Corner break in Anodized spool valves in transmission control
Corner break in Anodized spool valves in transmission control
(OP)
I have a automatic transmission control application with sliding aluminum spool valves running in a aluminum valve body. I am having difficulty with controlling the corner break in the spool valve, after the Hard coat anodizing process. The uneven corner profile creates a space for debris to collect and produces a sticky valve.
Are there any solutions?
Is this the right forum for this discussion?
Are there any solutions?
Is this the right forum for this discussion?





RE: Corner break in Anodized spool valves in transmission control
Could you do an afterstep similarly to dress the outside of the valves and the inside of the valve body?
btw your reamers will become undersized quite quickly from this so take that into consideration for whatever process you design.
RE: Corner break in Anodized spool valves in transmission control
The thickness of hard anodising can be controlled to some extent during processing. You can specify thickness up to a maximum. The maximum might be partly dependant on the alloy. I think the maximum I have seen is about 0.003" but that is from 30 year old memories so it may be inaccurate.
I am not sure it has anything to do with the anodising. It is hard to guess without seeing failed parts, but maybe the machining process is producing parts with:-
Bad fit.
A notch from machining tool tips in a critical area.
Poor original design without enough support for the load.
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RE: Corner break in Anodized spool valves in transmission control
Im only throwing out ideas maybe something you missed? Can you do trials where an alloy spool is used?Or a steel bore?An over length spool land?
goodluck...
RE: Corner break in Anodized spool valves in transmission control
The filtration is set to 50 microns.
I am pretty sure that the stickyness is from the corner radius (or the lack thereof).
RE: Corner break in Anodized spool valves in transmission control
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If the problem is that the dimension of the part varies at the sharp corner, could the corner be re-designed to have a controlled radius?
Would it be possible to re-machine or dress the corner in question to re-create a sharper corner after anodizing (i.e. rough machine prior to anodizing, leaving .015 inches or so extra "length", then anodize, then grind/mill the length to finish dimension). Realizing this leaves the end of the spool un-anodized, but it doesn't seem to me that the anodizing is for corrosion resistance, as much as for a harder surface area along the wearing (cylinder) surface. May be totally misreading the situation, in which case please ignore.
RE: Corner break in Anodized spool valves in transmission control
I ask because in hydraulic valves, a lot of transient behaviors are critically dependent on the overlap/underlap between the spool and sleeve, and moving either edge by microns makes a difference.
Mike Halloran
Pembroke Pines, FL, USA
RE: Corner break in Anodized spool valves in transmission control
ICZ
RE: Corner break in Anodized spool valves in transmission control
Btrueblood, is there any design solutions other than post machining.
They tell me that the common filtration in automotive application is 50 microns. Is this problem common in auto applications.
RE: Corner break in Anodized spool valves in transmission control
"is there any design solutions other than post machining"
I don't know, but it used to be (I got out of Aerospace >10 years ago, and haven't really had to worry about aluminum since then), and so we just planned on post-machining for critical details. But the web link I posted talks about the issue and claims that they can control the erosion/roughness of sharp corners by control of the electrical current (and presumably some of the chemistry details); I'd sure talk to them about it and see if they have any suggestions, maybe have them run a few parts and see if they can put out.
RE: Corner break in Anodized spool valves in transmission control
RE: Corner break in Anodized spool valves in transmission control
I used to reclaim cranks using hardchrome and would build up to .010" o/size and grind back to finish size including radii.You may have a problem as others stated of the radii contacting before the faces,the spool body internal radii should be ultimately smaller than the spool radii.
One other problem may be surface compatability Im not too sure about anodizing but with hardchrome you can't run chrome rings in chrome bores and some bearing materials were not suitable for chrome shafts.
Good luck I hope you solve the problem.
RE: Corner break in Anodized spool valves in transmission control
RE: Corner break in Anodized spool valves in transmission control
RE: Corner break in Anodized spool valves in transmission control
RE: Corner break in Anodized spool valves in transmission control
RE: Corner break in Anodized spool valves in transmission control
I figured if the finishing included deburring the valve bits the story might just be true.
RE: Corner break in Anodized spool valves in transmission control
I've worked on and used a number of those early Dual-Range GM Hydramatics that Rolls used into the sixties. My experience has been that the quality of the valve spools as they left GM was on a par with any more modern automatic I've had apart- very true and well-defined diameters, with neither corner breaks nor burrs. I do concede, however, that the precision of the valve bores in the valve body weren't held to as tight a tolerance as some later transmissions.
RE: Corner break in Anodized spool valves in transmission control
regards,
Dan T