Solutions Current Issues > July/August/September 2006 > TECH SESSION
Email LinkThe Perfect Drawing
Detailed information is the first step to a quality hose.
By LARRY PERES
It's all in the details: Step-by-step
instructions
on
preparing a hose
drawing that works.
As a hose engineer here at RL Hudson, I deal with hose drawings on a daily basis. One thing I've noticed over the years is that starting from a drawing with all the right information on it gets you a long way toward producing a high quality hose.
I'm proud to say that we at RL Hudson supply high quality rubber hoses for a variety of uses. Our formed radiator and fuel hoses are perfect examples. Manufactured per the Society of Automotive Engineers (SAE) J20 standard, our radiator hoses are mandrel-molded to fit specific curved spaces. Our fuel hoses are manufactured per SAE J30 to effectively resist oil and fuel. We also supply air hoses (for intake and vapor recovery) manufactured per both the J20 and J30 standards.
No matter what the application, quality hoses start with an accurate, detailed drawing, one that includes all pertinent data but nothing extraneous. A complete drawing facilitates the quoting process and helps minimize the need for follow-up questions. When we receive a drawing from a customer, there are certain things we hope to see, so we make sure those same things are present when we send out one of our drawings for approval. Here's what we typically include:
1) MATERIAL CALLOUT / SPECIFICATION This is the first thing I look for on a new drawing. Typically located within the title block in the lower right corner of the drawing, this line may be a specific material name, a standardized material callout, or a specification. Personally, I prefer not to see just a material name (such as "nitrile") because that gives me no parameters for physical testing the way use of a callout or full specification does.
For tube only hoses (those that feature neither reinforcement nor a cover), I prefer use of an SAE J200 or ASTM D 2000 material callout. The American Society for Testing and Materials (ASTM) D 2000 standard is virtually identical to the J200 standard, which finds its widest use within the automotive industry. D 2000 is the more common standard among rubber manufacturers. A sample material callout might read as follows: SAE J200 M2BG610 B14 C12 EO14. Among other things, this denotes a 60-durometer material with a tensile strength of 10 MPa that must have specific compression set, ozone resistance, and fluid resistance properties.
If the hose conveys fluid (and is therefore reinforced), I suggest use of an SAE (or JIS, the Japanese Industrial Standards) specification. For example, "J20 R4 Class B" calls for a molded hose with high oil resistance.
2) APPLICATION DESCRIPTION Also typically located within the title block, this field answers the question, "How will the hose be used?" Perhaps it is intended as a radiator hose, or a fuel hose, or an air intake hose, or as something else entirely. Greater specificity always helps. For example, it might just say "fuel hose." But is it a regular fuel hose, or a fuel injection hose? It makes a big difference, because fuel injection hoses require higher burst capabilities, so noting that extra bit of info can be very helpful.
3) VIEWS These are the actual images of the hose design. I prefer three views - front, bottom, and right side - in third angle projection. The views should always include a dashed centerline representing the spine of the hose, along with numbered points that correspond with the data in the coordinate block (see below). Views also need to include dimensional data, such as the hose inside diameter (I.D.). For curved hoses, radii should also be noted. Keep in mind that a drawing with good visual reference is helpful not only prior to manufacturing but also to the quality assurance inspectors down the line. When possible, I like for the drawing to include a full-size view of the hose oriented in a natural position; this will allow an inspector to place a sample hose over the view and do a visual comparison.
4) COORDINATE BLOCK On most of our drawings, the coordinate block table is located in the lower left corner, but it may reside elsewhere as needed. The coordinate block reflects X-axis, Y-axis, Z-axis, radii (for curved hoses), point-to-point values, and overall spine length. In so doing, it details and verifies the shape of the hose. This is particularly helpful with more complex hoses, such as those with multiple bends. In some cases, the coordinate block also includes information not found on the views. In the absence of drawn views, a complete coordinate block and I.D. measurement would allow us to create a drawing. The coordinate block is very helpful at the manufacturing stage because it assists with creation of the hose tooling. The inclusion of point-to-point data also helps our quality assurance inspectors verify hose arm lengths (the distances between successive coordinate points along the spine of the hose).
5) COORDINATE SYMBOLS Coordinate symbols are simple representations of the coordinate system used to generate the hose views. Coordinate symbols define the directional orientation of the X, Y, and Z planes of each of the views. Coordinate symbols also serve as handy reference for the numerical data in the coordinate block. When reviewing a drawing, I always double-check the orientations of these views to make sure they correlate with both the coordinate symbols and the data in the coordinate block. If everything doesn't correlate, manufacturing the hose correctly becomes unlikely or impossible.
6) NOTES The notes section is an opportunity to detail any special requirements not covered by a hose specification. This information typically augments the material and application information contained in 1) and 2). For example, if you need an internal spring in your hose, a special note is the opportunity to request that; such a need generally could not be reflected anywhere else. Other examples include requests for special hose markings and the need for special testing requirements.
7) REVISION BLOCK Normally located in the upper right corner of the drawing, the revision block is the space in which a code (typically a number or letter) is assigned to each successive version of the drawing and the hose it represents. The revision block also contains descriptions of the revisions, as well as corresponding dates, authors, and approvals. Keep in mind that revisions are usually small updates to the hose design or drawing (such as the addition of reference values) rather than major design changes. A change major enough to warrant new tooling is typically not a revision; that's a new part in need of a new part number and a new drawing.
And, finally, a word of caution: I see instances in which a new drawing is generated based on an old drawing. That's fine, except when the old drawing contains errors or is incomplete. If those errors and/or information voids are not corrected, then the mistakes get passed on to the new drawing. Vigilance in reviewing all elements of any new drawing can typically catch those potential trouble spots.
There are obviously many things to consider as you prepare or review hose drawings. If you have any questions, please do not hesitate to call us at 1-800-722-6766. We'll be more than happy to work with you during the design process and to provide you with high quality rubber hoses.
