topic Scissor arm movement in Dynamic Blocks Forum

Scissor arm movement

Rob_Molina — Mon, 14 Oct 2019 11:27:59 GMT

Dear all, I need your help please.

I have a complete scissors in which I want to make the movement of closing and opening with a fixed point and maintaining verticality. I found an example in the forum I tried to adapt it, but I don't understand it. Attached is my attempt at a dynamic block. see test_A and test (A7) copy of the Block on: https://forums.autodesk.com/t5/dynamic-blocks-forum/dynamic-block-scissor-arm-movement-please-help/td-p/5972015

Thank you for your help

Regards

Re: Scissor arm movement

j.palmeL29YX — Tue, 15 Oct 2019 05:38:12 GMT

@Rob_Molina wrote:

I found an example in the forum

~~Can you post the link to this example please (so we can see what you want to do)?~~

Ignore please - I found it.

Re: Scissor arm movement

j.palmeL29YX — Tue, 15 Oct 2019 08:41:53 GMT

Some first questions to precise the issue (based on your test_A-1.dwg):
- Where do you want to grab the block? As shown in this >>video<<? Or at another point?
- Or do you want to change the angle between the arms?
- Which point of the block should stay fixed? (In the video I choosed the insertion point).
- do you want to rotate the green geometry individually too or do you need it always in the vertical position as shown in the video?

- What do you want to show us in the test (A7).dwg? I don't understand its point.

I'm not yet sure if I can solve all your requirements but I'd like to try it.

Re: Scissor arm movement

j.palmeL29YX — Tue, 15 Oct 2019 11:03:17 GMT

Attached a first try.

If this is what you want, I can (if you need) tell you how to get it. If not - let me know what's not yet right.

Re: Scissor arm movement

Libbya — Tue, 15 Oct 2019 17:00:39 GMT

I have similar questions to those posted by j.palmeL29YX. I'm not sure if you want a vertical distance to govern the position or if you want to rotate one of the scissor arms. Anyway, I don't think I can do the vertical distance control without constraints but can do the scissor rotates all as dynamic actions as shown in the following screencast. It is quite complicated, though.

Re: Scissor arm movement

Rob_Molina — Thu, 17 Oct 2019 12:35:49 GMT

Thank you very much for the solutions submitted.
@Libbya, the solution is excellent above all because the lines indicative of the rotation are maintained.
My questions: is it possible that I can know how it is done?
it's possible that you' re sending me the DWG.
I have the Autocad LT, to do this is necessary the full version?
Regards

Re: Scissor arm movement

Libbya — Thu, 17 Oct 2019 16:13:31 GMT

I'm happy to show how it is done.

I will not provide the finished block. My purpose in posting is to help you learn, not to do work for you. Providing the finished block is counterproductive to that purpose. You will need to make the block yourself following the attached screencast. All steps can be done with AutoCAD LT.

Attached is a screencast that shows the step-by-step process for completing the movement. It is a complicated process and I attempted to show in the video what each parameter/action did and why I used it. The main rotation uses a rotate action with independent base in order to rotate a chained point/move. That chained point/move then stretches a point of a chained XY parameter (stretches it in a circle). The chained XY then stretches a chained rotation parameter with two actions that separate the X and Y components of the movement. The X component stretch is reversed and the result is that the rotation is reversed. That chained reversed rotation is then used to rotate the other arm of the scissors using a rotate action with independent base. That reversed rotation cancels the initial rotation. A second reversed rotation is used to induce a reversed rotation. Another normal rotation is added to the components at the end of the arm in order to cancel that second reversed rotation. See screencast.

Re: Scissor arm movement

j.palmeL29YX — Thu, 17 Oct 2019 18:17:32 GMT

@Rob_Molina wrote:

... the lines indicative of the rotation

I'm not sure - do you mean the circles? Or the (yellow ?) "lines" anlong the arm (in the middle)?

Re: Scissor arm movement

Rob_Molina — Fri, 18 Oct 2019 12:06:32 GMT

Thank you very much.

I tried to make the dynamic block according to the video.

I've got to the min. 7:36, all perfect. But I can't do the next step. It is not possible for me to change the selection to Rotate1. Please see my Photo

Attached is a photo for consultation:

I don't have the "Independet" option in the bar.

Could it be because of some adjustment that I haven't made?

Regards

Re: Scissor arm movement

Libbya — Fri, 18 Oct 2019 13:54:19 GMT

If you set the system variable BACTIONBARMODE = 0, you will get the option during creation of the rotate (and scale) actions. With BACTIONBARMODE=1 you do not get the option during creation but you can select the action, go to properties, and change the Base Type to 'independent'. A new grip will appear at the center of the rotation parameter. That grip can be moved wherever you want the center of rotation. That said, you will need BACTIONBARMODE=0 at other times in the process in order to add the independent rotate actions to the selection set of other actions, so it might just be easier to set it to 0 for the whole process.

Re: Scissor arm movement

Rob_Molina — Tue, 22 Oct 2019 12:32:11 GMT

I finally made the dynamic block, thanks to the video.
I only remain pending to erase the two points. It is not possible for me to select them independently.

Re: Scissor arm movement

Libbya — Tue, 22 Oct 2019 14:46:23 GMT

There are several ways to remove the grips.