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If you deal with CNC machines, cutter movement must come to mind. Yet G-Code can also do math and logic. This article introduces a few of these commands and then explains a program that drills an array of holes.
If you are interested, please see
https://rick.sparber.org/GcodeLogic.pdf
Your comments are welcome. All of us are smarter than any one of us.
Thanks,
Rick
I see more than 400 people have at least started to read this article. It is my first attempt at explaining G-code and I'm not sure if my assumptions about the reader's background are correct. Please let me know if you felt it was too simple, just right, or too complicated.
Thanks,
Rick
Thank you for the detail on the GOTO and IF-THEN-ELSE G-code Commands.
Rick,Quote:
Originally Posted by rgsparber
Your post has a limited readership, almost by definition so it would not be wise to limit it further by aiming it only at those with a higher starting knowledge. I think that you got the level about right. I assume that only those who have manually written G-code would be interested and so there should be no need to assume a lower starting level than that. For completeness you could add explanations of subroutines as well.
If I had to criticise, I would say that you might retain reader interest longer if you gave some very brief examples near the beginning of the document rather than starting off with the meat. As it is, you start off with "here is some great stuff that you might not know about", I imagine some readers thinking "so what?" and going elsewhere. If initially you showed some examples that would be long winded without these techniques and then offered them as a solution I think that more readers would stay the course.
My comments should be taken as from someone who has written engineering application software since 1960 and who regularly hand codes G-code. For me there was nothing new in your post so maybe i do not have the best perspective to comment on the level for your expected/intended readership. Take my comments with that in mind.
Great suggestion. How does this look (see page 2): https://rick.sparber.org/GcodeLogic.pdfQuote:
Originally Posted by tonyfoale
I have also rewritten the explaination of the code example. As the author, I am unable to see what does not work for the readers so PLEASE give me your comments.
Thanks,
Rick
As an author of two technical books as well as a contributing author to other books and 100s of magazine articles I am only too well aware of the difficulties of determining how the average reader interprets one's work. This applies much more to technical works because it is hard to strike the right balance between those with the minimum starting knowledge and those with much more. It is easy to lose one extreme or the other if the balance is wrong. I do not read fiction ( never get past the first page when I have tried ) but I guess that these considerations do not apply to that genre.Quote:
Originally Posted by rgsparber
I think that your page 2 additions are much more likely to suck the reader in. Great choice of variations on the same theme, very clever. You state that conditionals and navigation statements will be discussed but then you start talking about variables without initial explanation. I would suggest an early mention that variables are useful in conjunction with the conditionals and navigation statements.
Thanks Tony, changes now implemented. https://rick.sparber.org/GcodeLogic.pdfQuote:
Originally Posted by tonyfoale
Rick
I used to program& run cnc mills back in the mid 90's ( hurco mills) a lot of aerospace stuff, DOD mill spec stuff& prototype stuff. the boss said I did not want to try to learn G code for the other machines....I did some checking and reading and...he was right. I liked the simple programing the hurco's have. I dont understand why everything isant simple to program...why still G code stuff.....I sure would love to convert one of my mills to cnc but not if I gotta do the g code. these days I dont think my brain could stand the abuse.
You have to have some means of transferring instructions to a machine and it is hard to imagine anything simpler than G-code. The stuff that Rick showed could be considered advanced and be a bit intimidating to non-programmers but you do not need to write code using those advanced features. Mostly you can just use the simple commands which reduce down to only two sets of commands. One, to go from where you are to where you want to be in a straight line, and two, to do the same on a circular path. e.g.Quote:
Originally Posted by marksbug
G1 X20 moves in a straight line 20 units (usually inches or mm) in the X direction.
