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Can someone take a measurement on a HELLER oven please

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#81543

Can someone take a measurement on a HELLER oven please | 3 December, 2018

I have a Heller 1808 Reflow oven with the chain that has the edge hold to keep the boards off of the mesh belt.

The feed end was more narrow than the exit end, and some boards would fall off. So we adjusted both ends to be the same. Well now, when boards expand under heat, they get pinched at the end.

I'm wondering if there is supposed to be a specific measurement difference from one end to the other.

Could someone measure the width at both ends and tell me if they are exact, or if the exit is wider, and by how much?

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#81544

Can someone take a measurement on a HELLER oven please | 3 December, 2018

Sounds like bent rails. Do you have a laser pen you can shine down both sides of both rails to see if there is any curve?

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dwl

#81545

Can someone take a measurement on a HELLER oven please | 3 December, 2018

Are they getting stuck inside the oven or at the very end?

If thermal expansion is the problem the boards would be getting stuck in the reflow zone since that would be the hottest and therefore the point where thermal expansion would be the greatest. By the time the boards exit the tunnel they should have cooled significantly. In any event, the rate of expansion should be a matter of microns. You should have plenty of gap on the rail spacing to accommodate this.

My money is on the rails still being out of parallel slightly.

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#81547

Can someone take a measurement on a HELLER oven please | 3 December, 2018

We've been doing some testing. It seems that if you move the rail IN to achieve the correct width, the exit is maybe .125" wider than the entrance. If you move it OUT to achieve the width, the exit is .25" more narrow than the entrance.

So I believe we have some play at the exit end riding the lead screw. So the slop is causing the rail to lag behind at the exit.

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#81548

Can someone take a measurement on a HELLER oven please | 3 December, 2018

Ideally size should be the same all across - parallelism. If you see different you should fix it. I would suggest instead of measuring it, to use a huge PCB and move it all the way to prove rails are in parallel.

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#81549

Can someone take a measurement on a HELLER oven please | 3 December, 2018

Not sure how the lead screw drive gear is locked in place but is it possible that it's slipping in both directions (when driving the rail both forward and backward) and then not catching until after the other end has already moved some?

You could have someone adjust width back and forth and watch the lead screw for motion. I guess the ball nut could be slipping too but that doesn't seem likely.

That's about all I've got.

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#81550

Can someone take a measurement on a HELLER oven please | 3 December, 2018

Not sure how the lead screw drive gear is locked in place but is it possible that it's slipping in both directions (when driving the rail both forward and backward) and then not catching until after the other end has already moved some?

You could have someone adjust width back and forth and watch the lead screw for motion. I guess the ball nut could be slipping too but that doesn't seem likely.

That's about all I've got.

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#81558

Can someone take a measurement on a HELLER oven please | 4 December, 2018

You need to verify the Rail parallelism. Please contact Heller Service department ServiceNJ@hellerindustries.com to get procedure. Please make sure to provide oven model, serial number.

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#81580

Can someone take a measurement on a HELLER oven please | 7 December, 2018

I have a similar over and both in and exit should be the same distance apart. You can contact Heller for help. If you have maintenance manual if should tell you how to adjust the timing chain for the lead screws, I am assuming your over have three lead screw. I remember reading in some maintenance procedure the timing chain will get slack and will need to be adjusted. Look it up and see if that's what causing your problem.

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