diff --git a/LuaLibs/CalcPaths.lua b/LuaLibs/CalcPaths.lua
index b5766d0..6c5e57b 100644
--- a/LuaLibs/CalcPaths.lua
+++ b/LuaLibs/CalcPaths.lua
@@ -14,7 +14,7 @@ local AMD = require( 'AddManData')
 
 ---------------------------------------------------------------------
 local s_nPartId
-local s_dOffsCorr = 50 * GEO.EPS_SMALL
+local s_dOffsCorr = 20 * GEO.EPS_SMALL
 local s_vErr = {}
 local s_nCurrIdx
 local s_vtSlicing
@@ -108,7 +108,7 @@ end
 --------------------------------------------------------------------
 local function ComputeTrimSurf( nSrf, nGrpId, dStrand, dOverlap)
    
-   local nTrimSurf = ComputeSurfOffset( nSrf, nGrpId, - dStrand * ( 0.5 - dOverlap / 100) + s_dOffsCorr)
+   local nTrimSurf = ComputeSurfOffset( nSrf, nGrpId, - dStrand * ( 0.5 - dOverlap / 100) + 2 * s_dOffsCorr)
    local bNoOverlap = false
    if not nTrimSurf and dOverlap > GEO.EPS_SMALL then
       -- tento senza overlap
@@ -3216,7 +3216,7 @@ local function UpdateTrimSurfWithRibsMergedShell( nPathGrp, sName, LayerParams)
       -- calcolo la regione occupata dalla nuova shell
       local nType = EgtGetInfo( vNewShells[i], KEY_TYPE, 'i')
       dStrand = EgtIf( nType == TYPE.OUTER_SHELL or nType == TYPE.EXTRA_OUTER_SHELL, LayerParams.dStrand, LayerParams.dInnerStrand)
-      local nSrfShell = EgtSurfFrFatCurve( nCrvGrp, vNewShells[i], dStrand * 0.5 + 0.5 * s_dOffsCorr, false, false, s_dOffsTol)
+      local nSrfShell = EgtSurfFrFatCurve( nCrvGrp, vNewShells[i], dStrand * 0.5 + s_dOffsCorr, false, false, s_dOffsTol)
       if nSrfShell then
          if not EgtSurfFrSubtract( nNewTrimSurf, nSrfShell) then
             EgtOutLog( 'Error : EgtSurfFrSubtract with ribs-merged shell for TotTrimSurfRegion failed (layer '.. EgtNumToString( s_nCurrIdx) ..') - CalcPaths')
@@ -3528,7 +3528,7 @@ end
 --------------------------------------------------------------------
 local function UpdateTrimSurfWithExtraShell( nSrf, nCrv, dStrand, nGrpId)
    
-   local nSrfExtraShell = EgtSurfFrFatCurve( nGrpId, nCrv, dStrand * 0.5 + s_dOffsCorr * 0.5, true, false, s_dOffsTol)
+   local nSrfExtraShell = EgtSurfFrFatCurve( nGrpId, nCrv, dStrand * 0.5 + s_dOffsCorr, true, false, s_dOffsTol)
    if nSrfExtraShell then
       if not EgtSurfFrSubtract( nSrf, nSrfExtraShell) then
          EgtOutLog( 'Error : EgtSurfFrSubtract with ExtraShell for TotTrimSurfRegion failed (layer '.. EgtNumToString( s_nCurrIdx) ..') - CalcPaths')
@@ -3841,8 +3841,8 @@ local function CalcExtraShellsPath( nMaxShellNbrDiff, nShellNbrGrp, nCrvGrpId, d
             local nOffs, nOffsCnt = EgtOffsetCurveAdv( nCrvT, - dOffs, GDB_OT.FILLET, s_dOffsTol)
             for nCrvOffs = nOffs, nOffs + nOffsCnt - 1 do
                
-               -- calcolo la regione con cui fare trim
-               local nTrimSurf, bNoOverlap = ComputeTrimSurf( nTotShellTrim, nGrpTmp, dCurrStrand, LayerParams.dStrandOverlap)
+               -- calcolo la regione con cui fare trim ( con correzione extra per evitare tratti on)
+               local nTrimSurf, bNoOverlap = ComputeTrimSurf( nTotShellTrim, nGrpTmp, dCurrStrand - 10 * s_dOffsCorr, LayerParams.dStrandOverlap)
                if not nTrimSurf then
                   -- errore nel calcolo della superficie di trim
                   EgtOutLog( 'Error : creation of ExtraShell failed (layer '.. EgtNumToString( s_nCurrIdx) ..') - CalcPaths')