Which plastic to use.

[Peter G. ShawParticipant @peterg-shaw75338]

My daughter's dishwasher has broken. It's obsolete with as far as I can see with no spares available, yet with a bit of DIY it could be repaired.

What appears to have happened is that the wheels at one side of the upper basket have disappeared – one was found in the bottom of the machine – so all we need are a new set of wheels. Steel will rust, aluminium will corrode, although how fast I don't know, so the answer would be a plastic of some description. So, any thoughts on which would be the most suitable plastic.

The wheels themselves are similar to a sewing machine bottom feed bobbin, only slightly larger, and no holes in the flanges. The inside diameter consists of a short parallel section, perhaps 5mm long, then a ridge followed by a tapered section maybe 10mm long. Internal diameter about 10 to 12mm. The flanges are 1.5-2mm thick, 22 & 25 mm diameter whilst the centre portion is perhaps 19mm dia and 12mm wide.

MTIA,

Peter G. Shaw

Edited By Peter G. Shaw on 19/09/2014 16:48:06

[Peter G. ShawParticipant @peterg-shaw75338]

[Swarf, Mostly!Participant @swarfmostly]

Hi there, Peter,

I'd say, considering the likely operating temperature, you need a thermo-setting plastic rather than a thermo-plastic plastic!!

My suggestion would be a fabric-based grade of Tufnol (aka SRBF) machined from thick sheet rather than from rod.

Years ago, a candidate might have been Ferrobestos but I guess that's a No-No material these days!

Best regards,

Swarf, Mostly!

[Neil WyattModerator @neilwyatt]

Hi Peter,

You can get most bits from espares, but if what you see is in the picture below suit, I'll send you a few – once one goes, others follow. They are spares I kept in hand after many years of dishwasher resuscitation, but we bought a different type of dishwasher.

The white ones are new, the grey one, rather used but OK

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Peter,

Probably the best "engineering plastic" is PEEK

Fairly expensive stuff if you buy it as "stock" … but this ebay seller often has offcuts at a reasonable price.

… No connection except as a delighted customer.

MichaelG.

[Peter G. ShawParticipant @peterg-shaw75338]

Swarf, Mostly,

Noted. Thanks.

Neil,

I've been onto espares, Zanussi, and other sites, and whilst the wheels you show are relatively common, the ones that I need are similar to this:

http://www.spareparts.ie/shop/Zanussi-Basket-runner-%285031681371672%29.1538?layout=grid&filters=Zanussi-m24

except that it is, I think Irish.

This site:

http://www.buyspares.co.uk/zanussi/dishwasher/wheel-support/product.pl?pid=316144&shop=zanussi&path=10829

Shows something similar, but does not mention my daughter's Model No.. Or rather, says that it can't be found. Now I could order this up, on spec, and see what it looks like. On the other hand, I may give them a ring and ask for dimensions.

But just for the moment, making them seems to be the only sure method of getting exact copies.

Thanks anyway.

Cheers,

Peter

p.s. It's a Zanussi DI720 by the way. I've found references to a DI720B and a DI720W, but not the plain DI720.

 

Edited By Peter G. Shaw on 19/09/2014 17:22:49

[john jennings 1Participant @johnjennings1]

If you have already tried apologies , but I think that you may be unduly pessimistic concerning spares.

I had the same problem with a ten/twelve (??) year old machine finding the top wheels were disintegrating.

As a typical practical (tightwad?) model engineer I checked through what I had in the way of plastic bits.

Although I found possible material its boiling water resistance was unknown , it also on reflection seemed a lot of tricky machining that might end in melt down.

A bit of webbing and I found http://www.espares.co.uk that had pages of BASKET WHEEL spares (not manufacturers originals but manufacturer seem not to care for the older spare! ) and after a lot of gazing I picked a set that worked, if not an exact match, and gave another two years before another terminal illness intervened.

Alternatively a midway course of cannibalising a near match could be tried.

The only caution is that the wheels are relatively expensive ( with post c.£20 for four ) and buying a hat full to try is not really practical unless you employ a buy/try/return strategy

happy searching

JOHN

[FatgadgiParticipant @fatgadgi]

Hi Peter

The answer to your material question is almost certainly Acetal. There are some grades that are better than others, but I'd take a chance on the bog standard stuff.

Acetal has no problem with hot water and will be OK with the drying temperature.

Cheers – Will

[Neil WyattModerator @neilwyatt]

Sorry Peter, I've scrapped two machines in the last year and I'm sure BOTH would have offered you a donor part to match that.

My experience with espares is that if it looks right, it probably is – with white goods you will find that many machines are badge engineered across six or seven companies (especially 'Zannussi' dishwashers. Model numbers tend only to matter with control boards an fascias (extra buttons etc.) the mechanical bits are usually consistent across whole swathes of machines.

Neil

[John HinkleyParticipant @johnhinkley26699]

Peter,

Do any of these fit the bill?

http://www.candmdomesticappliances.co.uk/dishwasher-basket-spare-parts#limit=48&mode=grid&order=name&dir=asc&p=1

The place advertises 'obsolete parts'.

John

[Chris TriceParticipant @christrice43267]

There's always brass.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Chris Trice on 19/09/2014 18:37:05:

There's always brass.

.

Where there's Muck …

[and also where there's "special" plastic components]

MichaelG.

[Brian WoodParticipant @brianwood45127]

Hello Peter,

Experience from one who knows. We had the same problem; I made new wheels from nylon 66.

They have done more that 5 years daily service since and are still intact without showing any distress.

