Messages

51

General Mach Discussion / Re: Video of my setup and Mach3 lathe problem. Weird problem....

« on: December 18, 2011, 12:27:56 AM »

Hi,

Can you post your G Code so we can try to help?

Are you using Tool Tables and Tool Calls calls for each tool in the gang?  I have a gang tool setup & I do not use tool tables and tool calls.  I use G52 offsets to set the offset for each tool.

If you want, I can post or refer you to my typical G Code for Gang Tool setup.  Just let me know if you think it would help.

The fact that your simulated cut is on the far side of the stock looks to me like you have the turret set in Mach3 for the rear side.  I use a conventional turret setup from the near (front) side of the stock with my Mach3 setup.

Regards

Chrisjh

52

General Mach Discussion / Re: Drilling 3 holes on a lathe

« on: November 28, 2011, 04:48:42 PM »

Hi,

The method I use with my gang tool setup is to call G52 offsets for the X & Z Postions of each drill tip relative to a Master Tool Tip Position.  In your case each drill will need to be offset by 40mm.  

eg G52 X40 Z0 for the 2nd Drill (assuming the first drill is the master tool and that the tip of the 2nd Drill is aligned in the Z plane with the tip of the 1st drill).  

Don't forget to cancel the G52 Offset when each successive drill has completed its task with a G52 X0 Z0 before moving to the next drill position and on completion of the 3 drilling job.  

Make sure that you withdraw each drill to a safe Z position ( I use 20mm) before calling the next drill.

As to the Drill cycles I use the peck drill macros here:

http://www.machsupport.com/forum/index.php?PHPSESSID=k39gqcfsarabqj4bmakqaon960&topic=15205.0

G83 does not work in Mach3 Turn.

Regards

Chrisjh

53

G-Code, CAD, and CAM discussions / G96/G97 Command Structure

« on: October 17, 2011, 06:41:35 PM »

Hi,

I have been having random results with my G96 (CSS) and G97 (RPM Mode) calls.  I use mixed CSS and RPM routines in my programs.  Sometimes it works well as programmed and sometimes it drives me nuts.  The symptoms vary but, as an example, when I switch from CSS mode to RPM mode, the spindle will run at either max or min RPM and nothing will fix it.  The general fix has been to shutdown everything and start again.

Yesterday I stumbled on the Startup Modals Check Box" Use Init string on ALL resets" for Initialization Strings and setting the string to contain "G97 S500" helped to get Mach3 out of CSS mode without shutting down.

I carried out further investigations of the structure of the G96/G97 commands in Smid's CNC Programming Handbook and on the Internet in general.  Smid's G96 example is structured G96 S45 M03 and G97 S500 M03.  Programming like this seems to have fixed my lathe's random behaviours.  My coding included the M03 (or M04) command for the first G96 call but I had assumed that the M03 was modal and subsequent M03 commands were not necessary in C97 CSS cancellations.  It appears not to be case.

I have tried to find out why the inclusion of the Spindle On (M03 or M04) in G96 and G97 calls appear to be mandatory but with out absolute clarity.

Can anyone confirm my suspicions regarding the necessity to include a Spindle On command with every G96 and G97 block?

Regards

Chrisjh

54

Show"N"Tell ( Your Machines) / Re: Chrisjh Home Built CNC Lathe

« on: October 10, 2011, 05:59:08 PM »

Hi Hood,

Fear is what I felt when the boring bar with the threading insert plunged for the first time inside the job in the chuck!!!  I cut air just short of the job a few time before I plucked up the courgage to set the Z zero at the face of the stock.  All went well and I feel more confident now.

As you observed, I had to hand code the start of the cut from inside and move out to get a RH thread.

