Tag Archives: robotic weld cell

Jig or Weld Fixture Design — Five Items to Consider in V-Block Design

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Five items to consider when designing your V-block

In our last Jig or Weld Fixture Design blog we talked about different ways to locate a round rod or tube.   One of the more common ways is with a v-block.

Today we will discuss some of the questions that help you decide the material, modeling method using Pro/E  4.0, and fastener locations.

1)      MATERIAL  —

First decide what material you will need the v-block to be.

How much will the fixture be used?    That means knowing what the product is made of because we need the v-block to be strong enough not to wear down too quickly.  We want to be able to produce lots of product before we have to replace any of the parts in the fixture.    The more the fixture is going to be used the harder you need to make the v-block relative to the product tube or rod.

Do you need to plan for weld splatter?

If the v-block is located near the weld joint, you will need to consider using a metal that the weld splatter will not stick to as easily, or using a weld splatter shield.  Remember that like metals stick better.  So if you are welding steel, you may want your v-block to be Ampco 18 bronze or a hardened steel such as 4140 PH or A2.   If you are welding aluminum, hardened steel may work just fine.

2)      TOLERANCING –

Is the location of the rod or tube critical?

If the tube or rod needs to be located in just the right spot in order to work or assemble easily to the rest of the product parts, then you will want to design in adjustability with shim packs.  You will need to look at the product drawing and also know your customer’s preferences.

At Rentapen we design for many different customers.  So we have to consider the standards and preferences of each customer when we design.  Some of them love to shim every locator in a fixture.  Some of them don’t like to shim at all.   If you are a CAD drafter, you may be working under more than one designer.  Each designer may have their own preferences.  But it is up to you to look at the product drawing and then advise them when you think shims will be needed to meet the tolerances of the product drawing.   Then do what they say, they are your customer.

If it is a rough location, you may be able to use a purchased V-block from somewhere.  Do you have a favorite model or brand you would like to share?

3)      FASTENERS –

Once you have decided if your v-block will have shims to fine-tune its location before going into production, you can decide about the location of the fasteners.  If the tube or rod location is critical, you will need to use dowels to lock in the location.  If it is rough, you can just fasten the v-block directly to the base plate with screws.

4)      MODELING —

Locating the Vee in the v-block.

Here is how I model in the Vee cut.  Click on the video to see my method using Pro/E  Wildfire 4.0.

In this video I dimensioned the construction hole from the BOTTOM of the block.  However, the v-cut may fail if I make an adjustment too big in one direction or the other.  Some of the project engineers I have worked with prefer that the dimension for the V-cut be from the TOP surface of the block.  That way you can change the size of the block without having problems with the cut.

Some like to create planes that intersect at the center where the the construction circle will be located.  These planes are created before you start the sketch to cut the Vee.  I think your preference depends on your experience and how your brain works when making adjustments to parts while in the assembly.

5)      CLAMPING —

Clamping is a whole topic by itself that we will address in a future blog.  I just wanted to note that it is something that you need to think about.  We always clamp down our parts in weld fixtures, even if it is a table mounted fixture and gravity does its work.  You want to be sure that tube doesn’t move when the heat of the weld hits it.

 

And now I would like to share a couple of things with you.

First, Rentapen’s Holiday Greeting to our customers, vendors, students, and friends.

Second, we are in the news!  Check out the latest news at Rentapen by clicking here.

Till next time!

Susan Straley

The Queen of Lean Machine Design

Jig or Weld Fixture Design – 12 Questions

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What do YOU ask before you begin your Jig or Weld Fixture Design?  Here are some questions to start the discussion.

When you are presented with some product parts and asked to design a fixture or jig so they can be welded together,  what questions do you need answered before you begin?   It is important to get as much information on the project as possible before you even do a rough sketch.

For example:

1) How many parts will be welded together in this one fixture? 

The production planning team will need to figure this out.  The more parts they can fit on one fixture, the less fixtures and operators they will need.  However they need to take into account that if one station in the factory takes longer than the rest of the stations they will be creating a bottle neck that will slow the whole production line.  That could be fixed by having two of the same fixture, or by reducing the number of parts welded together in one fixture.

2) Is there another product line with very similar but different parts that could be welded together in the same fixture with a quick change over?  

Sometimes a fixture can be used for several products.  Just replacing one or two sub assemblies can quickly create a fixture that can run two or more products.    In a future blog we will delve into the different gizmos and tools you can use to make the change over fast and easy.

V-Blocks for two product lines

Designing for two product lines sometimes is easy.

 

 

 

 

 

 

 

 

 

3) Will the fixture be automated or manual? 

Will you be using pneumatic clamps or manual?  What about sensors that will sense if the part is in place before clamping or before beginning the welding procedure?   Will there be forward and back checks?

At Rentapen, our 3D models will show the placement and mounting of the sensors and clamps.  The design must allow for room for the hoses and wires.  At Rentapen we leave the design of the controls and electrical to the experts.  We focus strictly on the mechanical aspect of the fixture.  It is important to you and the team that there is a clear understanding of where your responsibility lies.   Tasks for who is responsible for what parts of the fixture (jig) or robot cell should be clearly laid out before  you begin the design.

4)  Will the fixture be trunion or table mounted? 

Will it be robotically or manually welded?  If it is robotically welded, what are the dimensions within which the fixture must fit?

5)  When is the project due? 

When should the preliminary design be ready for review?  When should the checked drawings be completed?  Is there a set schedule?

6) Where are the welds?

The answers to these question should be on the weld drawings for the product.  Usually, in a well planned out line, there is a product drawing of the sub assembly produced in the fixture that you are going to be designing.  Study the drawing for the location of the welds.   If there is no such drawing, ask!

7) What are the critical dimensions?

Study the drawing and identify those dimensions that are held to a tighter tolerance.   If there are no tight tolerances between welded parts, then the fixture may not require shimming.   It doesn’t hurt to ask to make sure.  Asking before you begin is much more efficient.

8)  Are there parts that could be put on the fixture wrong?

Study the product assembly and see if you may need to error proof the fixture so that the parts can only go into the fixture in the way they are supposed to.  We don’t want them welding something on backwards.

9) Do you have a list of preferred vendors?  Some manufacturers prefer Destaco or Parker for their clamps.  The larger companies always have a list of the vendors they use and the products they like.  For example, Genesis Systems requires all their vendors to use Rentapen’s RAPid Tooling Components (TM) wherever possible to reduce the costs of their weld fixtures.

As a design service company, Rentapen has even more questions to ask.

10) What are your design and detail standards?

We want to match the customer’s standards as best as possible.   We put the drawings on the customers format, and follow their standards.  We ask for samples of good drawings so that we can see how holes are called off and slots and chamfers are dimensioned.

11)  Do you put more than one detail on a drawing?

Some of our customers put everything on the same size format and put as many part details as will fit on D size sheet.   Other customers limit it to four details on a D size sheet.  And some customers like to have each part detailed on its own sheet.  A B C D or E.

12) How often do you want status updates?

For smaller fixtures, you will design it up and only have them look at it once before you start detailing it.  But for larger projects, usually the customer will want to see your progress once a week, or as you complete the design for each section of the fixture.  I use the term customer to mean who you report to, who you are serving, be it your production planning team or your manager … whoever your customer is.   As a fixture designer the best way to reduce costs for your time is to get feedback on your designs before you go too deep.

What questions have I left out?  What else do you ask? 

Please add to the conversation and let me know what you think!