Re: Standard Beam Approach - Rebuild update
Hi Richard,
For the insert I took the pin connector that I do have and put it on my home photocopier. I found that I got less shadowing if left the lid open and turned all the lights off. Next I take a fairly high resolution scan. It's entirely possible that the scan isn't symmetrical but it is not important at this stage.
I have a 3D drawing package - they are abundant these days and I suppose even a 3D CAD package would work. The advantage of my program is that it is mainly for c.g.i and so easily handles imported graphics, it also has 32-bit resolution. I get the program to make a cylinder (I know the diameter so that is precise). Next I project the image from the scanner onto the top of the cylinder. I can adjust the XY scale and do so until it fits - that is easy as I can cause the scanned image to go semi-transparent which lets me see through the image to where I am moving the cylinders. Now all the necessary holes are captured.
I did wonder for a split second if I might have done anything new, but it's not rocket science. Then I remembered when I was an apprentice 50 years ago the company I worked for had a machine that could project the shadow of a production item onto a screen which had go/no go markings on selectable transparent slides - no ideas are new.
Making more cylinders (of a size I have measured on one of the other inserts) I move these so that they are co-axial with each of the scanned pins as I see them. Once I am happy with one pin I can copy/paste all the pins in that row - these can be 'slid' along the axis so that each of those pins will be precisely level with the others (or precisely wrong of course) Any other pins that might need to be in line on other rows can be snapped on the same axis. This process much easier to see than to describe.
Now I have a big cylinder (the insert body) with a number of hopefully precisely placed smaller cylinders (the holes for the pins). Next I make the internal 'step' that stops the pins falling out. All the pin cylinders are 'cut' - but not split. Next the lower part of the cylinder is 'selected' and its X and Y dimensions are scaled - but not the Y. This causes the cylinder to flare. The dimension required is what I measure with a micrometer like tool - can't think what it is called.
So far this is all quick and easy. Next I make the program 'subtract' all the small cylinders from the big one - a Boolean operation. This is a pain as the dopey computer makes a real mess. Doing it by hand would take days so I have to 'pre-cut' the large cylinder to give the algorithm something to work with. Even after that I will spend 2 hours cleaning up the resultant mesh!
Once done - I check that there are no 'holes' in the mesh then export as an STL file and upload to a 3D printers web site! £35 min order with the one I chose, so I made two sets of parts.
The spacers and the cable guide are easy to do - just put in dimensions and the program does them for you!
The thread is actually simple! If I knew what the thread was I could get the dimensions off a drawing, instead I just measured the distance over a large number of threads and divided by the actual number of threads. Next some simple use of the micrometer thingy. Thickness of the shell and threads minus the shell alone = hieght of teeth.
Next I do a 2D drawing (spline) of the zig-zag that is the profile of the teeth - to the right size. Next I get the program to 'Lathe' that spline. This basically spins the spline around an axis while generating polygons in space as it goes and so generating a 3D 'concertina' shape. Now, happily, the program can also push the shape forward as it rotates it. If I get it to push forward at the same pitch as the thread it makes a screw! Now all I do is call up a cylinder and merge the two to make the bulk of the backshell.
So, not much skill in any of that thank goodness! And the bottom line is that if I get it wrong I can just tweak the drawings and repeat.
Cheers
James
Last edited by jamesinnewcastl; 26th Jan 2023 at 8:36 pm.
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