Sparx HotPlot

From: Terry Wohlers (
Date: Sat Jan 13 1996 - 02:30:19 EET

As promised, I have an update on the HotPlot system from Sparx. Today, I met
with HotPlot inventor Ralf Larson. He explained to me that the HotPlot system
is available from Trans Image AB (Sweden), fax +46 300 207 30. Ulf Carresjo is
the president of Trans Image. As I understand it, the company has not sold
many (if any) systems in the recent past. Ralf said that Sparx AB sold 15 or
16 systems total worldwide (4 in Japan) after the product was introduced in the
1991 timeframe.

For those of you who are not familiar with HotPlot, the system bonds 0.040 inch
(1 mm) sheets of polystyrene material. The machine cuts the sheets using a
flat-bed pen plotter equipped with a heated cutting electrode. A person
manually positions the sheets layer by layer. :( The system uses AutoCAD HPGL
as input. In 1991, the system sold for $12,900.

Ralf has many inventions and patents to his credit. I got the impression that
he was prouder of some of his other developments -- ones that have been
commercially successful. He was quick to admit that the HotPlot technology
produced poor quality parts and the process was too labor intensive. Ralf is
now managing director of Sparx CamModels Ltd. He has invented a new
"industrial" RP process that produces metal parts. That's all he would allow
me to say at this point. From what I can tell, the process shows a lot of

I hope everyone finds this information of interest.

Terry Wohlers
Wohlers Associates


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