Ejector question - electric machines

[dav612]

First off, let me state that I am new at this and am building knowledge as I go. So just bear that in mind.

I have recently purchased a nissei 120ton electric machine to make some parts. I am in the mold design process and have a question about the electric ejector rods/bars.

How do they hook up to the ejector plate? Two of the bars are flat an the one in the middle has a tapped hole in it. Am I supposed to bolt the middle ejector bar to the injector plate for ejector return? Do I still need ejector return pins that go through the B plates and contact the A plates. What about springs?

The problem I am having trouble grasping is how do set the retract distance for the ejector plate. If it is set to little the ejector pins will not retract all the way causing obvious problems. If I set the return on the ejector bar to a number that would want to cause the pins to bottom out and try to over travel it slightly, will the machine hold the ejector pins back? If this is the case the only reason for ejector return pins would be a safety precaution to keep the pins from being damaged.

The minimum set distance for the ejector system is in increments of .01mm; one setting will not return the pins enough and the next will try to over travel the ejector system. Will it cause problems if I try to over travel the ejector system on the return side by .05mm or such?

Thanks in advanced for any help,

David

[Jim Estes]

The tapped hole is so that you have the option of connecting the ejector bar to the ejector backup plate.

Most of the molding companies I deal with don't use the "positive pull" on the ejectors. Most of them will always have return pins in the b-plate. These pins will be ground to the proper length to push the ejector plate all the way back. Most of the molds I have built, I have installed die springs to push the ejector plate back and hold it back, this allows for "tip stroking" of the ejectors in case a part sticks to the end of the ejector pins. With the springs in each mold, and return pins, it makes mold changes much simpler (not having to connect the ejectors).

Of course, there is one advantage to having the "positive pull" on the ejectors, if for some reason the plate doesn't come back, the machine will not cycle, and the mold will not be damaged.
The fews cases I have seen the positive pull used, involved pins that were located under a cam. In this case, if the pins are not back completely before the mold closes, the cam will be damaged. The same is true for hydraulically operated core pulls.

Jim

[Jim Estes]

As for how to connect the ejector bars, they do make a quick connect type of coupling to connect thes plates, I dont' have any information about who makes them or where to buy them, sorry.

You also should check your machine to be sure that is has power forward and power back. Some machines will have power to push the plate forward, but will not have power to pull the plate back, in this case you will need to have springs in the molds regardless of whether you connect the plate or not.

I hope this helps.

Jim

[dav612]

Jim, thanks for the reply. I have decided to go with a quick coupler and use the positive pull method. It seems to make the most sense. My machine will pull back and also won't clamp unless it is back at the set point. That should be the protection I need. I do thank you for your help.

David

[robinhood2b]

we usually couple the ejection as we have found that components fall free better with this system.
as previously stated if the tool has side action cams above ejector pins then to prevent damage you have to returns the pins before the side action cams come in.
as a added safety feature with a tool like this we also fit a micro switch below the ejector plate such that if the link bolt breaks the tool wont shut and damage the tool.
My prefered method is to fit a DMS thin switch which is simple fit and forget item and is most reliable.