series one head drive conversion

[MARKG]

Right, finally got around to making a new set of pulleys to be able to run the spindle a little faster. Essentially a 2:1 ratio (8" driving 4") . In consideration of the possibility of slippage on the 4" pulley, I went to a 6 rib belt. We can get in the 4k range now.
Thanks to everyone here for their input and help.
Short vid clips here:
http://www.youtube.com/watch?v=klGpG8dYU7M&feature=mfu_in_order&list=UL]BRIDGEPORT CNC PROGRESS 2 - CONVERSION TO VFD & POLYV BELT DRIVE - YouTube
http://www.youtube.com/watch?v=uRZgb9F5jKs]BRIDGEPORT CNC PROGRESS 6 - POLY V BELT UPGRADE - YouTube

[mactec54]

MARKG

Looks good, when ever I did the 2-1 like you have I made the pulleys a double set, Having 2-1 in both directions, This was used instead of having a back gear, the back gear was removed, when doing this double pulley set up

[MARKG]

Great idea, thanks Mac, may have to add that too at some point!

[bugattiman]

Hi Martec, I am very impressed with yuor bridgeport head conversions. I see the motor is inverted compared with the position of my 2J2 head. Is this necessary or can it be left in the above position?

I am looking at doing away with the troublesome vari drive and plastic bushings which are giving me giref continually.

I have been advised to have a separate fan cooling the motor also?

I have a vfd and basically would need to make the pulleys and purchase a poly v belt. I'd like to go for an 8" pulley on motor and 4" pulley on spindle to achieve higher revs as I rarely do any heavy work on the machine. It's normally, cutting aluminum,brass,plastic or rarely steel.

Can I still retai nthe back gear and brake drum set up?

any help \ drawings very much appreciated, best regards,

Bugattiman

[mactec54]

Hi Martec, I am very impressed with yuor bridgeport head conversions. I see the motor is inverted compared with the position of my 2J2 head. Is this necessary or can it be left in the above position?

I am looking at doing away with the troublesome vari drive and plastic bushings which are giving me giref continually.

I have been advised to have a separate fan cooling the motor also?

I have a vfd and basically would need to make the pulleys and purchase a poly v belt. I'd like to go for an 8" pulley on motor and 4" pulley on spindle to achieve higher revs as I rarely do any heavy work on the machine. It's normally, cutting aluminum,brass,plastic or rarely steel.

Can I still retai nthe back gear and brake drum set up?

any help \ drawings very much appreciated, best regards,

Bugattiman

The inverted Motor placement was standard for the Boss Machines, even though they looked and used most of the same Head parts as your machine

Yes you can retain the Back Gear, how fast do you want to run??

You can with your VFD run to 100Hz on the standard motor you may be able to go as high as 120Hz, but with your country being 50Hz I would stick with 100Hz , if the motor is happy at 120Hz, then not problem, this will double the motor rated RPM, you can of cause change the motor for a higher RPM motor, and with the VFD you would not need such a high pulley ratio to get the speeds you want, you will loose a lot of torque at the spindle when you use a pulley ratio like this

[bugattiman]

Hi mactec54, thanks for responding so quickly. I would say 5,000 rpm as a max and I do not do any heavy work so to speak. I suppose a job like a cylinder head skim with a large flycutter is worst I'd be doing and I only take max 0.2mm cuts with a single point fly cutter so don't think torque would be an issue. I have a CNC miller I can run at 4,200 rpm and I have also made an attachment to hold a water cooled spindle that can get me up to 24,000 rpm for small cutter work like engraving etc. The main reason for wanting to convert is the noisy vari head and I don't particularly like the system of the speed changing. So are you saying the motor needs to be inverted or can it be left in its overhead position? Height is not an issue in my garage, cheers

[mactec54]

Hi mactec54, thanks for responding so quickly. I would say 5,000 rpm as a max and I do not do any heavy work so to speak. I suppose a job like a cylinder head skim with a large flycutter is worst I'd be doing and I only take max 0.2mm cuts with a single point fly cutter so don't think torque would be an issue. I have a CNC miller I can run at 4,200 rpm and I have also made an attachment to hold a water cooled spindle that can get me up to 24,000 rpm for small cutter work like engraving etc. The main reason for wanting to convert is the noisy vari head and I don't particularly like the system of the speed changing. So are you saying the motor needs to be inverted or can it be left in its overhead position? Height is not an issue in my garage, cheers

