Re: The scoop? SLA-500 heat exchangers

From: ERIC KING (lzrdude@earthlink.net)
Date: Fri Mar 12 1999 - 21:42:12 EET


DANIEL CHARLES DAVIS wrote:
>
> All,
>
> OK, I have dug further into this and what Eric is saying is true, to a
> point. It seems that 3D buys LaserPure 20 and upgrades them to an
> "LP40" at their manufacturing site. I was told (by 3D) that it is only
> a valve change (no specifics indicated) and the unit shipped with the
> SLA500 retains the "LaserPure 20" identification. There was no mention
> of a heat exchanger upgrade (indeed our units, installed 7/97, have
> model CB26-50H exchangers). The reason stated was that this method is
> less costly than buying the LaserPure 40 outright.
>
> What does this mean? I'm not sure, but Coherent's documentation specs
> an LP40, which is significantly different in terms of flow rates &
> cooling capacity, which points to a larger heat exchanger in the LP40,
> not just a valve. The chart below shows only the specs that differ
> between the two:
>
> LP 20 LP 40
> - Cooling capacity at maximum
> plant side flow rate 20 kW 40 kW
>
> - Temperature delta at maximum
> plant side flow rate 4C 5C
> (39F) (41F)
>
> - Plant water flow range 2-8 gpm 2.5-10 gpm
> (7.5-30 lpm) (9.5-38 lpm)
>
> - Laser side flow (nominal) 2-3 gpm 5-7 gpm
> (7.5-11 lpm) (19-26.5 lpm)
>
> - Laser side flow (maximum) 5 gpm 15 gpm
> (19 lpm) (57 lpm)
> Terms used in this table:
> Delta: The difference in water temperature between the
> laser cooling loop
> and the plant water source.
> Plant side: The side of the heat exchanger cooled by the
> flow through water source.
> Laser side: The closed water loop that cools the laser
>
> Interesting to me as we have been having condensation problems inside
> the laser power supply. This is because the plant-water chillers have
> been set at a low temperature to keep the lasers cool. We have been
> told be 3D to increase both the temperature & flow of the plant water to
> correct this problem. OK, no problem. The recommended flow rate is
> 35-40 litres/hour. If we do have the LP20 this cannot happen, as flow
> is limited to 30 lpm max. Hmmm, problem. Also, if the LP40 heat
> exchanger is larger, then maybe we can increase our plant water
> temperature, still cool the laser, and things will be OK.
>
> Should we install the LP40 heat exchangers (model CB26-90H)? We'll just
> have to wait & see...
>
> ---
> Regards,
> Dan Davis
> PROTON Rapid Prototyping & Manufacturing Center
> Hicom Industrial Estate, Batu Tiga, PO Box 7100
> Shah Alam, 40918 Selangor MALAYSIA
> +60 3 515-2380 phone/fax
> http://www.protoncar.com/rapid.htm
>
> > > > -----Original Message-----
> > > > From: ERIC KING [SMTP:lzrdude@earthlink.net]
> > > > Sent: Monday, March 08, 1999 5:56 PM
> > > > To: rp-ml@bart.lpt.fi
> > > > Subject: SLA-500, heat exchangers
> > > >
> > > > Dear list,
> > > >
> > > > Please check your heat exchanger.
> > > >
> > > > It has come to our attention that there are several problems
> > > > concerning the Laser Pure heat exchangers on the SLA-500 machines:
> > > >
> > > > 1) The Coherent "Laser Pure 20" heat exchangers out in the field,
> > > > are not the correct model, and may cause severe damage to your
> > > > laser. They were not intended to be used with this model laser,
> > > > and we can supply detailed literature upon your request.
> > > >
> > > > 2) We have also seen "Laser Pure 40" models with the wrong
> > > > internal components. Which also may cause laser problems.
> > > >
> > > > To check for the correct component, remove the top lid,
> > > > and remove the side panel from the LP-40 unit.
> > > > (the side that has all the water fittings)
> > > > Locate the stainless steel heat transfer unit.
> > > > The unit should have the model # CB26-90H,
> > > > if it does not, please contact us.
> > > >
> > > > We have only seen these problems, on systems with dates prior to
> > > > 1992.
> > > >
> > > > If you have questions, or need more info, please contact us:
> > > >
> > > > Laser Innovations
> > > > (805) 529-5864 tel
> > > > 6621 fax
> > > > sla-500@laserinnovations.com
> > > >
> > > > Best regards,
> > > >
> > > > Eric King
> > > >
> > > > For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
> >
> > Gary,
> >
> > I apologize for my late reply, I've been out sick.
> >
> > Yes, you should replace the bypass with the 2.5 GPM. That is one of
> > the upgrades / modifications to convert an LP-20 to a 40.
> >
> > What is the model # on the heat exchanger, itself ?
> >
> > Best regards,
> >
> > Eric King
> >
> > For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/

Daniel,

Thank you again for attention in this matter.

It's a shame that 3D would rather save a whopping ~600.00/each, by
purchasing the wrong LP-20, and trying to "upgrade" it to a 40. Then
to buy the correct piece of equipment for their customers.

Best regards,

Eric King

And a fitting quotation from a great friend of mine.

Jon Cooper "No man knows what price he pays
                                 for substandard parts and slipshod
Ventura, CA service until fate adds the cost
~~~~~~~~~~~~~~~ of tragedy to his bill"

For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/



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