End of Slot as Datums? 7

[SDETERS]

I have a part that has two protuding slot features on it. The part is made of Rubber. The two protruded slots are what locates this part in the assembly. I want to call out a profile of these slots but I also want to call the end radius as y and z datum Please See PDF. What is the proper way of doing this? Will the R.16 be basic or have a tolerance? Should I say three surfaces on the profile instead of all around? Suggestions. Wow two questions from me in same day. Sorry.

 

[PeterStock]

Kenat, your right I should have included a "4X FULL R" callout.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

http://www.infotechpr.net

 

[KENAT]

Or "4X R" would have done me, the full being 'implied';-) I wasn't a complet ogre as a checker.

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[SDETERS]

AXYM

This part covers a channel. Think of a long c shaped channel. This part just covers this channel using the two slot shapes to keep the part aligned in the channel. So the width of channel in the mating part is sand cast and has sand cast tolerances. The tolerance on the channel is +/-.030. This part is acting as a cover and we need to have the slots act as the guide during assembly.

 

[axym]

sdeters,

Okay, that helps a bit. But more details are needed on how the two slots align and guide the part. Exactly what are the slots in contact with? Are there some sort of pins or bosses on the channel?

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[SDETERS]

Please see pdf file. The cover is located by the side walls of the casting. These walls are as cast. The slots fit inside the channel. I hope this answers your question. It is a loose fit nothing tight at all we just need to cover this channel up and we are using the slot tabs on the cover to keep it in place during assembly.

 

[axym]

sdeters,

Okay, now I see it. The latest diagram cleared things up a lot. I had been picturing something very different. I got hung up on the term "slot", which I normally associate with some sort of cutout and not a solid feature.

I'll think about it during lunch and post something later.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[KENAT]

You know, I'd been wondering for some time if it was really a 'slot', as an elongated hole, or a male obround feature.

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[SDETERS]

Sorry sometimes I am not to clear.

 

[PeterStock]

Based on what Sdeters posted on how this is used I have redone my drawing.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net

 

[MechNorth]

From what the OP has provided, the length of the protruding slot (boss?) is not controlling any DOF. I agree with the width of the horizontal being shown as datum feature Z, however the Y on the length of the feature won't do anything for you in this situation. The horizontal location and rotational motion will be controlled by the width of the second elongated boss; so, the datum Y callout should be inline with the arrow of the other .316 width dimension.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[fsincox]

Now, with all of the extra information (and seeing the mating part), I like the way MechNorth is heading using the widths of the two slots dimensioned pretty much like PeterStock's second version. While I understand people like to start from the edges. I prefer to give some insight to the function. if the edges are not important I want it to look that way. If manufacturing wants to use an edge it's OK but it is'nt important to the function as I understand here.
Looks like the part locates on the face and the two widths. Why there is that angle to the maiting psrt I don't know but if it's the way it is so be it. I like where you are going MechNorth.

 

[fsincox]

Sorry, not slots bosses.

 

[fsincox]

The boss widths will locate the part and stop rotation the end radii, that we started with, just have to stay out of the way.(meaning controled not to touch, in istallation).

 

[MechNorth]

Tks fsincox

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[axym]

Here's a crude depiction of the functional situation (see attached). The cover (blue) is to placed on the channel (red).

So the first functional requirement is that the two bosses must both fit into the channel without interference.

The second functional requirement is that the outer edges of the cover must maintain some relationship to the channel. This needs to be clarified - perhaps sdeters can give some guidance on the requirements for the cover's orientation and location relative to the channel.

In any case, we know that the bosses are the datum features. That is, contact on the boss surfaces constrains the cover's remaining degrees of freedom (one rotation and two translations). Exactly which of the boss surfaces participate in the DOF constraint, and how, will determine how the datum features need to be defined and referenced.

Evan Janeshewski

Axymetrix Quality Engineering Inc.
www.axymetrix.ca

 

[MechNorth]

Evan! That looks like the same mfg workmanship as my last shop! ;~}

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[SDETERS]

The Outer edges in the original drawing posted was a just a rectangle I put on the drawing. Those edges did not serve no purpose what so ever. They are just tossed on there. I have attached a drawing please take a look. The outer edges (hidden) on the part need to cover the channel and not fall in the channel when the part is shifted around during assembly. This part seals oil in the channel. I will have another part that bolts to the channel that will squeeze the part in question for the seal.

 

[PeterStock]

Here is a rethink of my earlier drawing.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net

 

[axym]

sdeters,

Fit and function requirements for the assembly! Now we're getting somewhere.

You mentioned that the tolerance on the channel is +/- .030. Is this tolerance on the width of the channel, or the profile of each side of the channel? Also, what are the nominal inner width and outer width of the channel, and the nominal outer width of the cover?

Jim,

The profile accuracy of my sketch is what a mouse and two cups of coffee will allow. The thing is, the parts might literally look like that and still function. The as-cast channel surface probably does.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[fsincox]

I thought we were going to pick up both bosses simultaneously (sp?)?