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
