It is often desirable to make cutouts that are very close to each other. On square cutouts, either the rough or finish cut can cause the thin web to vibrate when the end mill reaches a spot near the center one third of the line. This can cause inaccuracy, poor finish, broken end mills, and the cause of an increased four letter word vocabulary.
The rough cut creates a lot of side force. Consider the picture below. The top slot is about 5.77″ long and about 1.125 high. The material is .090 2024T3. The bottom hole (which cuts first) cuts just fine. The top hole starts cutting in the upper right corner and cuts counter clockwise along the top and left edges. As it gets near the center the noise level increases dramatically. Pausing the Panel Pro, we can see that the cut is ragged indicating that a lateral vibration is occurring. This can easily be overcome with a thin web support tool that you can either purchase from us or make your own.
All that is required is that the 1/2″ angle on the tool is pushed gently against thin web from the direction of the already cut hole. This dampens the vibration in either the rough or finish cut. It needs to be held in place by hand or if structure is available such as in the picture below, a clamp could clamp it to the base material, making sure that the machine will not run into the clamp. The panel Pro should be paused while moving this into position and removing it.
The machine can be paused by hitting the ESC key. The router and coolant can be shut off with the switch on the controller.
When you are ready to resume, turn spindle (router) power back on and hit enter. Holding the tool at the end keeps fingers away from moving parts.
It is advantageous to cut the bottom hole first so that when you are holding the support bar in position, the x axis will be moving away from you. You can assure the bottom hole will cut first by using the LL to UR (lower left to upper right) cutting order on the cut dialog. This will result in a lot of rapid traverse movement as it works its way lower left to upper right, but it only adds a couple minutes to the cutting time.
If the top hole cuts first, you need to go around to the back of the Panel Pro and hold the support bar. Now unless you have a wireless keyboard, you cannot reach the keyboard to resume cutting 
and the x axis will be moving towards you.
The tool has a small lip so the tool does not drop below the material edge. The 1/2 x 1/2 x .062 angle will keep the tool from running into the end mill.
The key is to look on your design for thin webs. If at all possible, increase distance of the thin web. In this case it is about .24″
How much web is enough to avoid concern? I can’t give you a formula other than to be watchful if you have any features like this in your drawing. If you are installing individual annunciators, consider one or two to a hole instead of 6 or 7. You can put them edge to edge without any material visible from the front. The short sections of thin web between the annunciators do not seem to have problems with the resonance.
Download Support Bar to make your own.