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Messages - chrisjh

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I made some extended wheel nuts so I could mount tools like a shovel, an axe and a high lift jack on the spare wheel on the rear of my Toyota Prado.

I used my cnc lathe to make the wheel nuts.

The video tells the story http://www.youtube.com/watch?v=gsw5JtYMGSI&feature=channel


Thanks Ron & Rich,

I have now updated to the latest version of NFS Wizards.

I have also amended my code as Rich suggested and the toolpath approach arcs have shifted by 90 degrees solving my problem.

Attached are screen shots of the tool paths with and without G68/G69 commands.

Although I haven't cut metal yet, I am very confident.


Thanks Rich,

I had never heard of G68/G69.  It doesn't appear on the old list of G Commands that I printed out from Mach3 years ago.  I looked it up in Peter Smid's CNC Programming Handbook and I now understand.

Presumably Mach3 recognizes and responds to G68/G69 commands?

I'll give it a try as soon as I can get an opportunity.  (busy right now having been sucked temporarily back from retirement into the thrust and cut of the real world)

Regards and once again, thanks for the tip.



I use NFS wizards (I have V2.79) all the time.  Great CAM generator!!

Is there a way to specify the Approach Arc Start Position for external cuts on circles.  The default is approx +90 degrees (3 o'clock).  I am writing a step and repeat routine to machine multiple parts (a 50mm Fluted Knob) from a single block of material.

Problem is I have to waste a lot of material because the approach arcs are at the +90 degree position which means that my G52 offset for successive parts needs to be further to the right (+X) to allow for the arcs.

What I would like to be able to do is to specify that the start of the approach arcs somewhere near the 12 o'clock position (outside the +Y extremity of my material) to minimize wastage.

I could cut up my material to 51mm square blocks and do them one at a time but I would really like to be able to be 3 at a time with G52 step and repeats.



General Mach Discussion / Re: CSS with Mach3
« on: March 02, 2010, 10:21:01 PM »
Hi Phil,

Smoothstepper Plugin V015.meg as requested.



General Mach Discussion / Re: CSS with Mach3
« on: March 02, 2010, 06:50:18 PM »

I use CSS with Mach3 Lathe all the time.

I run a Smoothstepper currently with V015meg Plugin and Mach V3.042.037.  (I notice this morning that Mach3 R3.042.038 is released)

I tried later Smoothstepper Plugins but the all have a problem with indicating True Spindle Speed on the Mach3 DRO.  V015meg Plugin indicates accurate Spindle Speed.

As far as I can recall, CSS worked on my setup with all Mach3 variants that I have used.

I use Mach3s PWM output control to control my Danfoss VFD via a simple RC integration circuit.  Works a treat.

Here it is working.  In the Video I use CSS for the OD turning operation, then switch CSS off to perform the spot drill and drill operations, then switch CSS back on to perform the parting operation.




Show"N"Tell ( Your Machines) / Re: Chrisjh Home Built CNC Lathe
« on: February 27, 2010, 01:16:10 AM »
More Progress!!

I added the coolant plumbing and a parting blade. 

The parting blade is made from an old wood circular saw with tungsten carbide tips.  I got this great idea from Peter on the HSM forum.  Thanks Peter.  There is an excellent thread at http://bbs.homeshopmachinist.net/showthread.php?t=39202 regarding shop made tooling.  I have had great inspirations from that thread.  Peter's idea can be found here : http://bbs.homeshopmachinist.net/showpost.php?p=516034&postcount=328

For Peter's parting blade, I designed and made a special upside down tool holder for the gang tool post.  I am very pleased with the parting results.  Centre line adjustments for the tip are made with a rocking action around the centre of a 16mm Stainless Steel Rod held in the tool post. All I have to do is adjust the two M8 screws at the rear of the assembly to get the tip on centre.

It took me some time (2 days) to work out how to program the gang tool post.  Initially I tried to use Mach3's tool table which worked but the tool table offset calls were causing the tool to go indirectly (not directly as I expected) to the cutting position.  The result was that the cross slide would travel to the X+ limit switch on tools that were not the master. 

