Accurate procedure for fabricating Channels in fabrics

[baileyuph]

Fabrics/vinyls sewn to sew foam is the primary interest and would like to understand how others may be handling the issue to achieve precise spacing results of the sewn product. 

I am looking beyond of how to achieve straight lines in the top stitching.  The exact spacing between sewn channels given a foam thickness being used and covering materials. 

What is your procedure, for example chalk lines on fabric, and the sewing process (attaching the sewfoam to begin sewing and your complete strategy).

Frequently the requirement comes up in auto interior work, especially when matching the sewn spacing of other seats.  If the spacing between channels is off it will likely show - becomes critical.

Fullness in planning needs to be know up front to get the chalked sew lines spaced to meet spacing in factory work being matched in other seats and between the pleats being produced. 

Anyone "been there and done that" - this should be clear and hopfully clear enough for
all readers in our craft.

Doyle

[Mike]

if you meen   stitch line that are seem on the face of the vinyl   I  glue the vinyl to the foam then mark line on the back on the foam then sew stitch the line foam with line up vinyl side down   right I dono but works for me

[MinUph]

Works for me too Mike. I don't like having lines on the face of the vinyl or fabric for that matter.

[baileyuph]

One example - in auto trim, repairing original upholstery it is essential to be able to generate replacement panels ( for areas of wear) that duplicate the accuracy of the manufacturers.  When drawing lines and sewing down the line, due to the dynamics of going through fabric thickness and the backing foam (sew foam), the resultant sewn seam distance (from seam to seam) will not be the same distance as the drawn line. The distance is shortened based on the variables alluded to.

That distance is a challenge because like stated, need to match the seam spacing of the manufacturer and the channel fullness.  If a match isn't required, no problem.

This example of work is often with vinyl, leather, and body cloth.  These variables alone will cause some difference in channel calibration.

Given this overview, often if a similar foam (thickness and density) and auto seat material can be found in the shop, it is necessary to run examples.  Calibration and appearance can be an issue when repairing with expensive cars - understandable.

So, going on with this; calibration and such with working up these repair panels, a 1/16" or 1/8 "off" from the original can draw a concern.  Sometimes a 1/32 " in. can show up where seam lines match.

Input is appreciated, there is something to be learned from any technique from input as ideas, for applying to this or other situations that arise.  So thanks Paul and Mike, keep the ideas flowing.

We chalk with sharp chalk, for cannot afford to glue always (cloth?).  Lighter colors almost require colored chalk.

Anyway, as far as running samples to achieve desired calibrations takes time and scrap materials (leather can get expensive) and it would be good if there was some kind of math or judgment when using certain materials with a given foam density/thickness?  Factories have the advantage of having multiple needle machines and what ever they produce works out because that calibration  will be produced for the entire interior - no miss match. 

I just did a major seat repair in a Ford, after running test examples got a calibration that matched the factory with less then 1/16 inch variance.  That took time for it was tested on three different walking foot machines.  To say, this stuff varies by machine.

Sew foam for this work can routinely vary between 1/4 inch to 1/2 inch.  The thicker & higher density of the foam, plus fabric stretch, the harder to match - not surprising.

In Mike and Pauls case, I assume the there would be a difference in channel fullness when sewing channel lines on the backside as opposed to the finish material side.  That has been my experience, you can get a difference in channel fullness.  Again, no problem if every seat or surface of the job is being done by a given technique.

Oh.......the advantage of higher technology.

Doyle