Radii Question

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stsmetals
Posts: 17
Joined: Mon Mar 16, 2015 8:58 pm
Location: Carpentersville, Il.

Radii Question

Post by stsmetals »

I'm using Vcarve Pro 7.5 and trying to figure out how to make a radii tangent to two radii. A good example of what I'm trying to do would be a bicycle chain link or a roller chain link. I really cant afford a cad program after my purchase of my cnc and tried some of the free stuff but exporting and saving to a dxf file sucks. I can get close in Vcarve but since it's not a true tanget point,( in my drawing anyway ) how will Vcarve handle this. Thanks in advance for any help.
Terry

4DThinker
Posts: 951
Joined: Wed Jun 27, 2012 9:00 am

Re: Radii Question

Post by 4DThinker »

There is a tangent gadget for Vcarve Pro if that is what you are using.

On this page: http://gadgets.vectric.com/index.php?op ... Itemid=186

It require two circles to be select before selecting. If you are working with arcs then temporarily add a complete circle over each arc and then run the gadget. Delete the circles when you are done and any extra tangent lines you don't need.

stsmetals
Posts: 17
Joined: Mon Mar 16, 2015 8:58 pm
Location: Carpentersville, Il.

Re: Radii Question

Post by stsmetals »

Thanks! Just tried it and worked great. thank again.

Eagle55
Posts: 788
Joined: Sun Nov 20, 2011 8:44 pm

Re: Radii Question

Post by Eagle55 »

Hi Terry,
Did the tangent gadget work for what you wanted? I tried it last night and although it created the tangent line geometry it didn't do anything for tangent arcs that I could find, which is what I thought you were looking for. There may be another gadget that is available for that, I didn't have time to search for it. I too am really sensitive to spending more money on software even though its been over 3 years since I made my big purchase. After about a year since 7.5 came out I finally paid for the update only to find out that 8.0 came out the next month. Fortunately I qualified for the upgrade at no charge. Always remember that the forum is a great source or resource for help. There are those of us that have cad programs and would be willing to do things to help out anytime. I also think there are some free cad programs that might do reasonably well for certain things. I went to TurboCad after using AutoCad LT for several years. When they got to the point of "designed failure" if you don't upgrade regularly, I discovered that TurboCad work as well if not better for all the things I needed and in fact did 3D where AutoCad LT didn't. Anyway point being if you need anything along those line I would help if my knowledge is within your needs (and probably others would too). I to have found that sometimes its easier to design or manipulate a design in another program and bring it into VCarve even though VCarve is a decent "CAD" program in itself for many of the things that we do. I even did a logo that I was to carve in VCarve and exported it to use in a drawing in TurboCad. Anyway, point being that you have a lot more resource than you think when you hang around the forums.

Roger
CNC Shark HD ~ Control Panel 2.0 ~ Windows 7 & XP
Located in West Tennessee near the Tennessee River
http://www.eaglecarver4.com

stsmetals
Posts: 17
Joined: Mon Mar 16, 2015 8:58 pm
Location: Carpentersville, Il.

Re: Radii Question

Post by stsmetals »

Thanks for your input Roger. I started looking hard at the tangent points and saw that they weren't exactly what I was looking for. They were a line tangent to the radii but I needed an arc tangent to arc. What I wound up doing was knocking the dust off my trig tables book, taking 2 Advil and find my scientific calculator. It took a long time because I haven't had to figure anything like this in 15 years. The finish tool path is a smooth transition between arcs and exactly what I was looking for. Once again thanks for your input.
Terry

Eagle55
Posts: 788
Joined: Sun Nov 20, 2011 8:44 pm

Re: Radii Question

Post by Eagle55 »

Hi Terry,

I looked at your answer and tried to figure out what I would have used in trig to create tangent arc and just couldn't remember back that far, so I let it rest for a while. I woke up at 3 am last night and it came to me that drawing the correctly placed guidelines would place circles tangent to each other. What I did was right but in actuality it was slightly off for VCarve and had to manually adjust a tad to get the trim tool to work the way I wanted it to.

What I started with was 2 one inch radius circles and I wanted to connect it with a two inch radius arc. (all dimensions randomly specified). I drew the two one inch radius circles then I drew two circles for guide lines that were 3 inch radius (1" for the radius of the 2 basic circles that I want to create a tangent for and 2" for the circle that I want to make tangent to them). There where the two guidelines cross is the center point for the 2" circle that should be tangent to them, so I place a 2" circle at each of the center points where the guideline circles intersect. Theoretically this should be exact but in VCarve the circles appeared to be tangent but they didn't actually cross or intersect according to the "Trim" tool (little scissors), so I manually fudged the center of the 2" circles just slightly towards the two circles to insure that they touch and begin to delete guidelines and trim the unwanted vector segments and then joined the resulting vector segments came up with one "bicycle chain link" shaped vector that I desired on the start. With the first "chain link" joined as one vector you can now carve it as a profile, pocket or do a offset vector and engrave OR copy it and make several. All in all not too complex one the neutrons in my brain finally access what I already knew.

Roger
Attachments
circles and guidelines all together
circles and guidelines all together
partial circles remaining with the arc circle trimmed and all guidelines removed or place on an invisible layer for use later.
partial circles remaining with the arc circle trimmed and all guidelines removed or place on an invisible layer for use later.
CNC Shark HD ~ Control Panel 2.0 ~ Windows 7 & XP
Located in West Tennessee near the Tennessee River
http://www.eaglecarver4.com

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