Machining Design Guidelines

Transcription

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2 Machining Design Guidelines Milling Rules Issue IV, Jan

3 Copyright Notice Geometric Limited. All rights reserved. No part of this document (whether in hardcopy or electronic form) may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, to any third party without the written permission of Geometric Limited. Geometric Limited reserves the right to change the information contained in this document without prior notice. The names or trademarks or registered trademarks used in this document are the sole property of the respective owners and are governed/ protected by the relevant trademark and copyright laws. This document is provided by Geometric Limited for informational purposes only, without representation or warranty of any kind, and Geometric Limited shall not be liable for errors or omissions with respect to the document. The information contained herein is provided on an AS-IS basis and to the maximum extent permitted by applicable law, Geometric Limited hereby disclaims all other warranties and conditions, either express, implied or statutory, including but not limited to, any (if any) implied warranties, duties or conditions of merchantability, of fitness for a particular purpose, of accuracy or completeness of responses, of results, of workmanlike effort, of lack of viruses, and of lack of negligence, all with regard to the document. THERE IS NO WARRANTY OR CONDITION OF NON-INFRINGEMENT OF ANY INTELLECTUAL PROPERTY RIGHTS WITH REGARD TO THE DOCUMENT. IN NO EVENT WILL GEOMETRIC LIMITED BE LIABLE TO ANY OTHER PARTY FOR LOST PROFITS, LOSS OF USE, LOSS OF DATA, OR ANY INCIDENTAL, CONSEQUENTIAL, DIRECT, INDIRECT, OR SPECIAL DAMAGES WHETHER UNDER CONTRACT, TORT, WARRANTY, OR OTHERWISE, ARISING IN ANY WAY OUT OF THIS DOCUMENT, WHETHER OR NOT SUCH PARTY HAD ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES. 3

4 Welcome once again to another issue of DFM Guidebook! Milling is one of the most flexible and well known method of machining. Due to the high tolerances and surface finishes that milling can offer, it is ideal for producing parts with precision features and shapes. Milling is typically used to produce parts that are not axially symmetric and DFM guidelines recommend avoiding sharp internal corners inside pockets when it is to be manufactured using milling process. In this issue we cover important design guidelines for Milling such as Deep Radiused Corners, Sharp Internal Corners, Tool Accessibility, Narrow Regions in Pockets, Side and Bottom Radius, Tool Clearance Check and Angular Milling Faces. If you missed reading previous issues of DFM Guidebook, please visit our website, Rahul Rajadhyaksha Senior Product Manager Geometric Limited 4

5 Contents Deep Radiused Corners... 6 Sharp Internal Corners... 7 Tool Accessibility... 8 Narrow Regions in Pockets... 9 Side Radius and Bottom Radius Tool Clearance Check Angular Milling Faces

6 Deep Radiused Corners Flute engagement in the milling operation is important because it directly influence the forces. When the axial depth of cut is increased, the length of engaged flutes increases, and the milling forces also increase. Longer end mills are prone to breakages and chatter, requires longer machining time and results in increased tool vibrations. Vibration creates uneven wear on cutting tools and thereby shortens tool life. Designers should design milling areas such that longer end mills are not required to machine it. Example 6

7 Sharp Internal Corners Rounded corners provides number of advantages such as less stress concentration on part and tool, few operational steps and reduced scrap rate. Sharp inside corners cannot be produced by milling and require more expensive machining methods like EDM. When designing a three-edged inside corner, one of the inside edges should be radiused. It is advised to avoid sharp corners and use fillets and radii. If a sharp corner is required for mating clearance, then drilling a separate relief hole as shown below may serve the purpose. 7

8 Tool Accessibility Features should be accessible to the cutting tool in the preferred machining orientation. Example 8

9 Narrow Regions in Pockets It is recommended to avoid features that are too close to each other such that the gap between them is too narrow to allow milling cutter to pass through them. If narrow regions are unavoidable, then they should not be very deep. The size of the milling cutter is constrained by the smallest distance between the faces of the feature. Small diameter cutters are prone to breakage and chatter. Hence larger diameter, shorter cutters are generally preferred. Example 9

10 Side Radius and Bottom Radius Use of standard side radius and bottom radius for milling features will ease manufacturing of milling features with standard available milling tools. For reducing, machining cycle time and tool setup cost, it is recommended to avoid non-standard side radius and bottom radius. As a general guideline use single standard side radius and single standard bottom radius. Example 10

11 Tool Clearance Check Machining Features or slots should be accessible to the cutting tool in the preferred machining direction and at the same time there should not be any clash between tool holder and component while machining the feature. Tool clash with components leads to adverse effect like tool damage, component damage, and it will be unsafe for machine operator as well. Example 11

12 Angular Milling Faces Side and bottom faces of milling features separated by bottom fillet should be at 90º to each other to allow production with an end mill having bottom corner radius. Machining of angular faces require multi-axis machining, which leads to higher machining cost. It is recommended that side and bottom faces of milling features separated by bottom fillet should be at an angle 90º to each other. Example 12