what cause's coining aka dwell marks?

[lobust]

I had a chance to disassemble the drawbar on the fadal today, thanks to a 20 min cycle time on the other machine.
tearing it down only took about 45 mins.
all the beville washers were in tack not one broken, they actually looked pretty new as well. There were 44 pcs in there (what is required for my set-up). The drawbar itself looked in really good shape as well.
One thing I forgot to do (because I assumed there was broken washers) was make sure they were positioned correctly when I was taking them out.
I didnt look in the spindle yet to see if the sleeve was damaged. so I am kinda curious why the very low pressure on the drawbar. as everything looks really good.
My other fadal had most of the washers broke so that was a easy one to find the problem.
I wonder if the washers could have just worn out? no gunk build up in there either.

Also with the cover off I could see the other part of the counter balance chain. something doesnt look right links are crooked so to speak. will dig into that more once I get the drawbar back together.
I'm going to have to buy me a force gage one of these days soon, even though I would rarely use it $200 bucks for someone to come out and check drawbar force will pay for one after 2-3 times.

Shims/spacers (to preload the stack) missing? I am not familiar with Fadal, but ISTR Bobw or one of the other Fadalites on PM mentioning such.

Wrong number of washers?

Broken balls in the gripper?

Edit: sorry, missed the part about it being the correct quantity of washers.

Again, not fadal, but I have never had a washer break that I am aware of, but I have changed out a stack that plain lost their tension.

 

[Delw]

I saw that thread with the .007 shim a while ago.

Ive changed a bunch of drawbars over the years for different machines. some cat 50 machines as well. in almost every one there was a noticeable problem. Id say 75% were gunk/crude/rust build up. the rest and mostly on fadals were broken washers.. My old supermax mill had broken washers. that was the only non fadal I had seen with broken washers.

I'm going to check to see if this drawbar is a little longer compared to the new drawbar(stretched maybe?)
and also like you said could just be worn out washers.
one thing I did notice is that the top half of the washers had NO lube on them and were dry. bottom half down had the drawbar washer lube(looks like a copper grease)

 

[Mud]

I will also add that the quality of tool holders as well as pull studs can make a big difference in drawbar force. If the taper is slightly undersize the pull force goes down, same for over length pull studs.

When testing drawbar force it is a good idea to install the brand pullstud you run into the tester. Once I played around trying different pullstuds (cheap vs quality) in the same machine and it caused the readings to change.

The length of the stud makes a big difference, and not the direction I expected. Pulling the washers closer to flat reduces the pressure, letting them go more concave increases it (until they run out of travel).

 

[Delw]

I did find the problem, the washers are cracked. about 8 so far about 6 more starting to crack around the edges.
I noticed a washer laying on the bench it it looked not normal had a wavy look to it. so grabbed it and felt a burr cleaned them all off and you could see cracks some cracked all the way through some just starting on the O.D.
When there cleaned off you can see shiny spots ie rub marks and if you look at those under magnify glass there cracked.

hopefully I can have it up and running tonight. but forsure tomorrow.

The length of the stud makes a big difference, and not the direction I expected. Pulling the washers closer to flat reduces the pressure, letting them go more concave increases it (until they run out of travel).

definately awar of that.

 

[Mhajicek]

That'll do it!

 

[Delw]

What still blows my mind is my true postition was off a ton. with 2 different drills and 8 holes
I am thinking that one drill holder must have pulled to one side, but not having a bell mouthed hole doesnt make sense.

 

[Delw]

got it all up and running today finally. for a little over a week I was barely able to walk due to some intense knee pain. anyway I was bent over in the machine putting covers back on and felt a rubber band like thing move in my leg, figured I wouldnt be able to get out of machine. Nope I must have snapped something back into place cause the pain all but went away.

Anyhow it ran great today no dwell marks like that in the past pics. which is good cause I need that machine up and running.
will see how it works from here on out.

the whole job should have taken more than 3 hours from start to finish normally 2 but this machine has some wierd covers and there heavy as heck(its not a normal fadal),

 

[Herding Cats]

The length of the stud makes a big difference, and not the direction I expected. Pulling the washers closer to flat reduces the pressure, letting them go more concave increases it (until they run out of travel).

I believe a chart will look like an upside down bathtub curve. If that is actually the case what stroke you are at will determine if pressure increases or decreases with stroke.