Cuts from a sloped face with equal extrusion, not to same plane?

[Anonymous]

I freely admit that I'm an utter newb at this, so apologies for probably phrasing what I want to do incorrectly.

The goal is to wind up with a set of cuts that extend from a sloped face (the top of an object) towards the bottom (flat) face. However, each cut should be a fixed depth and with a flat (parallel to the bottom face) bottom.

Basic description of goal is an object holder (pens and other things) with a sloped top face and multiple holes (in several rows and more than one hole in each row). If equal-length objects are placed in the holes, the ones in the back (towards the back of the top face) should rest higher than those in the lower (towards the front) holes.

The first thing I tried (which failed) was sketching the holes on the top face and extruding cuts from them. This failed because the cuts extended perpendicular to the top face, Upon further thought, I realized that even if it had worked (extruding to the bottom face), it wouldn't have worked because the holes would be sized and spaced incorrectly (due to the distortion of projecting the sloped face onto the flat side).

Next attempt (which works, sort of) was to sketch on the bottom face and then extrude, starting at the top face and coming downwards for the desired distance. This "almost" works but the bottoms of the holes are sloped parallel to the top face, not to the bottom face.

The only other thing I've tried which "feels" like it should work (but doesn't) was to break the object into two "pieces" - a basic "brick" (extruded rectangle) with an extruded wedge on top of it and sketching the cut pattern on the top of the brick. My thought had been to do a two-direction extrusion from that pattern (to object to the top face) with, ideally, setting a total extrusion distance to the desired distance. I don't see any way to do that, though.

This "feels" like it should be possible without doing a whole bunch of external math or needing to fine-tune each of the cuts (or at least each of the rows) to get the extrusion length "just right".

What am I missing? Or is this just really something that there isn't an easy way to do?

[wmhazzard]

Is this what you want? Create an offset plane from the bottom, make a sketch and extrude cut. 

[davebYYPCU]

You are on the right track with the brick and wedge, change the order of business, and you will get it.

Set up the holes - shape and position on the base or top of the block, both will work,

Then cut to top of the block down to wedge shape.

Might help...... 

[Anonymous]

This puts the floor of each of the cuts at the same height from the bottom of the block. The idea is that the holes in the back will sit higher than the ones in front. A pen placed in the rearmost hole should wind up being higher than the same pen placed in a hole closer to the front.

If the holes from different rows have their bottoms on the same horizontal plane - that's not the right solution. The floors of each row of holes should be on a plane which is higher than the holes in front of it (and lower than any holes behind it).

Hope that helps to make it a little more sensible?

[wmhazzard]

Then use two planes for two sketches, one for the front holes and another at a different height for the rear holes.  You could also use two sides option for the extrude which allows you to raise the back holes off the bottom plane. 

[Anonymous]

Here's an example of what I was talking about for getting it right but not right because the floors of the holes are sloped.

[laughingcreek]

[wmhazzard]

Create multiple planes from the bottom to make the sketches for the holes, one for each row. 

[Anonymous]

Hmm... A couple of things that pop out at me.

1. The specified depth is from the original (pre-draft) top face, not an actual "depth of hole from top surface"
2. I haven't tried it, but I'm going to guess that the extrusions are all from the original top face, so something that wasn't part of the rectangular pattern wouldn't adjust depth. (The example image I uploaded has a "slot" as the forward-most row, not just more cylindrical cuts

Lest I appear unappreciative, please do accept my thanks for providing the input. This may be the programmer in me going "this should be easy because I can think of exactly how to do it that shouldn't involve me fine-tuning and individually-placing every little bit here".

[TheCADWhisperer]

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@Anonymous wrote:

.... "this should be easy because I can think of exactly how to do it that shouldn't involve me fine-tuning and individually-placing every little bit here".

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Fine tune your geometry, then File Export and Attach here and someone will show you the trivially easy way.

