Re: Looking for Service Bureau for Blower mold order.

From: B. J. Arnold-Feret (
Date: Wed Feb 10 1999 - 17:34:27 EET


I think that you are looking for someone with experience with blow molding,
and producing molds using either a composite tool from an SLA pattern or
going to a cast tool for blow molding using the SLA as a pattern.

I suggest that you may want to consider going to a cut tool or a cast tool
where the blow molder and the mold designer can work together closely. This
is due to the strength needs for the cut offs in the mold and the stress
that the blow molding tool will go throught with the closing of the mold. .
You may use insets for the cut offs, but the resulting shock to the
composite or cast tool mold may cause a premature cracking of the mold, and
hence lost of the mold. Temperature differentials from cut off inserts
versus the remainer of the cast tool can also increase chances of mold cracking

This is particuliarly true if you are going to use a ABS or PC material
during the blow molding process and the tool is large, since either of these
plastic materials has too much hang strength during extrusion of the
parison. Since the engineering material will quickly lose integrity after
the parison is extruded, the mold has to be quickly shut, in some cases even
prior to having the parison completely extruded. This quick closing is
pretty stressful for a tool, particuliarly a large mold. Pinholes and tack
off can be compromised.

There is another factor that must also be noted. Blow molded non HDPE and
PP materials requires a different set up in the blow molding machine. A
single flight secrew in the machine is a necessary component. A barrier
screw in the machine may cause excessive shear in the material and burn it.
There should also be caution in using large accumulator head machines (IE 36
lb. or more) since long residence time in the head may also contribute to
material degradation. Plus, if the material has to be UL rated or needs a
color added, the residence time in the acculmulator is a critical factor,
since it can contribute to many problems with additives coming out of the

As to design, there are a few houses that do design for blow molding that
have experience with SLA and casting. However, SLA going to cast blow
molding tools needs to be talked about first. If you want only cast tooling
from the SLA, considerations such as materials, volume, feature details,
materials, pinholes, tackoffs, tolerances, etc. need to be worked out prior
to start of the project so everyone will have the same expectations.

Pleae contact me so that I can help you.

Barbara J. Arnold-Feret
Ft. Worth Texas USA

> We are working with Auto motive company in korea.
> They are looking for the Service Bureau who has many experience
> in blower mold to produce several kind of ducts.
> We want to have a expert partner to make blower mold using SLA pattern.
> We will give him some orders first time and will increase orders.
> After accept the quality, delievery and price, we will expand the order
> to injection mold and metal casting step by step.
> I hope any company who has many experience in this technology using
> SLA would contact me as soon as possible.
> Thank you,
> TEL ) +82-343-421-6353~4
> FAX ) +82-343-421-6355
> Contact ) I.S.KIM
>For more information about the rp-ml, see
 * Prototyping and Rapid Tooling Services *
 * 1401 Summer Dell Court *
 * Roanoke TX 76262 *
 * 817-379-5629 voice - 817-431-5341 fax *
 * 817-979-0222 pager - *
 * *

For more information about the rp-ml, see

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