Making of large plastic plate with hole/ slot pattern

[BadBeta]

We are in need of a small prototype series (300) plates of 1 cm thick PE plastic with lots of round or slotted holes. The plate themselves are about 110x70cm, and the holes/ slot should have a 4mm opening. Total hole ratio should be about 30-50 percent. The edges and surfaces should be rather smooth.(We can alternativly use thinner stiffer plastic, though not brittle at 0 degrees C).

So far I've come up emtpy in my search for even an remotely economical method of manufacturing such plates. Any and all ideas most welcome and appreciated!

 

[Pud]

Hi BadBeta,

I guess for your small batch (lot) off you are looking at starting with pre-cut 10mm sheet and then machining the holes/slots in. The holes/slots could be water-jet cut to ensure smooth surfaces. (The sheet will be smooth surfaces anyway)

Have a search for water-jet machinists or plastic fabricators/machinists in your area.

What do you consider economical?

Rgds

harry

 

[BadBeta]

Hi Harry,

That was more or less the original idea, but the cut lenght for each plate is about 14000 cm making waterjet quite expensive (or having rough edges, or both).

Economical would be, say, around or below US$ 50 machining cost per plate. Of course, the lower the better - right now we are consider building the mother of all circular saws to make these plates...

 

[daveshoes]

You can buy perforated plastic sheet (plastic paneling pre-perforated with holes).

Try:

http://www.mcnichols.com

DS

 

[BadBeta]

They seem to have some interesting fiberglass products. I will certainly look closer at them. Thanks!

 

[patprimmer]

For 300 of at $50 each, that is a $15,000 budget.

I would expect that a prototype mould could be made for a lot less than that, and 300 parts could be injection moulded in about 4 or 5 hours plus a few hours set up. Call it a day on a machine with at least 50 tonne clamp. I don't know where you are, or machine rates in your part of the world, but call it 8 hours at US$ 40.00/hour. Thats only 320 bucks plus say 5000 bucks for the mould. Certainly change out of 10 grand.

An aluminium mould would make many thousands of parts. Even an epoxy mould can make a few hundred parts if handled very carefully

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[BadBeta]

I have been looking into that as well. Like you say the actual manufacturing doesn't cost much, but the mould cost is on the huge side.

The finished product is rather low full box, where this is the bottom, and the injeciton mould for the entire box is estimated at approx 250000 US$ from China. The people and plastic manufacturers I have discussed this with has put the seperate mould for the bottom part in the region of US$ 50000.

That said I still think US$ 15000 in machining, plus material cost, is a lot to pay for what are essentially a small lot of perforated plates. I want to make sure there isn't any less expensive alternatives which somehow has deluded me. Dave's suggestion above might be an alternative, but then we have to accept a somewhat diverging and less representative prototype.

Any way of making this work with rotomoulding? Mould for use in rotomoulding would be inexpensive, about US$ 4000-5000, but the 4mm holes and ribs are detailed and we want massive material. Still, I anyone know a way to work it?

 

[patprimmer]

I see my error. I read your 110 by 70 as mm where in fact they are cm. That makes the mould about 100 times as big.

For 300 off only, a cast aluminium mould might still be an option

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[BadBeta]

I guessed it was something like that. And you are not the first either - many experienced people have done that before during this project. I guess they are perhaps more used to mm .

If I remember correctly the US$ 50000 mentioned above was for a short run moulding, but I'll check up on that.

 

[mckirdy]

Hi,

Can you send me a print of what you want at smckirdy@easternplastics.com. We specialize in machining complex plastic parts. I can't promise anything, however, I would like to try and help.


Sean

 

[Pud]

Hello all,

Would it be possible to injection mould a smaller unit of which a number of them would fix/clip together and comprise the whole thing?

As Pat has pointed out, a small(ish) moulding tool would not be expensive and the parts should be relatively cheap due to the low processing cost.

Rgds

Harry