News from hotset

New high-end solution for hardening of adhesive

hotset implements together with thyssenkrupp temperature control system for fully automated two-component bonding of CFRP sheets.
The sub­sti­tu­tion of sheet steel by light­weight fiber-re­in­forced plas­tics for sheet steel is mak­ing great strides in au­to­mo­tive and ve­hi­cle con­struc­tion. In many places, this is al­so ac­cel­er­at­ing the process-re­lat­ed chang­ing of the guard in the area of con­nec­tion meth­ods and join­ing tech­nol­o­gy. Mod­ern ad­he­sive tech­nol­o­gy is tak­ing over where weld­ing was pre­vi­ous­ly used. The use of an in­no­v­a­tive mul­ti-seg­ment heat­ing “mir­ror” from hotset in ro­bot-as­sist­ed bond­ing of large CFRP body parts in a new pro­duc­tion cell of thyssenkrupp’s body con­struc­tion di­vi­sion il­lus­trates why cus­tomized high-end tem­per­a­ture con­trol sys­tems play a key role here. The trend seems ir­re­versible. Where­as met­al sheets were weld­ed to­geth­er in ve­hi­cle con­struc­tion in the re­cent past, 2‑component bond­ing of mold­ed parts made of fiber-re­in­forced plas­tics now dom­i­nates the scene. The in­no­v­a­tive leaps for­ward in this field are doc­u­ment­ed by a cur­rent project by thyssenk­rupp Au­to­mo­tive Body So­lu­tions: The im­ple­men­ta­tion of a ful­ly au­to­mat­ed, ro­bot-sup­port­ed as­sem­bly sys­tem for con­tin­u­ous high-pre­ci­sion bond­ing of the in­ner and out­er CFRP mold­ed parts of ve­hi­cle doors. The fact that the project, de­spite its com­plex­i­ty, is now about to be trans­ferred to se­ries pro­duc­tion of a well-known sports car man­u­fac­tur­er af­ter a run­time of just un­der one year is not least the re­sult of suc­cess­ful project co­or­di­na­tion. The Ger­man ther­mo­dy­nam­ics spe­cial­ist hotset played a cen­tral role in this re­gard. In close co­op­er­a­tion with the en­gi­neers from thyssenk­rupp, the Lü­den­scheid-based com­pa­ny pro­duced one of the func­tion­al cen­ter­pieces of the new pro­duc­tion cell: A pro­duc­tion-ready tem­per­a­ture con­trol sys­tem that heats both door halves quick­ly, pre­cise­ly, re­li­ably and si­mul­ta­ne­ous­ly to up to 90° C on­ly on those edge sur­faces on which the pre­vi­ous­ly ap­plied ad­he­sive beads are lo­cat­ed, so that these cure as quick­ly as pos­si­ble dur­ing press­ing – and can be passed on to the next pro­cess­ing stages af­ter just a few minutes. 
Robot-assisted bonding of large CFRP body parts: The multi-segment heating mirror (brown) from hotset in the fixture of the new production cell of thyssenkrupp’s body construction division. (Image: thyssenkrupp)
Ro­bot-as­sist­ed bond­ing of large CFRP body parts: The mul­ti-seg­ment heat­ing mir­ror (brown) from hotset in the fix­ture of the new pro­duc­tion cell of thyssenkrupp’s body con­struc­tion di­vi­sion. (Im­age: thyssenkrupp) 

