Revolutionary Meditation Bench

Congratulation to the winner,
i have a curiosity:
how weight the model?

congratulations for Pablo :)

Winner ?.

Dear Mr.Sentinel,
You have said that the bench that is to be designed should be a plastic part which is injection moulded. But you also say that it will have a thickness of 0.5 inch.
As per my knowlegde the injection moulding part can have a maximum thickness of 0.15 inch.
this is due to the flowablity of the molten plastic in the cavity. A thickness more than this will lead to filling problems and the design is going fail.

Thank you,

Rekha.

Hi Sentinel,
Can you rate please ! ?

Regards
REDA

Well the fact is that none of the posted designs meets all of the requirements (weight, thickness and strength), that I can tell just by the looks. And like you said, it is impossible to do so because of the construction techniques needed (because of plastic molding) and material properties that plastic has.
What I am more surprised of is that many of the designers here made their tables 0.5inch thick and with the right dimension but surely didn&;t do any FEM analysis to prove that their design really holds 100kg. I mean everyone that knows how to model in any of the CAD softwares can make a desk to meet the requirements, but not anyone can also prove that their design can withstand the required 100kg.
If I&;m going to post a deisign I will rather go on the save side and make a model with bigger thickness rather thjen make a model that will be useless.

Regards

Wow, is crazy rediculous. Awesome work Pablo

Hi,

I saw here very nicely handled proposals. However, for all is one of the great BUT:
Checked at least one of you the two key things - mass and strength?

I also spent some time on this project, still without posting anything.
Let&;s look at it from my party, so rather by the structure and the strength.
For the published geometry and human weight 100 kg.

1. If we are going to be based on the requirement of the maximum allowable weight, then the maximum allowable density of the material must be around 237 kg/m3 (118kg/m3 for 1" plate). The density of ABS plastic is around 1000 kg/m3, so for compliance with weight 1 lb would need only use 24% of the full volume of the individual parts (12% for 1" plate).

2. tensile strength of ABS plastic is about 30MPa. Then for full Board a minimum thickness of plate is 10 mm (based on maximal allowable stress. It is not necessary to do any FEA analysis, on this is sufficient just a pencil and paper. For this thickess of course, the total weight is about 1,5kg. This is 3,3 times more than is required, the maximum weight of 1 lb (0,454kg)

3. On some of the proposals, the authors tried to do some weight reduction by relief. I don&;t believe that much as they appear to be on to something.

4. And don&;t forget on deformations. If 1/2" plates will used then deformations can be around 10-20mm.

5. I don&;t know what you, but I have done few FEA analyses using software NASTRAN for various designs of lighted part "A". I have designed plate with thickness of around 15 mm. If I use this plate also for the parts "B" and "C", then the total weight of assembly is around 600 grams in the case of use the strength of ABS at 100% strength. Some weight could be save after optimization. However, still there are not included local stiffeners which are necessary in places of tilting and folding mechanism.

With regards

Martin

Hi,

The thickness of the bench should ideally be 1/2 inch or less, although consideration would be given to designs with thicker plastic, the ones with thinner and lighter designs would be considered superior.

cheers

The strengths of a plastic part are the material type and the ribs that are provided to the part with consideration of direction of the forces acting...
defects increase in plastics as thickness increases.

correctly said Mr. Luka B. i thought the same while designing the bench. being a mechanical engineer i can that the bench may get buckle easily for a load range of 80-100kg. (although i haven&;t done any FEA on my design yet) but i have a serious doubt about the thickness . thickness should be about 1 inch (specially for legs) when the product is to be made with plastics. no doubt the product can still be made with 0.5 inch thickness,but i can&;t guarantee it to be a highly durable product.

Hello sir,

I&;ve spent around 4 hours on this project but I havent posted anything yet. The thickness requirement is very harsh and since you want to make this desk out of plastic I highly doubt that it could carry a lot, like 100kg would be, from a mechanical point of view, nearly impossible. Even some of the designs posted here may look good, but I highly doubt they would be functional, even with as many strengthening ribs as possible.

Would you reconsider a bit bigger thickness, 3/4 or 1inch of the parts?

Regards

Luka

@Pablo - Its an interesting design ,Good work

@sldraftingdesign
I am improving the model, it will upload soon!

Would love to see how folds

is fantastic

is fantastic! Very good job Pablo

submitted, enjoy!

Hi Manuel, thanks for your estimate and the custom part website, I was not aware of it! Although I think we can do better than $100,000 in total cost for the first 10,000 through some contacts in China that specialize in high end snowboard bindings, this would not be an unfeasible cost. What parameters did you enter in the estimator to arrive at your numbers?

Wooden benches available online start at 5 lbs weight.

Hi Pat! I do not have a particular plastic in mind, and am open to suggestions regarding wall thickness as well. We were also suggested that a foam-filled product might be the way to go in order to get more strength.

Our main objectives (besides the desired functionality and strength) are light weight and small size. Of course the product needs to look good as well.

Thanks for your questions

Do you have a particular plastic in mind?
This will drive wall thickness on the plastic and correspondingly the design
http://www.protolabs.com/injection-molding/fundamentals-of-molding/wall-thickness-recommended