2.x for kbob's maker space

Post your build logs here

2.x for kbob's maker space

Postby kbob » Mon Aug 27, 2012 5:39 am

I have started building a laser cutter for my local maker space. Today I placed the big parts orders from Misumi and McMaster Carr.

I'm planning to follow the 2.x design as closely as possible for the mechanical assembly. For the electronics and software, I feel confident enough to step a little off the established path.

I found this site just a few days after Bart sold out the most recent batch of 2.x kits, unfortunately. So I'm going to have to improvise on those parts. I will buy a kit from Bart if/when he makes another batch. If I get to the point where I need the kit parts before Bart makes more, I will 3D-print them. That will work fine for some of the parts, I think. Others will just be temporary to get the assembly done, and I'll hand-fab them in aluminum later. I don't know what I'll do about the Delrin V wheels - modify the design to use Inventables' dual bearing wheels, I guess.

For the electronics, I have preordered an Azteeg X3. I will use that for as long as I can. If it can't spin the stepper motors fast enough, I will look at upgrading to either a BeagleBone or a commercial DSP.

So far, I've placed orders with Inventables, Automation Technologies, RadishWorks, Makerslide Store, Panucatt, Econobelt, McMaster Carr, and Misumi. The goodies have arrived from Inventables, Automation Tech, and RadishWorks. I have many more orders to place.

I'm building this for the maker space partly because we need one, and partly because I'm much more keen on building a laser cutter than on using one. It will be a challenge to get this finished to the point where it's not a "project" but a "production machine". But none of us would be here if we didn't like challenges, right?
Bob
"If you didn't code it, it will never own you." (-:
kbob
 
Posts: 151
Joined: Mon Jul 09, 2012 6:39 am
Location: Eugene, OR, US

Re: 2.x for kbob's maker space

Postby kbob » Wed Sep 05, 2012 2:04 am

Parts are trickling in.

I found one mistake with the parts I ordered. I got stepper motors with ¼ inch shafts instead of 5 mm. I naively assumed that NEMA standardized that stuff -- it turns out NEMA only specifies where a motor's mounting holes are.

So the couplers for the Y motor won't fit. I don't have a lathe to turn the shafts down, so I will order a replacement stepper for Y.

Fortunately, Stock Drive was back ordered on the 5mm toothed pulleys, so I haven't ordered those. I'll just order ¼ inch pulleys for X and Z.

Speaking of pulleys, Econobelt has pulleys in the right sizes, but they are metal, not plastic. Those should work, right?

Aside from the motor and pulleys, I've ordered all of the core mechanicals, optics, skins, and a quorum of electronics parts. I'm deferring the cooling system, ventilation, air assist, laser, and laser power supply until the chassis is built and the motors are moving the gantry and carriage.

I have received parts from:
  • Automation Technology
  • Inventables
  • Econobelt
  • dumpsterCNC
  • McMaster Carr
  • RadishWorks

I have tracking numbers from:
  • Makerslide Store (2)
  • Inventables
  • Misumi

I don't have tracking numbers yet from:
  • Panucatt
  • Newark Electronics
  • Kabelschlepp's distributor
Bob
"If you didn't code it, it will never own you." (-:
kbob
 
Posts: 151
Joined: Mon Jul 09, 2012 6:39 am
Location: Eugene, OR, US

Re: 2.x for kbob's maker space

Postby bdring » Wed Sep 05, 2012 12:43 pm

I have preordered an Azteeg X3. I will use that for as long as I can. If it can't spin the stepper motors fast enough


I don't expect to ever see an Arduino based board doing any high speed engraving, but I think in vector cut mode it should go fast enough to do anything you need.
Bart
"If you didn't build it, you will never own it."
bdring
Site Admin
 
Posts: 2966
Joined: Sun Nov 22, 2009 7:33 pm
Location: Chicago, IL, USA

Re: 2.x for kbob's maker space

Postby kbob » Wed Sep 05, 2012 2:55 pm

Comment From Buildlog Author
bdring wrote:I don't expect to ever see an Arduino based board doing any high speed engraving, but I think in vector cut mode it should go fast enough to do anything you need.


And that's okay. If I replace the Azteeg, it will find a home in a 3D printer.
Bob
"If you didn't code it, it will never own you." (-:
kbob
 
Posts: 151
Joined: Mon Jul 09, 2012 6:39 am
Location: Eugene, OR, US

Depth of Field

Postby kbob » Thu Sep 06, 2012 6:04 am

Here's a gratuitous photo of some Makerslide so this build log can have an image.

IMG_9237.jpg


Or maybe this photo instead.

IMG_9229.jpg


Since yesterday, more parts have arrived from Econobelt, and I have a tracking number for my Raspberry Pi.

And I'm writing another build log on Eugene Maker Space's web site. That one will assume a lot
less familiarity with lasers in general and the 2.x in particular, but more familiarity with the
maker space and with me.

http://www.eugenemakerspace.com/?cat=14
Bob
"If you didn't code it, it will never own you." (-:
kbob
 
Posts: 151
Joined: Mon Jul 09, 2012 6:39 am
Location: Eugene, OR, US

Parts Arrived

Postby kbob » Tue Oct 23, 2012 5:30 pm

It's past time to update this build log. Progress is very slow, but enough has happened that I can write a couple of posts.

