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Offline BR549

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Re: Physical buttons for plasma
« Reply #230 on: February 05, 2016, 02:46:01 PM »
Dave if you ever get a chance try a 5-8mm pitch on the screw/direct drive . As is you run out of motor speed/accel  before you run out of THC responce speed (motor stalls first)

Offline Davek0974

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Re: Physical buttons for plasma
« Reply #231 on: February 05, 2016, 03:17:51 PM »
Yes it would be a pretty easy swap too, 10mm trapezoidal screw fitted i think, will make a note and look out out for a steeper thread, i think 744rpm is right at the top of the scale for a nema23 on 50v and getting it lower would be good.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Physical buttons for plasma
« Reply #232 on: February 05, 2016, 04:41:36 PM »
Thanks for the numbers Dave.

What travel, dia etc of screw do you use. I may have a spare 10mm pitch ballscrew if I can find it, not seen it for a while but I know I bought more than one. It is 25mm dia screw and a fairly long nut on it and it has been shortened, prob about 100-120 travel, I originally had it fitted to the quill on my very first retro, a manual Bridgeport.

Hood
Re: Physical buttons for plasma
« Reply #233 on: February 05, 2016, 05:01:58 PM »
I'll get my specs later in the weekend

Suggestion on quicker z axis... Plus machining
http://www.ebay.co.uk/itm/251405700798

I've got to do a redesign on mine first (I know and am greatful for Russ' offer.... But I really need to do a redesign first)

I must say I am impressed with the ground and info covered and gained in a thread about buttons... Haha
« Last Edit: February 05, 2016, 05:04:35 PM by robertspark »
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

Offline Davek0974

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Re: Physical buttons for plasma
« Reply #234 on: February 06, 2016, 03:31:31 AM »
Thanks for the numbers Dave.

What travel, dia etc of screw do you use. I may have a spare 10mm pitch ballscrew if I can find it, not seen it for a while but I know I bought more than one. It is 25mm dia screw and a fairly long nut on it and it has been shortened, prob about 100-120 travel, I originally had it fitted to the quill on my very first retro, a manual Bridgeport.

Hood

Thanks for that, mine is only 10mm dia, i have emailed the maker as they do offer a 10mm x 4mm pitch screw that is a direct swap-in, that would be a nice easy upgrade. Its a two-start version of the standard unit.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline stirling

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Re: Physical buttons for plasma
« Reply #235 on: February 06, 2016, 05:20:09 AM »
Hood - 3Nm size 23 stepper motors. direct drive via mod1 rack n pinion with 15 tooth pinion.

Question to ballscrew/linear rail users - how do you protect them? Honestly not being funny here but unless you use bellows and such I just don't get how they survive.

Offline Davek0974

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Re: Physical buttons for plasma
« Reply #236 on: February 06, 2016, 05:49:36 AM »
Same R&P setup as mine Stirling, I have 4Nm motors though.

I was pondering ballscrew when I built my table but your point was one of the reasons i did not use them, the rack on my gantry (X axis) is exposed and I have concerns about that. The Y racks are nicely tucked away under cover plates on the sides and so far have remained clean. I fitted double wipers and muck scrapers on my linear blocks - it tightened them up a bit but hopefully will extend their life, I also grease regularly to flush any muck out.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives
Re: Physical buttons for plasma
« Reply #237 on: February 06, 2016, 07:36:20 AM »
My Z axis is the same as Dave's .... 10mm dia x 2mm pitch trapezoidal leadscrew with a delrin nut
(Marchant Dice)
http://www.worldofcnc.com/collections/trapezoidal/products/delrin-nylon-round-right-hand-lead-single-start-nut
http://www.worldofcnc.com/collections/trapezoidal/products/tr10x2d-trapezoidal-right-hand-spindle-leadscrew-din103-c15-c35

I did consider a 4mm pitch.... but would like to make a bit more of an improvement, as my travel distance is about 135mm and I have a 4th Axis (modified rotary table) that I'd like to integrate for doing lobsterback exhaust parts and roll cage / hoop bits.

My X and Y are HTD 5mm pitch belt drive, with direct 20T pulleys.

All belts are mounted on the outside of  the rails (opposite to the plasma torch) hence shielded from muck

The leadscrew is not really in the direct line of blowback as there is quite a bit in the way.

Belts are tensioned using some manufactured springs similar to what the 3d printer crowd use with their 3mm belts.
http://i.ebayimg.com/images/g/tEgAAOxyBotTWzgV/s-l300.jpg

Backlash is not much at all and not really something I'm concerned with too much with a blunt tool like a plasma (but I'm not doing artwork etc)

I have about 0.16mm (~6 thou) of backlash on the belt drives, but I suspect its the nature of using belts

All my motors are the same as posted earlier 3.1Nm.

I have been fiddling with my settings this morning given I can get higher acceleration that what I was running X and Y and both higher velocity and acceleration Z.... although I need to test it under instant acceleration of (slap and go) of THC as I dont think I had it set up the best following earlier discussions on here as I've learnt a lot.

My X and Y run 10uStep (0.05mm/step [~2 thou], Z is 1/2 step (0.005mm/step [~0.2 thou / step])

The Z can clearly been improved upon given that sort of resolution is not required, I did consider full step (but not sure what others run step/ unit wise on a plasma table)

I don't use backlash compensation.... but I can and hence the 10uStep resolution would tie in nicely with the ~3 steps of backlash compensation.

Again not sure what others do....
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

Offline Davek0974

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Re: Physical buttons for plasma
« Reply #238 on: February 06, 2016, 09:13:37 AM »
ok, some results from the test files...

3mm HR steel, 45A, 4100mm/min, 107v

On one of the very small holes i forgot to reduce my lead-in length so scam removed it for me hence to nasty divot.

I'm still messing with actions on corners, they are a mixed bag i think, slightly better internal corners but a little wiggle when the speed drop kicks in.

Be interesting to see how they compare.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Physical buttons for plasma
« Reply #239 on: February 06, 2016, 11:04:43 AM »
A little video i made this morning on 3mm Alu, at 1.10 you can hear the Z axis skip the rapid part of the G28.1 routine, it does this a lot but only when doing G28.1 I have tried using the MDI to do it and also the keyboard but so far it only ever skips on G28.1 and not every time either ???

I didn't realise it at the time either but from 1.10 onwards it is doing the last cut on the part and the material warps up about 15mm and the THC tracks it nicely so I think that's working OK, you can also see the motor spindle at the top and see it dip slightly on the corners, I have no idea if it only dips a little because tip-saver or anti-dive kicks in or just that its rounded the corner before it goes too far but it only drops a little.

Could really do with inset synced video of Mach screen :)

Too many things to watch in a short time

https://youtu.be/fgg7F8H7vno
« Last Edit: February 06, 2016, 11:12:22 AM by Davek0974 »
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives