[Mavigogun]

Anybody heard of a welding positioner employed as active 4th axis table and manual or active 5th axis? It may be the tolerances and runout would preclude use- or maybe not. What do you say? Here's an example: https://www.vevor.com/welding-positi...p_010496019988

[joeavaerage]

Hi,
it's not a bad idea.

All the welding rotary tables I've seen are not position controlled though, they have a knob to adjust the rotation speed, but not position.
Neither would I have called any of them a good proposition for CNC use, runout and lash.

I am quite a fan of Atlanta Drives servo reducers. I made my trunnion table out of a '4' size 19.5:1 <2 arc min lash (called a 58 model), and my fifth axis from a '3' size 6.75:1 <1 arc min lash (called a 98 model).
I paid $148USD and $180USD respectively for them new old stock off Ebay.

This is just a random example:

https://www.ebay.com/itm/18239602420...3ABFBMhIeKiJ5j

These units are something like $1500USD new, so Ebay is a useful source of much cheaper but still very usable parts.
Nor would I claim they are perfect for four/five axis use, but if you are on a budget they are bloody hard to beat.

This is my trunnion table and fifth axis. the whole thing weighs about 85kg, just to give you some idea of the scale. The motors for each axis are Delta 750W B2 series servos.

Craig

[joeavaerage]

Hi,
if you are looking then:

Atlanta 58-43-239 Servo-Drive System Gear Reducer

The '58' refers to the model, with 58 meaning High Performance and <2arc min lash.
Were the first two numbers '98" refers to the High Torque model and <1arc min lash.

For CNC purposes really only the 58 and 98 models need be considered.

The first digit of the second group, in this case the '4' of '43' refers to the size of the gear reducer. The 4 = 63mm between the centreline of the worm and the centre of the worm wheel.
This gearbox will weigh around 9kg, and have a max load of 400Nm (approx) and a continuous working load of around 120Nm.

The '3' size is 50mm between centreline of the worm to the center of the worm wheel. This gearbox will weigh about 7.5kg and have a continuous working load of about 80Nm.
They do sizes up to '8', but are getting very large, certainly bigger than would comfortably fit on my machine.

The remainder of the numbers refer to the style of output, keyed vs flange vs compression sleeve, and the gear ratio. The common ratios are 6.75:1, 9:1, 14:1, 19.5:1 and 39:1.

If you are patient you'll find a suitable gear reducer on Ebay. Both mine were new old stock and both less than $200USD. That it cost another $200USD to get them to New Zealand is a drag,
but it what it is. They have proven to be very useful, and for the sum expended I think very worthwhile.

Craig

[Mavigogun]

You're the best, Craig. I'll ruminate, ponder, rest- and, hopefully, return with some useful questions.

[joeavaerage]

Hi,
I realise the pic I have posted may not be especially clear as to how this thing works. I've taken a few extra shots. One looking at the platter or fifth axis from underneath.
You can plainly see the Atlanta gear reducer and the servo alongside it. There is another shot of the platter (fifth axis), but I have the vice attached but jogged the platter to about45 degrees.
Last pic is the servo for the trunnion, its sort of hidden from view in a front-on shot.

I have yet to make Home and Limit switches. Limit switches for the trunnion I consider a priority. If the trunnion rotates much past +90 degrees or -90 degrees then bad things happen.
I am anticipating hooking the limit switches (roller plunger snap action micro switches direct to the servo drive, rather than to the motion control.

Craig