Question about the small VSD's

[Sterob]

I've just bought a new bench drill press, and seeing as it has 16 speeds and looks like a pain to change speeds, I am contemplating fitting a 3 phase motor and a small VSD.
For those chaps who have fitted a VSD to a machine, are you able to adjust the speed via a pot ( either on the VSD or wire one in remotely ) or can you only ramp the speed up and down using the 'raise' and 'lower' buttons on the VSD?

Also, I assume I would need a separate tacho circuit on the output shaft to indicate the speed as I will still have *some* speed change via one belt, or can you compensate for that in the VSD parameters?

Steve

[Stustoys]

Hi Steve,
A VSD might not give you the speed range you are looking for, but it would certainly reduce the belt changes.
What min/max do you have in mind?
You can put the speed pot anywhere you like.
I havent made myself a taco yet(though the parts are on the way), I just do the math in my head. I'm not looking for the last rpm just a ball park.

Stuart

[Sterob]

Hi Steve,
A VSD might not give you the speed range you are looking for, but it would certainly reduce the belt changes.
What min/max do you have in mind?
You can put the speed pot anywhere you like.
I havent made myself a taco yet(though the parts are on the way), I just do the math in my head. I'm not looking for the last rpm just a ball park.

Stuart


Hi Stu,
I was hoping it would it would the whole range, but I guess I should brace myself to be disappointed...lol
Was thinking a range of around 200 - 2500RPM ish. I will have to experiment. Will probably be happy with a Hi and Lo range.( ie one belt change )
So they *all* have a pot on the front or if not, you can wire one in? ( I've not much experience with VSD's.)

The VSD only displays motor speed? You can't manipulate it at all?

Need to find a local source for a motor. Postage on a motor would be a killer, I reckon.


Steve

[Ueee]

Hi Steve,
With a cheap VSD you get about 4-1 speed range, so you could have 200-800 and 600-2400 through gears. You may want a real slow gear as well, just to kick the torque up for big low speed jobs. I think the DC motor would be better for a Drill press, a VFD and 3 phase motor for larger stuff. You need to add an external speed pot for control, and a tacho is pretty easy to hook up and gives you real time speed.

[Stustoys]

I was hoping it would it would the whole range, but I guess I should brace myself to be disappointed...lol
Was thinking a range of around 200 - 2500RPM ish. I will have to experiment. Will probably be happy with a Hi and Lo range.( ie one belt change )

Hi low might get you there. A 1400rpm motor at 1:1 ratio 25Hz to 100Hz gets you 700 to 2800rpm. Low ratio 3.5:1 200 to 800 rpm. Bear in mind that you will have about 1/2 the motors Hp at 25Hz and likely not that much at 100Hz



So they *all* have a pot on the front or if not, you can wire one in? ( I've not much experience with VSD's.)

They dont all come with a pot on the front but the cheap VSDs have a place for the pot on front. I'd say most can have a pot added, but I'd hate to say *all*.


The VSD only displays motor speed? You can't manipulate it at all?
The cheap ones no. I believe the better Vsds can. But if you have 1:1 ratio that wont matter.(low speed you'd have to do in your head)

Need to find a local source for a motor. Postage on a motor would be a killer, I reckon.
Even the Alum ones arent what I would call light ;)

What sort of Hp are you looking at?

Stuart

[Sterob]

Hi Steve,
I think the DC motor would be better for a Drill press, a VFD and 3 phase motor for larger stuff. .


It that because you get a better speed range from a DC motor?

[Sterob]

What sort of Hp are you looking at?

Stuart

Its only 1 HP.Its one of these Drills.
I could go DC I suppose but I think a VSD would be an easier conversion.
need to do some more research.....

239125

[acmegridley]

Do you mean something like the old Variac transformers,only trouble is you sacrifice torque in the lower speeds with them.so if you are drilling metal the drill will bind a bit, you have to work your way up in drill sizes.