Here is the code I used:

(Cut M27 x 1.5 Internal Thread)

(Select RH External Threading Insert Mounted On LH Boring Bar in Tool Block Hole 4)

(Tip to tip measurement between master tool and threading tool is 94.551mm, therefore X offset for threading tool is 2 x 94.551 = X189.1)

G52 X189.1 Z0 (Temporary Offset Position for Threading Tool Tip)

G00  X-23
G00 Z3 (Clearance for Start of Threading Routine)
G00 X-25.5 (Go to Minor Diameter Position)

G76 X-27 Z3 Q1 P1.5 J0.075 L0 H0.15 I29.5 K-18 C2.5 B0.025 T0

(X=Ø Last Threading Pass, R=Ø 1st Threading Pass, Z=Thread End Position, K=ZStart Position, P=Pitch, J=MinDepth/Pass, H=Depth1stPass, B=DepthLastPass)

(C=X Clearance Rapid Return, Q=Spring Passes, L=ExitAngle/Rev, I=InfeedAngle, T=TaperAngle)

G00 X-23
G00 Z20 (Go to Safe Position)

I use lots of comments in my coding to make it easier for me to recall what I did in the future and to make it easier for me to write the next routine.  Saves me having to use reference material (Mach3 Turn Manual, Rich's excellent threading manual, and Smid's CNC Programming Handbook) all the time.

Regards

Chrisjh

55

Show"N"Tell ( Your Machines) / Re: Chrisjh Home Built CNC Lathe

« on: October 05, 2011, 05:29:32 AM »

Hi,

Today I made a thread test gauge, I guess you would call it a go/no go gauge to be used on a part that I make from time to time.

This was my first attempt at internal threading.  I was pleased with the result.

Enjoy:

http://www.youtube.com/watch?v=B63tuYJB44E

There a few other videos that I have posted on youtube showing other bits being made for those interested.

Regards

Chrisjh

56

Show"N"Tell ( Your Machines) / How I solved my Stepper Motor Resonance Problem - Video

« on: August 25, 2011, 12:20:13 AM »

I have had a terrible problem with bad resonance with the Z Axis on my CNC Lathe.  The problem only appeared at certain feed rates.  The lathe has smooth operation at most feed rates.

In desperation, I had to try to program around the feed rate that I wanted to use (0.25mm/rev) to avoid the resonance; as it was affecting the quality of turned parts. I.e. I would use a non-ideal 0.15 or 0.35mm/rev to avoid the problem.

I tried all the advice that I could find on the internet to no avail. I even changed the Stepper Motor and Stepper Motor Drivers to a different makes.  No luck.  I tried varying the Power Supply Voltage to the Driver with absolutely no effect.

I then tried a mechanical approach by adding a flywheel to the Z Axis Stepper Motor.  Bingo!!!  Why didn't I do this 3 years ago?  So simple and so effective!!!

The video shows a wobble in the flywheel which resulted from my poor hand tapping skills.  I will make a new flywheel when time permits; now that I seem to have the problem licked.

The flywheel is Ø99 x 14 thick and made from mild steel.  There was absolutely no maths used; rather a simple application of the laws of physics and gut feel!!!

See video here  http://www.youtube.com/watch?v=mqCL7g4gwAU

Regards

Chrisjh

57

Show"N"Tell ( What you have made with your CNC machine.) / Re: Using Biodiesel as a machining fliud - Video

« on: August 16, 2011, 11:19:36 PM »

Hi All,

I thought this thread would invoke some comments!!

I agonized over the decision to switch to biodiesel but decided that because most of the work that I do is considered "light duty" and low frequency, I would try it.  I have 2 fire extinguishers handy but I am comforted by the high flash point of diesel and even higher for biodiesel; and an experiment that my Dad demonstrated to me in the 1950s.  He poured some diesel into a 44 gallon drum bung (well away from the drum of diesel) and threw lighted matches into the diesel.  It refused to ignite.  The same experiment performed with petrol produced predictable results; very exciting for a 6 year old lad.

I always use a fan in my workshop to blow the smoke away from me when cutting.  I used to use expensive Rocol cutting oil for heavy cuts in my manual lathe and it gives off  similar amounts of very obnoxious smoke.

I still use a water based coolant in my CNC mill as the ways and ball screws are better protected.

As for French fries, biodiesel derived from waste cooking oil when burnt, does indeed have that smell of "fish and chips" about it.  The first time I smelt the exhaust of my mate's Toyota Landcruiser, I commented to him that he would be likely to attract cats.

As to the height setting of the tools in the gang tool block, everything is totally dependent on the centreline of the bored 16mm holes being at exactly the same height as the centreline of the lathe.  That way, all drilling tools have to be correctly aligned. 

The master tool (it is a 35° diamond shaped carbide insert) is mounted in a homemade tool holder.  I carefully made sure that the tip of the insert was exactly on the centreline of the tool holder.  The same design approach was used for the threading tool holder. 

The parting blade holder (not shown in this video) was a bit trickier.  It is also homemade and mounted upside down and cuts from the rear side.  I fitted an "anti-rotation" block at the rear of the tool holder with 2 x M8 Screws that I adjust to "rock" the tip of the parting blade until it is on the centreline. 

The gang tool block is mounted on 2 x Ø32 aluminium blocks, secured by 2 x M8 Caphead screws to the main cross slide tool plate.  By careful skimming of the 2 x Ø32 aluminium blocks, I was able to “adjust” the tool tips to be aligned.  I checked all tools for correct height and was very pleased to see that theory was correct.  I can remove the gang tool block to fit other setups and when I replace the gang setup, I find that tool tip height is 100% repeatable.

Amazing what you can do with Solidworks.  You can check that everything fits, does not interfere, moves as designed and intended before you have cut any metal.  It invokes a high level of confidence.

Regards

Chrisjh

58

Show"N"Tell ( What you have made with your CNC machine.) / Using Biodiesel as a machining fliud - Video

« on: August 16, 2011, 01:27:03 AM »

I have been using biodiesel for some time now on my CNC lathe. The water soluble coolant that I used previously was causing problems with the linear bearings seizing (presumably from oxidation) following periods of inactivity.

I know of a professional CNC turning company that uses oil that looks like, and has the consistence of honey, so decided to abandon water based coolant for an oil based solution. The cost of such oil coolant is prohibitive so I decided to use biodiesel. This worked fine but left a sticky residue. I now dilute the biodiesel with ordinary diesel (ratio 3 parts biodiesel to 1 part diesel). This leaves no sticky residue and the machine is now very clean.

Biodiesel has a high flash point (higher than ordinary diesel) and has excellent lubrication properties.

The part being machined in the video is part of an oil filter adaptor I manufacture.  I had some 32mm threaded adaptors which were not popular so I decided to re-machine them to 27mm thread.

The material being cut is 12L14 steel and DOC during roughing is 0.4mm at a feedrate of 0.25mm/rev. The finish cut is done at 0.1mm/rev. Threading is done at 900rpm.
 
I also mix biodiesel with kerosene for manual applications with a squirt bottle on my manual lathe and milling machine. I also use raw biodiesel as a hand tapping lubricant (works great).

See video here  http://www.youtube.com/watch?v=jxEk4o5OLT4

Regards

Chrisjh

59

General Mach Discussion / Re: Mach3 Spindle Speed Problem

« on: February 17, 2011, 12:13:18 AM »

Hi All,
I am happy to report that the spindle speed problem that I have been witnessing for years now is FIXED!!!

I am also happy to report that Page 3 of my document describing PWM Control of Spindles using Mach3 is now inaccurate.

I have downloaded and tested Mach3_Rev3_043_030 from the yahoo site on two different machines as follows:

1.   A CNC Mill under Parallel Port Control from a Desktop PC, and

2.   A CNC Lathe under Smoothstepper USB Control from an older Dell Laptop.

When I request 500rpm from any input (MDI, From a G Code program, etc.), the spindle now goes to 500rpm as requested, and not some speed slightly higher as in all previous versions of Mach3 that I have used.
 
Pressing the Spindle Speed Override reset button now has no effect, unless the spindle speed override is set to other than 100%.

Thanks to Sparky whose tenacity is to be envied.  Like a bloody bloodhound!!!   If ever you are in Queensland, Australia, I owe you a carton of my favourite local brew, *********X Gold.

And thanks to Brian who found the pesky problem and corrected it.

Regards
Chrisjh

60

General Mach Discussion / Re: Mach3 Spindle Speed Problem

« on: February 10, 2011, 05:20:31 PM »

Hi George,

The problem still persists.  I believe that this bug does not cause most users any problems so a fix doesn't get high priority.

You and I seem to be the only ones concerned.

I continue to use my extra lines of code in cnc programs or, when in manual mode, I am in the habit of automatically hitting spindle override reset to achieve the correct rpms.

Regards

Chrisjh