No the motor does not need to be inverted, but would make it easier to install the belt J8 is the best in the poly V Belt which means 8 ribs a J6 will do the job but are marginal

[jake2465]

Hi redford1955

The back gear was only removed for the 6,000 to 8,000rpm spindle machines I did do one for 12,000 but this was not worth the extra spindle work needed to get the 4,000 more, doing 3D machining is no problem with 6,000rpm this you have a 2/1 drive pulley set, every thing has to be balanced very well, Bearings have to be high quality right through the head & motor

At 2/1 pulleys the motor is running at 3,000rpm the spindle at 6,000 The stock motor has a rated rpm of 3450rpm

The 2/1 is no good for heavy cutting, you have to change it back to 1/1 for normal milling,

At 1/1 you still can get the 6,000rpm but the VFD is then driving the motor at 120hz I have never run the stock motor at 6,000rpm for more than 30min so I don't know how long they would take the 6,000 rpm for.

What was the reason for 6,000 rpm spindle speed being ill suited for decent metal removal? Was it a case of spindle bearings not liking the loads at those speeds or simply a lack of torque to hold rpm?

[mactec54]

What was the reason for 6,000 rpm spindle speed being ill suited for decent metal removal? Was it a case of spindle bearings not liking the loads at those speeds or simply a lack of torque to hold rpm?

None of the above, if you want 6,000 RPM then this was a way I used to build them, Most CNC mill of this size and bigger have a minimum of 6,000 RPM as standard, these machines only had 4500 RPM max as standard

[jake2465]

None of the above, if you want 6,000 RPM then this was a way I used to build them, Most CNC mill of this size and bigger have a minimum of 6,000 RPM as standard, these machines only had 4500 RPM max as standard

The part I was referencing was "The 2/1 is no good for heavy cutting, you have to change it back to 1/1 for normal milling,". I could only assume that 2/1 meant that the spindle was set for a max speed of 6,000r/min. it was mentioned that heavy cutting was not suitable at that ratio and therefore would need to be changed to 1/1 for "normal milling". Was the mill not able in increase it's metal removal rate with the added frequency and amperage of the VFD coupled to the OEM motor?

Personally, I own a Boss 8 and have been running mine at 3,000r/min for just about all of my milling. I found that it tended to give its best removal rate at around that rpm for my carbide 3/8" end mills. trying to take it to 4,000 would take too much torque away from the spindle and cause the motor to bog more one I tried to do some hogging. Also, the spindle motor is rated for 2hp, but reading the data plate on the motor reveled that it would only produce 1.6hp without being overdriven. So, I would imagine by the time the power got over to the end mill, that machine of mine is really only generating about 1.3 or 1.4hp at the work piece.

I am planning to attempt this modification, but for me the point would be to machine at 6,000r/min and cut down cycle times.

[mactec54]

The part I was referencing was "The 2/1 is no good for heavy cutting, you have to change it back to 1/1 for normal milling,". I could only assume that 2/1 meant that the spindle was set for a max speed of 6,000r/min. it was mentioned that heavy cutting was not suitable at that ratio and therefore would need to be changed to 1/1 for "normal milling". Was the mill not able in increase it's metal removal rate with the added frequency and amperage of the VFD coupled to the OEM motor?

Personally, I own a Boss 8 and have been running mine at 3,000r/min for just about all of my milling. I found that it tended to give its best removal rate at around that rpm for my carbide 3/8" end mills. trying to take it to 4,000 would take too much torque away from the spindle and cause the motor to bog more one I tried to do some hogging. Also, the spindle motor is rated for 2hp, but reading the data plate on the motor reveled that it would only produce 1.6hp without being overdriven. So, I would imagine by the time the power got over to the end mill, that machine of mine is really only generating about 1.3 or 1.4hp at the work piece.

I am planning to attempt this modification, but for me the point would be to machine at 6,000r/min and cut down cycle times.

