Messages

361

General Mach Discussion / Re: Laser detector for tool setter

« on: August 10, 2008, 11:01:19 AM »

I dont see that this would be too difficult. I have lasers on my lathe/mill for positioning. The lasers shine at detectors, and are accurate to 1 thou of an inch. I dont see you are even asking for that accuracy.  A laser shining across your tool height setter at a detector would be picked up when the tool broke the beam.

I wont give details of my lasr and detector, because you probably can't get them - but the laser was £10 ($20) from Maplin, and the detectors are a few pence. They are very simple - three wire +5v. 0v and output. The output goes low when the laser is detected. Scmitt trigger output means it controls the input pin directly.

I made the laser and detector a little more accurate by shining them through 1mm holes about 12 mm long.

362

General Mach Discussion / Re: Mach3 Doesn't See Parallel Port Inputs

« on: August 10, 2008, 10:30:59 AM »

The parrallel ports are clearly not LPT1- which is already configured.

If you have put in cards for these ports, they will be programmable - and clearly you have not programmed them - or they are output only cards.

Have you used LPT1 (the old printer port) or not. Did this work .

I think it is the parrallel port cards configuration you need to look at.

363

General Mach Discussion / Re: Problems when posting

« on: August 10, 2008, 10:10:15 AM »

It's the scottish accent that upsets it - or it's too cold up there.

364

General Mach Discussion / Re: Mach3 freeze with my wireless network

« on: August 10, 2008, 10:07:13 AM »

I have a similar set up as described.

My office computer has the wireless router attached via a cable. My workshop computer has a wireless dongle in one of the USB ports.

I don't do anything fancy - just set up the wireless network using  Windows. and tranfer the files via the "My Network places" folders - works very well.

Perhaps the card insert has interference problems. I would try a wireless dongle on your workshop setup.

365

General Mach Discussion / Re: Very basic question about tool diameter compensation

« on: August 09, 2008, 08:25:23 AM »

Yes Gerry -
We understand the pros and cons - but what we need is someone who can properly explain G41 and G42 to us - i.e. comp left and right etc. - for example if you are cutting a window with the tool on the inside, which with standard bit rotation would probably mean you are cutting round in a clockwise direction, what do you use, and for example (since it says left and right) do you need to alter it when you come down the other side)

366

General Mach Discussion / Re: Very basic question about tool diameter compensation

« on: August 08, 2008, 04:43:59 AM »

It might be a bit late in the day (or the year, or in life) to try and get you interested in G Code, but it is very simple. The only trouble is that CAM programs write masses of it because they are so simple.

Each line of code is a move. All commands on a line are done simultaneously.
There are only two moves - G0 which is move fast - and G1 - which is move as fast as I tell you with the F command. There are other cutting moves, but I doubt your CAM program will do them - G2 and G3 - which cut circles.

If you are doing a shape - and you say you did one once - then you must know its dimensions. If you take the trouble to look at your GCode, and lay it out on graph paper, you will see the cuts follow, from one to the other, and all the GCode is telling the machine is where to go next (X and Y) and how high the cutter has to be (Z).

I take it you are using millimeters. So if your first cut is (starting at 0,0) G1 F5 X5, then the cutter is going to move to X5 - along the Y axis. Now if tool diameter compensation is applied by the cam - say for a 1mm cutter - then the Y axis must move from 0 to 0.5 first, and any subsequent moves will also be 1/2 milimeter offset or the inside of the shape if it is a pocket, or the outside if it is an island.

I am not suggesting that you now become a GCode buff - but have a look at the code and try to understand it a little. You will be suprised at how much you can decipher. All the umpteen other moves are to get the cutter to the right place to begin cutting and the only ones that mean anything at all are the G0 and G1.

You will see from the other answers that a lot of people are not certain how tool diameter compensation works - we could do with a comment from Graham Waterworth if he reads this - or pop a question on the GCode forum - and he might see it. He certainly knows his stuff.

367

General Mach Discussion / Re: PWM and Digispeed

« on: August 07, 2008, 12:47:48 PM »

I have two set ups - my machine is a lathe with a milling head. I was using the lathe and could not get the Omron inverter to react to the speed input - command S. The flash is only the slow double flash

Funnily enough - I was up in the early hours of this moring and fired it up in milling mode, and for a short time (no more than five minutes) the led was the fast flash. I saw this and changed my Omron to take orders from the Digispeed, but then the thing reverted to the slow double flash.

Peter - If you are looking at this - a screw down cable attachment would be preferable - my old eyes have difficulty soldering the tiny wires to a six pin mini din.

I am going to fiddle with it a little more and I will get back to you. Either the Digispeed goes down when it gets warmed up, or there is something wrong in the Mach output. Yes it has worked before - very effectively.

368

General Mach Discussion / Re: Creeping Y position. Anyone know something else I can try?

« on: August 07, 2008, 12:30:57 PM »

Just to repeat - are you on Constant Velocity or Absolute Stop.

Try running on Absolute stop.

369

General Mach Discussion / Re: Very basic question about tool diameter compensation

« on: August 07, 2008, 12:21:39 PM »

Cutter diameter compensation is governed by G40 (Compensation off) G41 (Compensation left) and G42 (Compensation right). What I must admit is that I have never been told what left and right mean - does that mean the tool is on the left or right - or the compensation is on the left or right.

In the case of the enclosed "window" - do you have to change as the cutter goes up one side, then down the other. I do not know. Perhaps someone versed in G Code could tell us. However I have no doubt that Mach does it correctly.

When cutting something like this, I have always written the code to cut, i.e. where I want the tool to go, and you can look at the code and check it before cutting, especially if your tolerances are so fine (a cutter less than a mm - phew).

There is another problem as well - where the cut finishes. Start the cut halfway along a straight edge and finish along the same straight edge, do not meet at a corner - because you do not know where the compensation is applied.

I hope you understand the diatribe - and perhaps spmeone will enlighten us.

370

General Mach Discussion / Re: Creeping Y position. Anyone know something else I can try?

« on: August 07, 2008, 04:29:25 AM »

Even is the traverse is set at the right (or wrong) steps per unit, this cannot be the reason for the progressive error because the steps per could be anything - but it goes one way, and comes back so they cancel each other out.

Check you are on Absolute Stop, and bring down your speed and acceleration substantially on your motor tuning, and try again and see if the error varies.

This could be backlash, but I cannot see how if you do not touch anything. On the first move you would be out (up and back - only one change of direction) - but the next move you would have two changes of direction so this would subsequently cancel out any further backlash.

You are loosing steps somewhere and the only reason I can think of is - your gearing, although substantial, is still quite high. and the motor is struggling as it sets off, to accelerate the whole contraption up to speed. One full motor step is nearly two thousanth of an inch - so you don't need to loose many of them each way to loose your distance.