G1 X15 Y10 Z5 moves the tool or work piece (depending on the machine type) in a coordinated fashion to the position (15, 10, 5)
If the tool centre is at (0, 20) then either of the following will cut a path to (20, 0) on a clockwise circular arc
G2 X20 Y0 I0 J0 (I and J are the absolute coordinates of the centre) or G2 X20 Y0 R20 (with R being the arc radius)
I find it hard to imagine how you could transfer instructions much simpler than that. In any case many machinists do not manually write the G-code. CAM software takes a CAD drawing and spews out the G-code for you. I don't use CAD and so I either write the code manually or write my own software to generate the G-code for specific purposes. You can also do a lot of machining using wizards ( pre-written G-code often called "conversational").
Thanks Rick! We've added your Gcode Methodology to our Machining category, as well as to your builder page: Rick's Homemade Tools. Your receipt:
<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="http://www.homemadetools.net/homemade-gcode-methodology"><img src="http://www.homemadetools.net/uploads/222076/homemade-gcode-methodology.jpeg"/></a></div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="http://www.homemadetools.net/homemade-gcode-methodology">Gcode Methodology</a> <span> by <a href="/builder/Rick+Sparber">Rick Sparber</a></span> </div> <div class="tags">tags: <a href="http://www.homemadetools.net/tag/electronics">electronics</a></div> </div> </div> </div>
I guess my brain needs to see it in "3d" on a good size screen when Im programing so i can see the finished part before I ever push start..it's been years since I did it, but only about 30 minutes of instruction from the boss and I was off programing without any issue..with a good print. a month lator I was programing the 3d milling and making stuff out of my head.I cant see any thing being easyer. I dont recall exzactly why he called it other than simple programing code ,but he said it was way faster and 4x eazer than "G" code. ,the older hardinge lathe was "G" code, I ran it some but didnt program it. I was the only one in the shop that could do the 3d programing for some reason. we only did a little of it for some mold injection dies.not needed for most stuff ,we only had 3-4 axis machines at that time.I dont know what he has now the small company with 5 employes at that time has grown to....around a hundred or more now. in 2 or 3 locations. I kinda wish i had kept up with him....it would be great to be on the "night crew"...I used to build a lot of stuff for his toys.never made squat for my self...well I did make 1 seal die for making a molded seal for a floor jack....what a waste of 30 min,it worked but...I bought a new aluminum floor jack a month lator,and never used that heavy steel one again. I wish I had patented or just marketed some of the stuff I made out of my head back them.like the swivel exhaust for the off shore race boats so they stop cracking the water jacketed ss exhaust they have.it worked great on his boat.them boats take a hell of a pounding and flex like hell.
Thanks Rick,
I found the level perfect for me, not quite a professional machinist yet but want to be. For some reason with the skills shortage they want me to be a snotty nosed teenager - go figure. I have some programming experience in C# and VB so if then statements etc make perfect sense. I have had colleagues in the past read my technical notes and complain about them being too complex. It really is a hard balance to find, anyone can find fault with anything if they try hard enough. I used to receive a lot of technical instructions for work with BP (British Petroleum - now Best in Performance as its no longer British) being asked to comment on the accuracy of the instruction. I cant believe how many Senior engineers couldn't write to save themselves. Double word entries, spelling mistakes really crap punctuation and that's without finding any error in the subject matter. They obviously needed their degrees and masters to be condescending and dumb. We were absolutely hammered one day about weather limits and when and if the job could go ahead - all documented in the Technical instruction. Unfortunately the whole section in the file had been left out, oops. Sorry rant over.
The subject you have chosen to write about is something that fascinates me immensely. Using GRBL freeware as a machine controller with its limited command set leaves guys at the self build hobby level trying to find antiquated coding techniques to achieve results where the Gcode commands are limited. I find that learning Gcode from the ground up is something that should still be studied even though conversational and canned cycle code is now the norm. To understand what the machine is doing rather than not doing what you expect it to do is much better that having no clue at all. So to speak.
I would like to call upon you to indulge us further with such coding mysteries, i have had no issue understanding all 3 iterations of your document.
