing]

If you need higher speed than your mill will provide, but need it only now and then, you might consider one of these. I use it for drilling PC boards.

http://www.macrotechnologies.com/hig...r_spindles.htm

[rsr911]

I have a VFD on my Boss Series I, it'll go to about 25% above normal top speed, after that the spindle gets warm pretty fast.

Tim

Thanks Tim, I assumed that would be the case with stock bearings. It also ties into what the spindle reconditioner told me as 5000 is about 25% more than my machines 4200 rpm max. My plan would involve good high speed bearings and extra lubrication.

I've often wondered about wood routers, 15,000 or so rpm. I guess the motor's fan keeps the bearings cool.

As for the air spindle that was recommended by the spindle conditioner but defeats my purpose of wanting to control spindle speed directly with G-code or Mach 3. I've got a month or two before I'll have enough inventory to take the mill apart so I'll see what's available for bearings at that time.

[snakebit95]

If you need higher speed than your mill will provide, but need it only now and then, you might consider one of these. I use it for drilling PC boards.

http://www.macrotechnologies.com/hig...r_spindles.htm

Bruce,
I have looked at the air spindles in the past, and they always have extremely high CFM air requirements. I looked on the website you posted, but could not find any volume requirements. They only list a pressure range. Do you have any idea how much air these spindles use?

Just to let you know, I also have a Boss 6 machine in the retrofit stage and would like to have a high-speed spindle option too; without toasting the stock bearings.

Thanks,
Wayne