Timothy Pan Portfolio

MOTORIZED DRAFTING MACHINE

MDM

MOTORIZED DRAFTING MACHINE

What is a Drafting Machine?
Making technical drawings in an age before CAD was an artform as exacting as it was necessary. To assist designers in this vital task was the drafting machine, a device which counterbalanced an adjustable protractor head even with the top of the board no matter where it was moved.
However, after the advent of CAD, the drafting machine quickly became obsolete. These ingenuinely designed machines have largely been forgotten.

But not by everybody! Come with me as we rediscover the genius of the old masters- and design the world’s first motorized drafting machine.

What is a Drafting Machine?
Making technical drawings in an age before CAD was an artform as exacting as it was necessary. To assist designers in this vital task was the drafting machine, a device…

CONCEPTION

>Inspo >Design Decisions

CALCULATION

>Range of Motion Model >3-D Sketching

CREATION 1 - HEAD

>CAD Best practices >Ergonomics

CREATION 2 - ARM

>Designing for Motorization >Counterweighting

CONCLUSION

>The Human Connection to Manual Craft

DESIGN DECISIONS

Drafting machines used various linkages to keep the head level, from gantries to virtual 4-bars. I chose a parallel 4-bar for its aesthetics, historical character, and the challenge of calculating its range of motion. Another key decision was balancing historical accuracy with modern advancements: I used updated materials and manufacturing methods but kept the manual spirit by making the machine completely operational even without power.

CALCULATION

THE RANGE OF MOTION MODEL

The main challenge with utilizing a parallel 4-bar is that the machine has a specific and limited range of motion. Using SolidWorks’s in-sketch relations, I was able to build a virtual simulation in which by changing the dimensions of a driving sketch, I could determine the maximum range the machine was able to reach. Using this model, I determined the optimum range of motion necessary for the machine to reach every part of the 3x4’ A0 drafting board.

After the key dimensions were determined from the model, I moved on to create a rough assembly using solids. This was to determine the overall layout of the machine, as well as troubleshoot collision problems. This also allowed me to test the machine out for the first time and confirm the accuracy of my motion model.

MOTORIZATION CONSIDERATIONS

By centralizing the motors in the ‘shoulder’ of the machine, the moving mass of the arm can be greatly reduced, improving accuracy. Using a 1:1 belt drive, both arm segments can be controlled by the stepper motors to make controlled movements.

COUNTERWEIGHTING

There were many options for counterweighting the machine, but I decided to use the simplest one that I could find historical evidence for to fit into the sleek, manual aesthetic.

MOTORIZATION CONSIDERATIONS

& COUNTERWEIGHTING

DRAFTING HEAD LAYOUT

For the drafting head, the key dimensions revolved around the size of the knob and the size of the angle indicator for legibility. The main goals were to make it as small and light as durability and function allowed. I used an ergonomics manual, and after comparing it with a historical drafting machine that I encountered later on in the process, I was pretty spot on!

CAD BEST PRACTICES

REFERENCE GEOMETRY

In order to maintain consistency and compatibility, I began each part with a selection of reference sketches that always included the underlying base geometry determined in the calculation phase and the location of fasteners and other relevant geometry. This tremendously expedited creation and helped avoid a lot of item conflicts later on.

REFERENCE GEOMETRY

CONFIGURATIONS

There are many parts in this machine that passively lock into one another, taking advantage of the complex geometry achievable through 3-D printing and waterjet cutting. By utilizing boolean intersects and configurations, these interlocking parts could be created responsively so that one edit changes many separate parts at once.

CONFIGURATIONS

CREATION 1 - HEAD

The drafting head is easily the most complex part of the machine. It needs to accomplish several tasks passively in a tight and ergonomically focused package, with no room to waste and no detail uncalculated.

ANATOMY

Stationary Plate

Spindle

Locking Mechanism

COTS

Solenoid + Attachments

DRAFTING HEAD OPERATION

Both buttons are located in the optimal position for depression with the thumb. Red button unlocks free rotation while the blue button snaps into 15 degree increments and can be toggled by pressing in and down to keep depressed. Rulers can be changed by unscrewing from the bottom.

BEARING SANDWICH

The spindle and stationary plates connect through a 4-part bearing sandwich which allows for smooth and continuous rotation while unlocked. The dimensions of the bearing drive many of the other dimensions in the draft head.

