[CNC] CNC from sketch to part the way I do it

[jumps4]

Thank you for your kind words FreeIdaho
I'm glad the videos are helping people
My latest project is designing a 15' x 6' x 8' tall cnc surfboard shaper/hot wire foam cutting machine for a friend and fellow member. I have just started drawing the parts today and I'm designing as I go. I have a picture in my head, now to get it in a dxf format. this machine is being designed to run at speeds of up to 500ipm rapids and will average 300ipm while cutting.
I have included the spec sheets for the plastics I'm considering for those who think I'm crazy it wont work. :nuts:
these plastics are self lubricating with a 7500psi load bearing, non-breaking, coefficient of friction as low as .02-.08 and temps of up to 500 degrees F.
thank you for viewing
steve

[video=youtube;-0zAVJsetWk]

 

[jumps4]

I haven't done anything here for a while and the shaper is on hold waiting approval so I thought I would post a project I just completed here.
These are handles/latches for the skylights in a 53' yacht, the original ones were made out of plastic and cracked, probably from sun load.
So I made a drawing of the contour shape and cut new ones out of aluminum.
I'll just post all the pics including the drawing of the contoured shape. I hope the order comes out right
thanks for viewing
steve

 

[jumps4]

In this video I'm going to start showing what I have learned about gibb adjustment and backlash compensation. i'll have to break it up into a few videos to keep them short, that away I'm already set up to do what I want to show.
I'm not trying to be a know it all and any corrections are more than welcome.
hobby cnc machines are different in the fact they have to deal with a lot more friction and adhesion problems not encountered in factory machines with roller linear rails, guide ways and massive ball screws . there are ways to improve these faults but not eliminate them totally in a hobby cnc conversion.
I chased my own tail for years until I understood what was happening under my mill table.
In this first video I talk about what I have learned about adhesion, torsion, friction, flex and stored motion
thanks for viewing
steve

[video=youtube;CfsiZ-6D0W4]

 

[Dan_S]

Great video Jumps.

This is one of the reasons I want to use dual closed loop servos when I eventually get around to cncing a mill. It's a lot more expensive to do, but it takes care of some of these issues for you.

 

[jumps4]

I did some research about a year ago on direct reading scales in each axis directly reading table movement and their use with mach3 and emc2 and at that time the only controller card I found that would support linear scales with custom written software was kflop by Dynomotion. I spoke to the man that designed the card and wrote the software for it and he said he could write me the software but the best mach3 could do with the information was to stop if a preset error level was triggered. if mach3 thought it was at one reading and the scales showed a different reading it would stop mach3 from running. at this time mach3 would not support error correction by moving the axis to where it should be or stop the travel if it is going to overshoot. I figured I could do that by measuring the part after the software ran and didn't invest in it until better software comes around at a hobby price. maybe mach4 will be able to self correct but it's still in beta. when they finally figure out how to do that the sloppiest machine built will make great parts because it wont allow an error to take place. that's going to require a lot of processor speed and programing to look ahead and determine prior to it taking place there will be a problem.
steve

 

[Dan_S]

Yea, that's what I was referring to, its talked about on these pages.
http://www.dynomotion.com/Help/Mach3Plugin/Mach3.htm
https://groups.yahoo.com/neo/groups/DynoMotion/conversations/topics/2297
http://dynomotion.com/Help/CoordinatedMotion.htm


as I understand it you take, mach3 out of the equation. the dynamotion mach 3 plugin converts the gcode to coordinate motion commands that get sent to kflop and stored in memory. this offloads the actual control grunt work to the kflop. you feed kflop 2 inputs per axis. A linear encoder provides position feed back and a rotary encoder on the servo or ball screw provides velocity feedback. You feed this into a custom C script that runs on the kflop to adjust the output signal to the amplifier that's feeding power to the servo. If I understand everything correctly you would need a kflop a kanalog and a couple snapamps, so the system would not be cheap.

