Radial Holes at Odd Angles?? (Alibre)

[Nigel Graham 2Participant @nigelgraham2]

I can place a radial hole in a cylindrical object provided it lies along one of the primary axes.

I can produce a second (or more) from that by using the radial copy tool and setting the copies to 2 (or more)… provided, I spent much of this evening discovering, I want to retain the original.

What though, if the hole, or any other feature such as a flat, is alone at any angle other than those primary right-angles? I guessed somehow it involves placing planes and axes in the right locations but after trying everything in the  book without success had to admit defeat, leave the unwanted “seed” hole there and add a note to remind me not to drill it!

[JasonBModerator @jasonb]

Faced with a job like that I tend to use the green “construction line” tool to draw a radial line out from the ctr and then dimention its angle from one of the main axis. For example this hole is set on a 15deg angle to the main axis and I have entered the 23mm distance.

Alternatively I could have used the drop down for those construction lines and done a 46mm circle to represent teh PCD and then placed my M4 tapping hole where they meet.

As for your hole at 62deg there are a couple of options other then placing a new plane.

Start with a green construction line dimensioned to 62deg. Then draw a rectangle of half the hole diameter with its long side on that green line. If you don’t know how to place a plane at 62 deg let us know and myself or David will explain.

Close the sketch and then select rotote-cut. Select the side of the rectangle that was drawn on the green line a sthe axis of rotation and it will form the hole

[David JuppParticipant @davidjupp51506]

My personal choice would be to define a new reference plane at desired angle to the axis of cylinder, and one of the default planes.   Then define another plane tangent to the cylinder based off the new angled plane.

Then use that second new reference plane to either sketch a circle on, or to use the hole tool with.

 

There is always more than one way to approach any task…

[JasonBModerator @jasonb]

Might as well show how I would do the radial hole using planes as it may be of use to others.

First create an angled plane using the existing geometry which I have done using the horizontal Zx plane and the central Z axis. The plane wants to be placed at an angle for you to sketch a circle on so I entered the complementry ange of 62 which is 28 and added a minus before it to place it correctly.

As you don’t want your hole going to the ctr I would then create a second plane that is tangent to the OD. So using the plane box agan select a parallel type plane, select the one you just created as the geometry and enter the radius of the main part in my case 37.5mm.

You can now sketch your circle on that tangental plane and use a extrude cut of 10mm deep to form the hole. here I have used a larger but shallower cut to form a counterbore

 

[David JuppParticipant @davidjupp51506]

Jason, there is a tangent plane option in the plane dialogue – no need to input radius.  Let the software work it all out (and update automatically if you change the size of the cylinder). See my post above (probably posted whilst you were preparing yours).

[Geoff RogersParticipant @geoffrogers81118]

Nigel

Thank you for raising this aspect – I was mulling over this aspect for a job I am using as a training exercise.

I am new to Alibre, but have used Turbocad for many years.

 

[JasonBModerator @jasonb]

Thanks for pointing out the tangent David. Works in this case where a hole is wanted but for something like a boss then a distance and extruding the sketch to the geometry of the cylinder would be what is needed. like on the oiler point of this engine.

 

[David JuppParticipant @davidjupp51506]

Jason – agreed.  Sometimes you might prefer to dimension the plane from the central axis, on other occasions it might be preferred to create a tangent plane then another plane offset from that by ‘boss height’.  No single ‘correct’ answer – many ways to skin the rabbit.

[Nigel Graham 2Participant @nigelgraham2]

Thankyou Gentlemen.

I see I was sort of on the right track with the tangent-plane tool but could not fathom out how to use it. The example in the pdf Manual, using a sort of extruded ‘P’-shape, is very odd, and just confused me.

 

To sum up, if I understand this correctly, for a simple cylinder create a radial plane through the axis of the cylinder, it asks you for the intended angle, then use “tangent slope” for the one parallel to that on the outer surface.

Something like my quick experiment shown below. I added the two small holes to show me I’ve drilled the radial hole in the “right” quadrant. (I used to use extra little features like that, which can be deleted later, in TurboCAD to help me view a symmetrical model the right way round.) The bit that takes some thinking about is the initial plane’s inclination.

If the surface is irregular, like Jason’s complicated casting, then I take it the appropriate tool would be the direct parallel-plane one with a known offset.

 

Jason – your first demonstration is of locating a hole in the face of a disc. I don’t seem to have a problem with them. I’m afraid I’m not sure I understand your suggested way of generating a radial hole though. Though I’d not helped myself by also trying to thicken the disc, a deliberate design modification, which put the central plane off-centre.

 

Geoff – Ditto! I started CAD with TurboCAD as at the time it was the only proper engineering-draughting package available to amateur users at reasonable cost and single payment; the same sales method now used by Alibre for its ‘Atom’ version.

I really struggled with TurboCAD’s 3D system, and its “‘Deluxe” (i.e. basic – ish) editions lacks the active dimensions, file-linking and movement-simulation Alibre has. One practical advantage of that file-linking (I think that is the “parametric” bit in describing CAD?) is ready Assembly building, and allowing common parts across different projects.

I still use TurboCAD occasionally, but in orthographic mode only, for geometrical constructions. I find it easier and more flexible than Alibre for that, by simulating standard geometrical construction methods; but otherwise have come to prefer Alibre Atom for designing machines.

 

So it should look something like this, for that hole at 45º…? (It took me a few tries.)

[JasonBModerator @jasonb]

Nigel, the method of generating a hole without the use of planes can be very useful at times. Really depends on the job in hand.

Take something that is often seen in model engineering – drilling steam passages at an angle into the ends of a cylinder to connect to the ports. You don’t know the angle so can’t set a plane to it but can easily sketch where the hole is wanted and pull the long side about to line it up.

Same with various holes in things like carbs where they may not be related to external features or at a known angle. Or what if the hole is not patallel sided, easy to sketch a sititable shape to rotate but maybe not so easy to cut extrude.

[David JuppParticipant @davidjupp51506]

Nigel, a minor point – the ‘parametric’ in parametric CAD simply means that everything in a model is driven by parameters.  These can be simple numbers, or equations based on other parameters.

This makes editing a design easier, whilst maintaining the original design intent.

The term doesn’t relate to linkages between files.

[Nigel Graham 2Participant @nigelgraham2]

Jason – I think I did indeed trying to draw slanting steam-passages in a cylinder but found it too hard!

 

David – Thankyou for explaining it. I first encounted the word “parametric” in the A-Level Maths I failed impressively to learn! It described a special type of simultaneous equation, I think.

Even so, the facility to set and alter a size in a CAD model by an active dimension, and have that change picked up in the related files, is very useful.

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