Stationary Plate

Spindle

Bearing

BEARING SANDWICH

LOCKING MECHANISM

All of the locking components are contained within the spindle. When the button is depressed, it simultaneously disengages the brake located below the bearing sandwich, which is where the friction between the bearing plate and the brake enable the machine to lock into place.
The second button has a toothed lower brake which locks into the similarly toothed drum which enables the 15 degree indexing action.

LOCKING MECHANISM

SOLENOID INTEGRATION

The solenoid sits at the core of the drafting head, and the connection to the pen-mounting nub is through a long, bent 3-D printed piece which is held straight because of its bent shape. A cable passthrough for powering the solenoid is considered

in the design.

HEAD RENDERS

SOLENOID INTEGRATION
… See More

USER INTERACTION

From my own experience making technical drawings, I wanted both rulers to meet at a crisp, convenient 90 degree edge and for the rulers to be transparent.

USER INTERACTION

From my own experience making technical drawings, I wanted both rulers to meet at a crisp, convenient 90 degree edge and for the rulers to be transparent.

CREATION 2 - ARM

The four bar linkage is based exactly on the preliminary sketch, but significantly more detailed. To reduce weight, the long bars in most places in the machine are hollow 10mm OD carbon fiber rods.

ANATOMY

Counterweight

Motors + Pulley

Motor Cluster Body

4-Bar Linkage

Draft Head

The four bar linkage is based exactly on the preliminary sketch, but significantly more detailed. To reduce weight, the long bars in most places in the machine are hollow 10mm OD carbon fiber rods.

ANATOMY

Counterweight

Motors + Pulley

Motor Cluster Body

4-Bar Linkage

Draft Head

EARLY ITERATION

EARLY ITERATION

EARLY ITERATION

A larger, more circular design for the motor cluster was almost adopted. However, in order to save material, the current, sleeker, more historically accurate motor cluster was developed instead.

MOTOR CLUSTER

The motors are mounted onto two metal plates, which are connected using a 3-D printed piece I produced using the loft function and sculpted for part clearance. The pulley is attached onto the motor using a collet with set screw, and the directly driven arm is attached using a clamping mechanism. I also included a cutout for cable management.

MOTOR CLUSTER

MOTOR SELECTION

In order to achieve high accuracy for utilizing the machine autonomously, I selected two stepper motors. By utilizing a 1:1 connection for each segment, backlash through a geared system is eliminated.

Potentially, if the motors are not strong enough, they can be improved using a cycloidal gear reducer similar to other industrial robotics applications.

MOTOR SELECTION

COUNTERWEIGHTING

The counterweight’s position and weight can both be adjusted by moving the weight or changing the number of metal plates in the stack respectively.

ELBOW CONNECTION

The counterweight directly influences the pivot point in the elbow and the lower arm segment via bent metal strips that are inserted into the driving gear and at a point lower down the arm.

ARM RENDERS

ELBOW CONNECTION

CONCLUSION

THE HUMAN CONNECTION TO MANUAL CRAFT

This passion project will never change the world. Although with some adjustments, I suppose it could be simplified and made cheaper to mass manufacture (standardizing more components, utilizing injection molding), but I never designed for it to be a household appliance. It promises no life-changing benefits to its users except for a very niche market who might get a kick out of using it to practice an obsolete craft.

The reason I designed this machine was not because I wanted to make something that would revolutionize drawing.

I designed this machine because I love what it represents.

Doing things manually and patiently is a dying art. We live in an age where our first instinct when we encounter a problem is to hand it off to someone else (like our wonderful AI friends) and I believe that we are losing a lot of knowledge rapidly and unconsciously in this process. In a design landscape that is accelerating towards an unknown criticality at an increasingly uncontrollable speed, it is so easy to become unchained from logic. This machine is my statement that I have not forgotten! In the development of this project, I solidified the fundamental design skills that I built my practices on- Committing to rock solid CAD documentation, thinking mechanically, ergonomically, and aesthetically simultaneously, designing products for manufacture and assembly…
Although drafting by hand is an obsolete skill, the value of doing things using your own creative energy will never become obsolete.

THE HUMAN CONNECTION TO MANUAL CRAFT