There are a few snippets of code i have found on the tinterweb to perform such functions as peck drilling, PCD's and auto seeking part zero's based on G0 & G1 moves only (GRBL code set being limited). Its hard to find basic coding techniques on the web which allows for complex canned operations to be carried out on hobby or self build machines. If you were to continue along those line with this thread then i would be much obliged. Particular code i'm looking for at the moment is to locate zero work coordinates based on circle centre.
Found this guy and i'm currently trying it out.
https://www.youtube.com/watch?v=thmX5ng00cs
Sadly the only way i can try the code from your example is using Macros.
still a good learning source.
Jason,Quote:
Originally Posted by MeJasonT
As an author, I find that it is best to first have a clear vision of the intended audience. Then start writing. Nothing worse than an article or document that jumps around on level of detail. However, it is certainly an art form and not a science. One thing that helps is to structure documents similar to newspaper articles. Start out with the conclusion, then give the high level view. Continue to go into more and more detail until you are done. No need for any fancy ending.
It is great that you are understanding the basics of G-code before dealing with machine generated files. You didn't mention your background, but having experience with manual machining is essential in understanding G-code and CNC.
If you are interested, check out https://rick.sparber.org/ma.html#Mill for more on CNC.
I have spent the last 10 years teaching engineering to "snotty nosed teenagers" (and older) at a local community college. They have taught me a lot during this time and it is also great fun.
Rick
Thanks Rick,
I clicked on your website link and realised just how many of your articles i had looked at.
Thank you for the advice on authoring, hopefully its something i will remember and refer back to.
The opportunities for people across the pond are far superior to those in old blitey. Our local college no longer teaches engineering and electronics but uses a private company to do it instead, the only way to do courses now is to be an apprentice or have your employer send you. not possible to walk in off the street and do short courses any more. The College sold off the 1x Lyon CNC Miller (i've never heard of one either) and the 8 Craftsman lathes. To say i'm disappointed is an understatement. I often bump into the retired Machine shop instructor (Tony Britain), oddly enough at car boot sales.
With regards my background,
I started my studies in electronics, joined the Royal Navy - got stitched up by Drafty and ended up a marine engineering mechanic.
I left the RN and started a career working with submersible vehicles (ROV's). There has been a few different jobs over the years but always an extension to my skills.
Now working for myself, attempting to run a job shop and producing garden architectural pieces and sculpture. Kind of given up on working for others as they were to eager and to quick to write me off. I have an old Elliot milling machine which i have converted to a CNC, a self built CNC plasma table and an Imported lathe like the Grizzly model B which will not become CNC - it just goes round and round whats the point lol. I caught the bug when i built a 3D printer, with my knowledge of electronics the rest was child's play.
My plan for the next 10 years is to become a humble middle aged machinist before i'm forced to retire, That plan is not going so well, companies, kids, skills shortage ha ha and nowhere to retrain. so fingers up at them and i will prove i can do it for myself. But still living in hope. I could always move out of the third world county which concentrates all its effort on becoming a theme park for tourists.
Rick
Just popped out and snapped a couple of pictures for you
Attachment 29549
Attachment 29550
My Electronics Shop, ROV pictured under bench on right.
Attachment 29551
And just to show your excellent instruction does reach the masses (please ignore the milky crap in the coolant reservoir)
Attachment 29552
Looks complicated. I grew up in a machine shop and during that time CNC came along. First with punch tapes, and progressed from there. But i was always involved with the second operations that CNC couldn't do at the time. Lately I have entertained the notion of a CNC router, but it's all the programming that has kept me from it. But keep up the good work.
It looks complicated because G-code is a very primitive programming language. In something like C++ it would be a few lines.
I recently aquired a CNC router/engraver for my "retirement" fun. I have not set it up yet but I have downloaded your information for future use. CNC has been on my bucket list for a long time and perhaps your post will help me along? Thank You!
