How would you make this simple part? 1

[kjcdb8er]

Hello,

I know nothing about plastics. I'm hoping to get some background before I walk into some local facilities. So, how would you make this part economically, either in your garage or manufactured at low volume?

The plastic needs to be rigid/resistant to gouging.

 

[Demon3]

That would be made by injection molding if you need 100,000 or more a year. You need to spend lots on an injection molding tool, hence you need to make lots before you can justify the tool / mold expense.

If you less than that many you can get a cheaper aluminium mold.

If you only need a few and can accept poor surface finish then you can try rapid prototyping, for example, contact Stratasys.


Chris DeArmitt

 

[patprimmer]

In the absence of almost all relevant information, I would recommend casting from a two pot resin like polyester, epoxy, silicone, polyurethane or acrylic.

I have seen injection moulds made to make less than 1000 parts, but the amortisation cost was high. In some cases that high amortisation cost can be justified. The sums are simple if you know how many you can sell at what price, at what piece cost and what tooling cost.

The thin wall will make it very difficult to machine from bar stock.

Do you mean gouging during machining or during use as a bearing.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[kjcdb8er]

First, thanks for all the replies. And sorry I didn't provide enough detail. I've updated the image to be more representative of the design.

From everything I've seen, if my idea can ever afford injection molding I'll be doing alright. For the foreseeable future, I need to look at alternatives.

>> For instance, that 0.5 mm seems dodgy to manufacture, using machining, for instance, due to low stifness of plastics (especially at a bit higher temps, as during machining).

Yes, I worried about that but those are my design constraints. Is there a stiffer material, like kydex, that retains strength/rigidity when thin?

To machine the part, I would route out the inner cavity from a thicker bar, and then thin it down and shape it from the outside. Does that seem reasonable?

>> Do you mean gouging during machining or during use as a bearing.

I meant that the material needs to be rigid and strong in the final product. The plastic is an encapsulation for some sensitive electronics. It needs to be aesthetically pleasing, and resistant to deformation. Since its thin, it also shouldn't gouge easily.

Hopefully that's enough information? Does anyone see how a vacuum thermoform, or press, or combination of the two might be employed?

Thanks!

 

[patprimmer]

If you work carefully with VERY sharp tools and good back clearance you can machine the part from acetal or POM (Delrin, Celcon, Duracon, Ultrahorm, Hostaform, Kemetal, Tenax etc)if you do as NunoH says and turn the inside to size first, then fit on a mandrel then use the support of the mandrel to accurately turn the outside.

Cutting fluid will help to cool the part, but you will need to take the last few cuts VERY carefully to avoid the cutter picking up the plastic and tearing it.

In my opinion, the simplest way as already mentioned will be to use a two pot epoxy and cast the parts in a simple mould, most likely made of wood or aluminium.

You seem to be at a very elementary level here, comercially and technically in all regards. Are you a student. Is ths a homework project.





Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[mcgyvr]

I would look into Protomold.com if you want it injection molded. They use aluminum molds built right from your solid model (assuming you have the required draft/corner radius,etc...) Their online quote tool with give you pricing and tell you where you need to apply a radius or drafts based on you uploading your 3d model. Price is great for the tooling. I find their piece pricing to be high though. But depending on the volume it might meet your needs just fine. They have a decent selection of resins also.

 

[ornerynorsk]

Injection molding can be very cost effective at any volume, depending on your target price or your design allowable cost. What is your annual volume? You can have a 16 cavity tool made for this part for around $5000 usd, sleeve ejection, sub-gate or hot runner, the works.

 

[Pud]

ornerynorsk,

Where on the planet are you? Last time I looked, hot runners were about £1000 per drop - cost price to buy in!. Your estimate of $5K for 16 cavity/sleeve ejection looks like the bargain of the century!

Let me know where this is - I have an application for an 8 cavity hot runnered job, ready to go apart from tool cost.


Cheers

Harry

 

[patprimmer]

I have ben involved with some cheap tooling, including from China, and making inserts to fit a std bolster, and cast epoxy inserts in a bolster and aluminum tools, but I find 16 cavity hot runner at that price simply unbeleivable.

A simple single cavity mild steel tool with no cooling for the OPs part I would expect could be done for under A$1000.



Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[bvanhiel]

It all boils down to how many you are making and what concessions you can make in materials and tolerances. In addition to machining and injection molding you could also rotocast the part depending the material requirements. You could spend anywhere $0-$100,000 on tooling and have per part costs ranging from $50 to $0.05.

Good Luck.

-b

 

[bobslo]

Hi guys

My proposal is to use thermoset material (phenolic CTI 175V or melamine CTI >300V) which can be compress moulded.
Such simple single mould inserts could be very cheap and installed in some existing mould.

Best regards
Boris

 

[sizzer33]

Hi,

from your comment, "I meant that the material needs to be rigid and strong in the final product. The plastic is an encapsulation for some sensitive electronics. It needs to be aesthetically pleasing, and resistant to deformation. Since its thin, it also shouldn't gouge easily."

If the wall is 0.5mm all the way to the top, you'll probably get a part that looks/feels like a drinking straw. But looking at the design now, it will deform and crack real easy. I suggest to increase wall thickness on the "closed section tip" (maybe to 1.5mm) and then on the open end, add a rib that goes round the open end. Sort of like, forgive my word, a condom.