All the parts I ordered in August arrived. The last item to arrive was the Azteeg, and I've had it for a month now. Others have already said it, but I'll chime in too: the Azteeg X3 is a very good looking little board. That really surprised me -- most semi-hobbyist designers don't put much thought into their projects' appearance. Now I'm thinking I want to build an ORDbot just so I can put an Azteeg (and Roy's heated plate) front and center.

I've been getting into programming the ATmega chip. I didn't realize how limited the AVR architecture is. Eight bit arithmetic. No divide instruction. No hardware floating point. And the version of Arduino + GCC I have appears to be generating broken code for the software floating point.

I am still going to try to use the Azteeg to control the laser cutter. I've figured out how to pulse a stepper from one of the counter/timer compare registers, so that means I can time step pulses to the resolution of the timer, up to 16 MHz.

I've spent the last two weeks proving that linear acceleration ramps are computationally infeasible on the Arduino. :-( So I'm thinking about either a stepwise approximation or trying to program an S curve. A S curve would be better, as (a) it minimizes jerk when starting, and (b) it reduces acceleration near max velocity when the motor is running out of torque. I'll have to find out whether that's computationally feasible.
Bob
"If you didn't code it, it will never own you." (-:
kbob
 
Posts: 151
Joined: Mon Jul 09, 2012 6:39 am
Location: Eugene, OR, US

Re: Parts Arrived

Postby kbob » Tue Oct 23, 2012 5:37 pm

Comment From Buildlog Author Here's a dumb question for you who already have laser cutters.

My UPS driver brings me about a cubic foot a month of corrugated cardboard wrapped around various items. Can you cut that stuff on a laser cutter? I have a nearly infinite supply available for free, so it seems like it would be better than buying plywood or acrylic sheets, especially when just starting to test/calibrate the machine.

Does that work? Or is it too flammable/too thick/too variable/other?
Last edited by kbob on Tue Oct 23, 2012 9:20 pm, edited 1 time in total.
Bob
"If you didn't code it, it will never own you." (-:
kbob
 
Posts: 151
Joined: Mon Jul 09, 2012 6:39 am
Location: Eugene, OR, US

Re: 2.x for kbob's maker space

Postby mattrsch » Tue Oct 23, 2012 6:13 pm

Cardboard cuts great. I usually try more complex assemblies in cardboard first since it cuts fast and it's cheap... And I'm prone to silly mistakes :-\
mattrsch
 
Posts: 98
Joined: Wed Jul 21, 2010 5:09 pm

Re: 2.x for kbob's maker space

Postby canadianavenger » Tue Oct 23, 2012 6:26 pm

I always do a test pass with cardboard first to ensure that there are no errors in the generated g-code. [my laser runs on LinuxCNC]
canadianavenger
 
Posts: 153
Joined: Wed Nov 30, 2011 3:24 am

Printing laser tube support brackets

Postby kbob » Tue Oct 30, 2012 5:38 am

Last night, after a little encouragement from Bart, I looked again at the laser tube support brackets. My recollection was that they were way too big for the four inch printer at my makerspace. I had tried laying them out diagonally, because some other long parts fit in that orientation, but the tube support brackets do not. They almost fit, though, in the regular orientation. We installed a new glass bed on the printer last Friday night, and it measures 110mm in the long (Y) dimension. The tube support bracket is nominally 120mm wide.

My first idea was to chamfer away the bottom corner so that the bottom surface is only 108mm. That looked like this in OpenSCAD.

Chamferred.png


After taking away material right where the post holes go, I thought I'd better add some material and move the post holes away from the chamferred corner. So I came up with this. There's no reason why the holes have to be on the part's center line.

Pillars.png


This morning I printed it. The print was pretty bad. The print shifted over as the printer reached the tops of the chamfers. That means, I think, that the printer has a full 120mm range of movement, but it is not centered over the table.

Misaligned Layers.jpg


Then I tried to drill out the post holes. The printed material split. Apparently, it's sort of like plywood. If you drill through the plies, the alternating grain direction of successive layers holds it together pretty well. But if you drill parallel to the plies, it's just pulp. Er, it's strings of plastic that aren't stuck together very well.

That piece was ruined, but I decided to drill out the holes for the alignment bolts anyway. I found that the dimples in the model aren't big enough to attract the drill bit on the rough surface of the plastic. Also, 8.5mm thickness with a 7/32 hole leaves very thin sides, especially in pulpy plastic. So I decided to go thicker near the alignment bolts and to print the holes instead of drilling them. I could have just made the whole piece thicker, but I was in a plastic saving mood.

It is conventional wisdom that you can't print a horizontal hole. But I've been printing horizontal holes with no problem on this printer. I don't know why it works, but it does. Anyway, those changes led to this model. Note that I also cropped 3.5mm off each end, leaving a fairly thin wall between the post hole and the end.

Version 2.png


I made two, and I made them mirror images of each other. That way, the "legs" will protrude to the outside on each piece. Tiny thing, but it would bug me if I hadn't. (-:

The nuts were a tight press fit — I had to push them into place with needle nose pliers. The bolts slipped right through their holes, no cleanup required.

Version 2 Printed.jpg


Here they are holding up an old fluorescent tube I found in the junk pile.

IMG_9297.JPG
Bob
"If you didn't code it, it will never own you." (-:
kbob
 
Posts: 151
Joined: Mon Jul 09, 2012 6:39 am
Location: Eugene, OR, US

Next

Return to Build Logs

Who is online

Users browsing this forum: No registered users and 42 guests

cron