6,000 RPM won't help you to cut down your cycle times, not on this machine anyway

Someone has changed your motor the Boss 8 Mills had a 3Hp with the option of a 5Hp so don't know where you got a 2hp motor from, none of the Boss machines even before yours all had 3Hp, you don't loose any Hp when you use your vari-speed drive, the motor is running at it rated RPM Torque and HP all remain the same, just the Vari-speed changes the speeds, when using a VFD then your motor performance will change

Yes any where from 2250 to 3600 is fine for milling steel, if you have very small cutters then you need the RPM as high as you can go for that cutter size

The 1:2 is for when you are using small cutters, then 1:1 or even the opposite 2:1 for when you want to use large cutters up to 3/4" a double set is the ideal so you can use the same belt, so a 2 pulley set is best having a 1:2 and a 2:1 available to you would be the ideal, I did them like this as well, and so have some others here on the zone, the one I still have has been 1:1 for a number of years, I recently have taken it apart and will do some major changes to this machine, one of the main changes is with mounting the head on linear rails and have a 14" travel Z axes, so everything will be changed this time round

There is a photo of one on the zone here with the double pulley setup I will try and find it

[jake2465]

6,000 RPM won't help you to cut down your cycle times, not on this machine anyway

Someone has changed your motor the Boss 8 Mills had a 3Hp with the option of a 5Hp so don't know where you got a 2hp motor from, none of the Boss machines even before yours all had 3Hp, you don't loose any Hp when you use your vari-speed drive, the motor is running at it rated RPM Torque and HP all remain the same, just the Vari-speed changes the speeds, when using a VFD then your motor performance will change

Yes any where from 2250 to 3600 is fine for milling steel, if you have very small cutters then you need the RPM as high as you can go for that cutter size

The 1:2 is for when you are using small cutters, then 1:1 or even the opposite 2:1 for when you want to use large cutters up to 3/4" a double set is the ideal so you can use the same belt, so a 2 pulley set is best having a 1:2 and a 2:1 available to you would be the ideal, I did them like this as well, and so have some others here on the zone, the one I still have has been 1:1 for a number of years, I recently have taken it apart and will do some major changes to this machine, one of the main changes is with mounting the head on linear rails and have a 14" travel Z axes, so everything will be changed this time round

There is a photo of one on the zone here with the double pulley setup I will try and find it

"6,000 RPM won't help you to cut down your cycle times, not on this machine anyway" , Would this be because it is a quill machine and possibly lacks the ability to hold up to the radial loads of higher metal removal rates? As a simple example: .002 chip load at 24ipm taken to the same chip load at 48 ipm with double the rpm. I can only imagine that even though the chip loads are the same, the metal removal rate would have been doubled which would may put higher radial loads on the quill. Is that a reasonable guess? Perhaps I am thinking too simple here, but my assumption is that if one increases rpm and likewise increases available power, then the result should be a faster removal rate (provided that the machinery can handle it).

That's very interesting about the 2hp motor. More specifically, mine is a R2E3 according to what is found imprinted on the machine. Is that not the same as a Boss 8?

[Jim Dawson]

I have mine set up at 1.5:1 overdrive. But, I have a sensorless vector VFD (GS3) and a 3 hp motor. Also my motor is rated at 6000 RPM max (no I don't run the spindle that fast) The sensorless vector VFD allows 100% torque at 0 RPM, but realistically about 60 RPM on the low end in direct drive is more reasonable. Including low gear, I have a speed range from 0 to 5000 RPM. I think you would be happier with a VFD rather that little RPC you have.

This is the first time I have seen your mill in a wide view, looking good. Nice lighting !

[jake2465]

I have mine set up at 1.5:1 overdrive. But, I have a sensorless vector VFD (GS3) and a 3 hp motor. Also my motor is rated at 6000 RPM max (no I don't run the spindle that fast) The sensorless vector VFD allows 100% torque at 0 RPM, but realistically about 60 RPM on the low end in direct drive is more reasonable. Including low gear, I have a speed range from 0 to 5000 RPM. I think you would be happier with a VFD rather that little RPC you have.

This is the first time I have seen your mill in a wide view, looking good. Nice lighting !

I think having a VFD even with the same rpm limitation would still be better than having to run an air motor off of an air compressor to get the rpm to change. Perhaps as an in between fix I could install a VFD on the same spindle motor I currently have and leave it like that for a little while until I can get to the rest of it.

Obviously I am not interested in damaging the spindle, but if legitimately it can be operated at a higher rpm without issue, then it would seem like a win to me.

[Jim Dawson]

I think the original max on that machine is around 4200 RPM. Pretty sure you could run it up to 5000 for short runs with no problem, mine gets warm at higher speeds. I had a VFD even with the manual speed adjust because I didn't have 3 phase power. It was kinda nice for those fine adjustments and being able to lower the speed without shifting into low gear, like for power tapping, reaming, and boring.

I didn't know you had an air motor on your spindle speed, I would put a hand crank on that. Most machines have a hand crank. I did put a stepper on the Shizuoka speed changer so I could have it under program control.