ejection question

[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

 

[patprimmer]

If you do not have the exact ejector return distance with the mould closed, the cavity will have depressions that will show as bumps on the moulding. Wether or not this is a problem depends on your requirements.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[dav612]

yes, I understand this. That is why I am asking if I will be able to overdrive the ejector retract parameter past the mechanical stop of the ejector system to ensure that the pins will be at their proper distance.

1) can I do this?

2) is it commonly done?

3) will it cause premature wear on the ejector system?

Thanks again!

 

[Pud]

Retract position is usually set by a "set zero" option on the ejector setting screen. If its an older machine, you need to set a limit switch or timer.

Most tools have "push backs", which you call "ejector return pins" which are large diameter pins attached to the ejector plate to push the ejectors back. These are OK if the parts eject with just one push forwards. If, on a recent machine, in the unlikely event the ejector return becomes disconnected, these are a "fail safe" feature. (Often, very old tools, designed for very old machines used this as the only ejection feature.) Some tools may require multiple ejection strokes, which will require mechanical attachment.

e.g. our Arburg machines have a custom coupling, whereby the ejector ram is advanced in set-up mode, engages with the bit attached to the tool, retract by hand until stopped and then press "zero" button. Done. Zero set. Speeds/pressures then set to suit.

Try contacting Nissei and get a manual for the machine - tell them it's a great machine and you are considering buying a few more and you may get it for free!!


Cheers

Harry

 

[dav612]

Thanks Harry. That is just what I was looking for. The machine is a 2001 ES2000 with from what I can tell has most of the recent features. I do have the manual but the section on ejector set up is limited and certainly doesn't explain what technique to use.

David