Cheap Mold for a 5mm width part 1

[petersi]

Hi,

I want to make some small plastic part using material PE or PE +10%GF. The quantity I need is 3000pcs. No need to be very accurate, +- 0.3mm is good enough.

I want to know the is the cheapest way to make the part I need? What should be the budget? It would be good if you can show me which company can handle my small order.

Please check the attachment of my part. It is very simple and small part. The width of the part is only 5mm.


Thanks

 

[MikeHalloran]

If the major diameter is 5mm, that makes the hole size what? 1mm? The pin to make that hole is somewhat delicate.

My favorite molder used to make smallish parts like that for me in many materials in built-up aluminum molds with no draft. They'd make the cross-hole with a steel pin, manually inserted.


Meister Tool Co Inc
853 King Hill Rd
Greenville, NY 12083 -
(518) 966-8295
It's a tiny outfit. If the weather is good and business is slow, they might be out skiing or flying model airplanes.


Mike Halloran
Pembroke Pines, FL, USA

 

[petersi]

Thank you for your help.

Do you know something how much am I going to spend around?

The hole is like 1mm width.

What does it mean "aluminum molds with no draft". What is "no draft mean?

 

[MikeHalloran]

No draft means there doesn't have to be a taper on the part in order to extract it from the mold. You should expect sink marks in PE.

Make a dimensioned and toleranced drawing and ask for a quote.


Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

The only real way to make the part is injection moulding.

There are several details in this design as drawn that may cause problems. They are:-

1) The small pins to make the small holes wil be fragile.

2) The small pins will be prone to build up heat and that will considerably slow cycle times.

3) The square edges on the slot will be crack propagation points.

4) The large changes in section thickness will make packing the part very difficult. This will result in low physical properties, sinks and voids and moulded in stresses.

5) The slot with sharp corners and thick and variable section of its walls will certainly warp and close down at the open end.

6) 5000 parts is an inconvenient number, especially for a very small part as it is probably to many to machine from bar stock but is not really enough to justify large tooling expenses.

This means it is probably going to be done with cheap tooling which will minimise the chance of overcoming some of the problems listed above.

It might just be possible to extrude the section and drill the small holes. Probably not as the slot will probably close in like the injection moulding.

The degree that the slot closes in will be very dependent on the grade of PE. Higher density grades will be worst.

Chemical blowing agents will help.

Beryllium copper small pins will help the moulding speed and will be stronger.

I know a number of moulders who could mould it. One regularly posts here as Pud. Others are C&C Plastics, Bestmould Plastics and Anchor Plastics.


Regards
Pat
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[MacGyverS2000]

Just looked at the part... I would want to machine it. Take a piece of round stock, drill holes, slot, then cut into individual pieces. With the proper fixture setup, I'd figure on one week for setup and one week to crank them out by hand.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[patprimmer]

Dan

On further reflection I think I agree.

It can be injection moulded but without a redesign to make moulding easier the development on the mould will take some trial and error to correct warpage.

By the time it is molding with the slot width uniform, you may have already machined them from bar stock.

OP Why PE. It will be faster to machine it from a plastic that is harder with a higher melting point like acetal or nylon. Despite the higher material cost, the finished part may end up cheaper.

Regards
Pat
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[petersi]

Thank you so much on everybody's response. I have learned a great lesson here.

Actually the shape of the part can be change. At this low production quantity, i think the part is easier and faster for machining.

 

[raynjer]

Petersi - you've been given good recommendations here. Machine the pieces instead of making an injection mold. For the quantities you require - this is likely the cheapest, fastest option.
I figured at an 8 sec cycle time on a single cavity mold (not including the cost of the mold), you'll be at about 4 cents each to mold it depending on the hourly rates for machine & operator (which is where the bulk of the cost is going to go)
The mold is going to cost you many thousands extra unless you can find a small existing mold or mud base that could be inserted with your part. This will drive your price to $2-4$ per part when you include the cost of the mold. Way too much money for such a small quantity.
You might also want to investigate the possibility of finding an existing part to purchase that is similar and if necessary adjust your product to fit.