Computer Aided Design

David French Partnership went over to CAD back in 1989 with AutoCAD release 10 running on the DOS operating system.  Our first CAD computers were a Dell 386 20MHz and a Dell 386 25MHz machine.  Back in those days to run AutoCAD you had to buy a ‘maths co-processor’ chip to do the calculations.  This cost £750 for the chip on its own!  Isn’t it amazing how things have moved on with modern high speed computers about half the cost of that maths co-processor!

From the outset David French Partnership planned to make our use of AutoCAD as efficient as possible and planned our approach carefully. We wanted to have a system that was uniform across the whole company so drawings produced from each technician all looked the same with uniform layering and styles. We recognised the advantages of being able to customise AutoCAD and our systems have always had time saving customisation. Our drawing template has many predefined layers, customised line types, hatch patterns and text styles.

One of the first problems we found with AutoCAD was that (in those days) there was no way to work with multiple scales on a drawing. We found this to be a big issue when producing engineering drawings and details.  Looking through CAD magazines I came across an advert for ‘MultiScale’ After trying a demonstration copy of the software we ordered it for all our systems.  This enabled us to achieve exactly what we needed.

We were so pleased with ‘MultiScale’ that we asked the developers, ‘Computer Draft Systems’ (CDS) if they had any other utilities.  Initially they were reluctant to talk about their software in development but eventually they admitted that they had a package ‘MultiSteel’ under development.  We saw this software about 6 months before its planned release and we were so impressed that we immediately ordered it for all our systems and had a Beta copy installed a few months ahead of its release.

Initially there was only the steel package but we then persuaded CDS to develop a reinforced concrete detailing suite which they did… and called it ‘MultiRC’.  With both packages we gave the developers input on the system operation and offered suggestions for possible improvements.

We now run with the full MultiSuite software on all our workstations and the developers have allowed us access to some of their special routines which allow our customisation to work seamlessly with their system.  As well as Beta testing their latest versions we are a reference site for them.

Architects and CAD
Not all architects have changed over to using CAD for their drawings and this is a real shame.  We appreciate that some architects like the flair and artistic scope of hand drawn drawings for the planning stage but we feel that a well executed CAD drawing can be equally good or even better.

The advantage of CAD drawings is they are more accurate and the big benefit is they can be shared between the design team.  If we are given a hand drawing and asked to do the engineering often we have to re-draw it, as least in part, to enable us to show the structure and detail it.  This takes time and adds unnecessary cost to the project.

Even a nice CAD drawing can still leave us with a lot of work before we can use it.  The drawing below was a drawing we received from an architect.  On the face of it, it looks fine and achieves what the Architect wants to achieve, looking acceptable when printed.

For us to use it we need to turn off the layers that we didn't need for our structural work. The architect had neatly drawn furniture and even hanging clothes in the wardrobes. When we selected one of the coathangers and tried to turn off that layer we ended up with the drawing below.

Most of the drawing had vanished!!!  When we investigated, it transpired that the architect had used very few layers, simply changing line colours and line types on one layer to produce his drawing.  This is very poor practice.  While it may achieve a drawing that's acceptable for him (and perhaps his client) it is useless to share amongst a design team.

What should happen is you have one line colour and one line type per layer. Different sections of the drawings should be on different layers so everything is easily identifiable and easily manipulated.  British Standard BS1192 covers layering but as so often happens when bureaucrats get hold of things their layering convention is not intuitive.

Using this convention the layer name for drawing a staircase should be:  A244_D02BD_ESTAIRS

This would be translated as the Architectural layer (A) showing spiral stairs (244_; using CI/Sfb), dimensions (D) on level 2 block B, zone D (02BD) with no status (_), at a detail equivalent to a 1:50 drawing (E). In more common applications, this layer name would often be shortened to A244_D using only the mandatory fields, or A244_DSTAIRS to help you understand the element type. How many of us know that element 244_ is a spiral staircase??

The logic behind a mandatory layering system is to enable drawings from different disciplines to be merged while each remains separate.  For instance using the example above A244_D is the layer for information by the Architect about the stairs whereas S244_D is the information by the Structural Engineer.  Merging a drawing between the Architect and Engineer should provide 2 sets of information on 2 separate layers that will match if they are right.

