XYZ Gantry Build with Rotary Axis

Andrew,

Thanks so much for the insight. I value the wisdon gained from experience. I checked out your site, looks like a lot there. I will have to visit when I get some time to absorb it.

I realized that I needed to set it up to define the extents of the machinable volume (including corners) of the rotary space as defined by the ability of the tool to reach all necesary areas. The problem was I defined that 'necessary' area based on the upper, inboard quadrant. I never thought I might want to cut beyond the verical plane defined by the rotary axis.

Of course once you enlightenend me it made sense. I really do appreciate that input.

Being able to lower the rotary table was built into the design at the concept phase.

Part of the reason I concentrated on that upper inboard quadrant is my idea was to have the best of both worlds, albeit in a limited way. I figured that if I could sacrifice a foot of X axis when the rotary was in the raised position, then that would leave me with a useable cutting area of 24"x36" on the table. If I need the whole table the rotary can lower out of the way and I can slide the table over (ingnoring for the moment the potential need to resurface the table).
The lowering of the rotary table would also allow larger project to be mounted, but I was only thinking of surface embellisment on a piece I turned on the manual wood lathe, or platter edge treatments.

I see two options. Make allowance for the tool to travel outboard of the rotary axis (at least to achieve an acceptable balance between outboard travel and remaining usagle cuttion area in the XY plane).
Or, chane the rotary axis orientation (B to A I believe), to be down the X axis. The XYZ Gantry Kit I'm using comes with extrusions between the X rails (along Y) so that it sits on the frame. I suppose It would be possible to either use braces on the ends (which would make stock loading/unloading uncomfortalbe) or use some angle stock and mount the X rails to the extrusions of my frame. I don't know if that will maintain rigidity though.

Anyhow, I will think about it some more and when I get furthur along I will have the frame finished and the XYZ stuff mounted (at least temporarily) and I can better envision the options I come up with.

You've give me a lot to think about, and once again, I appreciate it.

BobL.

Finished the design of the caster plate and made one out of hardboard. Also gave me a chance to play with the toolpath setup. I used what I though might be some alum. compatable settings (even though it took longer).

Anybody know what a decent ramp angle would be for a starting point? I used 10 degrees.

Next I figure I will roughly plumb the frame. Tighten it up and flip it. I have a 12mm tap and am going to tap at least on of the holes in the end of the GFS extrusion leg. Three 8 mm SHCS along the each lower rail.

Hey Will, how bout them casters? Look familiar? I knew I was gonna use them as soon as I saw them on your machine. Thanks for that :)

That dreaded aluminum cutting buisiness is getting closer and closer ;)

BobL.

Bob

You will not be disapointed with the casters. As of now I have only the front two down and the machine does not move. For me it was money well spent. The best part I can still move the cnc with ease. Your build is looking good. Having any fun yet?

Will

I guess I'm a little stubborn, but after 3 broken bits I finally gave up.

My MDF machines Z axis is just not stiff enough. I really had a feeling that was going to be the case. So, I'm just going to have to do it the old fashioned way.

Luckily, these will never be seen, and the dimensions are not critical.

Got one done and installed. Another one marked and ready for the sabre saw.

Won't be able to get back at it until Sunday.

BobL.

Now you have answered a question. What DOC and feed rate and RPM where you using. Were you machining dry?

So how big are they? If there was not a border it might be a reason to try out my mill again. ;-)

The good thing is you can always make a new set once you are up and running.
Dave

Dave,

It was definately flexing in the Z axis as I could see it, a lot !

I don't think it was a feed and speed issue (not that I know), but I was getting decent size chips and other than the chatter when the z started flexing, it sounded like some of the videos I watched.

You're right, I could make some more after the build, but ya know what, I'm guessing not ;)

Have a great weekend.

BobL.

Looking forward to getting back in the shop today. I will be bringing back a small 9" benchtop bandsaw. That will make cutting the rest of the caster plates easier.

