Revolutionary Meditation Bench
in
3D Modeling Design
held by
Sentinel
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Description:
A standard meditation bench made of wood gets a makeover. We are looking to create a fully-adjustable, lightweight, travel version of a wooden meditation bench for manufacture via injection molding (plastic). Here is a reference for what it usually looks like (not what we are making):www.samadhicushions.com/Meditation-Bench-Seiza-Kneeling-Bench-p/C-564.htm
The bench consists of 2 legs, of the same size, 7.5 inches tall. Atop is a main sitting piece, which is at right angles to the legs and is 18 inches long and 7 inches deep. All parts are ½ inch thick, or thinner.
The bench needs to be able to support the weight of an adult.
The main sitting piece (piece “A” in the sketch) needs to be rotational such that it can be tilted forward in order to create an angled seating platform. This adjustment is to conform to the seating angle of the meditator to create comfortable sitting position. The piece must lock out once in place at the desired setting, in order to provide stability while sitting on it (aka it does not move).
The legs must also be retractable, such that they fold in towards the main sitting piece in some manner, in order to make the bench small and practical for travelling or storage. When folded, teethe assembly should ideally be no more than 1 inch thick.
Wants:
Will be evaluated on how comprehensively the design meets and achieves all of the technical aspects from the description above.
Don't Wants:
An incomplete design that does not properly address all elements, in a way that is actually manufacturable per injection moulding process.
Ask for Sample:
Supported file extensions:
sldprt, x_t, igs, step
Software:
- SolidWorks
- PTC Creo Parametric
Additional Information
Please note that one of the main criteria for design is also the weight of the product. It is meant to be as light weight as possible, while supporting the functionality requirements. A perfect score on this point would be a weight of 1lb.
Prepaid PrizeEntries
Discussion
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Congratulation to the winner,
i have a curiosity:
how weight the model?
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.
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
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
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
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
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 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.
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
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!
I am improving the model, it will upload soon!
Would love to see how 
folds
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
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
This will drive wall thickness on the plastic and correspondingly the design
http://www.protolabs.com/injection-molding/fundamentals-of-molding/wall-thickness-recommended
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