Digital process water management

The most com­mon­ly used sys­tems for clean­ing and recy­cling the process water required in mass fin­ish­ing oper­a­tions today are cen­trifuges. For exam­ple, Weg­mann Auto­mo­tive, is uti­liz­ing a ful­ly auto­mat­ic Rösler cen­trifuge, mod­el Z1000. As a pilot cus­tomer Weg­mann expand­ed the soft­ware for its cen­trifuge with the “advanced ver­sion” of the inno­v­a­tive dig­i­tal process water man­age­ment sys­tem from Rösler Smart Solu­tions. Com­pared to the pre­vi­ous­ly prac­ticed man­u­al process con­trol the new soft­ware pack­age with its dig­i­tal algo­rithms has pro­duced con­sid­er­able ben­e­fits. It helped not only to improve the over­all prod­uct qual­i­ty but also result­ed in sub­stan­tial cost savings.

When it was found­ed in 1882, the com­pa­ny ini­tial­ly was build­ing car­riages. From these mod­est begin­nings Weg­mann expand­ed into a cor­po­rate enti­ty with three dif­fer­ent busi­ness units. Krauss-Maf­fei Weg­mann devel­ops and pro­duces a wide range of prod­ucts in the field of nation­al defense. Schleifring is a lead­ing provider of sys­tems for the trans­fer of ener­gy, elec­tri­cal sig­nals, data and elec­tron­ic media. With a huge port­fo­lio of bal­anc­ing weights, tire valves, bat­tery ter­mi­nals, tire pres­sure con­trol sys­tems, includ­ing suit­able ser­vice kits and spe­cial weights, Weg­mann Auto­mo­tive sup­plies not only numer­ous auto­mo­bile man­u­fac­tur­ers but also serves the entire auto­mo­tive after­mar­ket. The com­pa­ny, locat­ed in Veit­shöch­heim, Ger­many, pro­duces more than one bil­lion com­po­nents per year.

A mass fin­ish­ing oper­a­tion that must meet strin­gent demands 

The bal­anc­ing weights are made as stamp­ings from steel and gal­va­nized steel as well as die-cast­ings from zinc or zinc alloys. Eugen Weizel, the depart­ment man­ag­er for mass fin­ish­ing and coat­ing at the Weg­mann Auto­mo­tive com­pa­ny, explains: „After the stamp­ing or die-cast­ing process the weights under­go a part-on-part mass fin­ish­ing oper­a­tion in a rotary vibra­tor. The goal is to com­plete­ly remove the resid­ual oil left over from the stamp­ing process and the water-based mold release agent left over from the die-cast­ing oper­a­tion. At the same time the uti­lized com­pound pro­vides a cor­ro­sion pro­tec­tion for the steel parts. On the oth­er hand, the zinc die-cast­ings require a cer­tain sur­face ten­sion for the sub­se­quent coat­ing step. The sur­face ten­sion is care­ful­ly mon­i­tored and con­trolled.” Eugen Weizel’s col­league Manuel Salomon, at WAPS (short for Weg­mann Auto­mo­tive Pro­duc­tion Sys­tems) respon­si­ble for setups in the coat­ing depart­ment, train­ings and Lean Man­age­ment, adds: “A high com­pound con­cen­tra­tion in the process water is ben­e­fi­cial for the cor­ro­sion pro­tec­tion on the steel parts. But if it is too high, we will not achieve the required sur­face ten­sion on the zinc com­po­nents. This can cause inad­e­quate coat­ing results and may even force us to scrap some products.”

The prod­uct qual­i­ty depends on the qual­i­ty of the process water

Since the process water is recy­cled, the process water clean­ing oper­a­tion with a ful­ly auto­mat­ic Z1000 cen­trifuge from Rösler and the con­trol of the com­pound con­cen­tra­tion are key fac­tors that deter­mine the qual­i­ty of the bal­anc­ing weights.

Manuel Salomon: „When the mass fin­ish­ing machine and the cen­trifuge were com­mis­sioned, we quick­ly rec­og­nized that there is a close cor­re­la­tion between the process water qual­i­ty and the qual­i­ty of our prod­ucts. There­fore, we care­ful­ly mea­sured the com­pound con­cen­tra­tion once per week and record­ed the mea­sured results. This allowed us to pre­cise­ly define the com­pound con­cen­tra­tion for our fin­ish­ing process and cor­rect it as need­ed.” Since mea­sur­ing and record­ing the con­cen­tra­tion val­ues was quite time con­sum­ing, Weg­mann glad­ly accept­ed Rösler’s offer to uti­lize the advanced ver­sion of the “dig­i­tal process water man­age­ment sys­tem” as a pilot user. Eugen Weizel con­cludes: „We quick­ly rec­og­nized the ben­e­fit to fur­ther devel­op and refine the soft­ware pack­age togeth­er with Rösler, and, at the same time, to deep­en our process knowledge.”

The new, inter­ac­tive mon­i­tor­ing and con­trol sys­tem for process water clean­ing and recy­cling with semi- and ful­ly auto­mat­ic cen­trifuges is inte­grat­ed into the cen­trifuge con­trols and allows the mon­i­tor­ing, record­ing and eval­u­a­tion of all rel­e­vant process para­me­ters. At Weg­mann this includes mea­sur­ing the com­pound con­cen­tra­tion by titra­tion or refrac­tion (BRIX), the pH val­ue, the process water con­duc­tiv­i­ty, the water hard­ness, the micro­bi­o­log­i­cal con­t­a­m­i­na­tion with bac­te­ria, yeast and fun­gi, chlo­ride con­tents, CSB val­ue (chem­i­cal oxy­gen demand) and BIT con­cen­tra­tion (bio­cide in the process water). The sys­tem also mon­i­tors the appear­ance and the smell of the process liq­uid. The process water para­me­ters to be mon­i­tored can be indi­vid­u­al­ly select­ed and their val­ues adapt­ed to the respec­tive fin­ish­ing requirements.