We have a standard set of layers within David French Partnership which are matched to line colours and pen thicknesses in order to produce drawings to our satisfaction.  Within our MultiSuite software we have the ability to convert our layer system to any other layer system if required.  We also have tools to enable us to decipher Architects drawings that are poorly layered but this costs us time and money.

Anyone producing CAD drawings please:

1. Use one colour per layer – keep layer colour ‘Bylayer’

2. Use one linetype per layer – keep linetype ‘Bylayer’

3. Use multiple layers so the drawing can be easily used for other disciplines. 

For example put furniture on a separate layer so it can be turned off.

4. Try to avoid duplicate lines one on top of another.  We had one drawing where every line on the drawing was made up of 4 duplicate lines!

5. Use sensible layer names so it’s clear what you are drawing

6. Work accurately where possible. 

We had a drawing provided recently where the roof pitch was called up as being at 42.5 degrees however when we found intersections not working correctly we found the roof was actually drawn at 42.44553427 degrees.  In a way this is trivial but there were similar errors throughout the drawing and this meant problems with dimensioning.  With modern CAD packages it is easy to draw 100% accurately.

7. Do not cheat! 

This is a similar point to the dimensioning one above.  If you do the drawing and end up with a dimension that is not what you want, don’t over-ride the dimension to make it what you expect.  We had a drawing of a large building with many internal divisions.  Everything looked fine until we checked a string of dimensions and found it was out by almost 1000mm.  There was an error in the setting out and rather than find the error they had over-ridden a couple of dimensions!

The beauty of CAD is if you draw accurately you know if something will fit as the dimensions are 100% accurate. One of the dictionary definitions of a team is ‘acting as a unit’.  A design team on a building should work together and a key part of this is appreciating the needs of other members.  Producing CAD drawings that can be easily manipulated by other team members is a key part of the design process.

David French Partnership’s FREE OFFER
If you are an Architect or Designer and want some advice on how to make your drawings easier to produce and suitable for sharing between the members of the design team, contact us now. We are happy to offer a FREE, without obligation meeting to discuss how you can best produce drawings that suit your requirements AND are good to share amongst the rest of the design team.  We are pleased to offer this as it will obviously benefit the industry and we hope that you will also appreciate meeting us.  We won’t just offer you practical solutions to CAD we also anticipate you will see how we can bring the same practical expertise to engineering solutions.

Do you still draw by hand but want to learn CAD?
If you are an Architect or Designer in the Bedfordshire, Hertfordshire or Buckinghamshireand surrounding areas DFP are happy to offer you a unique learning experience. Very few working professionals can take the time out to go to college and try to learn CAD.  As well as the time issue, the biggest problem of this approach is when you try to implement what you have learnt at college in the real world. When you work on actual jobs, you suddenly realise all the problems and the things you don’t know.

Our approach is for you to learn CAD while you run your business! While you learn AutoCAD we will provide you with a workstation at our offices in Luton for an agreed period.  We will teach you how to draw using CAD on your real jobs within a timescale that suits you. You’ll benefit from initial help with selecting the computers and software best suited to your requirements.

The way the actual teaching works is we will give you one to one training on the basics and show how to apply this to your real jobs so you can “earn as you learn”.  Initially you will need a lot of help but very quickly you will be able to work on your own.  By being in our offices, if you hit a problem, there are a number of experienced CAD technicians available to help you.  Once you have gained the skill and confidence you can go back to your own office. Even then our Technicians are still available to answer your queries either by telephone or you can bring the problem to us.

We have developed this method with architects and it works very well.  Each course is tailored to your individual requirements and the charges are kept low depending on what facilities you require and your time span.

Why do we offer this service?
We think this is the best way to learn AutoCAD but obviously there is an ulterior motive.  While we help you learn to use AutoCAD you will get to know us.  You will get a great insight into us as individuals and our engineering skills.  If you are drawing a project in our offices we hope you will consider taking advantage of our services for any engineering input required.  More importantly we hope that you will then continue to use our engineering skills when you move back to your own office letting your CAD training be the start of a long term working relationship.