[luchifer]

Usa el procedimiento siguiente:
procedure TFpto_pollo.imprime_fac(stdoc, stipo:shortstring;sndoc:integer);
Var MyPrinter: TextFile;
xcan, xdes, xval, xtot, xpag, xcam:shortstring;
xsum:real;
consulta:string;
begin
AssignFILE(MyPrinter,'USB');
ReWrite(MyPrinter);
Write(MyPrinter, CHR(27) + CHR(64)); // Inicializar Impresora
//Write(MyPrinter, CHR(27)+CHR(67)+CHR(44)); // Fijar Tamaño en Lineas
Write(MyPrinter,CHR(27)+ CHR(103)); // Tipo de Letra Chicas
//Write(MyPrinter,CHR(27)+CHR(197)); // Negrita
//Write(MyPrinter,CHR(27)+CHR(179)+CHR(28)); // Espacio entre Lines
if stipo='FAC' then Writeln(MyPrinter,'MICROMARKET VIA RAPIDA') else Writeln(MyPrinter,'POLLOS ROSS');
if stipo='FAC' then Writeln(MyPrinter,'AV.ROQUE AGUILERA ESQ.RADIAL CASTILLA') else Writeln(MyPrinter,'AV.SANTOS DUMONT CASI 4TO ANILLO');
if stipo='FAC' then Writeln(MyPrinter,'NIT 2642735017 TELF.3513621') else Writeln(MyPrinter,'NO ES FACTURA TELF.3533417');
if stipo='FAC' then Writeln(MyPrinter,'FACTURA : '+wnrofac.text+' ALFAB.'+walfab.text);
if stipo='FAC' then Writeln(MyPrinter,'NR.ORDEN:'+wnorden.text+' FECHA:'+datetostr(now));
if wnomfac.Text<>'' then
Writeln(MyPrinter,'Senores : '+wnomfac.text)
else
Writeln(MyPrinter,'Senores : Clientes Varios');
//----------------------------
consulta:='select * from lgloprod where tdoc='+car+stdoc+car+' and ndoc='+inttostr(sndoc);
DModulo.QConsulta.Close;
DModulo.QConsulta.sql.Clear;
DModulo.QConsulta.sql.add(consulta);
DModulo.QConsulta.Open;
if wnit.Text<>'' then
Writeln(MyPrinter,'NIT : '+wnit.text)
else
Writeln(MyPrinter,'PARA SERVIRSE EN :'+DModulo.QConsulta.fieldbyname('refer').asstring);
//------------------------------
Writeln(MyPrinter,'-------------------------------------');
Writeln(MyPrinter,' Cant. Producto Valor ');
Writeln(MyPrinter,'-------------------------------------');
xsum:=0;
consulta:='select * from lmovpro where tdoc='+car+stdoc+car+' and ndoc='+inttostr(sndoc);
DModulo.QConsulta.Close;
DModulo.QConsulta.sql.Clear;
DModulo.QConsulta.sql.add(consulta);
DModulo.QConsulta.Open;
DModulo.QConsulta.First;
while not DModulo.QConsulta.Eof do
begin
xcan:=format('%6.2f',[DModulo.QConsulta.fieldbyname('cant').asfloat]);
xdes:=copy(DModulo.QConsulta.fieldbyname('descri').AsString,1,20);
xval:=format('%8.2f',[DModulo.QConsulta.fieldbyname('valor_bs').asfloat]);
xsum:=xsum+DModulo.QConsulta.fieldbyname('valor_bs').asfloat;
Writeln(MyPrinter,xcan+' '+xdes+' '+xval);
DModulo.QConsulta.Next;
end;
Writeln(MyPrinter,'-------------------------------------');
xtot:=format('%8.2f',[xsum]);
xpag:=format('%8.2f',[strtofloat(wpagbs.text)]);
xcam:=format('%8.2f',[strtofloat(wcamb.text)]);
Writeln(MyPrinter,' Total Facturado : '+xtot);
Writeln(MyPrinter,' Total Pagado : '+xpag);
Writeln(MyPrinter,' Cambio : '+xcam);
Writeln(MyPrinter,'-------------------------------------');
if stipo='FAC' then Writeln(MyPrinter,'MICROMARKET VIA RAPIDA LE AGRADECE') else Writeln(MyPrinter,'POLLOS ROSS LE AGRADECE');
Writeln(MyPrinter,'POR SU PREFERENCIA '+stdoc+'-'+inttostr(sndoc));
Writeln(MyPrinter,'');
Writeln(MyPrinter,'');
Writeln(MyPrinter,'');
Writeln(MyPrinter,'');
Writeln(MyPrinter,'');
Writeln(MyPrinter,'');
Writeln(MyPrinter,'');
Writeln(MyPrinter,'');
Writeln(MyPrinter,'');
//Write(MyPrinter,#12); // Expulsar la Hoja
System.CloseFile(MyPrinter);
end;

Me funciona de pelicula y es super sencillo y no te complicas como con las otras soluciones que te plantean