Messages

11

General Mach Discussion / Possible Parallel Port Emulation Problem?

« on: August 23, 2014, 03:05:26 PM »

My KX1 and PC running Mach3 stopped talking to each other last week after four and a half years of trouble free operation.   I had temporarily connected the PC to the internet to re-activate a copy of DraftSight on it and a load of updates seem to have been downloaded at the same time.   I wasn't aware of the updates until I noticed that the PC was still running after I had supposedly shut it down and when I fired the screen up,  I found it finishing off the installation of several updates.   I let it finish and shut it down.  but when I started the machine up the next day,  the Mach screens were changed and i couldn't talk to the KX1.

I spent a day or two checking everything,  trying to step back through updates to get back to the previous PC state,  then reloading Mach,  PCI card drivers, etc.  but still no luck.   I then dug out an old WinXP machine I had pensioned off a few years back and tried to get it back into working trim.  It had an onboard parallel port,  so should have been easy.  but it would not run Mach properly - i.e. I couldn't get a satisfactory driver test done.

I then went back to the original PC and tried checking the parallel port using Parmon.exe,  but couldn't see changes of the port using Parmon reflected on the output pins.  So I reckoned that the card was faulty and got a replacement.  On trying it today,  I found that port pin setting with Parmon was not being reflected on the output port pins on this replacement card either.   I went digging around on the Internet to see if this problem had occurred to anyone else and actually found someone who had had the same problem.  He had found that a parallel port emulation had been set up in his computer and that was what Parmon was seeing and interacting with.   It looks as though this might be my problem and might have happened after that [expletive deleted] update.   Any help on how I can confirm this,  and get rid of it?

Jim.

12

General Mach Discussion / Re: Scale Problem?

« on: February 26, 2013, 03:47:29 PM »

Jim,
Sorry, but I'm out of suggestions/thoughts other than trying a reload of Mach3.  Perhaps one of the power users here will step in with help.

John,

Thanks for your time in considering the problem.   I'll just keep making parts and checking each one after cutting so that if I hit the problem again,  I might be able to see what might have caused it in the machine setup at the time.

Jim.

13

General Mach Discussion / Re: Scale Problem?

« on: February 26, 2013, 05:27:21 AM »

John,

Just checked the X and Y axis for backlash.  There is no backlash compensation set up for these axes in Mach - both backlash settings = 0.  Both axes were the same - at ~0.0008"/0.02mm.  My dial indicator is graduated in 0.0005",  so the 0.0008" was a (hopefully) intelligent guess at the small amount under one thou for the backlash.  The metric movement was a bit more of a guess working on an imperial dial. 

Jim.

14

General Mach Discussion / Re: Scale Problem?

« on: February 26, 2013, 03:43:28 AM »

Jim,

X too large, Y too small.  Seems odd.  What is your backlash?

John,

I haven't checked the X and Y backlash recently since parts seemed to have been coming out the correct sizes and shapes until the problem parts of two weeks ago.  I'll get the dial test out this morning and have a look.

Jim.

15

General Mach Discussion / Re: Scale Problem?

« on: February 25, 2013, 11:26:20 AM »

Jim,
If just the X, and only sometimes, you may just be operating at the ragged edge of your steppers ability.  Not knowing more about your part or machine, I recommend that you try lowering the velocity and aceleration by 25% (or any % you choose) to see if the problem goes away.

John,

Last week I was more worried about the lengths of the parts so I've just checked the heights of the pieces which I hadn't done before,  and they are undersize!! - typically about 0.6mm in 30mm - approximately -2% error.   I've re-checked the piece I cut yesterday and both height and length are to size.

I don't think the machine is being worked too hard.  I'm cutting quite small detail in styrene with small diameter (1mm, 2mm) carbide cutters and the typical feed depth is 0.15mm,  with 25% stepover at 300mm/min and 3000 - 4000rpm.

Jim.

16

General Mach Discussion / Scale Problem?

