Aftermarket 4th Axis - Any experience yet?

[grossmsj]

I'm very tempted to put on an aftermarket 4th axis for my AR6 Pro.

I have the Axiom unit. It's okay, and it works, but the various chintzy bits of it are driving me nuts. The tailstock is slowly disintegrating (the bolt on the quill tightening lever snapped in the tailstock last night). It has always been sloppy. There are other issues with the tailstock that are also making me a little frustrated.

As I think about replacing that tailstock with something more durable, I know I'll have to modify almost any decent tailstock to a 75 mm height to fit the Axiom headstock. So, if I need to modify the tailstock, maybe I should think bigger picture for the whole system. For example, it would be really nice if the tailstock and headstock were forced to be aligned by a rail system like most lathes, instead of the jig we use to put it in line after each adjustment. A machinist friend of mine is happy to help here.

It would really be nice to add a higher quality headstock. It has worked for me, better than the tailstock anyway. But better drives would be nice. Especially something that was faster. A while ago there was some discussion about modifying the Axiom headstock. Has anyone gone further and actually replaced the headstock? Or has anybody tried and hit a dead end? I will admit I have no real idea of what is involved, and probably anything I think I know is not how it really works.

Gary Campbell , you seem to be "The Man" in this area. Do you have any thoughts about this? If you think it might be more productive to take a discussion offline, let me know. I'm just trying to get the benefit of the userbase here and perhaps share information among the interested parties.

[Gary Campbell]

Gary Campbell , you seem to be "The Man" in this area. Do you have any thoughts about this? If you think it might be more productive to take a discussion offline, let me know. I'm just trying to get the benefit of the userbase here and perhaps share information among the interested parties.

Not "THE" man, simply one the men that over the years have been prone to tinker.  Im not sure what you want from me here.  Of course, you can purchase or machine higher grade parts.  AXIOM's 4th axis kit is very reasonably priced, costing a quarter or third of what its competitors may cost and delivers at a quality level very close to them.  You don't note which type or diameter of project you are cutting, so my advice can only be generic.

IF I were to upgrade an OEM 4th axis (and I feel that they ALL can use an upgrade) I would do the following:
1) Use at least a 900 ozin (more would be better) stepper or better yet a servo.
2) Use a planetary reduction unit of at least 10:1 (25:1 for over 5" diameter)
3) Use aftermarket or custom machined head and tailstock
4) Mount the assembly on a machined rail system permanently mounted to the machine
5) install a homing switch to ensure position repeatability
6) Make sure that it can run in G93 (inverse time) mode to ensure proper feed rates while cutting

Here is a video from 4-5 years ago of a rotary axis I built, mounted on a generic chinese machine, showing similar parts:  

A number of the features shown in that video are not obtainable if using a DSP pendant controller.

Of course, by the time you buy the parts you will have spent multiples of what the AXIOM kit costs and still may not have a precision surface on which to operate.  This is the reason I have taken to building dedicated 4th axis machines on wood lathe beds with Centroid controllers.  My current project is capable of 4th axis 2D and 3D work on a 12" dia by 48" long blank

[grossmsj]

Thank you very much Gary Campbell. That's exactly the advice I'm looking for.
The diameter of the objects I'm doing is relatively small, so the general dimensions of the Axiom would suit me well.

One thing that is a black hole for me is how any OEM headstock unit would connect to the Axiom itself. I could probably figure out the electical connection side of things, but I don't have a sense of how the RichAuto B18 controller would match up with the 4th axis headstock. If it's a fairly generic thing, I could probably work through it. But if certain headstocks absolutely can't be used via the B18 controller, how would I know that?

For now, I'm going to take the information you provided and start to wrap my head around how this would go together, and whether the price is just too outrageous or not. I don't doubt Axiom's take on this is reasonably priced. But there are aspects of component quality that are pretty unpleasant in everyday use. I suppose like most things going up the ladder will cost exponentially more.

Thank you once again.

Scott

[grossmsj]

Gary Campbell, your information was what I needed to avoid making an ill-advised plunge into messing with the headstock. Maybe with a year of learning I'll feel more comfortable doing that. But right now would be a mistake for me. The headstock has never been a problem for me, so upgrading that can wait.

We plan to make some modification of the tailstock to make it more pleasant to use:
1) Tightening up the sloppiness in the quill.
2) Took out the broken bolt of the tightening lever on the top of the tailstock. Probably going to put a threaded hole on the side to hold the quill and get that big honking lever out of the way on top. It has always been an accident waiting to happen up on top like it is.
3) The center height of the tailstock is low compared to the center height of the headstock. It's also not parallel to the bed, pointing down 0.012" at 8 inches.
4) The allen bolts fastening the tailstock to the bed are a little less than ideal for how I use it.
5) As we all know, we have to use some sort of jig to put the tailstock in alignment with the headstock when it gets tightened down. So considering #3, #4 and #5, we're looking at making bottom plates for the headstock and tailstock which will allow them to slide in the extruded top and stay in alignment and fasten to the table easier.

It's weird the screws in the tailstock quill are reverse. Normally when you rotate the wheel clockwise it advances the quill. It's backwards in this tailstock. Not much one can do about that unless anyone has a thread reverser. 

I'll post pictures once this gets done. I've got a couple of machinist friends who are taking this on for me. They asked if I thought the bottom plates would be of interest to users. Their point is that they could make the solution more generalizable to all users if there was interest. Otherwise they'd make the fix specific to the issues of my unit.