RE: RP Paper

From: Prof. P. M. Dickens (
Date: Fri Aug 06 1999 - 03:33:18 EEST

I saw your message to the rp mailing list earlier and the comments that you
This is a subject that is dear to my heart.
You have started a very important thread here. The original work we did was
with a company called Flymo (part of the Electrolux group), they make garden
care equipment. We wanted to see if it was economically feasible to
manufacture end use parts by RP instead of injection moulding. We found that
RP cost about 100 times more and injection moulding was about 100 times
faster. With the development of newer machines such as the SLA 5000 and then
the SLA 7000 these numbers will have changed. However, what we also showed
was that it was economic to make even small simple parts in numbers up to
6,000 before injection moulding became cheaper!

We have just installed an SLA 7000 so it would be interesting to redo the

I am 100% convinced that RP will move into direct manufacture of end use
parts with numbers into the thousands. This raises lots of other issues.

1. If we use RP then assuming the material properties are okay how would you
change the design to make it better. Remember an RP machine (of some sort)
can make any geometry.

2. How often would you change the design if you are not limited by tooling.

3. Do other factors limit you e.g. physics of the process in the product or
other parts e.g. filters in your case.

4. How will manufacturing change. Is everything Just in Time. Why make to

5. Can you eliminate parts e.g. if you sinter the part could you also make
the filter as well at the same time.

6. How will this freedom affect part variation. Is greater variety a good
thing? We have spent a long time reducing part counts. What are the pros and

7. If you use RP instead of die-casting which process would you use? Would
you try and make a sintered metal part to get near to what you have now? Why
do you have a die cast part now? Would a plastic RP part be okay? Would you
need to change the design to make it okay in plastic?

These are the issues that spring to mind now. I am sure there are lots of
other issues. You could do your project in any one of these. Choose the one
that is of most interest to you. If you would like us to make you some parts
for this project let me know. We have a Thermojet, SLA 7000, FDM 2000 and a
new EOSint M extended (metal sintering) will be installed in September.

I am in Atlanta at the moment visiting Georgia Tech and then onto Texas for
the SFF Symposium and then onto University of Arizona and so I will not be
able to email the paper until I get back to the UK on the 19th. Please email
me then to remind me.

There must be lots of other ideas on this. Lets start sharing. Have I missed
some important points? Is this all rubbish? Don't just sit there. Get

Prof. P. M. Dickens
Dept. of Mech. & Manuf. Eng.
De Montfort University
The Gateway
England LE1 9BH

Tel: +44 (0)116 257 7689
Fax: +44 (0)116 257 7025
Mobile: +44 (0)468 827039

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