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Messages - jimpinder

581
General Mach Discussion / Re: GRex Spindle Step/Dir setup
« on: May 20, 2008, 03:56:12 AM »
Yes - There must be, to allocate the outputs to fixed outputs - unfortunately I am not privvy to that information.
Perhaps Brett can come up with something.

582
Yes - but you are wasting your time. Let Mach3 do it ALL for you.

Mach 3 can give you movement of X and Y - BUT - with a motor on your Z axis, you can move the tool down to the correct height for punching. If you then use a code such as M3 (spindle motor start) and M5 (spindle motor stop) you can control the punch via a relay. The Z axis can lift again, and move to the next position.

If you want to retain manual control you can use the G0 X* Y* to move the table, and then following these M1, which is the command to stop, The machine will stop, you can punch the hole, then if you press "Cycle Start", it will carry on to the next hole.

583
Having seen pictures - yes - servo motors are the way to go.

I must admit, I agree with Hood when I said a lot of my CNC friends have disposed of machines for a lot less than 15K.
If I had the space and that kind of money, I think a purpose built CNC machine would be the way to go.
The thing is, they were designed from the bottom up as a CNC machine. The motor etc will be all sized up, the power supply fitted, so it must save a lot of work. And a toolchanger !!!  ::)

584
General Mach Discussion / Re: motors stalling on start up
« on: May 19, 2008, 03:08:58 AM »
It's a bit like starting a car - either you haven't enough power - or as above, you are trying to get away too fast.

If you are satified that your motors are strong enough, then look to your acceleration. I don't know what speed you are trying to get up to, but start at an acceleration of 0.5 or 1, and work upwards til the trouble occurs, then knock it down again.

585
Kevin -
The first thing is you have to decide what you want at the end of it. To me 15K is a lot of money and several of my CBC friends have got rid of CNC machinee centres for a lot less than that. I don't have the space, unfortunately.What are you seeking to do with the machine. You have talked about the firearms work etc, but that doesn't seem all that much (to me), unless you are a registered dealer.

A CNC machine has two advantages. One is speed - but in actual fact if you add all the time it takes to program the thing, for a one off you could be better doing it manually. Having said that, I prefer to do the program in the comfort of my "office" (front room) and then transfer it to my workshop computer to run it, rather than be bunched up over the lathe all the time. The second is repeatability. If you are machining a number of the same parts, then CNC is the way to go. I think there may be a third - in that programing is easier to me that machining. I can program the machine, test the program, and then be confident the machine will cut it. Doing it manually, I could make a mess and spoil it.

My lathe is much faster now than it used to be, particularly on the rapid non-cutting moves (and it doesn't waste time thinking about it)
Cutting is much the same, you have to use the same cutting speeds anyway. To achieve this, I have not altered my balls screws, or anything, I have just installed stepper motors. Mine could be wired three different ways - see an earlier post - now thety are wired in parrallel, with the Geckos, they fly.

If your lathe is in reasonable condition then a regrind might be all that it needs. How is your backlash. Mine is a lot, but Mach 3 copes very admirably with it. Cutting ball shapes you cannot see the join.

If it were me, I would have the machine reground, and delivered back. Quite frankly, if you are a reasonable engineer, you can do the rest yourself.

If you are in UK - (you talk in £'s) - then purchase a motor from Arc Euro Trade. They sell a 650Ncm motor for £50. This is 3 times the power I use (my lathe is a large Warco combined lathe/mill - and I use the 220Ncm). They should drive anything and your machine looks like my friends Harrisson (of a similar size anyway). I would buy one motor for the time being, and see it's capabilities. Unfortunately I do not know of any simple way of calculating what power you will need, nobody on this forum has come up with any ideas.

