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Vari speed to VFD

The crayon eating is a new thing, and typically from the lesser branch that brought us bowe berghdal and bradley manning... am I right? :) When I was in, never heard of the crayon eating, but it seems the big thing right now.

TBH, i never ate crayons, but we did use to sniff dry erase markers while Gunny was chewing us out. :D

:D

Jon
 
So we have installed more of the kits on the 4HP head and then did one on a rigid ram BP (an old Boss retrofit). The installation was easy and I like the other All Machine stuff (we install ALOT of the Maxi-Torque Rite power drawbars) however we dont operate them except to ensure that they function before we send them out. So TBH, I can't give any insite into them except for how easy they are to install and how we don't have any complaints from the ones we install.

I have never installed or seen one of the Servo ones. I think their basic version has a better price point than the All Machine one, but again, I cant talk about how well they operate or install.

Re-reading that, I totally sound like a politician lol

Jon
H&W Machine Repair

Here's my Servo VFD Plus. After you rip the guts out of the mill, it's really a piece of cake to install the new unit. It's 2 v-belts and smooth as can be. Bought in 2014 for $2422.62. Never the first problem.
Servo VFD Plus by Ray Behner | Photobucket
 
It's not really so much that, as much as they just don't have enough time in the day to explain why the workers keep licking the markers and eating the crayons.

#ShotsFired

:D :D :D :D

When i started pre school i was in a class with mathew, Mathew decided to conduct a crayon eating experiment, for reasons i don't know he started with purple which made purple sick, next day we have a supply teacher, orange and the corresponding colour sick really freaked the teacher out. By then end of the next week they finally banned him from crayons, after we had conducted the exact same experiment 3 times with red crayons turns out red crayons also make orange sick?? We never got as far as solving the why on that bit.
 
One thing I didn't see in all the discussion about persistent VFD head vibration: The diameter of the motor shaft is an important item to check while replacing the plastic bushings. Over time the shaft can get worn or "necked" in the most common running position. So you should check it for consistency across its length. If it's out of spec it can cause vibes. Solution is to replace the motor shaft assy or to have it built up with weld and re-machined back to factory spec. H&W has a good video on how to do this.
 
That was not my issue, my issue seamed to revolve around the belt being some what uneven, but honestly, its like trying to polish a turd, it may end up shiny but not for long and it still stinks. This being the 21st century i think its easier to just simplify it to a VFD.

Playing with some new + calibrated electrical power metering - supply monitoring a friend left for the week end, turns out the bridgeport is only pulling about half the power at idle too. Before it use to consume about 550 watts with nothing other than turning the spindle at circa 1-2Krpm, now its down to about 210 watts. Not vast i give you either way, but its sure is noticeable that the new motor never yet seams to feel more than warm and even after extended running the alu upper parts of the head don't get warm either, before it use to get hot to the point it was getting towards uncomfortable to touch. So i think its fair for me to say the vari drive system was probably sucking up just shy of the half horsepower mark in losses.
 
Ok decided to fit one of the cheap led RPM readouts off ebay to know the exact spindle speed, simply mounting it in a small enclosure were the original speed adjust dial was.

Too many hours later and chasing my tail, if your using a hall effect NJK-5002C sensor then magnet pole orientation matters, one side - pole of the magnet it sees, one it does not! Guess you learn something every day!
 
Playing with some new + calibrated electrical power metering - supply monitoring a friend left for the week end, turns out the bridgeport is only pulling about half the power at idle too. Before it use to consume about 550 watts with nothing other than turning the spindle at circa 1-2Krpm, now its down to about 210 watts. Not vast i give you either way, but its sure is noticeable that the new motor never yet seams to feel more than warm and even after extended running the alu upper parts of the head don't get warm either, before it use to get hot to the point it was getting towards uncomfortable to touch. So i think its fair for me to say the vari drive system was probably sucking up just shy of the half horsepower mark in losses.

That fits.

MG-era 10EE "waste" nearly half of what leaves the wall.

