operation cnc

[Kerryfisher]

Coming along nicely KC, I'm researching building a plasma table, thanks for some good info along the way, good luck with the rest of the build.

[JAZZCNC]

Jazz will now vote for option 1.

Won't go there regards stalling/racking has it's all been said.!! But there is more to this than just Stalling motors racking gantry's.?

The Main reason why I like it is Synchronization.?
My machine never loses position and the two ball-screws are synchronized exactly the same today has they were when first installed.
I don't have to worry that on long Jobs the machine will lose sync has the slaved steppers drop the odd step here or there running out of sync with each other slowly racking the gantry.

Don't have to worry that after 10-12 hours cutting I'm going to find that holes aren't where there supposed to be.!! Or the part isn't actually square after cutting profile out because the gantry slowly racked fraction of degree.!

The only way to ensure slaved steppers stay in sync is to either have very accurate Home switches or Home to hard stop and do it often. Certainly after every Job to be safe.
Even then if motors are tuned anywhere near close to the edge, esp regards Acceleration, they can easily lose steps without realising on jobs just a few hours long.
On Jobs that run non stop for 10-12 plus hours like litho-pains this could and has been for some slaved stepper users disastrous often resulting in not just in in-accurate work but stalls thru accumulative error over hours.!

Both work and won't argue that fact but I know which works best.!!

[Jonathan]

has the slaved steppers drop the odd step here or there
[...]
On Jobs that run non stop for 10-12 plus hours like litho-pains this could and has been for some slaved stepper users disastrous often resulting in not just in in-accurate work but stalls thru accumulative error over hours.!

I have never seen any evidence of stepper motors on any of my machines loosing 'the odd step'. If it did they would be practically useless - it's either stall and loose lots of step or run perfectly.

If a motor does stall (which it wont if set properly) then it will only start moving when the step frequency has dropped to a low frequency, so it is possible to loose maybe a few steps (or tens of microsteps) if the motion is very small movements which constantly accelerate each motor, but that's still likely to damage the part whether it's one motor or two. Again, if the motors are tuned properly then, just like on Jazz's machine, you wont loose position so it doesn't matter if it's one motor or two. The only difference worth discussing is the input power considered with the whole system - if the basic calculations show that the motor and driver you can afford to use if just using one will perform better than the same calculation with two motors then go for it. If not it's illogical to use one.

[JAZZCNC]

I have never seen any evidence of stepper motors on any of my machines loosing 'the odd step'. If it did they would be practically useless - it's either stall and loose lots of step or run perfectly.

Jonathan I've had to correct stuff you made because the fucking things weren't square or correct so don't give me that bollocks.!!

Also if your going to quote me then make sure you quote the whole fucking picture not just what you want to make fit.!!

Even then if motors are tuned anywhere near close to the edge, esp regards Acceleration, they can easily lose steps without realising on jobs just a few hours long.
On Jobs that run non stop for 10-12 plus hours like litho-pains this could and has been for some slaved stepper users disastrous often resulting in not just in in-accurate work but stalls thru accumulative error over hours.!

Both work and won't argue that fact but I know which works best.!!

[Swarfing]

You can get open ended belt in any width up 30mm in HTD flavour. I used 5M HTD15 on my build of the reinforced polymer type. This works great but out of choice doing it again would stick with screws.

[wilfy]

from a neutral point of view with no experience just thinking about it logically. i'd want to reduce anything that could complicate things.. and to me that means running 1 motor even if that means on this axis you have to buy a big ass one to cope with it.

if your BoB/drivers are running 2 steppers on the same axis then you have 3 circuits there straight away that have room for error... the data comes along in 0's and 1's and all it takes is for a little interference on one driver circuit and one stepper didnt move as quick as the other.. bam your work is knackered and the machine is out of line....

now a single stepper has the same interference but this time the whole gantry didnt move.. only problem you have this time is take the wrecked piece of material shove where you like put a new piece down and start again as the machine is still straight


i'm not saying it wouldnt work.. and i have no doubt that yours works flawlessly jonathan, but my mind tells me to simplify to reduce the chance of error

[Jonathan]

from a neutral point of view with no experience just thinking about it logically.
[...]
i'm not saying it wouldn't work.. and i have no doubt that yours works flawlessly jonathan, but my mind tells me to simplify to reduce the chance of error

That's the point though - by agreeing with that you're agreeing that your logical thinking earlier in the post is based on a false premise, therefore you may not be arriving at the correct conclusion even if the points you are valid. In other words, if my system did have a 'little interference' which caused one stepper to slightly loose position we wouldn't describe it as working flawlessly.

Either way, if you buy the right electrical parts either system can work flawlessly, so in the end it's just a case of working out which is the most economical.

[JoeHarris]

I have not assembled a thing yet and this scares the hell out of me too, with buildings (what I'm used to on a day to day) the tolerances are like 5-10mm no 0.00 something! My thinking for what it's worth is that If you build enough adjustment into the design then you can shim things to perfection later...

[Swarfing]

Guys i really think you are worrying about very little. I've used twin steppers and it was fine. I have belts running my machine with a single stepper on the X axis. It works great for the home machining i do......But! i have two ballscrews sat there ready to change to once i get round to it. If i can make a belt fit to control the screws from one motor then i will, if can't then i will just use two motors. Stick to your budgets up most and don't let bling go to your head. At the end of the day you are machinists now whether you like it or not, your nature will want you to change things later. There is no right or wrong way just preferences? I like both!

[Jonathan]

You can probably just saw off the two flanges then drill and tap some holes in the bottom, then it'll be 52mm wide.

Here's some I made earlier...I've got one left if that's any use to you? I just copied the dimensions of the ones on eBay.