Knee Mill with Variable Drive Head

[apakesha]

I have a Chevalier Knee Mill with an Anilam CNC controller. The spindle speed is adjusted by turning a crank. The variable speed is controled with two sets of pulleys just like the speed control on a snowmobile. Well it sounds like it has a rod knock. It doesn't affect the operation of the machine.....just sounds like it has a rod knock and is very annoying. I took it apart and replaced the brass keys on the front and back spindle, bought and installed a new variable speed belt and timing belt. Replaced the front spindle hub with the teeth for timing belt. Starting to replace the bearings. I just put it back together and it still knocks. I can't pin point where the noise is coming from. I tried the poormans plastic tubing stethiscope but still can't pinpoint the source. Has anyone encountered this on their knee mill with variable speed drive and if you have how did you rectify it?

 

[shortgrass]

Does it have a "high" and "low" range for quil speed?

 

[Robert]

I have a Chevalier Knee Mill with an Anilam CNC controller. The spindle speed is adjusted by turning a crank. The variable speed is controled with two sets of pulleys just like the speed control on a snowmobile. Well it sounds like it has a rod knock. It doesn't affect the operation of the machine.....just sounds like it has a rod knock and is very annoying. I took it apart and replaced the brass keys on the front and back spindle, bought and installed a new variable speed belt and timing belt. Replaced the front spindle hub with the teeth for timing belt. Starting to replace the bearings. I just put it back together and it still knocks. I can't pin point where the noise is coming from. I tried the poormans plastic tubing stethiscope but still can't pinpoint the source. Has anyone encountered this on their knee mill with variable speed drive and if you have how did you rectify it?

Apakesha,
I took away all the elements of the belt variable spped, installed 2 timing pulleys and belt with a reduction of ½. Powering the motor by mean of a variable frequency changer. With our 50 cycles power supply, the changer delivered from a few cycles up to 144 cycles maximum which allowed the 1500rpm motor to run up to over 4000 rpm.
By the turn of a potentiometer, it was possible to vary spindle speed from very little (50rpm maybe) to up to 2000rpm.
Advantages; adustable deceleraton, immediate reverse with a certain torque control allowing even operations such as tapping..
Mpreover, there are frequency changers who can deliver 3 phase from single phase, some single phase only and other 3 phase entry eand exit.
FWIW
R.G.C

 

[apakesha]

Shortgrass, Yes it does have high and low range for quill speed. It makes noise both in the high range and low range.

 

[apakesha]

Robert , I have a serviceman who told me he has knowlwdge of a mill with the electronic variable motor setup. He said that it originally cost around $3000 new but he has one that is used and he would sell it to me for $1200. I was in the midst of trying to repair the one that I have when I found out about the one he has.

 

[Robert]

Robert , I have a serviceman who told me he has knowlwdge of a mill with the electronic variable motor setup. He said that it originally cost around $3000 new but he has one that is used and he would sell it to me for $1200. I was in the midst of trying to repair the one that I have when I found out about the one he has.

Apakesha,
I know, it is an expensive solution, but, if you have to undertake repairs on this variable speed system, i twill be costly as well, with uncertain results.
The frequency converter will add A LOT of flexibility to your machine. The timing belt drive will require minimum belt tension as compared to a vee belt drive, a good thing for the spindle bearings a,d the flexibility of the drive a dream.
As you probably have a lathe to make the necessary adapter hubs; ½ ratio pulleys can be taken from automotive engine distribution timing….
Milling and lathe were so equipped, and threading inperials with a metric leadescrew with the progressive reverse change was also a dream….
RG.C

 

[drumcorpschamp]

Apakesha,

Questions for you......The knocking that you hear coming from the head, does it:
1.) increase and decrease in frequency with spindle speed changes?
2.) does it change in frequency in High or Low range?
3.) never change in frequency regardless of speed or range changes?
4.) sound the same in forward or reverse?
5.) sound the same regardless of spindle load? i.e; milling, drilling or tapping

Check these if you have not already. The answers may narrow the search for the solution. Good luck.

Jerry

 

[apakesha]

Questions for you......The knocking that you hear coming from the head, does it:
1.) increase and decrease in frequency with spindle speed changes?
1.It seems to sound less when speeding up

2.) does it change in frequency in High or Low range?
2. No

3.) never change in frequency regardless of speed or range changes?
3. Less when speeding up, but still there

4.) sound the same in forward or reverse?
4. Yes

5.) sound the same regardless of spindle load? i.e; milling, drilling or tapping
5. Yes

Consensus out there suggests that it might be worn brass keys on the vari shafts. I made one key to original specs, the other key was OK. Another cause might might be worn plastic bushings on the vari shafts. My machine has no plastic bushings.

 

[butchlambert]

I'm with Robert on this.

 

[apakesha]

I think I have the sound pin pointed at the motor shaft. I took a rubber hose (stethiscope) which dampens the sound rather than a plastic hose which amplifies the sound and it sounds like it is louder on the motor shaft. I am going to replace the bearings on the motor shaft and see if that solves the problem. If it does then "yipee". If it doesn't then I think I'll spring for the EVS motor drive.

 

[apakesha]

I found the problem. On the vari drive pulley there "are" two bushings on the pulley center. I don't know at this point if they are glued in place but they are there and they are worn. You can rock the pulleys on the motor shaft. My parts breakdown does not show these bushings. They are available from bridgeport but I don't know if they will fit. It depends on how closely the "chinese copied the bridgeport". If they are not available I will machine some delrin and make my own bushings.

 

[drumcorpschamp]

I was typing this as you posted your latest........"Check the bushings in the bore of the (sheaves) cone plates. When these wear out or go away completely, the result is a knock.".....Glad you found the cause!

These parts may be available from Chevalier. The company does still exist. www.chevalierusa.com Making them yourself is an option. They should be split lenghtwise and have a shoulder.

Good luck!
Jerry

 

[apakesha]

Well I have half of the problem fixed. On the motor side I fabricated my own bushing out of bronze and fabricated a new key out of steel. It is now quieter. I've got a replacement bushing on order from Chevalier for the spindle side of the vari drive. I'm getting real good at taking this thing apart.

 

[apakesha]

Finally got it fixed. I've taken this thing apart 5 times. I replaced the variable speed belt, the timing belt. I've fabricated bronze bushings for the vari drive and fabricated keys for them as well. When put back together it still made a noise like a rod knock. I finally replaced 7 roller bearings and that did the trick. I've become an expert at taking it apart and putting it back together. I'm glad it's over. Amen!
To test it under power I made some recoil lugs. Came out sweet!