[Ueee]

The DC controllers Rob (nearnexus) and i use advertise 50-1 regulation. With useable torque though its more like 15-1. That would give you your entire speed range with good torque and IR compensation. I would still allow for a lower gearing though, for when you wand to drill big holes, just to push the torque up.
As you say though, the conversion is harder than a VFD, you need to find and fit the motor, which will probably have a strange shaft size, and put a fan on it so you get good cooling at lower revs. Then you need to wire up the controller, although for a drill press it doesn't need to be anything like as flash as the lathe controller with reverse, braking etc

[Sterob]

The DC controllers Rob (nearnexus) and i use advertise 50-1 regulation. With useable torque though its more like 15-1. That would give you your entire speed range with good torque and IR compensation. I would still allow for a lower gearing though, for when you wand to drill big holes, just to push the torque up.
As you say though, the conversion is harder than a VFD, you need to find and fit the motor, which will probably have a strange shaft size, and put a fan on it so you get good cooling at lower revs. Then you need to wire up the controller, although for a drill press it doesn't need to be anything like as flash as the lathe controller with reverse, braking etc


Ok, Thanks Ueee. A treadmill motor looks like the goods and I just need to find a reasonable priced KB controller.

[BobL]

If you drill metal it's often useful to be able to go as low as 120 rpm and as high as 3000 rpm so if you are planning a variable speed system you may wish to widen your range a little.

[Sterob]

If you drill metal it's often useful to be able to go as low as 120 rpm and as high as 3000 rpm so if you are planning a variable speed system you may wish to widen your range a little.


OK, thanks Bob. Will keep that in mind.

[cba_melbourne]

> I've just bought a new bench drill press, and seeing as it has 16 speeds and looks like a pain to change speeds, I am contemplating fitting a 3 phase motor and a small VSD.

Excellent idea Steve, you will never look back. If you replace the existing motor with a same power 3-phase motor, you will still need about 3 belt settings. But you will change belt setting MUCH less often. I leave the belt of my Waldown at the mid setting about 95% of the time. I only change it if I need lots of power and smooth control at very low speeds like for trepanning. Or if I need very high speeds (my old Waldown easily does 6,000rpm at high setting and 100Hz). I highly recommend you toss away the two Vee belts, and replace it by just one "Fenner link belt". This will provide a quiet and smooth running, in addition to the variable speed you gain with the VFD.

> For those chaps who have fitted a VSD to a machine, are you able to adjust the speed via a pot ( either on the VSD or wire one in remotely ) or can you only ramp the speed up and down using the 'raise' and 'lower' buttons on the VSD?

all VFD's, even the cheapest ones, can be fitted with an external speed pot. Only some VFD's have a buit-in speed pot as standard, for some it is available as an option, for some it is not available at all. All modern VFD's designed in the past 15 years have ramp up/down buttons as standard. Some better VFD's have detacheable control panels, so you can install the VFD on the wall but have the controls on the front of the drill spindle. Some other VFD's have remote control panels available as an option.

> Also, I assume I would need a separate tacho circuit on the output shaft to indicate the speed as I will still have *some* speed change via one belt, or can you compensate for that in the VSD parameters?

Almost all VFD's, even the cheapest, can at least display the motor frequency. That is not as good as a spindle rpm display, but you get quickly used at knowing what frequency at which belt setting equals to approximately which spindle rpm. Look at it this way, 50Hz lets your spindle turn as quick as it did with the stock motor. 100Hz is twice the rpm. 25Hz is half the rpm. 12Hs is 1/4. And yes, even with the cheapest v/hz technology VSD, you can use speeds down to under 10Hz for low power things like countersinking a hole.

More modern VFD's let you enter a correction factor to display rpm instead of Hz. The factor needs to reflect the "gear ratio" between motor and drill spindle. It is of course only valid for one belt setting - unless you were to enter a different correction factor after each belt change which is impractical.

Separate RPM panel meters can be bought, either using a hall sensor to sense a small magnet attached to the spindle, or a capacitive proximity sensor to pick up a small metal object like a screw attached to the Aluminium spindle pulley, or a reflective optical sensor to detect a refective/IR absorbing mark on the pulley. It can be done, but it seems to be quite a luxury for only a drill press. Maybe the money would be better spent in a double foot-switch to control FWD/STOP/Reverse with the foot whilst holding the quill with the right and the vise with the left hand..... How often did you have both hands busy and were looking for the main switch?

Chris

[Sterob]

Thanks Chris. Some good points there.