Thread: It's begun....
Just for giggles I set up my machine to where it stalled and then backed it off. Now this is a rough set up and I have NOT gone back and tuned the drives so that would change things as well. Given that I was able to get x(x/c) axis up to 17m/min V with 450mm/sec^2 A; Y axis was gotten to 11m/min V with 350mm/sec^2 A and Z to 7.5m/min V with 250mm/sec^2 A. Let's just say that is a bit scary in speed.
-MichaelLife is Live it
CAD software VIACAD Pro v9 (Beta testing x64) Also Aspire v8
CAM Software Aspire v8, PhotoVCarve, CamBam
Machine: Custom built see build log: http://www.mycncuk.com/threads/3661-...Second-machine
Work with Solid Surfaces, Acrylics, Woods, Foamboard.
Wow - effective limit switches are a must at those speeds I expect ;)
Even 4m/min was hairy compared to what I've been used to previously when I tested it last night.
Oh and a quick question or two: I'm running the same test job "cutting air" to see what progress I'm making as I make mods etc. to the machine and I notice that whatever max speed I set the motors to is what the test run seems to use as its rapids - I'm assuming that's normal behaviour?
The other thing is when I first power up and load MACH3 the motors always seem to need one axis setting up in MACH before they "remember" the settings from the last session?
Quick update (no pics or vids yet).
Last night I completed the mechanical option for running two ballscrews (I still have parts for plan b if needed), by adding some extrusion bracing and additional bearing to the long "bendy" extension on the back of the 2nd ballscrew. Alignment was surprisingly easy, as it was a case of using the already aligned ballscrew and using a transfer punch to mark, drill and tap the new bearing mounting holes. Things are much more sturdy there now.
I have also added a 3rd pulley mounted on more extrusion and an axle, which I can adjust up and down to increase or decrease tension on the belt (better than what my car engine uses methinks :) ).
So ran some tests - 4,000mm/min was no problem at all, so upped it to 6,000 mm/min and its still fine, but getting quite scary at that speed (I'm wondering if I should back off of 500mm/s/s acceleration?).
I'm going to start some cutting jobs, once I have solved my VFD issue (see other thread in Electronics section) and then its back to the feeds and speeds learning curve :)
For example, in this video I set the acceleration lower and put a bigger pulley on the motor, and got 60m/min:
... but it's not terribly useful.
Love those Ball nuts
Like Jon's says it a compromise of velocity or Accel so if your happy 6mtr/min then wind the acceleration up until motors stall and then back off 10-20% and you should be fine.
Yes, clearly if you set the acceleration higher you want to test the system thoroughly to make sure the motors wont stall. After doing what Jazz suggests, I suggest running some code from here:
Then you can change from 'should be fine' to almost certainly fine.
Some progress tonight, whilst I had some "workshop time".
I decided to do a complete re-wire of the VFD a. to give me some more space with the machine and b. to ensure that the old stuff was not at fault. I also replaced the RCD in the workshop and now rely on the RCD at the consumer unit which feeds the barn/workshop where its split off from the main house supply.
The VFD fired up first time and still had my old settings in it, which was nice. So I then ran a quick 2D job on some 6082 aluminium, which was very light work i.e. one central 3mm drill mark at 0.1mm deep and then 4 surrounding 6mm "dowel hole" marks at 2mm deep using ramping. Used a 3mm 2flute carbide bit at 16800rpm and 800mm/min. The job itself ran a treat apart from 3 spurious e-stops (tried a debounce setting in MACH3 of 1000 and 3000, but still had a phantom e-stop). I'll have to check earthing continuity on all the CY going back to the control box, as I know my spindle is earthed back to the VFD and the CY carrying the spindle cables is also earthed at the VFD end only i.e. no loop.
Interestingly I checked continuity/resistance from the spindle to various parts of my machine and I'm getting negligible readings from the spindle, through the gantry and all the way to the main frame.
Still some progress and light possibly at the end of the tunnel - at least the job I did complete showed very little grumbling from the tool and ripped through what it did have to do, with nice chips, which gives me some hope that I can start doing something other than work on the machine and make the machine do some work for a change ;-)
More as I get time....
Another quick update:
I still have spurious e-stops, which I thought I might get rid of by running the VFD off of a circuit in the workshop which does not go through the dado trunking next to the control box supply, but to no avail. Also checked all my earthing for the control cables and that is OK i.e. CY shielding going back to the control box star point, with good continuity. Also tried Mach3 de-bounce settings up to 3000. Only thing I have left I think is I replaced a big chunky, but very long (3mtr) parallel cable with a shorter one, so will switch that back to see if there's an improvement.
On the bright side, to do the testing for the spurious e-stops I ran a job in beech block just to try and the following pic resulted, which despite the e-stops probably losing steps when incurred, is at least something and came out nice and clean apart from where the wood won't hold the very thin details. The 3mm end mill went through the wood like it was not even there (ran at 18600 rpm at 800mm/min on a 3flute), so aluminium next :-)
BUILD LOG: Web Goblin cnc has begunBy Web Goblin in forum DIY Router Build LogsReplies: 147Last Post: 12-02-2012, 07:49 PM