Scrim Foam Orientation

[baileyuph]

Over years, it has been observed that, scrim foam which serves as a backing to the upholstery covering material involved, is orientated differently, by OEM manufacturers. 

It is oriented differently with respect to what is sandwiched in the layering process, the foam of the scrim or the fabric like covering of the scrim.

What is the logic behind layering the materials one way or the other?  Why isn't it consistently done one way?  There is a reason that might be interesting to know.

I understand doing channels with the foam side sandwiched, the seam is stronger with the bobbin thread against the cloth part of the scrim.   It would more easily tear through the foam.

But, the logic of the foam placed as the bottom surface of the layer, any ideas?  I was doing some Ford OEM duplication this week and all the scrim was oriented this way.  I did it like OEM but not clear on why.

There has to be a reason, I can think of some possibilities, but not sure if I am on the right track?  Before divulging my WAG  maybe someone else has it figured out?  Let me hear about it.

Thanks,
;D

Doyle

[SHHR]

I'm probably way off on this, but I'll give it a shot. Possibly could it be the people in the factory putting these seats together (or not knowing how to)? I mean some guy working through a temporary service at the factory making barely over minimum wage surley doesn't have the skill or maybe the desire to learn it correctly. The only way I would know for sure is to check multiple seats of the same design done on different shifts or days to see how the foam is oriented, which would be next to impossible.

  I have a friend who's a supervisor at a factory that does seat upholstery for new Toyota vans and he told me you'd be suprised what he sees pass through quality control since you can't see the underside of the covers.

I just recovered 20 chairs for the church we attend. One chair would have a few staples holding the covers on and  another would have way more than necessary and not put in in any certain order. Obviously two different people working on an assembly line somewhere.


Like I said though just a guess. I'd like to hear other thoughts about it.
Kyle

[Rich]

I can't imagine any reason for not having the scrim backing as the lowest layer since it provides a means to keep the thread from cutting into the foam. I've never seen it done the way you describe, but then, I haven't done auto trim work for many years.
Another function I have found for the backing is to enable the whole assembly to slide through during sewing. With foam as the bottom layer, it tends to grip the bed of the machine.
When I read the subject heading, I thought you were going to say something about the backing itself. I don't like using the standard cheescloth type scrim backing on this foam b/c since it is rolled with the backing out, it tends to wrinkle when laid flat and this results in visible lines in the finished cover. I always specify the bi-directional stretch backing I get from 3 Rivers supply in PA. That backing doesn't show ridges in the finished product like the scrim does.
Rich

[MinUph]

I would have to agree that there is no reason to place the foam out on any cover for any reason. If there was a reason then there would not be a reason to use the scrim backing in the first place. The covers must look awfully flat as there will be no padding between the layers. If not now very soon as the thread pulls through the foam.

[Mike8560]

if you lay up some scrim foam with your vinyl sandwiching the foam if you do a inside curve you will get wrinkle on you face vinyl

[baileyuph]

you lay up some scrim foam with your vinyl sandwiching the foam if you do a inside curve you will get wrinkle on you face vinyl

Well Mike, your experience is same as mine.  On a crown surface, convex, it will create wrinkles, that is your inside curve example.  The degree of wringkles will depend on scrim thickness, size of the panel, and radius of curvature.

I do agree with Kyle that stuff happens during fabrication and installation in manufacturing. 

I have noted that the sandwiching question is not as much an issue on thinner scrim and on heavier materials like leather.  Another factor discovered is smaller panels reduce the sandwiching issue,  less bending.

To the concern that the foam won't last if the foam isn't sandwiched, it has been noticed that the foam holds up fairly well on the bottom.  The rather large Ford project just completed, the foam did hold up.   The quality of OEM foam might attribute to that. 

On the boat scene: Mike I encounter seat upholstery (skins) with bonded foam directly to the vinyl, no scrim cloth involved.  I know you have seen that.  It sure facilitates a nice looking cover, er ah, skin!

Good input guys, your discoveries are in parallel with mine, this was just something I wanted to check out.

Last observation, I noted that the edges of the OEM scrim foam is previously serged to the covering material after patterning and cutting, this obviously helps the material to flow through the machine during final sewing, particularly when the foam is not sandwiched.

Good input, thanks.

Doyle