Non-Conductive Work-Piece and Probing
The Ghost Gunner’s sensors require a conductive workpiece to properly function. The workpiece is charged with 5 Volts DC by the red probe wire. This is so it can be detected by the end mill probe.
The end mill should barely touch the lower during the probing sequence. If the workpiece is not properly connected to the probe wire, or shorted to the t-slot platform, the end mill may bore into the workpiece during the probing sequence. It is important to avoid this situation by ensuring that 5 Volts DC is detectable when touching the voltmeter leads between the lower and the spindle.
Forged lowers, often present probe errors due to an electrically insulating outer layer created by the forging process.
Anodized or coated lowers, require some prep work to ensure that the GG’s sensors will detect the position of the workpiece.
Coated lowers, such as those coated with Duracoat or Cerakote, will often present probe errors and cutting errors due to the electrically insulating properties of the coating. Such coatings can also result in rapid tool wear. They can also reduce tool cutting effectiveness.
The key to successfully detecting an anodized lower in a Ghost Gunner is to run a 1/4-28 tap in the grip bolt hole to remove anodization from the threading. This ensures that 5 volts are charging the lower.
For best results, use 80% lowers, jigs, end mills, and bits designed specifically to be compatible with the Ghost Gunner.
Checking Voltage on all Ghost Gunners
Remove anodization from above the FCG pocket location to get a clear voltmeter measurement. Even if properly prepped, anodized lowers often present issues with offset cuts due to probe errors. These prober errors are caused by the electrical properties of anodized material. The USB cable connection to your computer powers the Ghost Gunner’s probe circuit with a 5 Volt DC electrical signal.
Dial your voltmeter to 20 Volts DC, and touch one voltmeter probe to the exposed metal on the lower. Proceed to touch the other probe to the spindle to verify the 5-volt signal required to locate the workpiece. The probe signal is detectable by the computer if it is between 4.5- and 5.5- Volts DC.
Note | Do not measure voltage from the grip bolt-probe wire connection. Detecting 5 volts from the probe wire does not indicate if the lower itself is being charged with the 5 Volt probe signal.
Checking Voltage on Ghost Gunner 3
The Ghost Gunner 3 is equipped with a green LED light that will turn on whenever the part is shorted to the table, the endmill is making contact with a charged workpiece or if the probe wire is unplugged.
You can use this feature to help you detect any possible probing issues before you start the probing sequence. When the workpiece is installed and ready for probing, make sure the end mill is not contacting the workpiece. The green LED light should be off at this point. If it’s on, the workpiece may be shorted to the table.
To check if your workpiece is getting voltage, you can short the part to the table by using a metal Allen wrench. Touch raw metal on the workpiece with one end of a wrench, then touch the endmill or table with another part of the wrench, so that the wrench is touching both the workpiece and the table or spindle at the same time. The green LED light should turn on when the part is shorted. Remove the wrench and make sure the green LED turns off. Then proceed to probing.
A Workaround for Non-Conductive Lowers
If you choose to use anodized or non-conductive lowers in the Ghost Gunner, be aware that some anodized lowers simply will not work with the Ghost Gunner’s probe system. You’ll be able to read 5 Volts DC between the lower and table, yet the machine cannot detect the probe signal due to the properties of the anodized metal. Polymer and other non-conductive lowers require a firm understanding of the Ghost Gunner’s probe system. Refer to section 5.6 in your Ghost Gunner 2 Operator’s Manual or section 9 in your Ghost Gunner 3 Operator's manual for more information on using non-conductive parts.
“It is probably a given, but the probe doesn’t work on non-conductive parts. Traditional X/Y/Z touch-off methods are of course supported - paper snagging, roller gauges, etc. -- but they’re not automated. One possible nonmetallic probing method is to connect the probe cable to adhesive aluminum tape mounted on three surfaces (X/Y/Z). We leave these implementations to the traditional machinist, as Ghost Gunner’s primary focus is automated aluminum machining.”
You’ll need a voltmeter to check for 5 Volts DC from the red probe lead charging the conductive tape on the probe sites. Trigger well-cut probe sites are on top of the bolt catch site, in the center of the rear mag well wall, and in both mag well walls near the rear. Holes cut probe sites are in the corner on the right side of the grip tang, as well as where the trigger pin hole will be.
The conductive tape method for bypassing the probing system may result in offset or inconsistent cuts.