I realize I may well get blasted for this post BUT I just gotta say these things anyway.
When the top and backing is loaded onto a quilting frame it is pulled taught, not tight enough to bounce a quarter off of it but taught enough for tension when rolling it onto the rollers and back and forth while quilting. If the backing has been pieced, this is when the problems begin. If the seam(s) go from top to bottom of the quilt, when the backing is rolled on the frame there is build up from the seam(s) laying atop one another that can AND will cause several problems from the longarmer. So if the backing has multiple piecing the longarmer is faced with multiple problems.
Now for the top. Hopefully we all set the stitches then press seams to one side with an iron. We are taught to press to the dark or one side by setting the seam then flipping the top fabric over and pressing. Here is where a LAQ problem will arise. Make sure you are NOT pressing in a tiny bit of a fold. We've all done it. That tiny bit of fold, albeit may only be two or three threads of fabric, will raise it's ugly little head to a LAQ. Now if you have done this teeny tiny fold more than once in your piecing, each one WILL cause it's own problem.
If you have a top like a pinwheel or kalidescope (sp) block there is quite a build up of fabric in the center of the block. You may have pressed, ironed, hammered, steamed, steamrolled, ran over, hammered more, and the like to flatten that center. Okay, it looked really good on your ironing board. Well, give that block a bit of a stretch. That center will pop up. It isn't that you may have pieced the block wrong, it is just the nature of the beast. Now a LAQ has to figure out a way to quilt that block AND have the center lay down. Please remember, the center seam of that block is THICK! When we go to quilt over it our machines may get stuck in the fabric. For most of us, the only way to correct this problem is to turn the machine off, turn the flywheel to lift the needle, then turn the machine back on. In most cases, this will appear as a skipped stitch. Worse yet, when the machine gets to the fabric build up, our hopping foot may not be able to clear the build up and kind of "push" the center to one side. Then we always face the problem of the needle breaking at the intersection. (I have learned the hard way to never quilt without some kind of eye protection) I have had to replace eyeglasses from broken needles that have put a chip in my lens right in my line of sight.
Now about those wavy borders. The most common cause of wavy borders, whether cut cross grain of straight of grain is the cut ACTUALLY BEING ON SOME KIND OF GRAIN! If you did not prewash your fabric and set the fabric on straight of grain, most likely your borders are off grain. Off grain fabric WILL wave. We all complain about fabric "shrinking" when washed. Actually the fabric does not shrink. (no I'm not nuts) The fabric is returning to actual size! When fabric is made the fiber is stretched. After the fabric has been created, it is then stretched in pressing. The fibers are treated with chemicals to "relax" the fiber so that it will lay more flat. Then at the end of it all, once again the fabric is stretched to be rolled onto bolts flat. (I worked in a fabric mill for many years, this is why I know this) Now, I'm not telling you that you have to prewash your fabrics, that is your personal preference, but I will say I prewash all my fabrics before I start a quilt. Also, I do purchase at least a quarter yard more than the pattern for the "just in case" problems.
So, for the piecers, if you want to take the time to do this, there is a way you can foresee SOME quilting problems. No one will be able to foresee all the problems. Make sure your top and backing if VERY WELL PRESSED. You need to clip all threads that may show thru. If you see a ravel problem, trim it! Once you have these problems addressed, lay your top (and backing if pieced) on a large surface. Carpeted floor works perfect for this. Give it a bit of a stretch and pin it. Stand up, back up, and give a look. Do you see any ripples? If so, you LAQ will have to deal with those.
I fully expect to get some flack over this post. I am fairly certain most longarm quilters will agree with what I have written. But I know there are some piecers out there that will think I am entirely NUTS. For those of you that think that, go spend a day with a longarmer, you will change your mind.
Now, about "certification" for longarmers. What I am about to say IS MY OPINION, like it or not. If a person goes thru medical school and BARELY passes the board because they really didn't study, they are still going to call themselves a Doctor. May not be a good doctor BUT people will go to them AT LEAST ONCE. If a person goes thru beauty school and comes out barely knowing the difference between a razor and pair of scissors, they can still call themselves a hairdresser. So, with knowing these facts, what is the purpose of making a LAQ get certified? Also, that person will be judged (or graded) by another HUMAN, leaving the results to PERSONAL CHOICE.
Okay, I will jump off my soapbox now and go attempt to finish the quilt that is currently on my frame.