A mirror with 17 segments

“The tech­no­log­i­cal bench­mark was very high for this project from the very be­gin­ning. In ad­di­tion, the in­no­v­a­tive na­ture of the project re­quired a cer­tain de­gree of flex­i­bil­i­ty, as new ques­tions fre­quent­ly arose in the course of it”, re­calls An­dreas Filler, who has been project man­ag­er at hotset for many years. How­ev­er, the so­lu­tion im­ple­ment­ed un­der his re­spon­si­bil­i­ty is a process en­gi­neer­ing high­light of mod­ern tem­per­a­ture con­trol tech­nol­o­gy and could be ground­break­ing for the fur­ther es­tab­lish­ment of CFRP bond­ing in oth­er in­dus­tries. It is a sys­tem con­sist­ing of two large heat­ing frames whose geome­tries and di­men­sions fol­low the de­sign of the ve­hi­cle doors (1,290 x 636mm). “How­ev­er, while such frames – al­so known as heat­ing mir­rors in trade lan­guage – have so far usu­al­ly been man­u­fac­tured from one piece, thyssenkrupp’s de­sign spec­i­fi­ca­tions in this case called for the new tem­per­a­ture con­trol sys­tem to con­sist of a to­tal of 17 firm­ly in­ter­con­nect­ed heat­ing seg­ments, whose con­tact sur­faces are pre­cise­ly con­toured to match the var­i­ous topolo­gies of the door ar­eas to be bond­ed”, ex­plains An­dreas Filler. In its de­sign, each of these seg­ments is there­fore a three-di­men­sion­al unique spec­i­men, milled with high pre­ci­sion from a spe­cial alu­minum al­loy, re­fined with fine­ly fin­ished con­tact sur­faces and equipped with an in­ter­nal ar­chi­tec­ture of heat­ing el­e­ments. Since each seg­ment al­so has sev­er­al in­di­vid­u­al­ly con­trol­lable con­trol zones, the heat­ing en­er­gy of the com­plete tem­per­a­ture con­trol sys­tem can be pro­vid­ed pre­cise­ly, ef­fi­cient­ly and as need­ed via a to­tal of 19 con­trol zones. Patrick Hof­som­mer, project man­ag­er at thyssenk­rupp Au­to­mo­tive Body So­lu­tions, ex­plains what this means in prac­tice: “Due to its unique con­trol tech­nol­o­gy and the pre­cise­ly fit­ting seg­ments with their per­fect­ly con­tact­ing sur­faces, the new heat­ing mir­ror is a re­al in­no­va­tion. It en­sures op­ti­mum, high­ly uni­form and at the same time al­so flex­i­ble tem­per­a­ture con­trol to all glu­ing seams of the two door halves. In hotset’s high-pre­ci­sion de­sign, it makes a de­ci­sive con­tri­bu­tion to the process ef­fi­cien­cy of our new CFRP bond­ing line.” 
Precise heat control through segment design: The new temperature control system from hotset consists of 17 interconnected heating segments whose contact surfaces are precisely contoured to the various topologies of the areas of the carbon door to be bonded (black in the picture). (Image: thyssenkrupp)
Pre­cise heat con­trol through seg­ment de­sign: The new tem­per­a­ture con­trol sys­tem from hotset con­sists of 17 in­ter­con­nect­ed heat­ing seg­ments whose con­tact sur­faces are pre­cise­ly con­toured to the var­i­ous topolo­gies of the ar­eas of the car­bon door to be bond­ed (black in the pic­ture). (Im­age: thyssenkrupp) 

Cured in minutes

Two such mul­ti-seg­ment heat­ing mir­rors act as tem­per­a­ture con­trol per­for­mance com­po­nents of thyssenkrupp’s new as­sem­bly cell. They are func­tion­al­ly in­te­grat­ed in­to the com­plex han­dling and con­trol sys­tem of the 11 x 9‑meter sys­tem, which glues four CFRP mold­ed parts to form two ve­hi­cle doors – one left and one right – in a clocked and syn­chro­nized in­ter­play of five ro­bots. One in­ner door shell (in­ner as­sy) is tak­en from each of the load car­ri­ers pro­vid­ed and placed in the low­er fix­ture of a clamp­ing de­vice, which al­so holds the low­er frame of the heat­ing mir­ror. Short­ly af­ter­wards, ad­he­sive beads con­sist­ing of a two-com­po­nent ad­he­sive are ap­plied to the de­fined edge zones. When the out­er pan­el and the up­per frame of the heat­ing mir­ror are placed and clamped, the tem­per­a­ture con­trol sys­tem boots up and heats the ad­he­sive beads uni­form­ly from both sides, i.e. through the CFRP half-shells, to up to 90 °C. Cur­ing of the ad­he­sive is then com­plet­ed af­ter ap­prox. 4.5 min­utes. In to­tal, the process cy­cle time is eleven min­utes for each two ve­hi­cle doors. Both CFRP door halves in­clud­ing ad­he­sive bead are be­tween 6.0 and 7.0 mm thick. 
Patrick Hof­som­mer: “Due to its unique con­trol tech­nol­o­gy and the pre­cise­ly fit­ting seg­ments with their per­fect­ly fit­ting con­tact sur­faces, the new heat­ing mir­ror from hotset is a re­al in­no­va­tion.” (Im­age: thyssenkrupp) 
Patrick Hofsommer, Project Manager from thyssenkrupp Automotive Body Solutions

