Draw Bar force HELP please!

I know there are a lot of gurus here that can help me out. I have a Haas Mini Mill, 4 years old with minimal usage, perhaps 12 to 1500 hours on it. Feeds and speed are always on the conservative side, so it is never abused. On my most recent job, I noticed the tools popping out of the spindle normal tool changes. Upon closer inspection it was one tool: 1/2 inch carbide rougher. Depth of cut was 1/2 an inch roughing out a .375 radius, so it was cutting full diameter for a couple seconds at most. To be scientific about it, I changed the cutter to a brand new one, and changed the tool to another location in the ATC. I should mention that I was using an ER-20 holder. None of the above releived the popping. I then switched to an ER-32, which minimized it but did not make it go away.

That said, I then checked the draw bar force with a newly purchased gage from Clamprite. I was astounded to see that it was only 900 pounds, especially after I was informed as to what other machines run. So my question to you folks is: what is a good number to have on a 40 taper spindle? And will the actuator on my Mini be able to move it?

Thanks,
Dan

Draw Bar force..

You should really check with the manufacturer however......
You can't go too wrong with 2000 pounds for a 40 taper spindle and 4000 pounds
for a 50 taper spindle.
I know this will start a lot of arguments but, thats my story and I'm sticking to it.
Regards Walt...

find a break-down in your manual

I'm unfamilliar with haas,
just never called to attend to one.

Draw-bar force isn't your concern .
draw-bar malfunction IS.

There are different methods that tools are retained .
you need to understand how yours works first.
THEN you can figure out why it's not working.

I don't have time to dig for you .....if you can find a page on the net or scan one (break-down / Blow-up ) .

Then we mave material.
or just wait till a member that knows your machine turns up.

Phil

Walt-
That is what I thought. The folks at Clamprite said the same thing as well. At 900lbs., it is a wonder that the tools stay in under load. Even more surprising is that 900 lbs is the spec from Haas. To address Phil, drawbar clamps the pull stud with 4 eqaullt spaced ball bearings. The draw bar, when actuated, released the pressure on the ball and releases the tool. Upon retraction, the balls are forced inward by the housing being pulled through the spindle sleeve, thus clamping the pull stud. Thanks guys, I will continue to await more guru input.

Dan

You can check the tool knockout. Hold a tool in with the drawbar unclamped and the clamp it. You should see a difference of about .015". But since you say it is only one tool, I wouldn't think that would be it. What is the tool that runs just before the sticky one doing? If it is creating any heat, the that could also be the culprit. Hot spindle, cold tool, things expand and contract and there you go. Stuck tool. Just a couple of more ideas.

Rocky

My 99 VFOE does this with mills that are used hard, especially when corkscrew milling. Oiling the shanks when you start helps but it doesn't last long. I turned up the pressure on the regulator 5-10lbs and it seemed to help and kept the tools from sticking and alarming out. If i have a series of difficult features i'll program a tool change and then change back to the sticking tool which keeps it from getting really stuck. The contact pattern on my holders is real good over the length of contact. I just put a new drawbar in and Haas said it would be 1300lbs, i don't have a gage to measure it though.

Just curious what is a typical draw bar force on a big horzontal 40 taper, like a Makino or Mazak?

Dave

My guess as to why Haas runs lower draw bar force than others is that I don't think they use any kind of floating system for the draw bar cylinder. The force of the cylinder is applied directly to the spindle bearings, which over time can effect preload among other things. I was told that the "shakes" some Haas vmcs get over time is not the guides or screws wearing out, but loss of preload in the spindle bearings due to the above. I have no first hand experience if this is true, but it does make sense.

I had a TM-1 it had 900#. I think the minimill has the same spindle. It used to pop after taking a big mill cut. I think it's just the nature of the beast with these smaller mills. I have a friend with a TM-1 that uses it for stainless alot, and he has the same popping sound when the tool released.

The newer haas have 1800# for the 40 taper. My Okuma 40 taper has 1800# also. The good thing about the okuma is you can adjust the pressure without shims. It also has a collet to grip the pullstud instead of four balls.

Don't get me started on spindles. This POS is on its third and the machine has maybe 1800 hours on it. The machine is great as far as its control and operation, but the service and the spindles are a nightmare. I won't bore you with the details, but I would not buy another. I'm sure we will be re-building the current spindle sooner or later, given the course already run. Now that it is out of warranty, it will be re-built correctly to get rid of the heat shrink bearing retention. I'm going to up the weight of the draw bar and see how it works, knowing that I can always go back. Thanks to all who offered their knowledge and experience.

Dan

D Rey

Makino A55 40 taper will run normally in the range of 2200-2500lbs. Mazaks vary a little, but most will be around 2000lbs.

Rocky

turning up air pressure

As I understand it, the air is only used to RELEASE the tool while a spring holds it in????????

The draw bar uses bellville (sp) washers to hold the tool in the spindle. Air is used to release it.

Tim

Just to follow up and share the experience, we replaced the Belleville discs and improved the draw bar strength to about 1500lbs. Had to jack the air pressure up that feeds the actuator pancake. Without a different system or stronger actuator, any more force would be too much. It is working quite nicely now just how it is, however, and tool changes are smooth... with no popping. The job presently in the machine does not move a great deal of material, so I have not yet had the opportunity to whitness tool changes after a heavy cut/tool load, but I think it should be ok.


Thanks,
Dan