diff --git a/AdjustLoops.cpp b/AdjustLoops.cpp
index 86447e0..df4d6f5 100644
--- a/AdjustLoops.cpp
+++ b/AdjustLoops.cpp
@@ -226,14 +226,14 @@ MyAdjustLoops( ICurve* pCurve, ICURVEPLIST& CrvLst)
             Point3d ptEnd2 ; pCrvCo2->GetEndPoint( ptEnd2) ;
            // se aperta, verifico se concatenabile alla principale
             if ( ! AreSamePointEpsilon( ptStart2, ptEnd2, 10 * EPS_SMALL)) {
-               if ( AreSamePointEpsilon( ptEnd, ptStart2, 10 * EPS_SMALL)) {
-                  pCrvCo->AddCurve( pCrvCo2, true, 10 * EPS_SMALL) ;
+               if ( AreSamePointEpsilon( ptEnd, ptStart2, 100 * EPS_SMALL)) {
+                  pCrvCo->AddCurve( pCrvCo2, true, 100 * EPS_SMALL) ;
                   CrvLst.erase( iIter2) ;
                   ptEnd = ptEnd2 ;
                   iIter2 = next( iIter) ;
                }
-               else if ( AreSamePointEpsilon( ptEnd2, ptStart, 10 * EPS_SMALL)) {
-                  pCrvCo->AddCurve( pCrvCo2, false, 10 * EPS_SMALL) ;
+               else if ( AreSamePointEpsilon( ptEnd2, ptStart, 100 * EPS_SMALL)) {
+                  pCrvCo->AddCurve( pCrvCo2, false, 100 * EPS_SMALL) ;
                   CrvLst.erase( iIter2) ;
                   ptStart = ptStart2 ;
                   iIter2 = next( iIter) ;
diff --git a/CurveComposite.cpp b/CurveComposite.cpp
index bdfda4c..228752d 100644
--- a/CurveComposite.cpp
+++ b/CurveComposite.cpp
@@ -2039,7 +2039,7 @@ CurveComposite::ModifyCurveToArc( int nCrv, const Point3d& ptMid)
    if ( nCrv < 0  ||  nCrv > nCrvCount - 1)
       return false ;
   // recupero la curva corrente 
-   ICurve* pCrv = *(m_CrvSmplS.begin() + nCrv) ;
+   ICurve* pCrv = m_CrvSmplS[nCrv] ;
   // recupero gli estremi
    Point3d ptStart, ptEnd ;
    if ( ! pCrv->GetStartPoint( ptStart)  ||  ! pCrv->GetEndPoint( ptEnd))
@@ -2072,7 +2072,7 @@ CurveComposite::ModifyCurveToLine( int nCrv)
    if ( nCrv < 0  ||  nCrv > nCrvCount - 1)
       return false ;
   // recupero la curva corrente 
-   ICurve* pCrv = *(m_CrvSmplS.begin() + nCrv) ;
+   ICurve* pCrv = m_CrvSmplS[nCrv] ;
   // se gią linea non devo fare alcunchč
    if ( pCrv->GetType() == CRV_LINE)
       return true ;
@@ -2880,6 +2880,39 @@ CurveComposite::ArcsBezierCurvesToArcsPerpExtr( double dLinTol, double dAngTolDe
    return true ;
 }
 
+//----------------------------------------------------------------------------
+bool
+CurveComposite::StraightArcsToLines( double dLinTol, double dAngTolDeg)
+{
+  // controllo le tolleranze
+   dLinTol = max( dLinTol, EPS_SMALL) ;
+   dAngTolDeg = Clamp( dAngTolDeg, EPS_ANG_SMALL, ANG_RIGHT) ;
+  // verifico le singole curve
+   for ( auto Iter = m_CrvSmplS.begin() ; Iter != m_CrvSmplS.end() ; ++ Iter) {
+      CurveArc* pArc = GetBasicCurveArc( *Iter) ;
+      if ( pArc != nullptr  &&
+           abs( pArc->GetAngCenter()) < dAngTolDeg  &&
+           pArc->GetRadius() * ( 1 - cos( pArc->GetAngCenter() / 2 * DEGTORAD)) < dLinTol) {
+        // recupero gli estremi
+         Point3d ptStart, ptEnd ;
+         if ( ! pArc->GetStartPoint( ptStart)  ||  ! pArc->GetEndPoint( ptEnd))
+            return false ;
+        // creo la linea
+         PtrOwner<CurveLine> pLine( CreateBasicCurveLine()) ;
+         if ( IsNull( pLine)  ||  ! pLine->Set( ptStart, ptEnd))
+            return false ;
+        // elimino la curva originale e la sostituisco con la nuova
+         delete (*Iter) ;
+         (*Iter) = Release( pLine) ;
+      }
+   }
+
+  // imposto ricalcolo della grafica
+   m_OGrMgr.Reset() ;
+
+   return true ;
+}
+
 //----------------------------------------------------------------------------
 static int
 MergeTwoCurves( ICurve* pCrvP, ICurve* pCrvC, double& dCurrLinTol, double dCosAngTol, bool bNeedSameProp)
diff --git a/CurveComposite.h b/CurveComposite.h
index 80ea1d6..eac578d 100644
--- a/CurveComposite.h
+++ b/CurveComposite.h
@@ -156,6 +156,7 @@ class CurveComposite : public ICurveComposite, public IGeoObjRW
       bool ModifyCurveToLine( int nCrv) override ;
       bool ArcsToBezierCurves( void) override ;
       bool ArcsBezierCurvesToArcsPerpExtr( double dLinTol, double dAngTolDeg) override ;
+      bool StraightArcsToLines( double dLinTol, double dAngTolDeg) override ;
       bool MergeCurves( double dLinTol, double dAngTolDeg, bool bStartEnd = true, bool bNeedSameProp = false) override ;
       bool RemoveSmallDefects( double dLinTol, double dAngTolDeg, bool bAlsoSpikes = false) override ;
       bool RemoveUndercutOnY( double dLinTol, double dAngTolDeg) override ;
diff --git a/EgtGeomKernel.rc b/EgtGeomKernel.rc
index 1d89882..dd55861 100644
Binary files a/EgtGeomKernel.rc and b/EgtGeomKernel.rc differ
diff --git a/OffsetCurve.cpp b/OffsetCurve.cpp
index 64254bc..e7c1de0 100644
--- a/OffsetCurve.cpp
+++ b/OffsetCurve.cpp
@@ -161,10 +161,16 @@ OffsetCurve::Make( const ICurve* pCrv, double dDist, int nType)
    bool bClosed = ccCopy.IsClosed() && ( nType & ICurve::OFF_FORCE_OPEN) == 0 ;
 
   // elimino eventuali piccole Z
-   RemoveCurveSmallZs( &ccCopy, 10 * EPS_SMALL) ;
+   if ( ! RemoveCurveSmallZs( &ccCopy, 10 * EPS_SMALL))
+      return false ;
+
+  // converto archi diritti in segmenti di retta
+   if ( ! ccCopy.StraightArcsToLines( 10 * EPS_SMALL, ANG_TOL_STD_DEG))
+      return false ;
 
   // unisco parti allineate (tranne gli estremi)
-   ccCopy.MergeCurves( 10 * EPS_SMALL, ANG_TOL_STD_DEG, false) ;
+   if ( ! ccCopy.MergeCurves( 10 * EPS_SMALL, ANG_TOL_STD_DEG, false))
+      return false ;
 
   // calcolo le lunghezze delle diverse entitą
    DBLVECTOR vLens ;