Temperature-compensated design

In­volved as a project part­ner in the de­vel­op­ment of thyssenkrupp’s new CFRP bond­ing line, hotset ac­com­pa­nied the project over sev­er­al months, ul­ti­mate­ly pro­vid­ing its in­no­v­a­tive tem­per­a­ture con­trol sys­tem as a com­plete so­lu­tion. In con­crete terms, this means that the sys­tem man­u­fac­tur­er re­ceived sev­er­al cus­tomized, ready-to-use heat­ing mir­rors in­clud­ing in­su­la­tion tech­nol­o­gy, sen­sor tech­nol­o­gy and de­cen­tral­ized con­trol tech­nol­o­gy for in­te­gra­tion in­to its han­dling and con­trol tech­nol­o­gy in­fra­struc­ture (Siemens S7/ CAN bus). It is ob­vi­ous that all kinds of spe­cial as­pects had to be tak­en in­to ac­count here. This in­clud­ed, for ex­am­ple, hav­ing to re­peat­ed­ly adapt the en­gi­neer­ing of the tem­per­a­ture con­trol sys­tem to the var­i­ous it­er­a­tion stages of the project and de­sign­ing the heat­ing mir­ror and its seg­ments sub­ject to the spec­i­fi­ca­tions for tem­per­a­ture com­pen­sa­tion. “In such cas­es, all crit­i­cal com­po­nents have to be de­signed and man­u­fac­tured a few per­cent­age points small­er be­cause, af­ter all, the sys­tem ex­pands in prac­ti­cal use due to the in­flu­ence of tem­per­a­ture”, ex­plains An­dreas Filler. Oth­er im­por­tant re­quire­ments in­clud­ed the fact that the en­tire heat­ing mir­ror had to com­ply with de­fined weight lim­its, as the ro­bots of the as­sem­bly sys­tem can lift and po­si­tion a max­i­mum of 300kg, and that sil­i­cone was ruled out as a ma­te­r­i­al for bond­ing right from the start. 
“Our new heat­ing mir­ror with its seg­ment de­sign and the re­sult­ing ad­van­tages for con­trol ac­cu­ra­cy and con­tour-pre­cise heat guid­ance rep­re­sents a new gen­er­a­tion of high-pre­ci­sion heat­ing el­e­ments for use in mod­ern bond­ing tech­nol­o­gy.” (Im­age: Hotset GmbH) 
Andreas Filler, Project Manager from hotset

Groundbreaking system solution

Once again, hotset was able to demon­strate its ca­pa­bil­i­ties as a com­pe­tent en­gi­neer­ing and sys­tems part­ner dur­ing the re­al­iza­tion of the new heat­ing mir­ror for thyssenkrupp’s CFRP bond­ing line. As is usu­al with projects of this com­plex­i­ty and size, the Lü­den­scheid-based com­pa­ny has thus al­so con­sid­er­ably ex­pand­ed its prac­ti­cal­ly us­able ex­per­tise in the field of pro­duc­tion-in­te­grat­ed tem­per­a­ture con­trol sys­tems for in­dus­tri­al plant en­gi­neer­ing. In this con­text, An­dreas Filler par­tic­u­lar­ly em­pha­sizes that “the new heat­ing mir­ror with its seg­ment de­sign and the re­sult­ing ad­van­tages for con­trol ac­cu­ra­cy and con­tour-pre­cise heat guid­ance em­bod­ies a new gen­er­a­tion of high-pre­ci­sion heat­ing el­e­ments for use in mod­ern bond­ing tech­nol­o­gy”. It is there­fore quite con­ceiv­able that this high-end so­lu­tion, ini­tial­ly de­vel­oped for the sports car in­dus­try, could al­so pro­vide for­ward-look­ing im­pe­tus for the fur­ther es­tab­lish­ment of 2‑component bond­ing of CFRP sheets in many oth­er ar­eas of se­ries-ori­ent­ed light­weight con­struc­tion. The ther­mo­dy­nam­ics spe­cial­ists at hotset have their sight set on nu­mer­ous ap­pli­ca­tions, for ex­am­ple in electromobility. 
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