learning cad

[jixxerbill]

Hope this works...

 

[wildun]

I have been stuck on my soapbox ever since I did my post! guess I'll have to wait till my wife comes home from work!

 

[aonemarine]

Chris, I really dont know why you are saying sorry... Your students are very talented. Keep on teaching and inspireing them, god knows we need them to take over and lead one day.

 

[wildun]

LITTLELOCOS,
Very impressed with the 3 cylinder radial! and also with the renderings, I like those who can both "render" and make the rendering reality!

 

[Chriske]

LITTLELOCOS,
Very impressed with the 3 cylinder radial! and also with the renderings, I like those who can both "render" and make the rendering reality!

Yes indeed,

littlelocos could you tell us something more on that 'Green machine'..?

Chris

 

[Auzzie53]

DraftSight -
Download
draftsight.en.softonic.com/

This is a full blown Cad package (looks and acts like Autocad) I have training notes as I used to teach Autocad.

Regards
John

 

[Dave Sohlstrom]

Auzzie53

I have a copy of draftsight. Can you tell me how I can get it to tell me how long the line I am drawing is. Other CAD programs I use have a read out of some sort tht tells me now long the line is as I draw it. I like drawing to the grid

Dave

 

[littlelocos]

Yes indeed,

littlelocos could you tell us something more on that 'Green machine'..?

Chris

Hello Chris,
The Green Machine is a 1/3-scale 1/2Hp Parsell & Weed engine as described in "Gas Engine Construction" first published in 1900. I recently bought a complete set of foundry patterns, AutoCAD files, and the rights to produce kits for this little guy and his vertical brother. Currently, I am spending my evenings converting the original 2D design to 3D, correcting minor errors and making the drawings presentable. 0.850" Bore, 1.312" Stroke, 5" flywheels. I hope to have a prototype built and castings available by next year's Cabin Fever show.

The book was reprinted by Lindsay Publications until he (sadly) retired. It is currently available in PDF on Google Books.
http://books.google.com/books/about/Gas_engine_construction.html?id=MO1MAAAAMAAJ

A pic of the original prototype (1993) is attached.
Enjoy,
Todd.

 

[kf2qd]

Auzzie53

I have a copy of draftsight. Can you tell me how I can get it to tell me how long the line I am drawing is. Other CAD programs I use have a read out of some sort tht tells me now long the line is as I draw it. I like drawing to the grid

Dave

There is a readout at the bottom of the screen that you can configure. I used to use it, but found it much easier to draw lines long and then trim them afterwards. Unlike drawing on paper, you don't have to worry about the marks left after erasing and it is often easier to treat your detail lines like construction lines and then trim them to clean up after you get the pieces sketched in. I start a lot of parts with a linr in the X direction, then a line in the Y direction and then use the chamfer tool with the distance set to zero to make a square corner. The offset those 2 lines to the part dimensions and once again use the chamfer tool to square up the corners.

The CAD process allows you to use some of the ideas from sketching to get the drawing started, and then you clean up the details and have a finished drawing. As teh erasing just takes place with numbers, you don't have to worry about the mess left behind from erasing. If I used my CAD procedures on paper I would wear holes it the paper. But I can get from Idea to finished part much quicker than I used to, and I can easily modify a previously created drawing too make a new part.

Probably the hardest thing to learn is LAYERS. Once you figure them out, you can put each part of an assembly on a layer and turn layers on and off or Lock certain layers to work on portions of your without affecting previous parts. Works nice for 3D so you can get rid of some part while you fit other parts in place. Layers can also be used to provide colors for different materials. Everything on a given layer shares the same properties.

http://www.homemodelenginemachinist.com/f12/some-3d-models-19374/ has some 3D model of Elmers Engines that I started that I need to get backl to and finish...

 

[Auzzie53]

Auzzie53

I have a copy of draftsight. Can you tell me how I can get it to tell me how long the line I am drawing is. Other CAD programs I use have a read out of some sort tht tells me now long the line is as I draw it. I like drawing to the grid

Dave

Dave send me your email address and and I will send you some stuff.

for a line set your units imperial or metric if you a normal person (sorry) pick a point to start and type in distance. I will send you a how to any questions fire in I been on cad since 83

Regards
John

 

[kvom]

My techniques in Draftsight for positioning lines are these:

1) if I know the start and end coords I just type them in.

2) Draw a vertical or horizontal infinite line at the start point, then use move or copy function with the Displacement option to control length. Then trim as needed.

