VF2 Drawbar

[rrbmachining]

I am unable to insert any tooling into the spindle, when pressing the tool release button you get a noise from the spindle like an air blast, but it wont take up the tool holder. I know I have the right holders and pull studs. Looking into the spindle there is no movement of the pull fingers when pressing the tool release.
This is my first Haas and as yet I have never been able to put a tool in the spindle, maybe I am doing something wrong here !
Any helpwould be appreciated

Richard
RRb Machining Services

[HuFlungDung]

Was the machine working at the time of purchase, assuming it is a used machine?

The tool release piston assembly is at the top of the spindle. It should move down and contact the drawbar when you press the tool release button. Since it is air operated, it is possible that something is gummed up. Sorry, I've never delved any deeper into the workings since mine has always worked

[Geof]

When the tool release button is pushed you should see the gripper inside the spindle move; this is the thing with the balls in it that lock onto the pull stud.

On one of our VF2s a while back the gripper stopped working and the reason was a circlip (or some type of retaining ring) had broken at the top end.

You need to start taking covers of to find out what moves and what doesn't but should when the tool change button is operated.

[rrbmachining]

it was working at the time of purchase, as yet i have not taken any of the covers off to see what is happening. At the moment I have no idea of how the drawbar mechanism works and am looking for guidance on the operation. I cant afford to get a Haas technician in for what might be a simple thing to fix

[HuFlungDung]

What kind of air pressure are you maintaining? What size air line and how long is the run from the compressor to the mill? If it is starved for air, or if the continuous air pressure in the feed line is below 90 psi, it may not work right.

[rrbmachining]

The air line is 3/8 bore, 150psi line and the compressor is right behind the Haas. The main regulator at the back of the machine is set at about 85psi I think. The compressor has a 200 litre tank so there should be plenty of air capacity

[Geof]

Originally Posted by rrbmachining ... At the moment I have no idea of how the drawbar mechanism works and am looking for guidance on the operation....

The drawbar is inside the spindle(obviously ). At the bottom end is the gripper which holds the pull stud; this gripper has steel balls in it and there is a taper where it moves up and down so when it is pulled up the balls are forced in to grip the know on the pullstud and pull the tool in.

The drawbar is pulled up by a bunch of belleville washer springs inside the hole through the spindle and extends out the top end of the spindle. Belleville washers sometimes break but this weakens the pull but having so many belleville washers break that the drawbar does not get pulled up seems very unlikely.

At the top of the drawbar a bit above the spindle is the retaining washer/circlip which broke on our machine. This retainer is what takes the upward force from the springs and applies it to the drawbar.

Above everything is the tool release cylinder. During a toolchange the piston on this cylinder move down and hits the end of the drawbar pushing it down to release the gripper balls as the move down their taper and let the toolholder come free. If the cylinder is not moving then obviously nothing gets pushed down.

Normally it is possible to hear a sharp clack when the cylinder operates and if nothing can be heard except air escaping when the button is pushed it is possible the cylinder is not moving. This could be due to a leak in the air line.

If the machine has been unused for a while it is possible the piston is just stuck; try cranking the regulator pressure up to 100 or 120 psi and see if that creates movement.

If you take all the spindle cover off you can see the top of the drawbar and piston moving when they work correctly.

[charly2]

It sounds like the solenoid valve is not doing a good seal when is activated (by the button or program).
I had the same problem 6 months ago, my vf2 is 2005, and I was terrified just to think abut the drawbar, I had to check all the system and, I found a problem on the solenoid valve.
This valve has 2 filter elements (stainless steel wire net) one on each end (in-out), when you push the button the solenoid seals a relief end and let the air go to the piston, then when you release the button the valve open the seal and in a fraction of a second the cylinder sneezes all the air, this caused the filter element in the out side blow out inside the valve and get stucked, not allowing to seal when was necessary.
You need to remove the cover, the solenoid is in the font side and is conected directly by a hose to the cylinder, just remove it and check the ends tho be sure the filters are still there, if not, open up the valve and remove the rests.

Good luck

Charly

[rrbmachining]

Thanks Geof for the info, I will try increasing the pressure to see if it free's things up, If not its time to get the covers off to see what is moving.

I appreciate all the assistance I have had

[rlabonte18]

What year is your machine? is it an ss model? depending on your model and year there are a few different types of tool release pistons. It is most likely a blown air line or a bad pushlock connector most common on a belt driven machine. An inline spindle will have two pins that connect the drawbar to the release piston which are not uncommon to break. These pins should be checked regularly for cracks.

[1ctoolfool]

I agree it is most likely the release cylinder or plumbing to the release cylinder, which is easy to troubleshoot. The drawbar mechanisms are tough with very few moving parts and unless abused they tend to last beyond the spindle. usually they fail in the area of the grippers when a failed tool change, crash, or wrong pull stud.

[rrbmachining]

I have had the cover off today and checked all the air lines and connections, all seem to be good. When pressing tool release the drawbar cylinder is moving slightly, but not even enough to break the limit switch which detects tool clamped.
I wound up the air pressure of the main regulator to about 100 psi to see if the extra pressure would help release a sticky valve but made no difference.