To power this motor you need a stepper driver. Buy single units - do not be tempted to buy a three in one - if one breaks, it's easier to fix. If I were you I would buy Gecko drives - American - very good and the standard Gecko has the voltage and current capabilities to drive the 650 motor. All you have to do is fit them to your lathe. My photograph on the earlier post shows the one fitted to the lead screw. Yes, I have used a toothed belt drive, these are cheap, they transmit the power without slipping, and the range of sizes is enormous. The advantage is - if you fit your motor - say with a 1 to 1 drive - and you find you need a bit more power - then fit different cogs and you can scale up your power ratio (for a loss of speed I admit) - but you will be able to find the ratio you are comfortable with that gives you enough power - with a speed you can live with. Merely remove your handwheel, fit a toothed cog, mount the motor in a suitable place and then buy the correct sized belt. My belts are 9mm wide, 5mm pitch. On your machine I would use the next size up. These should be available from any bearing supplier - and haggle the price - they give up to 90% discount - I kid you not. I WILL fit covers on them sooner or later (probably later knowing me).

I don't have a problem with speed on a lathe. These lads that have aircraft carrier flight decks for their router tables like the thing to travel at the speed of light. I got mine up to 40 inches per minute ( with a 3 to 1 reduction) so with less than 20 ins travel, I could be up and down in no time. I have cut the speed to 20 ins so that I trade accuracy (less chance of missed steps) for speed.

If your leadscrew is in reasonable condition, then don't change it, unless you really want to - but I would try with it at first and see the results. As you gain confidence, you will decide how far you want to go. For the sake of simplicity I would use the same motor on the cross-slide - which is why I said only buy one to start with. A 650 motor should certainly cope with the cross-slide - and you can probably use a higher gear if you wanted, although again - speed isn't everything. If the motor is too small for your leadscrew, use it on your cross-slide. If it's OK then but another one.

For £500 you should be able to buy 2 motors, Gecko drives, gearing and belts to get started. The only other thing you will need is a power unit. For this, you have little option but to buy a professional power unit. The motors are rated at 5 volts - steppers are "over driven" so a 30 volt power unit able to give about 20 amps should do the job. This may be expensive, but we are still well short of the 15K

Don't get the idea that these "machine shops" can do any better at retrofitting a lathe than you can. All they do is cover it up so you can't see what they have done - and charge you a hell of a price for it. You can buy ALL the parts for £1000. Yes you could spend a lot more I am sure, and other people will probably advise you to buy something different. Certainly for £2000 you can get the best - certainly to do a two axis lathe - so where does the other 28K come in.

Have a try - very little will be wasted and you will gain a lot of knowledge, even if, in the end, someone does most of the work for you.




586
General Mach Discussion / Re: Brand new problem
« on: May 17, 2008, 03:29:51 AM »
I'll leave Hood to talk about slots!

In a general vein - is your computer connected to the internet - I assume it must be if you are getting downloads. The trouble with Windows, it downloads all sorts of ****** into your computer - most of which you don't need in a workshop. I would consider disconnecting it from the internet and using another computer for your downloading.

I leave my Laptop in the workshop running the machine. I have stripped everything off it apart frpm Mach. If you have Mach running succesfully, you don't need any upgrades - and anything I need to put on it I do with a memory stick - then at least I know what's on there.

587
General Mach Discussion / Re: GRex Spindle Step/Dir setup
« on: May 16, 2008, 06:38:40 AM »
Three things came to mind.

1. I don't think the first is feasable - run the spindle step/dir through two of the other 16 output pins - I dont think it will be fast enough.
2. There must be an allocation table somewhere, to allocate the info from Mach 3 to the Ethernet transmitter. Can you not swap the allocation of say, axis C with the  step/dir of the Spindle Output.
3. Will Mach 3 run a second port when running the Ethernet. You would only need three wires to run a drive for the Spindle. I would hard wire this to a printer type lead and run it seperately.

588
General Mach Discussion / Re: Saving DRO Values
« on: May 16, 2008, 06:14:24 AM »
Carl.

I use a lot of DRO's for some of my Macro programs - these are user DRO's. Mach 3 saves all these, and they appear untouched the next time you start up.
Other DRO's (not USER DRO's) may, I think, change on start-up dependent on what triggers them.

Which DRO's change ? ???

