Messages

5641

General Mach Discussion / Re: Problems threading on the lathe

« on: October 05, 2009, 07:43:36 PM »

ART,
Did a few more test pieces today. Same 115 rpm, 40 passes @ .0001" deep for 10,20,40 TPI.
I used the standard lathe screen and threading wizard.
Now we know that the tracking was good but the lead was decreasing. So i tried the tests with adjusted lead.
The rounded lead error was a decrease of .008" / inch. So I just changed the lead to be used in the wizard as follows:

TPI       TRUE PITCH     MODIFIED PITCH
10         .1                  .1008
20         .050               .0504
40         .025               .0252

The Gcode provided by the wizard will post the modified feedrate ( namely .1008 / .0504 / .0252 ) even though it rounds it in the wizard screen.

The lead error in 1" was almost un-measurable ( including each crest / root distance ............ 0 or under .0005" / inch. That's about as perfect as you can get! Heck, what are you measuring, the lead screw accuracy if you know what i mean.

You can also decrease the inputed lead if you want to take care of an advancing cut lead.  I haven't tried a 0-80 to see if the lead should be modified to .01256 ( don't cut to many 1" long 0-80's ).

Will relative /  ratioed numbers hold true for other rpm? I don't know.

So, if you left the threading code alone, and a user tested ie; cut a scribbed test piece at .1" pitch for 1 or 2" long and very accurately measure the lead, then adjust feedrate accordingly, they may just solve their problem.
It's a work around, an easy one, but users must remember that there are a lot of other influences that can play into threading.

Is John S doing any testing?
          
RICH

5642

G-Code, CAD, and CAM discussions / Re: widening a line in LC

« on: October 05, 2009, 06:56:00 PM »

locktech,
You can add a line a distance away from the other in CAD and if they are on the same layer then you can assign the same cutting cutting parameters to them. So consider it as a  single machining operation. I just can't remember now without trying, but , I believe you can create an offset of a line, in this case .003" . Then move the offset to the other layer and do as first stated.
RICH 

5643

LazyCam (Beta) / Re: lazycam lead in

« on: October 05, 2009, 10:41:49 AM »

skipper,
The manual is located in the Members Docs along with the files used for the tutorials.
Here is the link:

http://www.machsupport.com/forum/index.php/topic,12078.msg77415.html#msg77415

RICH

5644

General Mach Discussion / Re: I can't seem to get Backlash Compensation to work...

« on: October 05, 2009, 12:38:11 AM »

Rule of thumb i have recommended to start with is  50-50-50.
-BACKLASH SPEED = 50%
- SHUTTLE SPEED = .050  ( i use .005, but try the slower speed first )
- MOTOR VELOCITY SETTING = 50% of max velocity ( if motors skip at 100 ipm reduce to 50 ipm)

Now increase your velocity up to 70%  of max ( you are leaving 30% margin for cutting ) and try,
then start decreasing the shuttle speed down in increments to .005, trying each downward setting.
I would leave the backlash at 50% but if your velocity setting is at 70% of max, then 100 % may be just fine.

You need to play some as each machine is different.

RICH

5645

General Mach Discussion / Re: Problems threading on the lathe

« on: October 04, 2009, 06:10:05 PM »

Winters coming and you need to get the shop done.
A user enter correction factor would be nice.  I certainly would want others to confirm what i found. So if it's user correctable and they do testing, than at least It comes from a know base point of reference.

RICH

5646

General Mach Discussion / Re: Problems threading on the lathe

« on: October 04, 2009, 05:54:22 PM »

Steiner,
The best i can do "easily" is measure visualy when the sensor turns on and off and that is repeatable within 5 minutes of an angle. So that's one ball park useless number.  A 0.003" error between two actual scribed lines was around 10 degrees of a rotation. Now doing 50 moves using a G32 Z-2.0" F.050 from Z=0 showed all 50 moves ending within a 0.001"distance which tells me that the trigger is very repeatable and the axis travel and acceleration together was consistent. Then i even broke that down by .1" moves from Z=0 to 1,1.1,1.2, etc and all was good. The start Z=0 and ending point Z=-2.0 was confirmed using a calibrated allignment telescope and scale. The scope is 40X at 12" and has an optical micrometer ( measures to 0.0001" ). So can't do too much electronicaly, but, the end physical result is what is important.

ART,
When i run the driver test PPS is 25455. The kernal speed viewed on Chips lathe screen that we used before for testing, shows a pulse frequency of 25452, but if you go out and come back into Mach it will change to 23654. It will continue to show the 23654 for however many times you exit and come back into Mach. Now reboot and the the above numbers will repeat as described again.

I did a third test piece at 0.1" pitch, the lead decreased by .008" /  inch and the pulse frequency on the screen was 23654.

Like that show that was on TV " You Asked For It". Well they are the pulse frequencies. 
RICH

5647

Show"N"Tell ( Your Machines) / Re: emco pc5 lathe

« on: October 04, 2009, 01:22:43 PM »

Looks like you will be having some fun making chips. The smaller  lathes don't leave much room for converted items.
 Thanks for the info on the modifciations and do post your testing.
RICH

5648

General Mach Discussion / Re: Problems threading on the lathe

« on: October 04, 2009, 11:55:39 AM »

ART,
OOPS!
I did something realy stupid and caught it today. All of my recent post's which say that the lead is increasing is wrong.  The LEAD IS .......DECREASING. The amount of lead decrease is 0.008" / inch.
I found and used Chip's Screen set,  so now have kernal speed information.
I'll go back and modify my recent posts. The data is good, just again, it's decreasing.
RICH

5649

Show"N"Tell ( Your Machines) / Re: CNC CONVERSION - 6" ATLAS LATHE

« on: October 03, 2009, 10:59:36 PM »

Hi All,
The lathe is working great, but a sore spot was my computer.  I have never recomended a specific computer in any of my postings. I finaly broke down and had one put together. The company said it would work with me and put a solid computer together for running Mach. If it didn't satisfy the driver test, then components would be changed unitil it worked as I wanted. So off we went for a 1/2 hour lunch, returned and it was put together!
Good price, unbeatable service, with an absolute guarentee you could't beat!
Like, if the mother board was the problem  they would change it out, processor, and any component, with the cost only changing if the component cost more!

I need to get back to the company ( they have been around a long time and i have purchased pc's from them before)
and confirm that all is well. Then i will modify this post with their info.

The PC is solid. Here are some basics:
- Asus motherboard - M2N68-AM SE2
- 2 GIG Ram
- AMD  64X2 Dual Core Processor 5200+ 2.7 Ghz
- Asus graphics Card - EN9600GSO
- Rosewill PCI pp card - RC302

The pc will run my steppers at the same speeds as the SS. The PPS in the driver test will only change by 1 at 25khz and maybe 4 at 100 khz. Single line  with no bumps and you can play with the mouse and it dosen't screw it up.

This is the pc i am using for the threading tests if you have been following that thread.

RICH

5650

LazyCam (Beta) / Re: lazycam lead in

« on: October 03, 2009, 10:05:25 PM »

Skipper,
Just move the drawing in CAD such the the corner or center is at the origin ( 0,0,0) in CAD.
Save the DXF that way. When LC opens, and if you have "AS Drawn" box checked in the loading options LC will keep the original origin created in CAD. ( see page 16 section 6.2.3 in the manual ).
There are other things you can do and they are explained in the Manual.

RICH