What spindle moulder RPMs are most needed?

[heimlaga]

As I am collecting parts to rebuild my Jonsered FM-C the question of RPM arose.

Jonsered FM-C was primarily designed to be line shaft powered. One could get an electric motor with a very solid motor mount as an extra. Mine has that factory made motor mount but it lost the original motor long ago. The current motor is a 4kW 2800RPM VEM made in East Germany. With the home made wooden pulley currently fitted the spindle speed should be somewhere around 8000 RPM though I could not get an exact measurement of the spindle pulley in the darkness of the barn.
I am pondering over if I could make the motor pulley easy to shift so I could get two different speeds with two different pulleys.
Which speeds should that be?

 

[blackrodd]

I would have thought that the first concern would be the rpm recommended by you're tooling cutterblocks and
any relieving saw or wobble saw you intend to use.
This may not help much but see if it is of any use to you.
http://en.wikipedia.org/wiki/Wood_shaper
Different speeds are on this,-----
http://www.axminster.co.uk/jet-jws-34-l ... le-moulder

Or this may help,----
http://www.woodworkersinstitute.com/page.asp?p=1257
Regards Rodders

 

[cerdeira]

Hi.

My rules of thumb re speeds are as follows:

1500rpm -> sanding
3000 rpm -> large tenoning discs (ø 250mm or 300mm)
6000 rpm through 8000rpm -> general profiling blocks
10000rpm -> large diametre router cutters

 

[heimlaga]

Thanks a lot cerdeira! According to your rule of thumb I would have my uses covered with three speeds. 1500 and 3000 and 6000 RPM.
Is your tooling carbon steel or HSS or carbide?
Apparently I have played safe so far. The spindle moulder on my combination machine has 3 speeds. They should be at roundabout 2000 and 3000 and 4000 RPM. I have run the largest diametre heads 2000 and the rest at 3000 RPM to stay on the safe side but after 3 years I think it would be time to find out what is correct! Especially I am looking for pulleys for another machine.

Some of my cutter blocks have their maximum allowed speed inscribed on them but many don't have. Neither of my two wobble saws do. Nor my tennoning heads. Getting information from the manufacturer isn't easy as all tooling is secondhand.

As I have understood it that inscribed maximum speed is a kind of safety limit with the proctical speed being lower? Doeas hand versus power feed affect the correct RPM?

 

[James-1986]

If you can get hold of a two speed motor that will save changing the pulleys. Is the spindle unit designed to run at high speed?

3000 revs is getting towards the top end for most wobble saws. I do a lot of moulding around 4500 revs, don't see the need to run it at high speed if its cutting well. If the machine is three phase then consider getting a drive controller, changing the speed by 500 revs can make a good difference on certain timbers.

 

[blackrodd]

I've seen 2 spindles currently for sale and they were 3,500, 5,500, and 7,500.RPM.
So you aren't too far out with you're conclusion.
Regards Rodders

 

[dzj]

Depends what you plan on doing.
If I had to choose two different speeds it would be 3000/4500.
Most cutters that fit on a 30mm spindle would be covered.
Higher speeds are nice to have, but that also requires well balanced cutters and
a higher quality of machining of the moulder
When altering rpms, you should also look out for resonant frequencies. At some speeds the vibrations become intolerable and all you need to
do to remedy this is to increase or decrease rpms by a 100 or so.

 

[heimlaga]

Thanks a lot!!!!!!

Finding a two speed 4kw 3 phase motor secondhand would not be easy and a new one would cost quite a bit of money I think. The original motor may have been two speed. I don't know if there were any two speed motors on the market in the 1930-ies. All FM-C spindle moulders I have managed to find pictures of have had their motors replaced or have been line shaft driven.

As all my tooling is secindhand and some of it has an obscure past I think I will ailm for a slightly lower top speed. I will look for pulleys that would give about 1500 and 3000 and 4500 RPM and then see if I have hit a reasonant frequency or not.

Now I know what to look for.

 

[cerdeira]

4500rpm will be on the low side for modern cutter blocks with replaceable knives, unless they are around 200mm in diametre. you can use low speeds but you will have to feed the workpieces more slowly if not using a power feed.

look here for a reference:
http://flury-systems.com/katalog_detail ... orien=1998

 

[heimlaga]

I see.
I was just worrying for age and wear related problems but maybe I was worrying too much. I will aim for 1500-3000-5000 then. The exact RPM depends on what sizes of flat belt pulleys I have or can get.

 

[acewoodturner]

Why dont you get a 3 phase motor and use a variable frequency drive to convert it to sigle phase. You will be able to vary the speed by using the controls on it instead of changing the belt and pulley. Much easier, although a little more expensive, with the ability of being able to slow it down in under 10 seconds.

 

[heimlaga]

I am looking for a suitable 1400 rpm 3,7 or 4 kW 3 phase motor. I run everything on three phase electricity. A three phase variable frequency drive costs several thousand euros and I cannot afford that.

 

[dzj]

Just curious, why would you opt for 1400 rpms?
Would that not cause wrap angle problems with the higher speeds?

 

[heimlaga]

A good point dzj. I don't know how many degrees of wrap I would need on the spindle pulley? This is a flat belt drive of cause.

I just thought about the fact that I cannot make the spindle run slower than some 2500 RPM with a 2800RPM motor because that would be the minimum size of motor pulley.

 

[dzj]

I'm sure there is a way to calculate this, taking in consideration various things like torque, distance, speed, friction...
But I can't offer a suitable equation.
From past experience, if a ~1/3 of the pulley circumference is covered by the belt you should be OK.
If it's less then an idler would do the trick.

 

[heimlaga]

Then I have no reason to worry. The motor and the spindle are quite far apart so the belt will wrap almost half the spindle even with a fairly large motor pulley.