2017. július 31., hétfő

Pen Plotter 3. - Working

It is finally working.
Built the whole thing, assembled, then redesigned most of the pen holder.
The problem was the following:
  • The SG90 microservo I intended to use was not strong enough
  • The line I wanted to use to pull up the Z carriage was a bad design decision
  • The arduino was not able to provide enough current to the stalled microservo, so it rebooted when the pen pulled up.

In the new design:

  • The SG90 replaced with a more powerful MG995
  • The servo moving the carriage directly
  • Added a 6V regulator for the servo, what gets its power from the beefy 12V PSU and not the arduino.

The electronics on the head still messy as I don't designed a proper PCB yet (but it will only happen when I finish the milling and the laser engraving head design):

And finally here is the first video of the working unit:

2017. július 27., csütörtök

Pen Plotter 2. - Measuring Proxxon

I've a Proxxon Micromot drill. I'm planning to attach it to the plotter as replacement to the pen, to be able to do some light cuts.
For this I don't want to use it's original power supply unit. As the speed control is located in the power supply I wanted to know it's properties:

  • How the motor driven? Pure PWM or filtered to DC?
  • What is the PWM frequency?

To measure this without disassembling, not looked like an easy task. The reason is that Proxxon uses a proprietary connector, what is not available on the market. So I measured the diameter of the pins and looks like with two 2.3mm drill bit I made it:

The measurements:
Without load:

At minimum speed:

At maximum speed:

It is a bit noisy to my taste and figured out that it runs at 100Hz and not really filtered.
Based on this I can design the new electronics into the plotter.

2017. július 5., szerda

Pen Plotter 1.

I'm not documented this project deeply, step-by-step. Now I'm just writing where am I today with the build. Mainly pictures.
More than three month ago I had a conversation with my son. He told me that he want to build a "drawing machine" essentially a pen plotter together with me. I started to design one. After a few conversation he told me that he wanted to build it from Lego.
I was already too deep in the designing already, so I didn't want to stop. In addition I was planning to add exchangeable head to be able to use it as a light router and a laser cutter/engraver.
I think the design mainly finished:

I left out a few things from the design, like drag chain, screws, spacers, timing belts.
During the design process I already printed some of the parts:

As you can see, there are some assembled parts also on the picture, like the Y axis drive (round white thing in the center) and Z axis carriage (the green thing).
How the Y axis timing belt mount into the holder:

Lots of holes, the base plate:

X axis assembled: