Messages

21

Tangent Corner / Re: Strange banding on lathe finished part.

« on: March 08, 2012, 04:30:25 PM »

I'm not sure of the quality of the center, it runs smooth and I've used it on other lathes without problems.
There is a quill lock in use.

Is the head/tail stocks in perfect alignment along their center lines?

I checked a while ago and there was 0.015mm in 200mm travel. But that was with a cold rolled stainless roundbar located in the chuck and live center.


It might be somthing to look at closer, I'm also going to try a shallow cut without the tailstock end supported.
and then try to cut some solid bar between centers to see if I get the same effect.

22

Tangent Corner / Re: Strange banding on lathe finished part.

« on: March 08, 2012, 03:57:03 PM »

As a picture is worth a thousand whatevers, here's a pic of the tube with the banding.

23

Tangent Corner / Re: Strange banding on lathe finished part.

« on: March 08, 2012, 03:11:08 PM »

Hi, Thanks for the quick replys.  I realise I'm running the tool backwards, it's not something I usually do but I was just trying to see if the same problem occured whilst the tool was working in that direction.

I remade a slug with a tight fitting shoulder, made no difference at all. I am also using new inserts, the CCGT are very sharp. I've tried taking light cuts of 0.1mm so not to load the live center end and it makes no difference I still get the banding along the length.

Logically trying to work out the problem, it's worse at the tailstock end so I would expect there's movement there somewhere although I have the live center well tight against the stock.

As i'm using new inserts there may be rubbing going on so I have reset the tool height several times above and below as well as on center.

As I have found that by running the tool backwards I get a very nice finish I am trying to think why, If the problem was with movement of the material I would have expected a poor finish in any direction.

24

Tangent Corner / Strange banding on lathe finished part.

« on: March 08, 2012, 12:08:34 PM »

Hi, Although probably not a Mach related problem this one has me head scratching once again.

I'm hoping one of you kind folks might give me some insight for the cure.


I'm cutting some thickwalled 6082 tube 34mm diameter and 150mm long on my Denford Orac running Mach3.

The tube is located in the chuck on the ID hard against the chuck nose and the other end is supported by the tailstock
with a revolving center and an ally slug fitted into the tube on a 45deg taper.

The turning tool is LH insert tool with insert CCGT 09T304.

When taking a cut from the tailstock end and travelling in Z 100mm the finish of the turned part has undulating banding the
peaks are approxamately 5mm apart. This is most pronounced at the tailstock end and diminishes as the cut gets nearer to the
chuck. If runnning a finger along the part, the finish has a ribbed feel to it.

Things i've tried to correct the problem,

Differing speeds and feeds.
Changing the tool height.
Trying different depths of cut.
Checking flexture of the chucked part.

None of the above made any difference to the depth or pitch of the banding.

So I changed the tool for a TPUN insert and tried again. Same effect even with a 0.2mm depth of cut.

I then had an idea and re-wrote the G-code to take the final pass starting from the chuck end and finishing at the tail stock and
the finish of the part came out perfect.

Any ideas to what the problem might be?

Cheers
John

25

General Mach Discussion / Re: Mach3 Ignores Feedrates In G Code

« on: February 07, 2012, 01:28:06 PM »

If you go into Config/General Config, on the page there is a place to put code which is run on first start up (Initialisation string).

26

General Mach Discussion / Re: VB calculation behind button is possible?

« on: January 17, 2012, 07:56:10 AM »

It should be possible, You could create your four user Dro's using MachScreen

http://www.kd-dietz.de/index_eng

Add a calc button with your code in.

Have a browse in the documentation for the Mach3 programmers reference PDF which will give you all the info you'll need.

Also a reference to the VB script

www.indusoft.com/pdf/VBScript%20Reference.pdf

27

General Mach Discussion / Re: What's your fastest feed rate for your mill/parallel port.

« on: January 13, 2012, 10:16:09 AM »

Ah, Is that Mr Bill's Servolight? I just looked it up on the net, The web page states that tops was 135ipm for the board.

When you get the scope, check the printer port and then do some checking on the driver board. Check part numbers for chips and specs to check the upper limit for pulse through put. It might be that the board just cant run those high freq pulses.

A drive that doesn't fault, not sure I'd be happy with that, I've had a few mishaps knocking into fixtures and have been thankful the drive faulted instead of carrying on regardless.

28

General Mach Discussion / Re: What's your fastest feed rate for your mill/parallel port.

« on: January 13, 2012, 09:09:48 AM »

Hi, What servo driver are you using, I just read the thread through and as said previously servo drives dont lose steps or pulses. If the motor cant drive the axis to keep up with the sent pulses it will fault the drive. That said, if the drive does not fault but the position if off a small amount then the drive's PID or tuning needs tweaking to provide a stiffer positional response.

I also found that if I ran a high kernal on the 1.2ghz computer I am using the pulses output on the printer port became less square and erratic when viewed on an oscilloscope which would cause the drives to fault intermittantly.

If you cannot tune the drive to get the accuracy then you need more powerful motors.

29

General Mach Discussion / Re: Just baffled by G54-56 Offsets

« on: May 15, 2011, 10:40:20 AM »

Thanks guys for the advice, As you can see in my macro I was getting desparate and willing to try anything.

On reflection it seems writing to the Dro's in turn and waiting for them to update is a slow way of doing things. I increased the sleep times to 450 and still had problems with some of the offsets not getting set correctly.

Thanks for the script Gerry, I'll give that a go. Looks very tidy.

30

General Mach Discussion / Just baffled by G54-56 Offsets

« on: May 14, 2011, 11:52:01 AM »

Hi, I've been trying to write a macro to set my Z offsets to the same number whether I am using G54 through G59.

See Macro below. I have noticed that without the wait states Mach will not update the Dro's quickly enough and the Z Dro's are still different even with running the macro.

If I single step through the macro, it seems to work as I intended.

Is there another way to achieve the same thing with one command?