 

[jumps4]

I'm a member of the yahoo group and followed it daily until a few months ago
there is way too much code work required to operate the system and you have to do your own code work
it has been in beta since I first read about it with no stable release to date
at the time I stopped reading it daily there were nothing but " how do I code this " questions on the forum
at my level or lack of knowledge I should say, I didn't want to take on learning the code to run a hobby machine in my back yard making no money lol
but believe me I'd love to see it really work.
join their yahoo group and read it daily you will see what I'm talking about
my primary interest in the kflop was speed and it has that but for my needs I settled with a usb uc100 at 100khz and for $149 It has been just great for everything but threading on a cnc lathe, at this time I cant give real time feedback to mach3 to sync the motion to the spindle correctly. but then again mach3 has a problem doing it itself and that's one of the main reasons for mach4, the way mach3 was originally written could not be fixed to hold the sync and required a complete rewrite . mach3 will thread for short distances but nothing more than a couple inches without loosing track and starting out of location destroying the thread.
I'm into building the best I can for the least amount of money invested, trying to keep it in an affordable price so others can play too.
you have my interest back up though I'm going to see if I can find a video of a kflop system up and running.
steve

 

[Dan_S]

you have my interest back up though I'm going to see if I can find a video of a kflop system up and running.
steve

I'm about ready to order a mill (pm45-pdf most likely) and then a bigger lathe probably within the next year and then I'm going to cnc my little 8x14 lathe. I actually want to use kflop for the reason you mentioned threading. I probably have a step on most people though, as I'm a programmer by day and was a computer physics major in college. The biggest hurdle for me will be building up my electronics vocabulary and knowledge, because while I took some basic electronics courses in college, that was 10 years ago, and it wasn't anything advanced.

 

[JimDawson]

I did some research about a year ago on direct reading scales in each axis directly reading table movement and their use with mach3 and emc2 and at that time the only controller card I found that would support linear scales with custom written software was kflop by Dynomotion. I spoke to the man that designed the card and wrote the software for it and he said he could write me the software but the best mach3 could do with the information was to stop if a preset error level was triggered. if mach3 thought it was at one reading and the scales showed a different reading it would stop mach3 from running. at this time mach3 would not support error correction by moving the axis to where it should be or stop the travel if it is going to overshoot. I figured I could do that by measuring the part after the software ran and didn't invest in it until better software comes around at a hobby price. maybe mach4 will be able to self correct but it's still in beta. when they finally figure out how to do that the sloppiest machine built will make great parts because it wont allow an error to take place. that's going to require a lot of processor speed and programing to look ahead and determine prior to it taking place there will be a problem.
steve

This is exactly why I wrote my own CNC control software. After about a year of playing around with Mach3 / Kflop, and Mach3 / Galil trying to get a high speed CNC router to run correctly I finally gave up designed a system that works like I wanted it to.

The up side of my system is that it uses a Galil Motion Control board, the down side of my system is the Galil card is expensive, and may be priced out of the hobby range for that reason. They are available on Ebay sometimes. Some day I may make my software compatible with the Kflop board and some others.

I offload all of the motion control duties to the Galil board, that's what it does for a living and is very good at it. It will run servo or stepper motors, and supports single and dual loops when using servos, and supports single loop and open ended stepper control.

I am using both a stepper and servos on my mill, all with a single loop via magnetic scales. All of the velocity feedback that is required comes from the magnetic scales, there is no need for an encoder on the motor unless the servo drive requires it. There is no under or over shoot, it goes where it is told to go and is accurate to within plus/minus 1 pulse. In my case, 1 pulse is 0.000039 inches (1 micron)

As soon as I get the tach sensors installed, it will also be controlling my spindle drive VFD.

 

[jumps4]

it's good to see more programmers showing interested in hobby cnc and I hope they can get something to market in an affordable price range, I have no problems with mach3 and the uc100 controller running my mills I have built but I have found nothing I feel comfortable with to run my cnc lathe, it works if you babysit it but there always seems to be a lack of trust on my part. my mill I can just install the stock and hit cycle start over and over the lathe seems to lack my trust it just does weird crap whenever it feels like it.
I have just done a redo on my lathe setup this week and will start testing to see if I can get better repeatability.
http://www.hobby-machinist.com/showthread.php?t=8692
steve