Pressure foot pressure control

According to the manual, your machine does not have the capability to drop/raise the feed dogs. Instead, there is a cover plate that is installed over the feed dogs when performing darning or free motion quilting.

Check that your stitch length is set high enough to actually move the fabric. Some machines also have a presser foot pressure adjustment that will increase or decrease the amount of pressure the presser foot applies to the fabric and the feed dogs. If your machine has this adjustment, it may help to increase the pressure so the fabric will move better. Another thing to check is whether you are using the correct presser foot that will actually rest on the feed dogs.

Reading the hints on pages 28 and 29 may be helpful.

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Another possibility is that the feed dog points have been worn off. When the points are worn, they no longer grip the fabric like when new. When stitching, be sure to never run the machine with the presser foot setting directly on the feed dogs, it without fabric.

Make sure the presser foot is down.
Have the feed dogs been dropped, as for darning?
Is the stitch length set to a higher number to make bigger stitches?
Does you machine have a pressure adjustment for the presser foot--check the owner's manual. The pressure adjustment increases or decreases the amount of pressure the presser foot applies to the feed dogs--makes it easier to switch between stitching light weight vs heavy weight fabrics, ie chiffon and wool.

Are you saying the presser foot has very light pressure on the fabric? If so, most machines have the ability to increase the pressure the presser foot applies to fabric and feed dogs. It depends on your machine's make & model where & how that pressure is adjusted. Older machines usually have a large skrew or knob at the top of the needle bar that tightens down on a big spring, thus the tighter spring increases the pressure. Newer machines sometimes have a dial usually located on the top left or side of the machine head. (Consult your owner's manual.)

http://makeitsew.biz/presser-foot-pressure

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Parts of Sewing Machine Pressure Adjustment

Under Pressure Adjusting Presser Foot Pressure

your model doesn't have this feature Janome 7100QDC Computerized Sewing Machine , it it did, there would be a knob on the top left of the machine above the presser foot which you could screw up or down to increase or decrease the pressure. Its not a feature on many machines, the presser foot bar has a big spring internally which applies the pressure and this will just adjust to suit the fabric under the foot.

I'm confused by your question, which mentions two machines. The presser foot pressure on a Tacsew T111-155 is adjusted by turning the knob on the left side, top of the machine that is directly over the needle. The Designer 1 mostly sets its own presser foot pressure, but it can be increased or decreased by following the procedure on p. 13 of the manual: http://new.husqvarnaviking.com/SiteMedia/Products/Machines/Support/Designer_I_manual_EN.pdf

There's a white knob on top of the machine, directly over the presser foot bar. Twist to the right to increase pressure, left to decrease pressure.

There should be a control on top of your machine that is directly over the needle OR, if you have a "door" on the left side of your machine that exposes some of the workings, then there might be a dial inside there. The pressure refers to the amount of pressure the sewing machine foot applies to the fabric. For thick fabrics, you will want to lighten that pressure. For thinner fabrics, you might want to increase that pressure. Use those controls to set the foot pressure. Try it out with a scrap to see if the pressure is to your liking. Good luck!

I would suggest that the machine needs to be serviced to find out why it not responding the way it should.

The rotary control on the left-hand end of the sewing arm controls the foot pressure. You shouldn't normally need to vary this, except when quilting thick materials. The control is normally set with the 'bar' in the middle of the knob straight up-and-down, but you can reduce the pressure by turning it - the markings on the head cover correspond to increasing and decreasing the foot pressure.

The knob on the left is the Pressure Foot pressure dial. Here is what the manual says about it: " This dial regulates how hard the presser foot is pushing down on the fabric. To little pressure may cause poor feeding of the fabric, skipped stitches, or difficulty in guiding the fabric as you sew. Too much pressure may result in one layer feeding ahead of another or feed teeth or presser foot marks on the fabric. For most fabrics set the dial at 2. For thicker fabric increase the dial to 3 and for thin fabric decrease to 1." The red dial on top, the far left one, is the tension dial. Just have to play around with that til you get it like you want. Hope this helps!