Cheap and cheerful

Regards Brian

[Peter G. ShawParticipant @peterg-shaw75338]

John J,

Tried espares. I didn't actually find one that looked similar. At least I don't think I did – I find that after a while the brain starts "boggling" with an overload of information and I lose track of which websites I've visited.

As far as being pessimistic is concerned, I've already had a similar problem with a Zanussi fridge and been told by Zanussi that it was now obsolete. In the end, I sourced a replacement sheet of 6mm glass to replace the broken 4mm one and got the supplier to smooth off the edges. Both these appliances are built-in and it's logical to assume that both are of similar vintage. I did manage to find a Users Guide for the dishwasher somewhere.

Swarf, Mostly, Will, Brian, Michael,

Tufnol, Acetal, Nylon66, PEEK. College Engineering certainly do Tufnol, Acetal and Nylon (but no other info). RS do Acetal, Nylon (and the one I looked up was Nylon 6) and PEEK.

According to CES's website, Acetal is easier to machine than Nylon so that may be the way to go.

One thing that does concern me is that I have read adverse comments about certain plastics creating toxic fumes. I think this is mainly PTFE, but I think more reading may be required.

Chris,

Interestingly, I had thought about brass, but thought it might run out rather expensive. Same with bronze.

John H,

The very first item looks to be identical to one from Spare Parts.ie except that C&M is for an AEG whilst Spare Parts is for a Zanussi. Which does rather seem to suggest badge engineering.

I think what I'm going to do is to measure the one remaining wheel, then contact either C&M or another UK company I found selling the same item, and ask them to check their dimensions. If satisfactory, then I think that will be the way I shall go. Otherwise, it's going to be one of the plastics as discussed above.

Final question. How easy is PEEK to machine?

MTIA,

Peter G. Shaw

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Peter G. Shaw on 19/09/2014 20:39:14:

.Final question. How easy is PEEK to machine?

MTIA,

Peter G. Shaw

.

Very !!

MichaelG.

.

Edit: Here is some useful info.

Edit: For critical work, it's worth Annealing PEEK, see here

Edited By Michael Gilligan on 19/09/2014 20:53:54

Edited By Michael Gilligan on 19/09/2014 21:03:52

[Keith LongParticipant @keithlong89920]

Peter

PM sent

Keith

[Frank.N StormParticipant @frank-nstorm18349]

Nobody here sharing my opinion that using PEEK in a dishwasher is a (very large) bit over the top?

Peter, stay with Delrin or Nylon. My dishwasher washes with 55 deg C. Some grades (of PEEK) have a useful operating temperature of up to 250 °C (482 °F) (cit. Wikipedia). Do you think you need that?

Regards, Frank

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Frank.N Storm on 19/09/2014 22:53:57:

Nobody here sharing my opinion that using PEEK in a dishwasher is a (very large) bit over the top?

.

Well … The originals have failed … and in Peter's position, I would only want to do the job once.

Offcuts are cheap; so what's the problem?

Good practice for the day you need to use the stuff.

MichaelG.

.

P.S. … Nylon is hygroscopic, so I would certainly avoid using that.

Edited By Michael Gilligan on 19/09/2014 23:27:30

[FatgadgiParticipant @fatgadgi]

Hi Michael

Isn't PEEK normally very stiff but can be quite brittle ? I think it's the wrong material to use in this instance as the flanges are thin and I would expect them to break off after a short time of use.

You are right about nylon being hygroscopic, which is why I doubt it would be used in original parts, but in reality the only real downside is that it causes a dimensional change and they actually get tougher and practically I'm sure they would be OK.

PEEK is also hygroscopic if I recall correctly.

Cheers – Will

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Will Bells on 20/09/2014 00:27:52:

You are right about nylon being hygroscopic, which is why I doubt it would be used in original parts, but in reality the only real downside is that it causes a dimensional change

.

Will.

The dimensional change is what makes Nylon risky for [what I presume to be] "plain-bearing" wheels.

It's past bedtime now, but I will have a peek at PEEK specifications tomorrow.

MichaelG.

[Jeff DaymanParticipant @jeffdayman43397]

Acetal or nylon (zytel engineering nylon is good if you can get it) will be fine for a home dishwasher.

I specified both in my work in industry on designing instrument washers for medical and dental use (very much like a dishwasher, but they run at 90 deg C + and use disinfectant). Most dishwashers run at 65 – 70 deg C.

No trouble with either material over many years testing and in-field use in these instrument washers.

PEEK is ridiculously over the top for dishwasher parts.

It's extreme cost is justified if the item to be made has to be steam autoclaved at 134 deg C+ for 15 minutes repeatedly, or item is to be implanted in a human. Otherwise, cheaper stuff does the job.

JD

[jim’Participant @jim11037]

here are a few charts on plastics

**LINK**

 

think i'd go with delrin

Edited By jim’ on 20/09/2014 02:39:17

[Michael GilliganParticipant @michaelgilligan61133]

Jeff,

I bow to your wisdom.

MichaelG.

[FMESParticipant @fmes]

Peter,

If you actually contact e-spares http://www.espares.co.uk/contact/sales they will get back to you very quickly.

Just did the same thing for my Hotpoint washing machine drum bearings.

Unfortunately for me the answer was not what I was looking for – the whole drum assembly has to be replaced as the bearings are moulded into the outer casing

Not good for a machine just over five years old.

[FatgadgiParticipant @fatgadgi]

Hi Jim

That's an excellent comparison. It's bookmarked !

Delrin is a type of Acetal from Dupont. I think slightly better strength and doesn't squeak as easily but slightly worse temperature and chemical resistance on average. But for Peters application it would be as good as anything. And bog standard acetal would be good as well.

Cheers Will

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