Messages

131

G-Code, CAD, and CAM discussions / Re: CAM ( or CAD/CAM) software for horizontal drilling in MACH3

« on: December 07, 2017, 01:19:08 PM »

A thought for you. In CamBam I can create a custom drill cycle that is just G code but is modal. Code it once and it repeats for every hole location.  Picture your panel with the edges rotated onto the XY plane. The custom drill routine for the edges would specify drilling in the XZ plane and use G1 on the Y axis to do the drilling. It would then move to the next hole and repeat the motion. Other custom drill routines would do holes on all sides. They can be saved and reused easily.

132

Mach4 General Discussion / Re: Just a Little bit bigger :)

« on: December 02, 2017, 01:02:44 PM »

Tool diameter offsets are really useful when hand coding as you can write code for actual part size then use radius compensation for whatever tool you want to use. However when using Cam you almost always do the compensation in cam  as part of creating an operation because it is also use for stepover. Tool compensation is really only needed on finish passes so if you make those separate operations in cam then it is fairly easy to add g41/42/g40 to the code for the finish path. It can then be tweaked at run time.

133

General Mach Discussion / Re: Digitizing Point Cloud Or "Bed of Nails" type

« on: December 01, 2017, 12:51:35 PM »

How would mach 3 know that the next horizontal move won’t be a crash into a higher surface?

134

General Mach Discussion / Re: CNC Router "Stutters/Loses Position" on Faster Feed Rates

« on: November 28, 2017, 07:39:24 PM »

Simple answer, you are losing steps because of lack of torque at the speed you are trying to run. That comes from motors too small, or motors with high inductance. Nema 24 is a frame size and the range of torque for that size can be 3 or 4 to 1 from one motor to another. A motor with high inductance will greatly reduce the available torque as the speeds go up.

 It can also be from a power supply that is too low of a voltage or actually can’t supply enough current when all three motors move at the same time. Switching power supplies cannot absorb the regenerated power from the motors where an old fashioned linear can. Your screw pitch is also very fine and if it isn’t a ball screw there will be lots of friction losses at higher speed, plus the motor needs to turn much faster.

For comparison I got the lowest inductance motors I could find. They are driven by 80 volt rated drivers supplied by a massive 1500 watt 68 volt linear power supply. The machine has 5mm pitch ball screws and this gives me rapids of 300 ipm and cutting speeds of 200 ipm in plastics and wood. It never misses steps.

The good news is you can incrementaly improve what you have. In order of cost/benefit: 36 power supply would be a good step. Motors with a higher torque rating and lower inductance in the same frame size. Coarser pitch or ball screws.

135

General Mach Discussion / Re: VFD Noise

« on: November 17, 2017, 12:18:28 PM »

Bill,
Show us a picture of your control panel wiring and we may be able to help easier.

136

General Mach Discussion / Re: Alright fellow campers...a frankenstein moment!!

« on: November 15, 2017, 08:39:01 PM »

Bob,
Not to be harsh, but your pictures give me an OH MY! moment as I have been building control panels for about 50 years. It is really easy to see why you are having noise problems. A couple of things really need to be done. The step and direction wires from the breakout board should be shielded or at least twisted in separate pairs of signals and commons. Same with the DC power to each drive. If the stepper motor wires are not shielded twist the four wires into a cable of sorts.  It actually helps if different pairs of wires are twisted in opposite directions and even different twist per inch rates.  Totally separate the DC feed and the motor wires from the drive signal wire. If they have to cross one another try to do it at right angles, don’t put them parallel. The number one mistake that everyone makes, including me way too often is a panel that is simply too small for all the stuff that needs to fit. That often leads to noise problems.

137

General Mach Discussion / Re: Non-continuous motion

« on: November 12, 2017, 10:04:00 AM »

Have you got Exact Stop turned on?  That would cause an axis to decelerate to 0 between each move.

138

General Mach Discussion / Re: A-axis rotary lathe question for Mach 3

« on: November 10, 2017, 12:46:54 PM »

Bob,
I have never seen a 4 flute wood cutter, and 1 flute cutters are quite popular! The reason is that soft materials can be cut at such high speeds that chip packing in the cutter flutes and the cut itself is a big problem.

139

General Mach Discussion / Re: General question about small CNC mills

« on: November 10, 2017, 10:14:52 AM »

Billy,
When I was programming by hand I used the G40 offsets all the time. Few low cost cam programs do G40 offsets and you find that you don’t really use them once you use a Cam program.

A little secret if you want to try them. Add a short approach move in X and Y to the start of cut location. Before lowering the Z call G41 or G42 then move to the start point. You will see the tool move off to one side by the radius value then move to the start point. Now you can lower the tool in Z without gouging the part.  When the cut is finished raise the Z before issuing G40 to cancel the offset.

140

General Mach Discussion / Re: A-axis rotary lathe question for Mach 3

« on: November 10, 2017, 10:04:26 AM »

Rich,
Good write up. Another thing to remember with a rotary axis. Unlike a linear axis the cutting force available varies with the radius of the work. Milling on a small diameter part may work fine, but you could experience stalling on a large diameter part making the same cut.