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Making sure this automation part is manufacturable

Strostkovy

Titanium
Joined
Oct 29, 2017
I am a sheet metal guy professionally, but also an electronics and robotics hobbyist. I would like to dip my toes into professional automation equipment, and in this particular case I need to design and make a variety of spindles for various rotating components that need to be precise.
The attached image is of a trailer spindle, but it's close enough to my actual designed needs (I actually prototyped some robot ideas using trailer spindles). I have colored in areas that would need to be ground after rough machining and heat treat:
gie7S9Jh.jpg
Starting from the left, is the mounting flange. It will be smaller in diameter with more bolts, but is extremely critical to be perpendicular to the bearing bores and parallel and the correct distance from the edge of the first bearing seat.
The stem from the mounting flange is the pilot that locates the spindle in the assembly. It just needs to be concentric. The internal radius between the mounting flange and the locating pilot can be large and unground.
The middle feature is the important bearing seat that holds a pair of angular contact bearings. The flat edge needs to be ground, and the diameter, but not the radius between them, which can either be large or undercut.
The last feature just needs to be concentric and on size, as it is for a floating radial bearing.

Not shown on this part is a few details like a feature for a retaining collar to secure the angular contact bearings and a feature for spring preloading the radial bearing, and features to seal against, but that isn't too important.

I will be getting a lathe soon but will definitely need to sub out heat treat and grinding (if not the whole part). These mostly mate up to sand castings or die castings that get machined by the vendor, depending on the size and purpose of the spindle.

So my questions are as follows:
Is it practical to grind both the diameters and faces in one setup? Maintaining perpendicularity is hugely important to me on these.
How much deadspace do you need between a face and a diameter, to avoid complicating things?
What features would make work holding easiest?

I think I have bearing and pilot diameters and tolerances sorted, and I'm sure I can figure out the best material and heat treat, but if you have input on these I would love to hear it. The part shown is cast, but I would use solid bar stock, and maybe eventually bar stock with a flange forged onto it for strength and material savings.

Thank you all for your time.
 
What does deadspace mean?
I think he means how big an undercut or runout groove is needed at the inside corner so that adjacent face and diameter can each be ground. If so, the answer is "pretty small". 1/16" would be ample for most cylindrical grinders. Maybe twice that if your operators will be doing this manually in a hurry without hardstops.
 
What does deadspace mean?

A centre hole in each end so it could be held between centres.
By deadspace I mean a relieved area between ground features that does not have to be ground.

Does there need to be any feature for a dog to connect to or is grinding low enough force that it doesn't matter?
 
I have another question. Since some of the spindle extends past the seals and won't be oiled, I would like to coat the spindle after heat treat but before grinding. Is a nickel plating any nuisance for grinding? Grinding depth will be below the plating.
 
By deadspace I mean a relieved area between ground features that does not have to be ground.

Does there need to be any feature for a dog to connect to or is grinding low enough force that it doesn't matter?
If I was doing the job I'd have the threaded end at the headstock with the driving dog on the thread. The forces are quite low.
 
By deadspace I mean a relieved area between ground features that does not have to be ground.
If you're fitting normal ball or roller bearings you shouldn't need an undercut as bearings usually have a fairly big radius on their ID. You can usually grind a sharper corner than the bearing radius for any given diameter.
 
Have you considered hard turning. If you can get away with it, it should be much cheaper.
I haven't since I'm still learning on lathes. Definitely something to try out.

Once I have all of my tolerance requirements nailed I can see if that's viable.
 
Is it practical to grind both the diameters and faces in one setup?
+1 with seesecurity, easy-peasy. Grinder with an angle head does this all day long. Straight wheel can but it's a lot more of a pita.

How much deadspace do you need between a face and a diameter, to avoid complicating things?
I always put a grind relief in, even if you don't need it it's easier on the wheel. 1/16" full radius would be fine.

What features would make work holding easiest?
Again +1 to seesaw, just put it on centers. Little drive dog will push it around fine.

And no, I wouldn't bother with hard turning. Hard turning sucks compared to grinding. Grinding heap good. Just ask Buck, no comparison :)

The part shown is cast, but I would use solid bar stock, and maybe eventually bar stock with a flange forged onto it for strength and material savings.
Material is going to be the killer on that, will make your raw material much larger than you'd like. Down in LA, still have anyone doing friction welding ? This looks like a good application for that.
 
I haven't since I'm still learning on lathes. Definitely something to try out.

Once I have all of my tolerance requirements nailed I can see if that's viable.

This definitely looks like hard turning to me, not grinding. But you haven't shared your tolerances.

Within a tenth or two is grinding. A few tenths is hard turning.
 
Gag :) Finish is shit, tolerances shit, roundness shit. Long live grinding !!

I don't know how you built your products, but I build mine using the lowest cost process that does the job well.

Why use D2 when a light case on 1018 works great?
 
I don't know how you built your products, but I build mine using the lowest cost process that does the job well.

Why use D2 when a light case on 1018 works great?
I'm not suggesting he use D2. But grinding is easy, simple, fast, and does a better job than turning. Much better. Hard turning is an abomination. It doesn't do the job well.

Do you like your blanchard ? Would you like to do that work with a big vertical mill and a fly cutter ? Same thing.
 
Material is going to be the killer on that, will make your raw material much larger than you'd like. Down in LA, still have anyone doing friction welding ? This looks like a good application for that.
Fortunately the actual parts have a flange that's not as dramatic as this, but still wasteful. The lower bearing race will be larger and many of these actually need a through bore. I think the real key to saving material will be to make it as stubby as possible though.
 
We have replaced a lot of cylindrical grinding with hard turning. With a rigid, well tuned CNC lathe and the right insert, we get 8-10 micro inch finishes (measured with a profilometer) and +/- .0001 accuracy, roundness, and perpendicular faces. Interrupted cuts are a challenge, but CBN holds up fairly well. Hard turning has come a long way in the last 10 years. We are doing this in tooling parts (not production) in the 2" and under range.
 
Hard turn or grind?
Part volume? Machines available for use?
Bearings have a corner radius.
From past experience I'd stay away from undercuts on an axle shaft.
I know this not a drive axle but still.....
 
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What kind of equipment do you have at your disposal? CNC lathe? Manual lathe? CNC grinders? Toolpost grinder on said manual lathe? Hard turning would definitely be good enough, it doesn't sound like this thing is going to the moon.
 
What kind of equipment do you have at your disposal? CNC lathe? Manual lathe? CNC grinders? Toolpost grinder on said manual lathe? Hard turning would definitely be good enough, it doesn't sound like this thing is going to the moon.
I just have a manual lathe and am getting a CNC lathe early next year, but nothing fancy. I would have to sub it out for either grinding or hard turning I think.
 








 
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