Messages

141

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

« on: November 09, 2017, 07:47:58 PM »

Do not download demo version of CamBam. Get full version which is free for 40 sessions

142

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

« on: November 09, 2017, 07:46:28 PM »

Billy,
You actually will learn hand coding faster by using a Cam program because you get to see code generated essentially by an expert for your part. I generate all my code with Cam and I start every new program in single block mode, reading each line before executing it until I am confident it is where it should be and won’t crash.  The nice part is when it needs a small adjustment that happens quickly in Cam and I keep moving forward.

143

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

« on: November 08, 2017, 06:34:57 PM »

Billy,
All good advice on cutting stainless.  I had a Sherline spindle, 1/8" is it for stainless. but it works.  One more, use the shortest cutter mounted as short as possible, as this makes a big difference for a small machine.

The problem with hand coding the angles is that you need to know exactly where the end points are.  This is really tough working from paper.  The next thing is you have to deal with tool radius offset, using G40, G41, G42 and specifying the tool radius, then using a short move to get it applied after calling the tool offset number.  This is not something for the novice programmer.  

So the other option by hand is offsetting the part outline by the tool radius and programming that path.  On a small machine on hard material you may have to adjust the tool path for deflection and that means rewriting all your code.

I worked as a CNC programmer coding by hand, and I can tell you that life is too short for that crap in this day and age.  So get an inexpensive CAM program like CamBam so you can enjoy the machining.  I have two seats of CamBam, one for my homebuilt minimill and one for the big machine at work.  CamBam has a rudimentary drawing capability so you don't need a Cad program for stuff like this part.  CAM is what really makes CNC practical.

144

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

« on: November 07, 2017, 07:58:02 PM »

Gary,
May want to start a new thread about use of that PLC for a turn / mill combo.
I assume your are aware of Simpson's work on the matter.
Would make for an interesting topic.

RICH

Was not aware of Simpson's work, got a link?

145

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

« on: November 06, 2017, 06:06:50 PM »

Yep,
Send me a PM with your shipping address. It's tiny, like 2" square.  Don't remember what I paid for it but it wasn't much, doesn't matter.

146

General Mach Discussion / Re: what kind of device do i need

« on: November 06, 2017, 02:58:13 PM »

Half,
See my reply to your other thread.

147

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

« on: November 06, 2017, 02:57:07 PM »

Half,
Since I got my BRX plc I have no need for another device I bought. It is a step pulse driver with a potentiometer input. You can have it free. If you hook a double pole double throw relay to be activated by a M code from Mach 3 you could then hook step and direction inputs to the drive to the common terminals and the step and direction output from mach 3 to the normally closed contacts and the pulser step and direction to the normally open. It is a mill with 4th axis when the relay is off and a lathe when it is on.

148

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

« on: November 06, 2017, 01:26:18 PM »

Rich,
The problem of Mach 3 being able to run an axis continuously is the whole problem for turn/mill machines. Currently my machine has DL06 plc in it that handles all the I/O like coolant, two different mill spindles and 3d printing extruder, lights, vacuum, heat for 3d printing etc.

I just got a DoMore BRX plc to replace the DL06. AWESOME little PLC!  It has analog inputs and autotune PID to control heaters and such. Analog outputs to control spindle speed for conventional drives that don’t use PWM, and can accept PWM from Mach 3 and translate it. It has high speed inputs for encoders, and high speed outputs to drive servos or steppers  and can do 2 axis coordinated motion on its own. It speaks modbus, USB, Ethernet, serial Rs232 and Rs485.

So I am going to drive my lathe spindle stepper driver through a double pole double throw relay getting pulses for postiong as 4th axis from Mach 3 or as spindle drive from BRX reading Mach 3 PWM spindle output.  It can also generate an index pulse for threading. The analog inputs will read the thermocouple sensors from the 3d extruder and the heated bed and PWM outputs to the heater solid state relays will control temperature. M code inputs from Mach 3  can turn heat on and off and change set points. I am hoping this will end all the crazy work arounds and give me capabilites for othe stuff like an auto tool changer too.

149

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

« on: November 04, 2017, 03:40:45 PM »

Half,
If you have fusion 360 you can make a 3D model of that part and fusion should easily handle machining it with just 3 axis.  The way I would approach this is to 2D mill the rectangular raised protrusion and slot, and the top of curved area for length, width, and a little extra on top.  Then use a 3D milling operation on the curved portion with a ball mill.  In CamBam from a 3D model I would create a single mregion by putting a slightly more than tool diameter rectangle around the whole part, and a rectangle equal to the raised portion.  Then CamBam would recognize to machine only the area within the outer rectangle and outside of the rectangle around the raised part. You might use a routine typlcally called waterline rough and waterline finish.  Rough will make multiple passes at a specified depth to remove most of the material leaving a defined roughing clearance.  A waterline finish would then cut the surface to finished size and you would specify a small stepover so the ripples are minimized.  There is usually other 3D methods that may do the job better.

150

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

« on: November 04, 2017, 12:59:19 PM »

Half,
Are you programming by hand or using a CAM program?  Do you use a 3D modeling program?  The big advance in CNC is really in 3D modeling and CAM programming. I have lots of hand programming experience but life is too short for that!  I use CamBam, both on my hobby machine at home and the big machine at work. I wouldn’t even think of making your bridge with a rotary axis, it’s just too much work that way. It is mostly a 2D job with a little surfacing of the curved part using a ball mill.