Because I did not understand how the tool table movements were programmed internally, I gave up with the tool table approach.  It was not going to work the way I thought it should.  It also added more time to the program with its indirect route. 

I then manually programmed the spot drill and drill to go to their respective absolute positions.  This worked but had the end result of buggering up the Constant Surface Speed (CSS) operation.  Large offsets caused the CSS to command the spindle speed to go too slow (makes sense when I now think about it).

Then I tried G54 to G59 fixture offsets but this had the same problem with CSS.

Then the penny dropped after doing some research with Peter Smid's bible.  I used temporary offset command G52 X??? Z??? to move the non master tools to their respective cutting positions.  This solved the CSS problem and worked so well that I have decided to do all my future programming for the gang tool post this way.

I am currently making drip directing devices for the coolant.  The coolant travels along the frame and drips outside the catch area of my coolant return tray.  Next will be a mudguard (Some call them wings or fenders) for the chuck.  I had to dodge the spray from the chuck a couple of times.

Here is the lathe in action with coolant and parting added:  http://www.youtube.com/watch?v=55SLUjDg5go

General Mach Discussion / Re: Peck Drilling macros for the Lathe
« on: February 06, 2010, 03:51:08 AM »
Hi Dave,

I have attached Mick's macros published 30Dec09.



General Mach Discussion / Re: Peck Drilling macros for the Lathe
« on: February 05, 2010, 06:05:37 PM »
Hi all,

This is my way of thanking publically Mick for his help in writing peck drilling macros that are easy to implement and use and work great in Mach3.

In the video at this link, there is a spot drill and deep drill routing using Mick's macros.




Show"N"Tell ( Your Machines) / Re: Chrisjh Home Built CNC Lathe
« on: February 05, 2010, 04:31:16 PM »
Making Progress!!!

I had a serious vibration problem when doing OD Cuts.  Facing seems to give good results but the surface finish on OD cuts were terrible not to mention the soul destroying noise emanating from the machine when performing OD cuts.

Long story short:
I dismantled the spindle assy from the headstock and checked the bearings.  Ah ah, I noticed that the tapered roller bearing cage was fouling the bearing housing.  This is it, I thought.  I checked my Solidworks models and there should have been clearance?  Problem was that the Solidworks bearing model I downloaded was different from the actual bearing that I had (the cage stuck out approx 1mm more than my CAD model).  This meant that the cage was touching the bearing housing before the outer race bottomed.

I countered bored the spindle housing 3mm deeper and amended the model and drawing.  I reassembled the spindle assy, making sure that the outer race was “bottomed”, and tightened the bearing preload to “tight” with a 150mm pipe extension on the C Spanner and back off a bit.

There was no improvement!!!

I gave up for 3 months and did other things. (Rather despondent mood.  I had convinced myself that I had a terrible design and the bed/frame structure was too weak).

I decided to get scientific about it and measure the flex in the bed/frame structure.  I mounted a dial gauge between the bed and the top of the head stock.  Stuck a 1m long piece of 38mm steel rod in the big 6 jaw chuck sticking out approx 800mm.  I put all my weight (approx 80kg) on to the rod and all I could measure was .003" movement.  Upwards pressure produced similar results.  Not too bad, I thought, so what was wrong?

During this process I noticed a visible minute movement between the front bearing housing and the spindle.  I clamped a piece of 19mm brass rod across the 6 jaw chuck and rotated the spindle until the rod was stopped at the bed/frame.  Then I fitted the C Spanner to the preload nut and extended the handle with a piece of pipe 500mm long.  I was able to tighten the preload nut approx 1 turn (pitch is 1.5mm).  The spindle at this stage could be rotated by hand but I could feed that it was too tight. I backed it off 1/3 turn and the spindle freed up.

I ran the spindle for a few hours and noticed that it sounded better.  I tried and OD cut 0.25mm deep and results were astounding.  The noise and vibration had gone and the surface finish was as expected.
Proof was to make something.  Here it is: http://www.youtube.com/watch?v=9kRHpfDiRsE

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