I was sitting here sipping coffee and looking back at Dave and Will's build logs to pick up on anything I might have missed and I noticed something.

My XYZ Gantry kit came with what appears to be a fully assembled Z axis. The parts box only contained the cable chain and mounting harware, gearboxes, two motor couplings and the hard stops for the X rails (from memory, I'm not there now).

The screws and bits were in what appeared to be plastic sandwich bags with hand written notes in the bags describing what they were for.

There is also evidence that the gear boxes have been mounted.

I find this encouraging. They must have assembled my machine to check parts and tolerances. Will be interesting to see if the Z axis is really aligned all the parts are there.

I know the company offshoot is going through growing pains and have had some issues with previously shipped systems. If they did in fact test assemble my system, seems that would eliminate all problems. Don't know if they are doing this for every kit now or not.

BobL.

Bob,
A small bandsaw will really speed up you project.
I am glad you are happy with you kit.
Mine was really nicely packed and I had very few loose pieces. I can remember if the Z axis was shipped bolted on on not. If it was there was only 4 SHCS to attach it.
My unit had all the gear reducers etc attached. Ready to bolt on the motors.
I had to assemble the rails to the cross pieces, Then take off the end stops I think then slide on the gantry. It did not take long at all.


Did they have provision for limits switches on yours?

I am happy now that the backlash is within acceptable limits now after the ball screw replacement.

If you have a chance please check on deflection in your Z axis parallel to your racks. Mine seems to have more than I thought it should have.
I checked it by mounting a dial indicator. Z down as far as it will go. And some gentle finger pressure back and forth. I was surprised. It might be an adjustment on the Z rollers.
Let me know what you see.

Keep up the great job and lets see lots of pictures.

Dave

Dave,
You're right, that little bandsaw and an 18TPI blade made short work of cutting out the rest :)

Quote:

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Originally Posted by dfmiller

Bob,
Mine was really nicely packed and I had very few loose pieces. I can remember if the Z axis was shipped bolted on on not. If it was there was only 4 SHCS to attach it.
My unit had all the gear reducers etc attached. Ready to bolt on the motors.
I had to assemble the rails to the cross pieces, Then take off the end stops I think then slide on the gantry. It did not take long at all.

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Hmm, I guess it may depend on who packed it then? My gearboxes wern't attached.

Quote:

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Did they have provision for limits switches on yours?

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I'm not sure, I'm not expecting them to have. I haven't unpacked the large pieces. I've attached a couple of pics to show how mine came.

Glad to hear you're backlash issue is solved. You're a patient man Dave.

Quote:

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If you have a chance please check on deflection in your Z axis parallel to your racks. Mine seems to have more than I thought it should have.
I checked it by mounting a dial indicator. Z down as far as it will go. And some gentle finger pressure back and forth. I was surprised. It might be an adjustment on the Z rollers.
Let me know what you see.
Dave

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I can't right now of course, but I will. If I forget, please remind me.

BobL.

Nothing really spectacular today, but I did get the caster plates finished and mounted.

I need to finish squaring up the frame.

Will, nice find on those casters. Those things are sweet.

No doubt this frame will be sturdy enough :)

I'm looking forward to being able to set the XYZ Gantry parts in place.


BobL.

Bob,
That looks really nice. Those bracket do remove the requirement for counter boring the rails. Do you recall what they cost?

It does look like they don't have any limits provisioned. :-( It might make sense to think about that before you do much more assembly. Much easier to drill some hole on the rails before put it all together.

Thanks for the pictures.
For reference what size is your machine? You have told me.

I was at a woodworking show and General was showing their new router. The one that was about 2'x3' they wanted 17.5K. I tried to keep my laughter as brief a possible. It looked rather flimsy and did not have anything high end on it.
Dave

Bob,
Re read page 1.
24" x 48"

It would be easy to make it 48X48. :-)
Its too bad you did not get it 48"X24"

Looks really sweet. Its just crying out for some sawdust.
Dave