find the start point of a polyline

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jamby
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find the start point of a polyline

Post by jamby » Fri Jun 24, 2016 3:06 pm

Hi


I am new to qcad having just purchased 3.15.3.. running on Centos I am trying to work with a series of dxf files that I purchased to make cnc files for my machine. While cutting out these parts i need to start and end the cut froms certain locations so the parts don't break loose before the profile is finished. For the round parts now I have to create the gcode and watch the verification to see where they will start. I am hoping there is a function in qcad that would allow me to see the start location of the polyline that defines the part. Once I know where the part start point is I can rotate the part to a position that I need.

For the other parts (non-round) I have been exploding the polyline, deleting a straight line segment, joining the lines, then recreating the deleted line and finish by creating a new polyline with Draw>Polyline>Create from Segments.

If anyone knows of a function that would allow me to locate and move the start point of the polyline it would make this process much easier.

Thanks for your time
Jim

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Husky
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Re: find the start point of a polyline

Post by Husky » Fri Jun 24, 2016 8:16 pm

Hi Jim - welcome to the forum.
jamby wrote:... i need to start and end the cut froms certain locations so the parts don't break loose before the profile is finished.
Whats about holding tabs to keep the part in place?
jamby wrote:I am hoping there is a function in qcad that would allow me to see the start location of the polyline that defines the part. Once I know where the part start point is I can rotate the part to a position that I need.
Select the Polyline - check the Property Manager for Vertex/Index. Play around with the numbers - 0 should be your Start point (maybe you have first to switch to 1 and then back to 0 to see an indicator circle).
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jamby
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Re: find the start point of a polyline

Post by jamby » Sat Jun 25, 2016 2:45 am

Husky

Tabs, that maybe the answer. Right now I am cutting 1/4 mdf with a one legged .125 which cuts .132? Its held down by double back tape and if I pay attention when I put it on, I don't have to much problem with the parts moving. But some of the parts have narrow slots in them and if the cut starts there it can be a problem. So finding the start point early is helpful.

I found the "View > Property Editor" and as you say if I click the index number up then back the 0 index highlights.

Is there a way to reassign the Zero index to another location easily? Currently I rotate the part to reposition it.

Thanks
Jim

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Husky
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Re: find the start point of a polyline

Post by Husky » Sat Jun 25, 2016 9:15 am

Hi Jim,
jamby wrote:Is there a way to reassign the Zero index to another location easily? Currently I rotate the part to reposition it.
Not that I know of.

How do you create the G-code? Manually or you are using a CAM Program which creates the g-code? A Program should be able to determine the "Start position" / or maybe a "Lead in" or a "Ramp". Everything what helps to have less stress at the sensitive parts.

You are cutting your parts with just one path to come through the 1/4 mdf? Maybe it makes sense to use 4-5 paths at the narrow slots - will also reduce stress on the material.

Whats about to clamp the material down with a second mdf on top of the workpiece? Sandwich processing ...
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jamby
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Joined: Fri Jun 24, 2016 2:41 pm

Re: find the start point of a polyline

Post by jamby » Sun Jun 26, 2016 2:25 pm

Husky

All excellent ideas. For now on the smaller (less surface area) parts I've gone to cutting all but the last .03 of the profile on the first pass then cutting to finish depth. (.25 stk). One problem is once they are cut loose the vacuum makes them disappear.
I was using cambam v8. the free version to create the code. I've played with the newest version, and while its a much better product its a bit of overkill for what I am doing. I have Visual Mill 4.0 (another dinosaur) but it does not like the dxf files from Makecnc.com. However Visual Mill does have a function that allows you to move the start point around the periphery.
A lot of times I use Rhino 3d to produce a file for Visual Mill. That's the most common way I've been doing things. When really pressed I can use Apt360 to produce a cutter path.

Hey thanks for your help and advice. I am getting a bit better with qcad now and do like it. Its somewhat like Visual Cad a offshoot of Gcad. They all use two letter hot keys and I like that feature.

Jim

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