Tabbing Small Parts
Tabbing describes the process of leaving a small amount of material uncut so that the part is left still attached to the original workpiece. Tabbing comes in handy for several reasons:
- Prevents small parts from falling into the waterjet tank
- Keeps thin gauge materials from moving around during the cut
- Reduces the possibility of parts tipping up and colliding with the nozzle
After the cut has been completed, the parts can be easily removed by breaking the small tab between the part and the scrap material. It may be necessary to grind off the extra material that is left on the part from tabbing.
There are a few things to take into consideration when utilizing tabs:
- Place tabs on the outside contours of the part. This will make them easy to locate and reach so that the operator can grind them off when the part comes off of the waterjet.
- Try not to place tabs on corners of parts; it can be difficult to recreate the exact corner dimensions when grinding tabs off.
- Try not to place tabs on radii if at all possible. The best place to position tabs are on straight lines due to it being easier to grind something flat rather than trying to grind to a specific radius.
- Be mindful of how the software you are using measures tabs; some software takes kerf into account while others do not.
When programming in IGEMS, a tab value of 0.060” works pretty well. IGEMS activates kerf over the lead in and does not put kerf on lead outs. So, a 0.060” tab will leave approximately 0.020” to 0.030” of material for the tab when cutting with a 0.040” nozzle. This is just enough to hold on and not too much so that it is difficult to remove the part from the surrounding material.
When programming with WARDCAM, a 0.025” to 0.030” tab value is recommended. WARDCAM accounts for kerf value on tabs, so you want to enter the size of the material you want left for the tab.
Keep in mind as your orifice / nozzle wears and the diameter of the stream grows, more material will be eroded and the tab will become smaller. If you find that your tabs are not holding, you may want to increase them in the programming, or you may want to look at changing your orifice / nozzle.