Last week we finished assembling the latest T-Rep prototype. To celebrate, we cleaned it up and took some nice photos:
We’ve been printing with it for the last few days and are very happy with the operation. I’ll try to post some video later this week.
Here’s a quick preview of my latest t-slot RepStrap design, the T-Rep 2.
I’ve incorporated a few things I’ve learned from building my first t-slot RepStrap. But I’ve also approached the problem with different set of goals.
I’ve just completed a new control box for my RepStrap. It houses a PID temperature control & SSR, 24V power supply, Gecko G540 4 axis stepper controller, fan, E-Stop switch, and other associated switches/connectors. Some pics:
I attached the heater element to the bottom of my build surface, and mounted the thermocouple (not shown).
The PID control is very easy to use. It has an auto-tune mode that quickly dialed in the appropriate PID parameters. Upping the set point to 120C, it took about 5 minutes for the temperature to reach that value and stabilize. The heater duty cycle appeared to be somewhere around 60%.
I’m really happy with how easily the heater system came together, and the performance seems more than adequate for my needs.
My concern now is for that 120C plate. This plate is really HOT! In my previous machine with no heater, or with the 60C heater, I’m constantly touching the plate. Now, it is a real hazard for the unwary or someone as forgetful as myself.
My previous attempt at building a heated build surface seemed like a success. Then Nophead came along and demonstrated beautiful results with his Kapton/high-temp approach (>100 C) which immediately made my work obsolete. I couldn’t easily achieve temperatures that high without moving to higher voltages, which would then necessitate a redesign of my controller.
This time around, I’m trying the off-the-shelf approach:
It’s not the cheapest approach, but it should be a pretty simple system to get up and running, and produce more than enough heat for any printing scenario.
I haven’t yet tried the Auber Instruments controller, but if it works, $40 for PID control seems like a great deal. For the baristas out there, they also sell a kit to upgrade your high-end espresso machine to PID temperature control — awesome!
Yesterday I finished assembling the z-axis and installed it on the support structure. This photo shows the bot pretty much complete, sans extruder and drive belts:
All in all, a pretty nice looking machine.
The z-axis is a self-contained unit, making it very easy to assemble and maintain:
I’ll be assembling the control electronics this week.
A few more pics from my RepStrap build:
Adding a build surface:
And then adding the gantry:
Somehow I ran out of T-nuts, so I’ll be working on other stuff until the parts arrive. Here’s a quick video showing the movement of the Y-Axis:
Just returned from a week of vacation - time to get back to robot building!
A desk covered with robot parts is always a beautiful sight:
The 8020 stuff assembles very nicely, as you can see here:
All the flat parts were cut with a waterjet. I buffed the outside edges with a Scotch-Brite wheel, and reamed the close tolerance holes. There were also a few holes that had to be tapped. Lastly, I pressed the bushings into their locations. All told, it took me about 2 hours of prep to get to the bolt-together stage.
Here’s a closeup shot of some flat parts:
More to come…
I’m jumping on the heated platform bandwagon:
With 4 x 1 Ohm power resistors the output is around 36 Watts. Testing has shown that it will hold 60 C at at 70% duty cycle (178 pwm) — too hot to touch for more than an instant.
I’m driving it with my Arduino Pro Mini-based temperature controller, shown here:
This board provides two channels of thermistor based PID temperature control. The sensor and driver circuits are borrowed from the RepRap extruder controller. The controller will run stand-alone using pre-set temperatures, or will respond to Gen3 protocol commands over RS485.
It includes a standard PC power connector (molex) for easy RepRap use, and jumper selectable RS485 termination.
When I complete the move to a stepper driven extruder this board will control both the extruder and platform heaters.
After a day of adjustments and tweaking, I finally have the bot all assembled. Next step: Smoke test!
I started with testing the heater element. A little bit of smoke as the heater came up to temp, but otherwise, everything seemed fine, and I was able to get temp to stabilize around 220C.
Next, I put a short length of abs in the extruder and turned on the drive motor…
Success!
Some pics of the completed machine:
I’m pretty sure I completed all of the machine work today, so assembly should start tomorrow. Lots of time at the drill press:
Laying out components in preparation for riveting:
I forgot to post a pic of the electronics mounting, so here it is:
