Hello Guest it is March 29, 2024, 07:32:42 AM

Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - jimpinder

781
Is this a spoked wheel for a railway locomotive ???

I would be interested in seeing the code for it.
I am wanting to write the code for a spoked wheel for my next locomotive - a Garratt 2-8-0 0-8-2 which I was thinking of milling out of a blank - about 8" diameter (10 spoke, I think). I say this becasue good foundries, to do small work are a bit few and far between up here now.

I have a Warco lathe/mill which I have converted to CNC

782
General Mach Discussion / Re: A Long Sad Story
« on: March 25, 2008, 09:24:21 AM »
Yes - we seem to be a bit off post now, but I was thinking of  starting in the lathe for the rim, and facing and bore etc, then mounting it on a circular table to cut the spokes. In that wau I only need one profile, and then turn the appropriate number of degress and do it again.

Still - that's a bit in the furture - thanks for the info.

783
There are two ways of running - Constant Velocity and Absolute Stop - see on the Config page.

In absolute stop, the cutting axis will come to an absolute stop BEFORE the other axis starts to move - this will produce a "square" corner - althoug cutting internally you do, of course loose the tool radius - which you can file out if you wish.

In Constant velocity - Mach3 reads forward and anticipates the next command, and as one axis is decelerating, the other axis accelerates so the tools ic constantly cutting - but this leads to a rounding of the corners - and the faster you go the "worse" it gets, becasue the axis need more time to accelrate/decelerate.

As Hood stys there is the ability to alter the parameters of Constant Velocity to make the acceleration/deceleration quicker, or only active between certain distances,

On a right angle cut as you are doing, absolute stop may not be too much of a distraction. Where you get an arc to cut, which a cad program makes up of many small straight lines, then Mach3 still stops between each one - producing a very jerky movement - hence the need for constant velocity.



784
When you say dynamically, do you mean while everything is actually in motion, or can the machine stop until it changes.

As far as I know, there is no method of changing the configuration of Mach 3 from G Code - except through the known commands e.g. absolute and incremental positioning, or constant velocity mode, or other things.

Unless someone else can tell us, it would seem to me that what you are wanting to do is change the configuration of the spindle from a "spindle" to an axis. I am sure this could be done by writing a Vis Basic Macro, although where I peek and poke the relative information, I do not know.

I did, however, just think of a simpler way (perhaps). Have you tried controlling the spindle as though it were an axis yet.

Assuming that you can - and assuming the spindle stays in the correct position when you have done it, then why not resort to a relay system - a two pole change-over should do - controlled by an output from Mach3 - there are several available.
The machine stops - having been in "spindle" mode. The relay switches from the control wires for the spindle, to the control wires for the C axis - and you then control the c axis for your machining.

At the end, the relay disengages and you are back to a spindle again.

If you can drive your spindle from both types of output then that would seem the simplest way to me -



785
General Mach Discussion / Re: Laser Gunsight
« on: March 25, 2008, 05:42:07 AM »
Yes, there is another post about encoders somewhere.

I suppose I will go down that road, eventually. As I say, I do not trust my lathe - that might be me, becasue I am not used to CNC, and it has certainly worked on the bits I have done. I must admit, though, I do keep thinking that I will design some nice complicated piece of kit - (I am thinking of a spoked wheel at the moment) - and set the machine to cut it, only to have it loose position and foul it up.

Encoders - which are seperate from Mach 3 drivers and DRO's - as a secondary check would be useful. :'(

786
General Mach Discussion / Re: A Long Sad Story
« on: March 25, 2008, 05:27:49 AM »
I haven't tried drawing with a CAD program, most of my work is relatively simple, and I can write the G Code straight to the machine (or on here and transfer it).

I have two of the programs mentioned in this post - Turbo Cad - which I find excellent as an accurate drawing tool, and I have just found a version of Coral Draw in my discs - which I must confess, I haven't tried.

I am wanting to design a spoked wheel, which will be then milled out of a solid disc - the wheel is approx 8 inches in diameter and about 1 inch thick. (It does not matter how long the program takes to mill it).

I can draw it in Turbo Cad and probably Coral Draw - but can anybody advise me what program to use to then translate that drawing into G Code for the machine - in fact - forget the wheel - has anybody any experience of converting drawings from Turbo Cad or Coral Draw into G Code.

I have converted simple 2D outlines into G Code milling patterns, using a program called Ace.exe - but how do the programs convert 3D drawings - I ssume they must layer them for the cutter depth.


787
Jeff - I had a look on the web at the board - it looks OK.

It seems they have done a lot of thinking for you, in that the x.y.z and a drivers are already allocated, and they are making suggestions about the other inputs and outputs.

What I said about wiring the switches still holds good by the look of it - and you can still daisy chain them if you want. I can't quite read the pin numbers on the side of the board - but they look to have an associated ground wire with them. Since the board is isolated, you will probably have to use the pull up jumper shown.

Have a go at wiring it on the workbench, with some switches and short bits of wire - connect it to the computer and see how you get on. The kit seems to have the little jumper cables to go from the breakout board to the driver cards. I think you will have to supply the cable from the driver cards to the motors.

You can even test one of the motors on the workbench too - connect that up to one of the driver cards and plug it in. Because Mach 3 can be configured, you can test all axis just using the one motor, just by changing the configuration and leaving the wiring as it is.

788
General Mach Discussion / Re: Laser Gunsight
« on: March 24, 2008, 04:23:30 PM »
Another method I was thinking of, but I haven't the foggiest how to implement it (yet) was with the laser reading the distance (which is what we are after in the first place). For my last few years in the Police force, I was experimenting with laser speed guns, and they quite simply measured the distance to anything you could see in the sights. The speed of light is constant, therefore timing a pulse from sending to return provided an accurate method of measuring distance without holding a tape. This was, in fact how they measured the speed of a vehicle - by taking two distance measurements in a given time and working out the speed.

Two of these mounted on the carriage pointing at targets at the end of the machine would give a constant x,y read out. One on the spindle would give a constant z read out - no doubt a PIC chip would be involved, somewhere !!!

789
There has been quite a few posts on limit switches - there is one just going on now.

Limit/home switches can be wired up any number of ways to suit you. Basically all the switch does is send a signal (on or off) to the computer. All can be configured in Config/Ports and Pins/Input. There are five input pins to your computer - 10 to 13 and 15. All these pins are internally connected to a pull up resistor in the computer - i.e. if they are not connected to anything, they show a 5v signal to the computer.

You can test this by going into config, setting the pins, and then switching  the inputs to "active high" i.e. active low is off (red cross). This should, without any machine being connected to the computer, show the led on the Diagnostics page as lit.

It is normal to use the switches in "active high" mode. This is because any fault in the switch or wiring is then detectable, before any damage is caused to the machine.

To set up the switches, all you need to do is connect the limit/home switch to a 0v terminal (pins 18 to 25 are at 0v - although check on your computer if all are being used). Fasten the NORMALLY CLOSED output from the switch to one of the input pins. Set up the Config page with the pin as active high.

This means that the pin into the computer is held low (off) in normal use. The carriage comes along, hits the switch, which opens, cutting the 0v signal. The internal resistor pulls the input high, and the led lights.

You do not need to install everything on the mathe/mill before you try this, you can experiment on the workbench before installation and see how to set everything up. You will see that any bad switch, loose wiring etc will cause the input to activate - warning you of any trouble, before it happens.

You can repeat this with all the other switches. You do not need any complicated wiring from +5 to 0v or anything like that.

You can save input pins by wiring from 0v to Sw1 to Sw2 to Sw3 to an input pin (use the normally closed contacts again). This means that all your home switches and limit switches go into one pin. Mach3 can sort out which one it wants to use.

Home switches can double as limit switches - again Mach3 sorts it out.

Again - your Estop switch can be configured in either way - active low or active high - or you could include it in the daisy chain above.
Why bother with 5 volts - connect it via 0v as above.

The 3 axis ProboStep Kit - does it include a breakout board to make connection to ??? If so the instructions above should still hold good. The thing about Mach 3 is that is so configurable that a lot of the rigid wiring diagrams (whilst they would work) can be simplified. If you keep it simple, it is easier to use and troubleshoot.












790
General Mach Discussion / Re: Laser Gunsight
« on: March 24, 2008, 06:06:40 AM »
Because of the position of the lathe,(in a corner) I need two mirrors at 90 degree angle to reflect the laser beam back.  I tried this with blue tack (sticky stuff), but the mirror kept slipping. I am going to try again over the next couple of days. If I reflect to the back of the workshop, I should get a factor of about 20 - whether this will be enough to detect small distances - we shall see. I suppose in theory, with a couple more mirrors I could even double this up as well.

I screwed the detector strip to the motor housing yesterday - for some reason now I home and zero, home again +5 thou out, zero, home again - 5 thou out - and so on. Must be something simple - probably my logic !!