[Anonymous]

Ok. Attached is a somewhat-edited version of what I'd done. Please note that this is the first thing I'd ever designed, so I know it shows a lot of stuff that I didn't know to do then (better design approaches, patterns, etc.). I'm certainly not saying that this is how I would approach designing this (at least in terms of sketching and such) today. [With that said, this  was done about a couple of months ago or so, so I do try to be a fast learner.]

Also, I know that the extrusions seem to be weird and not all done at once and what-not. Again - not the approach I'd use today, but I think it gives at least a beginning sense of what the design was trying for? I hope...?

Thanks again, and I'm not trying to be an absolute tool about this. It's just my instinct saying "there should be a way to do a sketched set of cuts off a sloped plane such that all the cuts are the same depth (vs *to* the same depth) with the bottoms of the cuts parallel to the bottom of the object, not the face of the sloped plane.

I can work on refining this (to actually produce the parallel bottoms) if needed, but I'm hoping this may provide at least a much better sense of what the goal was? [The refinement I can think of the "easiest" here would be to do a sketch on the side and draw blocks at the base of each of the rows of cuts such that extruding them as a join would serve to flatten the bottoms. These new (internal) blocks would rest at the highest point of each of the rows' cuts - if that makes sense?

[davebYYPCU]

I think this is what has been described as the desired outcome.

2 Sketches and 3 extrudes, one of many ways.  

My first sketch is freehand, you can have as many holes and shapes as you input.

Second sketch is where the work gets done.

1 Extrude the material,

2. Extrude the holes through all.

3 Add material for the internal hole floorss as a join.

Add your appropriate dimensions, this is just a guide to a process.

Might  help....

[Anonymous]

So ... from all of this, it seems that the answer is that there isn't a way to make holes off of a slope such that each has an equal depth with the floors parallel to the lower surface (not the sloped surface)? That's unfortunate ... 😕

[Anonymous · Accepted solution]

Here is a redo of the block with a bunch of better design to begin with and the flattened floors of the holes as I'd desired. Finding the "highest" and "lowest" bottom points of each row to generate coincident constraints for the "cross fill floor" wasn't quite as difficult as I'd imagined it would be, so that wound up being the easiest (?) way to do this.

I still wish that there were an even easier way to do this that didn't involve needing to "fill" the floor to generate the proper parallel to the base of the block (vs parallel to the top surface).

[wmhazzard]

If you extrude from object, you will get the same surface as the object, it is not unfortunate, it is the way that it is. Is there some reason that you don't want to extrude from the bottom?

[davebYYPCU]

There is one elephant in the room, 

What shape is the desired tube?

Elliptical or cylindrical.  

I was of the opinion the you wanted cylindrical tubes to align to the top face, you have eliptical edges at the top face. 

Might help.....

[Anonymous]

Not extruding from the bottom: I want to be able to set a constant depth of the holes. So that an equal length object placed in a higher hole will sit higher than one in front of it, etc.

As far as the hole shape goes - the holes themselves need to be cylindrical. Yes, I understand that results in an elliptical opening (just like an angled slice of a cylinder would).

The goal is to have holes that I can (easily) dictate the shape of (round) with the ability to specify a known / common depth of each hole - regardless of where on the slope the hole is positioned. Hope that helps to clarify it more?

My original (start of thread) idea was to be able to use to “top of brick” surface to just do a two direction extrude (cut), specifying the total extrusion length, and using one face as a “to object” end point. In retrospect, I realize that probably wouldn’t work since it would still wind up with sloped floors.

[davebYYPCU]

Then we are back to Alex's pattern. 

[chrisplyler]

I'm going to suggest something different:

Just make the first, lowest row of holes, using the Extrude tool from the bottom up out of the top. Pull the top of the Extrude up some extra distance while you're making it, such that they will protrude enough to cut the full length of the holes even if they were deeper.

Now Pattern>Features that Extrude feature upwards and backwards, which will make new rows behind and upwards from the first row.

[Anonymous]

That only works if all of the cuts are the same. As I (tried?) to show in my example, the first row isn't cylinders, but, instead, is a slot. Thanks, though!