No need for the processes field in products and use process in product - bom relationship.

__init__.py

@@ -15,6 +15,5 @@ def register():
         Route,
         BOM,
         Production,
-        Product,
         ProductBom,
         module='production_process', type_='model')

product.py

@@ -4,29 +4,10 @@ from trytond.model import fields
 from trytond.pyson import Eval, Get, If, Bool
 from trytond.pool import Pool, PoolMeta
 
-__all__ = ['Product', 'ProductBom']
+__all__ = ['ProductBom']
 __metaclass__ = PoolMeta
 
 
-class Product:
-    __name__ = 'product.product'
-
-    processes = fields.One2Many('product.product-production.bom', 'product',
-        'Processes', order=[('sequence', 'ASC'), ('id', 'ASC')],
-        states={
-            'invisible': Eval('type', 'service') == 'service',
-            },
-        depends=['type'])
-
-    @classmethod
-    def copy(cls, products, default=None):
-        if default is None:
-            default = {}
-        default = default.copy()
-        default.setdefault('processes', None)
-        return super(Product, cls).copy(products, default=default)
-
-
 class ProductBom:
     __name__ = 'product.product-production.bom'
 

product.xml

@@ -3,23 +3,25 @@
      copyright notices and license terms. -->
 <tryton>
     <data>
-
-        <record model="ir.ui.view" id="product-bom_view_list_process">
+        <record model="ir.ui.view" id="product-bom_view_list">
             <field name="model">product.product-production.bom</field>
             <field name="type">tree</field>
             <field name="name">product_bom_list</field>
+            <field name="inherit" ref="production.product-bom_view_list"/>
         </record>
 
-        <record model="ir.ui.view" id="product-bom_view_form_process">
+        <record model="ir.ui.view" id="product-bom_view_list_sequence">
+            <field name="model">product.product-production.bom</field>
+            <field name="type">tree</field>
+            <field name="name">product_bom_list_sequence</field>
+            <field name="inherit" ref="production.product-bom_view_list_sequence"/>
+        </record>
+
+        <record model="ir.ui.view" id="product-bom_view_form">
             <field name="model">product.product-production.bom</field>
             <field name="type">form</field>
             <field name="name">product_bom_form</field>
-        </record>
-
-        <record model="ir.ui.view" id="product_view_form">
-            <field name="model">product.product</field>
-            <field name="inherit" ref="product.product_view_form"/>
-            <field name="name">product_form</field>
+            <field name="inherit" ref="production.product-bom_view_form"/>
         </record>
     </data>
 </tryton>

view/product_bom_form.xml

@@ -1,9 +1,10 @@
 <?xml version="1.0"?>
 <!-- The COPYRIGHT file at the top level of this repository contains the full
      copyright notices and license terms. -->
-<form string="Product - Process" col="4">
-    <label name="process"/>
-    <field name="process" widget="selection"/>
-    <label name="sequence"/>
-    <field name="sequence"/>
-</form>
+<data>
+    <xpath expr="/form/label[@name='bom']" position="before">
+        <newline/>
+        <label name="process"/>
+        <field name="process"/>
+    </xpath>
+</data>

view/product_bom_list.xml

@@ -1,7 +1,8 @@
 <?xml version="1.0"?>
 <!-- The COPYRIGHT file at the top level of this repository contains the full
      copyright notices and license terms. -->
-<tree string="Product - Process" sequence="sequence">
-    <field name="process"/>
-    <field name="sequence" tree_invisible="1"/>
-</tree>
+<data>
+    <xpath expr="/tree/field[@name='bom']" position="before">
+        <field name="process"/>
+    </xpath>
+</data>

view/product_bom_list_sequence.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0"?>
+<!-- The COPYRIGHT file at the top level of this repository contains the full
+     copyright notices and license terms. -->
+<data>
+    <xpath expr="/tree/field[@name='bom']" position="before">
+        <field name="process"/>
+    </xpath>
+</data>

view/product_form.xml

@@ -1,9 +0,0 @@
-<?xml version="1.0"?>
-<!-- The COPYRIGHT file at the top level of this repository contains the full
-     copyright notices and license terms. -->
-<data>
-    <xpath expr="/form/field[@name='boms']" position="replace">
-        <field name="processes" colspan="6"
-            view_ids="production_process.product-bom_view_list_process,production_process.product-bom_view_form_process"/>
-    </xpath>
-</data>