Where can I get recommendations for designing parts (thickness, etc)

I have designed a part for my micro-mendel version but I don't know if it has correct thickness, etc.

Are there any recommendations for designing parts anywhere?

If not, perhaps someone with experience could comment about this part that I designed?


Edited 1 time(s). Last edit at 10/11/2010 02:43AM by cluso99.

is this for you to print on a reprap or commercial printer? Or are you continuing to woodwork?

Quote

If not, perhaps someone with experience could comment about this part that I designed?

Well, on what should we comment? You neither tell us what you want to achieve, nor which size this part is. In CAD, scaling is trivial, so you'd have to add at least one measurement to provide an idea on how big this red part is.

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY

mlagana: I want to print it on a reprap. The wood was only for checking the basics and get a feel for the size and some measurements to see exactly how the motors will fit. Now I am embarking on designing the plastics for the actual model. My woodwork is far too sloppy (poor construction) for it to ever really work.

Traumflug: Sorry I didn't include measurements here - they are in the heekscad file and [forums.reprap.org]

I am using 6mm threaded-rod and round-bar for this part. I have allowed 5mm around the holes except for the slot where currently I allowed only 4.25mm (error in my other thread) on each side of the 1.5mm slot. The depth of the part is 16mm (5mm plastic + 6 hole for the rod + 5mm plastic) and the other dimension is 10mm (the rod bolts to this with washers and nuts at each end). The slot is designed for the threaded rod to compress and clamp the round bar which forms the X axis.

So what I am after is either a reference giving recommended thicknesses around bolts, etc, or at least a discussion about this?
Otherwise, is 5mm plastic enough or overkill around a 6mm rod or bar?
Can a slot of 1.5mm gap be produced by the reprap or is it too small?
Is there anything else I should be aware of?

Let me have a go at this:

Without having the practical experience, if I am in your shoes, I think one way would be to find out would be to perform a stress-strain analysis on the desired position you want to know.

Where (around which area?) and what kind of loading (tensile? Compressive? Shear?) will be exerted on this part when it is in action.

At the end, you might want to think of the safety factor you are comfortable with. Example like if you know your part will fail (due to whatever loading) @ 150N and you wish to have a safety factor of 2, then you might want to change your part to take on a max load of 300 N.

Hopefully these questions will help you get started.

TC

TianChang: I have no idea about this. This part is to be used in a micro-mendel version at the vertices. I do not know if any stress analysis has ever been done for the mendel or mini-mendel which could be used for this.

My background is in electronics so I would have no idea how to go about calculating this or for that matter how to calculate what the part would provide.

What is it that you mean by "correct"?
Is the question :
Can this part be fabricated using a given method (in this case printing on a RepRap or similar)?
Are the dimensions of the part suitable for a given load?
Does it look right?
Are the dimensions given correct for the part to fit?

You are making a part for a machine that no one has built before (assuming your version is unique) so it's going to be difficult to answer if it's "correct". I'd make it and see, which will give you the best answer. You can do a stress strain analysis all you like, but that will be a best case scenario at best, which doesn't account for poor build quality, or not a 100% dense object.

Plastic is cheap. Print one out, test it, make refinements. It'll probably be faster than theorizing about it.

The only thing I would recommend is fixing that bend in the middle, so that it's one box rather than two.

The less base shapes you use, the less chance for issues caused by overlaps not being 100% correct. The last thing you want is for the part to assume there is a small gap somewhere in the centre of that, which if printed could lead to it being no where near as strong (by lack of infill across that area).

Also, the top of the clamp part has less plastic anchoring it to the bend compared to the bottom. Not so much a problem, as a statement. Not quite sure how you'd easily fix it apart from changing the angle of it into the bend, but that could create other issues.

Please let me explain a little further.

My machine is not functional yet so I will have to pay someone to produce my parts. I do not want to give them part files that will not work because I have not allowed sufficient plastic thickness. As far as the angles and positions of the rods are concerned, I know these are where I want them.

So, I know the part will (should) work if there is sufficient plastic in there. There are no gaps of any significance in the diagonal part as I have zoomed in to be sure. However, I now understand Heekscad a little better and can build this part mathematically using the rotate by angle.

My questions still remain...

1. Is there anywhere (link) where part designs and recommendations are discussed as I have not been able to find any. This is probably due to the fact I do not know correct wording for searching, nor where to search.

2. Have I allowed enough plastic around the part?

My discussion on the reprap thread now has another part posted. This is a combined socket for the Z axis bearing and a pulley mount for the X axis. This part mounts on the right and left lower front-to-rear frame rods. I now have the top frame mounts with combined Z axis bearing socket and then the X & Y carriages. Then comes the X & Y carriages, the Z carriages plus the extruder mounting. Last will be the motor mounts. Maybe I will do the pulleys and cogs (to be decided).

if it's reprapped, and you're printing on ABS, think LEGO hardness. Maybe not *that* hard but pretty hard.

hard to comment on the part you posted without seeing it in full context, if the part is taking a lot of pressure you want it to be thicker. If this part is just holding a guide rail for x or y i'de say it is fine. if it is a structural support for the z axis maybe something sturdier.

oh and i'm pretty sure a slot of 1.5 can be printed.

i have a similar question, if a person is printing with a filament of .7, is .7 your minimum wall thickness?