Doc's Patented Stupid Questions Thread!

[DocsMachine]

You'll have to forgive me a bit, gentlemen, but I am, in fact, a bit stupid when it comes to both the Acorn in particular and CNC in general.

Apart from a Shapeoko router, which I have about an hour's total actual time on, my converted Logan lathe is the first functional CNC I've ever used. Prior to these, I'd rarely even been in the same room as a CNC... well, anything. I'm not a complete dolt- no matter what my mother says - and I have a good overall concept of how they work (as well as a pretty solid idea of how they work mechanically- the hardware is the easy part. )

But I'm still very green on the actual use and application, that is, pretty much everything from tool offsets to even just loading new programs into the system. (I don't even have any new programs. I haven't gotten that far yet. )

As such, considering I have pretty much zero options for local mentoring (I may have the only Acorn in the entire state of Alaska) I need to lean on some of you fellows to answer my stupid questions. And I'm sure most of them will be stupid, but as they say, the most stupid question is the one you didn't ask.

To start with, I have a first-gen Acorn, currently running version 4.12, with a wireless MPG, feeding two Automation Technologies "hybrid servo" motors with encoders. The encoders only feed back to the drivers, not the controller, and basically just watch for slippage/missed steps. (They fault out and stop if that happens.)

I recently upgraded to 4.12 to activate my MPG, and after a minor glitch or two, it's working as it should, barring an ongoing issue being discussed in another thread.

I just spent this afternoon, as I was digesting my way to more pie and maybe some more German mashed potatoes, setting up the first four tools in the tool offset library. I happened to have some of the tools already listed by default in the CNC12 software, so I just set the offsets for four of the first five or so (55 degree diamond, 80 degree diamond, .125 parting blade, and OD threading tool.)

I then set up a chunk of 1" bar in the chuck, hoping to turn another pawn, and set the work offsets.

I thought I had at least the minimum amount of information for the lathe to make the pawn- I've done one before- but when I press cycle start, the carriage zooms off to the right, hits the limit switch, and cancels the job.

So, first stupid question: What should the machine do when you start the pawn?

I assumed that, as it'd already been homed, and the tool offsets set, that it would have started the spindle (it didn't) and started moving the tool into position. When I saw it heading to the right, not the left, I assumed it'd home itself, then go find the workpiece, but it didn't do that either.

Sorry, I just simply don't have enough experience yet to know what it should or should not be doing, and that makes it very hard to know what needs to be fixed or adjusted.

Doc.

[Hugham]

Hello Doc.
Look at Keiths video on setting tool offsets and there you will find out how to set you G28 return point.

I think that is all you will need to set as you are homing to switch, as opposed to simple home

You are not alone at this point in you learning curve and I for one am pretty much the same place with the
lathe .

Hugh

[DocsMachine]

Well, I was going by the manual, and set a return point... or at least I thought I did. (Which is notable as I didn't set one, when I ran the previous pawn.)

But I'd watched the video a while back, and was going by the manual this time. I'll give it another watch. (I also found Franco's "cheat sheet" and printed that out. I'll double-check my work in the morning.)

Doc.

[Dave_C]

Just a thought here: Your G28 settings will be in machine coordinates and not part coordinates!

So if your lathe homes all the way to the operators right hand (it normally would) then that becomes the "Machine" zero. So your G28 numbers will be negative numbers, not positive numbers.

The part zero then (for Z) will be the end of the stock if that is where the G code wants zero to be. (It does not have to be the end of the stock but that is the most common for a lathe)

So after the machines homes, you still have to go through the steps to set your part zeros.

Dave C.

[tblough]

Return Point is not a magical thing. It's the place where the machine will go at the start of the program to allow you to load the first tool. It's the point the program will go to whenever you program calls a tool change, and it's the last place your tool will go when the program ends.

When you finish setting your tool lengths, put your longest/largest/most badass tool you are using on the job, and then position the tool a comfortable distance away in X and Z from your part. Comfortable means enough room to change the tool, but not so far away you are waiting all day for it to move to and from a tool change.