Easiest to maintain of all the 10EE tribe, but there's a price paid in a hotter shop, even were electricity to be "free".

VFD or DC drive, by contrast "waste" only about 5 Watts at idle, mebbe 55 Watts at full-gallop that doesn't make it into the motor.

Then, too their best-performing DC motor itself (large-frame, and 3 HP, nominal) is still only about 73% efficient itself. The price a "Type T" winding pays for a wide, smooth power-band vs AC 3-P motors in the 90% -plus efficiency conversion class.

World is full of that sort of "side effects".
 
Ok a update, after extensive and varied use, i have kinda decided i have geared it too low, i have yet to need back gear for the extra torque even when power tapping M12 into hardox 450, simply dropping the speed with the VFD. Hence with a load of upcoming small end mill cnc work for her i have decided to bump the ratio from motor to spindle upto 1:1 try that for a few months and if still seams like torque a plenty for my typical work flow probably then gear it higher still. That will bump my spindle top speed to 4500RPM and with a lot of what its looking like im going to be running i can use that and more, really becoming a question of what im confident in running the head upto. gut instinct says anything under 6Krpm should be no concern from the bearing perspective?

Even with the spindle running nearly non stop for hours nothing gets warm any more. Motor and head stay cool now unlike the vari speed. The reduced noise is a god send, my location noise is a issue, so long as im not milling too hard its now barely audible at the edges of my property, hence im definitely no longer disturnbing anyone working the odd hours some of the stuff i do calls for. I really should ditch the shaft mounted fan and fit a small separate dc fan as it really gets loud as you go much over 2x base speed. Motor heating whilst it possibly increases a bit with speed its currently so far and so well under control a bit less cooling will cause me no concerns. My general experience with motors if they simply run warm to the touch they tend to last longer as the heat simply keeps the insulation drier.

Also despite having the L series pulleys and still using them for the revised gearing change, (have a bunch of sizes to hand to swap around) i think once i settle on a ratio im going to ditch them and go to a SPAX belt and sheaves, think it will just be quieter and i don't think the toothed drive gains me much. Raw edge wedge belts run a lot quieter and smoother in my experience, just at the risk of some slippage.
 
Right the results, its now geared 1:1 using a 1" wide L series belt and circa 34 tooth pulleys. Actually got to make some progress on the lathe at last again!

Previous ratio it would tap M12x1.75 in hardox 450 with out back gear, but running at 2K + RPM made more noise than i liked, even drilling 16mm in steel was no issue and the back gear - aka high low was unquestionably going to waste ergo under geared at circa 0.7:1 ish

Now it still power taps M8 with out issue in std cold rolled mild steel. M10 though its kinda struggles, gotta be above 300RPM to get enough tourque, im certain it would stall on M12 in high - be too fast to be comfortable now! Hence its now forcing me to make use of the low ratio for larger taps than that which feels about right. Not had to drill any big holes yet above 10mm though, but i have had to mill a load of small 1/8" cutter brass bits and the extra top end and the noise reduction of the less motor speed to get there is best summed up as pleasant.

Hence anyone out there with a Bridgeport wanting to go a new motor + VFD route, my recommendation is a true 1.5Kw continuous, 2.2Kw 1 minute setup geared 1:1 being about right. Then using the high low to get its 1:1 reduction for the higher torque jobs. On my Bridgeport i kinda run out of rigidity pushing that hard in steel, hence a more powerful motor really would not help me achieve work done any faster.

The Chinese RPM readout has been faultless too. Kinda hoping this will help someone in the future get to were i now am a lot faster. Really glad i got rid of the single phase motor and getting rid of the vari speed sheaves is even better! Add in instant reverse for tapping and i should have done this years ago!
 
Adama, I'm hoping you're still around !

My BP clone with variable speed is getting very noisy.
I have some experience with VFD's so this thread is excellent - thanks !

Tell me the min and max frequency you run your motor at please ?

Follow up question - do you have any idea what the frequency range might be for the typical Taiwan BP clone motor ?