I think I would create my settings on an ALL UserDRO table and then transfer them across to the "correct" DROs when you run your Macro. If some of them involve active DRO's, you may have to copy them back to your table before you close down (using another Macro)

Jim

589
General Mach Discussion / Re: If interrupted, how to resume?
« on: May 16, 2008, 04:10:53 AM »
Having read through the post again -

If you are using over size pieces then that is where offsets can come in again. If your wood can fasten in two different positions, one hanging of left and the other hanging of right, then you can either write two programs. Start the first program with your wood in one position. Use  say G56 offset to bring you cutter to the correct start point for that. Let it cut, then move the wood to your second start point and use say a G57 offset for the second program and cut the rest.

Once you understand offsets, you can do all sorts of things to enhance your work

590
General Mach Discussion / Re: If interrupted, how to resume?
« on: May 16, 2008, 03:58:16 AM »
Jeff - You may kow a lot of this - but here goes -

Your machine needs to know where it is. The professional way it to have switches fitted on the machine, then you just say to the machine "Ref all home" and it does. It sets all the DRO,s to zero. This position is 0,0,0 in machine co-ordinates and shows on the DROs when the Machine Co-ordinates button is pressed and the button is illuminated. You can only zero machine co-ordinates by using the "Ref all Home button". The button zero,s any DRO that does not have a home switch designated, and it moves any other axis to the switch, and then zero'0 the DRO if it does have a home switch.

This position could be anywhere, and is probably not a convenient poisition from which to start machining, and will probably not be the start position from which your GCode position was written. We will assume that position is in the centre of the table, and you have fitted some studs, poking up from the table, onto which you put your workpiece. (All the other workpieces you are going to machine also have stud holes and will fit in the same position)

The GCode is written to start at the bottom left hand corner of the workpiece - which the program knows as 0,0 (X and Y). Z0 is the top of the workpiece.

To reconcile the two is the job of the "offsets"

You start with your machine and "Ref all Home". This sets the Machine Co-ordinates to 0.0.0. and the machine knows where it is.(If you have limit switches - and your Z is homed to the top of it's run) You then jog your machine to the start position for your work. At this stage note the readings on the DROs. Press the Machine co-ordinates button and the button surround will go out. The DRO,s will not change BUT they are now showing "work co-ordinates or program co-ordinates" and can now be zeroed. If you zero them, they will change to 0,0,0  - in line with your program.

You can now start the machine and away you go. - What have I achieved you ask - well you have the "offsets" which you noted.

You can enter the offsets in the offset table - I don't bother with the offsets page - I put them straight in the table. Offsets are numbered G54 to G59 - and G59 has 255 sub groups so there are plenty. We will assume that you enter the offsets for this program in G56.

When the man presses the Fire Alarm you say "Up your's" and walk out. When you come back you press the button for Machine Co-ordinates and  " Ref all Home" - the machine knows where it is (quite important because E stop sometimes causes missed steps).You then enter the "offset" on the MDI (G56) and switch to program co-ordinates. Tell the machine to go to G0 X0Y0Z0 and the machine will move back to the position that you started machining. Start the program and away you go.

The offsets can be made fully automatic, in that they can be entered in the program. The program can "Ref all Home" and then enter the offsets. You can, at the end of the program, change to "Absolute Co-ordinates" (another name for Machine Co-ordinates) and move your tool out of the way of your work. If you change your workpiece by mounting it on the studs I talked about, then start the program again, the machine will reference itself, move to the work, cut it, and then return, ready for the next one.

To clear up any more problems, have a look at the tutorial on Co-ordinates, which deals with the subject step by step.

The toolpath display on Mach 3 is very good and I find it a great help when writing programs. It does respond to the "program" entered in the GCode - i.e. it takes its 0,0,0 position from that. What you must be careful of, however is the position of your Machine/Program co-ordinates button - and if you press this, then also regenerate the toolpath. There are some errors in the display, however, particularly when dealing with osffsets and sub-programs, so don't take it as gospel.