With your machine positioned, go into F1 Setup/F1 Part/F9 WCS Table/F1 Return. Centroid switches automatically to machine coordinates in the DRO. Just copy these values (round up or down to a decimal place if you want - it was arbitrary after all) into the X and Z values of Return #1.

That's it. That's all you have to do and you will probably want to do this on every job. Of course you can set the return point at the travel limits and you'll never have to set it again, but you'll wait all day for the machine to move at the start and end of your jobs. If your part size changes, or if you change from a collet to a chuck, or if your tools change, you'll need to change the return point.

Of course everyone graphs their program before running it, right? Run the graph with the feedrate knob turned down and you can watch the graph get drawn step by step. If you ever see RED RAPID LINES moving through your part, SOMETHING IS WRONG. If it happens right at the beginning of the program, it's because your return point is set wrong.

[DocsMachine]

With your machine positioned, go into F1 Setup/F1 Part/F9 WCS Table/F1 Return. Centroid switches automatically to machine coordinates in the DRO. Just copy these values (round up or down to a decimal place if you want - it was arbitrary after all) into the X and Z values of Return #1.

-See, I did that. That's basically how the manual spelled it out, even noting, as Dave did above, that the DRO automatically changes to the different coordinates.

I can't say with perfect certainty I did the procedure 100% properly, but the instructions aren't that convoluted, and i can say at least that I thought I did.

Getting back to my original question, what should the machine have done? Since it was, at the time, still sitting at that return point, should it have simply headed straight for the workpiece to begin the cut?

Also, I was wondering if the pawn program included a spindle start command. My spindle was still manually started and stopped last time I tried this, but now it's under Acorn control. Will I need to start the spindle manually when I try this again?

Doc.

[Dave_C]

Doc,

Can you cut and past the first few lines of the Gcode so we can take a look at it?

Dave C.

[DocsMachine]

Dave- the program is the "pawn" program that comes preloaded with the lathe software. At the moment I have no idea how I'd copy and paste part of the program to show you.

But, on that note, can anyone tell me how big that pawn is supposed to be?

I ran one about a year ago, when my controller was still very much a prototype- that is, nailed to a literal board. I finally managed to turn another one today- after merely two crashes, and being utterly unable to successfully repeat the event- but it's bigger than the first one. height's the same, with some variance as I hand-parted both on a different lathe, but it's 'fatter'. Clearly even though I got it just good enough to work, I also clearly had the X set too far positive.

And I'm not sure which one's correct. I assumed the first one was, but that, too, was blind luck, and could have been mis-set.

Also, I'm clearly doing something wrong. I've been following Franco's "cheat sheet" for setting part zero and tool offsets, pretty much to the letter, and I keep getting different results- usually crashes- every time.

I've watched virtually all the videos I could lay my hands on, is there's a "for idiots" video or write-up or instructions out there somewhere that I haven't found?

Doc.

[Dave_C]

Hey Doc,

At the moment I have no idea how I'd copy and paste part of the program to show you.

The manual shows you how to go into gcode edit mode. From there you will be in wordpad or whatever text editor you set up to open. From any editor you can copy and past the text and your clipboard will hold whatever you copied until you come here and paste it into a thread.

If you pawn came out to fat, then your X is not set true to the centerline of the lathe.

As far as the size of the Pawn. Just look at the program and see how far the Z axis moves from part zero? It is about 2" I think. [I don't have the program open]

What concerns me is that you are not getting the same results each time you run the program. That would make sense if you aren't getting your machine set the same each time.

Just another thought, have you checked your axis travels to see that they are "spot on"? In other words, when commanded to move 1" does the axis actually move 1"?

Dave C.

[Johnnytoro]

I've got a more stupid question...lol. Hate to use this as my first post, but as you get older hair becomes something you do t want to rip out of your head. About a week ago the graphing trail disappeared and I haven't been able to get it back f9 doesn't work and a reinstall of the mill software didn't do it either. Any help in this matter would be greatly appreciated. BTW thanks to everyone who contributes here. Tapping into the threads really answered most every question I came across and save a lot of hair.