Thanks
Bob
 
Oh shoot !
Never knew the guy, but he's inspired me to more than fix my machine, but really improve it.
A nice legacy perhaps, because I'm sure he's helped many others as well.
 
I've just done a little analysis seeing how much variation there would need to be for the upper and lower speed ranges to "touch" using a 8:1 backgear ratio.

1800 rpm motor
1:1 drive belt ratio motor to spindle.
120 Hz in backgear would be 450 rpm (1800x2/8)
15 Hz in high gear would be 450 rpm (1800/4)

This means to me that I'd need to run the motor up to almost 200 Hz and down to almost 15 Hz to get full coverage of speed range.

Does anybody know if this is realistic with a typical 3 hp Taiwanese motor ?

Thanks in advance.
Bob
 
Most of the people contributing to the original discussion have passed on, Jon from H&W just recently. Good guys all.

I re-motored a Bridgeport BOSS mill, series 1 size, with a 3HP motor and VFD about ten years ago. I chose a 3HP motor because I wanted to increase max spindle speed to 5000 RPM, so the 1728 RPM motor is belted to the spindle with a 1:1.5 ratio. At 60 Hz the spindle runs 2592 RPM, and has the same torque that the original had at 1728. I over-speed the motor to 116 Hz. to get my top speed, which runs at 625 in back gear. I set the minimum frequency to get some overlap with the low range (I forget what I set it at). The machine does mostly small cutter work in graphite, but I occasionally pocket mold plates with a 3/4" end mill, and have not found it lacking.

Dennis
 
Thanks Dennis.
I did a little analysis of the speeds I think I need.
I have a 3" insert face mill I use for steel: 600-700 rpm seems to be a good speed.
Drilling large (1") holes in steel with HSS bit: 300 rpm.
These seem to be my highest hp needs, more so the face mill.

This suggests I should "gear" the belts to give me 700 rpm at 60 hz in hi gear as I need the power for the facemill. Seems very slow though.

I did a little test running a 1" drill at 30 hz with existing 3 hp motor. Very easy to bog it down. I was not impressed.
So "gearing" as above would be ideal for facemill, but not good at all for drilling large holes at 300 rpm.

I have read that inverter duty motors provide constant torque as you lower the frequency, but its not obvious to me its the case with my motor. From what I understand, Inverter duty motors are basically the same design with improved winding insulation and cooling. So would they give me a benefit over my existing motor ?

Bob
 
Thanks Dennis.
I did a little analysis of the speeds I think I need.
I have a 3" insert face mill I use for steel: 600-700 rpm seems to be a good speed.
Drilling large (1") holes in steel with HSS bit: 300 rpm.
These seem to be my highest hp needs, more so the face mill.

This suggests I should "gear" the belts to give me 700 rpm at 60 hz in hi gear as I need the power for the facemill. Seems very slow though.

I did a little test running a 1" drill at 30 hz with existing 3 hp motor. Very easy to bog it down. I was not impressed.
So "gearing" as above would be ideal for facemill, but not good at all for drilling large holes at 300 rpm.

I have read that inverter duty motors provide constant torque as you lower the frequency, but its not obvious to me its the case with my motor. From what I understand, Inverter duty motors are basically the same design with improved winding insulation and cooling. So would they give me a benefit over my existing motor ?

Bob


Hi Bob,
I would think you'd want the high HP needs to be speeds capable when in back gear, where you have the advantage of the the 8 : 1 gearing to multiply motor torque. You'll note that my modification of the BOSS mill almost attains this. One thing to realize is that mechanical speed reducers are also torque multipliers. Reduce the nominal 1800 RPM at the motor shaft to 600 RPM spindle speed, and you've tripled the torque available. VFDs don't work this way, which is the reason that modern CNC machining centers that use a VFD to set the spindle speed tend to have ten and fifteen horsepower motors to drive essentially the same tools as a 2HP Bridgeport.

Dennis
 








 
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