« on: February 25, 2013, 06:13:28 AM »

I machined a load of parts on my Seig KX1 a couple of weeks ago and when I got around to assembling them last week I found that some of the parts were oversize - typically +0.35mm in 75mm on the X axis,  or just under +0.5%.   I've audited the CAD and GCode and all the values are correct.  Unfortunately I was producing the parts as fast as I could over two or three days and I can't remember any peculiar conditions that might have existed when the oversize parts were machined.   I re-machined one of the oversize parts yesterday with the same GCode files and it turned out dimensionally accurate.

I checked the motor settings in Mach3 and they seemed to be OK - Steps Per = 500; Velocity = 1000.2;  Acceleration = 150; Step Pulse = 2; Dir. Pulse = 0.

I remember having the same problem about a year ago when another part turned out oversize,  but I was able to re-machine it to correct dimensions using the same GCode files.

Any pointers to what might be happening?  At the moment I'm going to check the motor settings before I start any machining.  I never normally touch the scale settings on the MDI and always assume them to be 1,  but I will keep an eye on them as well.  I also checked the code from Cut2D for the possibility of any G50/51 entries,  but there are none.

The mach version is 3.043.022.

Jim.

17

G-Code, CAD, and CAM discussions / Re: Problem with ARCs

« on: February 14, 2013, 05:37:47 PM »

Isn't it great how you can miss a hash sign on the problem line.   After I posted the last message I decided to have another look at the code and at last saw the missing hash in the "Y" parameter.   I've been missing that all day today and spending hours checking out the original CAD work and double checking figures, 

Jim.

18

G-Code, CAD, and CAM discussions / Re: Problem with ARCs

« on: February 14, 2013, 05:22:09 PM »

I've attached the file.       It stops at the problem block.

The funny things is that this part is the right hand mirror image and the left hand original one has coded with no problems,  including the slight drafting error.  

The point variables hold the co-ordinates of arc centres of both the right and left hand polygons - #x00 = left hand "X",  #x50 = right hand "X" and #x01 = the "Y" for both sides.   I split the right hand coding out of the left hand coding to try and sort out the error.   This will become a subroutine to generate waterlines round the polygon by varying #600 and #700

Jim.

19

G-Code, CAD, and CAM discussions / Problem with ARCs

« on: February 14, 2013, 03:30:21 PM »

I'm writing GCode to cut a polygon with several arcs in it.  In one place,  three arcs follow one after the other and Mach shows an error reading the block for the third arc with the  "Radius to end of arc differs from radius to start" error message on that block.   I did discover a small error in the original CAD drawing and corrected that and adjusted the GCode,  but the error still happens.

I am using the SIN, COS and ARCTAN trig functions in Mach to calculate the parameters in the GCode.  When I single step through the code in Mach,  I note that when I come to the part with the three arcs the DRO readings start to deviate from what they should be - based on the co-ordinates from the CAD program (AutoCAD LT) and my checking the calculations with my HP35s calculator.   

Start of first arc
DRO readings          33.1302,30.8210

Start of second arc
DRO readings          34.3560, 31.6840
CAD co-ords            34.3560, 31.6848
HP35s results           34.3560, 31.6848

Start of third arc
DRO readings          40.3720, 28.9010
CAD co-ords            40.3731, 28.9013
HP35s results           40.3731, 28.90136

The next point at the end of the third arc is a hard reference from a fixed point,  so it looks as though Mach is throwing an error with a deviation of 0.0011 in X and 0.0003 in Y at the start position

Am I pushing the accuracy of the Mach trig functions too much?

I've also tried switching between incremental and absolute IJ working,  but with no change.

Any suggestions?

Jim.

20

General Mach Discussion / Re: New to CNC, seeking sources

« on: July 26, 2011, 02:30:45 PM »

You might try downloading the free trial versions of programs like Vectric Cut2d or Cambam.  I started out with Cut2D and it gave me a good start into what was going on.  You can draw your designs in Cut2D or you can import DXF files from a CAD program.  It only cuts pockets and profiles,  so is a bit limited in that way.  You could look at something like Cut3D if you want to do full 3D work but you have to generate your drawings in a separate 3D CAD package then import them.   Messing around with Cut2D is probably a better starter and you can look at the Gcode it generates to give you a good idea of what's going on.

Jim.