In the basic ver­sion of the dig­i­tal process water man­age­ment sys­tem from Rösler Smart Solu­tions the sam­ples are tak­en man­u­al­ly and ana­lyzed with suit­able mea­sur­ing devices that can also be sup­plied by the com­pa­ny. After the data have been entered into the sys­tem, the algo­rithm in the soft­ware deter­mines if the mea­sured val­ues are with­in the spec­i­fied lim­its. In case of devi­a­tions the dash­board dis­plays suit­able actions, which can be imme­di­ate­ly imple­ment­ed. In addi­tion, the tech­ni­cal back­ground and cor­rec­tive actions are explained in detail. This allows the oper­a­tor to under­take the mea­sures required to bring back the val­ues into the accept­able range and to secure the desired process sta­bil­i­ty. Since all para­me­ters are stored in the sys­tem, they can be retrieved at any time, for exam­ple, in the form of a table or a chart. The lat­ter helps to pre­vent unwant­ed and cost­ly down­times by car­ry­ing out nec­es­sary process water changes dur­ing peri­ods, when they are not inter­fer­ing with the man­u­fac­tur­ing oper­a­tions. The com­plete doc­u­men­ta­tion of the oper­a­tional para­me­ters is also a valu­able tool to prove the process qual­i­ty and process sta­bil­i­ty dur­ing qual­i­ty audits as well as for val­i­da­tion purposes.

Rec­om­mend­ed actions can also be called up in case of events that affect the over­all qual­i­ty of the mass fin­ish­ing process. This includes foam­ing dur­ing the process, cor­ro­sion of the work pieces or insuf­fi­cient work piece clean­li­ness that could neg­a­tive­ly affect sub­se­quent man­u­fac­tur­ing steps. Manuel Salomon com­ments: „The point­ers and rec­om­mend­ed actions are extreme­ly help­ful. In the past we mea­sured the process para­me­ters. But when it came to the nec­es­sary cor­rec­tions, we were entire­ly on our own. And in case of process prob­lems we had to search for solu­tions our­selves, or we had to ask for help by tele­phone. Today the dig­i­tal sys­tem pro­vides all the sup­port we need. This is espe­cial­ly help­ful for col­leagues with lit­tle knowl­edge of mass fin­ish­ing and process water clean­ing and recycling.”

A sim­ple solu­tion that can be quick­ly implemented

The smart process water man­age­ment sys­tem has been in oper­a­tion at Weg­mann Auto­mo­tive since the mid­dle of March this year.

Eugen Weizel remarks: „The soft­ware struc­ture is well orga­nized and eas­i­ly under­stand­able. And the sys­tem can be ful­ly uti­lized after a short train­ing. All crit­i­cal data are arranged so that they can be viewed at a glance. And the entire infor­ma­tion is pre­sent­ed in an easy-to-under­stand manner.”

While in the past the com­pound con­cen­tra­tion was only mea­sured once per week, now it is mea­sured twice, once in the morn­ing and once in the after­noon of a par­tic­u­lar day. In addi­tion, the pH val­ue is record­ed, and the appear­ance and smell of the process water is mon­i­tored. „This approach pro­vides us with valu­able infor­ma­tion about our process. For exam­ple, the devel­op­ment of the com­pound con­cen­tra­tion tells us that due to a higher

vol­ume of oily work pieces we must increase the com­pound dos­ing rate to main­tain the required process water qual­i­ty,” explains Manuel Salomon, who con­tin­ues: „Anoth­er exam­ple is the micro­bi­o­log­i­cal con­t­a­m­i­na­tion. In the past we did not con­trol this at all. If the con­t­a­m­i­na­tion is too high, it can have an adverse effect on the cor­ro­sion pro­tec­tion of steel parts.”

Sig­nif­i­cant­ly improved process sta­bil­i­ty and cost-efficiency

For mon­i­tor­ing the var­i­ous para­me­ters with the dig­i­tal process water man­age­ment sys­tem Weg­mann Auto­mo­tive needs about 20 min­utes per week. Com­pared to the once-per-week mea­sure­ment of the com­pound con­cen­tra­tion this requires about 15 min­utes more. But the tech­ni­cal and eco­nom­ic ben­e­fits achieved by the dig­i­tal sys­tem are so sig­nif­i­cant that the com­pa­ny glad­ly accepts the fact that a bit more time must be invested.

Eugen Weizel con­cludes: „With the dig­i­tal process water man­age­ment sys­tem we find out quick­ly, if for exam­ple, the com­pound con­cen­tra­tion is no longer ade­quate. Since this could have an adverse effect for sub­se­quent man­u­fac­tur­ing steps, we are grate­ful to have such a valu­able, ear­ly warn­ing sys­tem. Our fin­ish­ing process is now not only a lot more sta­ble but also more economical.”

There­fore, it is not sur­pris­ing that the com­pa­ny is inter­est­ed in the next ver­sion of the dig­i­tal process water man­age­ment sys­tem from Rösler Smart Solu­tions. This allows the auto­mat­ic mea­sure­ment, eval­u­a­tion and record­ing of the process parameters.