 

[dman]

to really get efficient at cad learn a little about geometric construction, you don't need geometric construction as much in cad as you do on paper but it still helps. also don't rely so much on the mouse. the more you get familiar with keyboard input the better. some programs are very flexible on how to construct lines and arcs, others are not. so some programs will need adjustments to your style, others will be more free flowing. the more ways you get to know how to put a feature where it needs to be the better when it comes to using different programs.

learn to make up construction lines for the basic geometry using infinite lines or if they are not available lines of an arbitrary length that are longer than the part. use the vertical and horizontal line features in the software and either use the keyboard to input the x or y coordinate they pass through or make a cross off the origin and use the copy function (sometimes under a translate menu) to make lines where significant features lay. once you have starting points for the geometry laid out then using the mouse to put in the real outlines becomes a lot easier. i find grids to be much less helpful than my own construction lines and never show grids or snap to grids. if the program has layers that can be used for lines then you can put construction lines on a seperate layer so they don't have to be deleted later.

 

[lohring]

Around 50 years ago I was employed as a draftsman. I worked for a lot of companies that made things from atomic submarines to zippers. It paid for the schooling my current carrier required. I started 2D computer drafting as a hobby with Generic CAD. I believe it became Autocad Lite after Autocad purchased the company. I'm currently learning Alibre so I can 3D print parts for investment casting master patterns and cores.

I have problems with complex 3D passages and parts like the two stroke engine transfer passages pictured below. The only way I can think of to do this is to define a lot of planes at various angles and locations, draw cross sections of the passages then loft extrude the passage through these sections. Is there a better way?

Lohring Miller

 

[wildun]

I have problems with complex 3D passages and parts like the two stroke engine transfer passages pictured below.
Lohring Miller

LOHRING & DMAN
I admit that I have only dabbled in CAD and using a low end program, (Design Cad) which is fine for me, but I have just downloaded Nanocad out of curiosity, so maybe I can rely on you guys to keep me straight.
I'm retired and perhaps getting a little old now, but still as enthusiastic (just found out lately) as I ever was!

Lohring, your complicated core looks very impressive! - the whole design looks to be for extreme competition (motocross or kart maybe?).

The reason I am so interested is that I used to do factory development work mainly in CNC tooling, coreboxes and some wooden patterns for fluid valves ( nothing overly complicated as in your work) but I often got to design these or modify existing ones on the drawing board as well and I loved it! - I worked on the shop floor of course so my draughting experiences were relatively limited but I did consider them a bonus.

There was no CAD in those days, so now I would like to get to grips with the basics of CAD and find a program later with good 3D rendering (and for a reasonable price!).

At first I thought that your core was a rendering, but it looks too real for that! - dare I ask what make and purpose the engine in the drawing was to be used for?

 

[Maryak]

Maybe try sweep or rail sweep with both twist and draft angle along a path between start and finish sections.

Hope this helps and works for you.

Best Regards
Bob

 

[littlelocos]

Lohring,

Lofting would probably work well for complex shapes like that. I have usedit for rendering guitar necks and lapstrake boats to good advantage. If youtook each passage and cut a section thru the entry, the exit, then one or twoothers to control the loft, it would probably work very well. I usually end up adjusting the sections and tweaking individual nodes to get the final shape to "look" right.

I don't know how sophisticated the lofting functions are in Alibre, but theones in Turbocad can actually be branched if needed.

Another possibility would be the SMESH function - Smooth-Mesh. Draw the part roughly to shape, w/ square corners, etc. Apply SMESH and the whole thing is smoothed out to whatever level you want.

Enjoy,
Todd.

 

[vascon2196]

All of the above...

- Sweeps with guide curves
- Loft with guide curves
- 3D sketches and surfacing

All of which can be tricky and in most cases require a work plane or axis.

 

[petertha]

I have problems with complex 3D passages and parts like the two stroke engine transfer passages pictured below.
Lohring Miller

I use Solidworks (un-professionally), mostly self taught, so take that FWIW. From what little I understand of Alibre, maybe it has similar 3D commands.

I'll show some pictures of different methods I was mucking around with, maybe that will spark something you can replicate in Alibre.

- make the basic cylinder chunk, extruded circles
- make a profile sketch of the port outline on the base plane
- extrude the profile straight up some distance along inside the wall
- fillet the end nice & purdy

 

[petertha]

method 2, very similar, this time more control of the shape
- make a sketch defining a path which the profile will follow
- use the cut-sweep command
- this removes the port solid shape from the cylinder solid resulting in this representation

 

[petertha]

method 3,
- use a 3D curve to define an even more complex path for the port profile
- this one gets a bit funky because you then have to use a different SW command called 'intersect' to remove one from the other (port from cylinder).

Different cad programs handle this operation differently, some subtract boolean solids of 2 distinct solid bodies. Anyway, just intending to give you some food for thought. You are probablynot limited to one section shape, you could vary it along the path. (That makes my head ache!). Best of luck, I hope to see your castings & engine one day!