Reconsidering the Electronics…

After consulting with folks on WeldingWeb and cnczone, I’ve redone my trusty electronics comparison chart.  A new entry that I was previously unaware of uses Mesa Electronics’ breakout cards and torch height control with Keling stepper motor drivers. It also uses the open source Linux CNC instead of Mach 3. The consensus among those polled who had used both Mach 3 and LCNC was that LCNC provided better performance in terms of speed, flexibility, and reliability… AFTER you conquer the somewhat steep learning curve.

Ad Hoc Mesa/LCNC Ad Hoc Proma/Mach Partial Kit/Mach Turn Key Kit/Mach
Motors $220 $220 incl. incl.
Controllers / BOB $280(KL5056)+ $199 (7I76+5I25PNG) $260 incl. incl.
Power Supply $120 $120 incl. incl.
Enclosure $100 $100 $100 incl.
Torch Height Control $70 $268 $268 incl.
Misc. Cables, Switches, Cooling $250? $250? $200? $100 (recently learned limit switches not included)
Time 60 hrs? 30 hrs? 20 hrs? incl.
Kit $0 $0 $668 $1575
Support Community None None Included + 2 yr Warranty
Software $175 – SheetCam $350 $350 $320
Total $1414 + time $1568 + time $1606 + time $1995

I’ve seen LOTS of folks using Mach 3 and the CandCNC kit who are doing great. I’m sure I’d be up and running quicker if I went that route. However, I’m going to take the $600 bet on LCNC and Mesa and hopefully have a more robust machine in the end. I’ll undoubtedly learn a lot in the process.

Surgery

After I welded the first wheel bracket onto the one of the legs, I realized I had totally messed it up. I used one of my new Harbor Freight pipe clamps to hold it in place and somehow I missed the fact that it wasn’t remotely square.

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Fail.

After some deliberation as to how big a deal this was (it would be attached to a wheel, after all), I decided it’d be better just to cut it off and try again. Problem was that I couldn’t get a grinding wheel into the welded joint due to the vertical walls of the U channel. I thought about using a cutting wheel on the walls to give access to the joint, but in the end I decided it’d be easier to use the chop saw on the leg and start over.

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The amputation. Used the blue legged table to hold the frame up and let the saw cut through the square tubing at an angle.

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Someone should play “Taps.”

Made another wheel mounting bracket.

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Cutting some more U channel to make another wheel bracket. Cut the walls….

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…Then the back.

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Using one of the wheels to line up holes for the bolts.

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The wire cup brush does a nice job cleaning up the bracket.

Once I had cut, drilled, and cleaned up the bracket, I grabbed a piece of scrap tubing and ground angles in it and the leg. I used some heavy bar magnets to line the two pieces up and then tacked it together.

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Used some heavy bar magnets to line up the prosthesis.

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Tacking up the leg extension.

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Welding the leg extension.

On the last bead of the weld, I decided it’d be a good chance to practice some vertical welding. This did not go well. I’m not sure how I managed it but I blew a big hole in one edge and the wire just started feeding into the hole. It was pretty ugly. Should have gotten a pic but I was too focused fixing it.  I did some grinding, laid the piece flat and put down a big fat bead to fill in the hole. I’m going to have to grab some scraps and practice welding in the vertical and overhead positions before I weld the frame together. Good news is the leg seems to have ended up pretty much straight.

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Another ugly attempt at out of position welding.

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Cutting the leg back down to size.

Once I cut the leg back to size and welded the new bracket on, I was finally able to test fit the four sides and start to get a sense of the scale of the monster I’m creating. Can’t wait to clamp it together and start tacking it up!

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Finally able to test fit the four sides of the base.

 

Catching Up

Well hello. I started researching this project several months ago, so there’s a bit of catching up to do on documenting the process. As such, this post is meant to start bringing you up to speed on where I’m at and where I plan to go.

The Goal

The goal of this project is to build a CNC table. CNC stands for Computer Numerical Control. Basically, the idea is to be able to put a sheet of material (metal, wood, vinyl…) on the table and have the machine cut out a two dimensional design from a computer file. This is accomplished by moving a cutting tool over the material using a gantry (sort of like the one that moves the printer head on your inkjet printer except with another axis or two). Stepper motors or servo motors move the gantry and the tool mount. A motor controller interfaces with the computer to interpret a CAM (computer aided manufacturing) file. Don’t worry, I intend to delve into all of these components in much more detail as I come to them in the process of building my table.

The Motivation

My reasons for taking on this project are few and nebulous. I’m fascinated by the possibilities of locally manufacturing digital designs delivered via the web. Part of this is due to my living in a place where almost everything is shipped in on a barge or an airplane. I suppose this is true of America in general. The difference in Juneau, AK is that we don’t have the economy of scale in shipping that others enjoy. It seems like local manufacturing could be a boon in isolated places such as this. Raw materials are still required to be shipped in to the extent that they aren’t able to be produced or recycled locally. I still see a couple benefits to local production though. One is that products can be made more speedily than they could be ordered and shipped. Another is the benefit of just-in-time manufacturing. If less inventory is required, fewer resources will be wasted by shipping goods in quantities beyond the actual demand.  All of this is just to say that I think a machine like the one I’m building has the potential to add a lot of value to the local economy.

In addition to making stuff for locals, I want to be able to make stuff to sell to tourists. According to this report, over 1.1 million tourists came to Juneau in 2007-2008. I think a subset of these visitors see the environmental and economic value in purchasing locally made souvenirs. I have some ideas of things I could make to help these folks remember their trip to Alaska.

I am enormously fortunate to have a job where I have a fair amount of time on my hands. I feel a responsibility to make good use of this time. I’m going to have to learn a lot of new skills, from welding to gcode, in order to complete this project. If you follow this blog, I can guarantee you’ll have a front seat for a lot of mistakes. Hopefully we can prevent your making the same mistakes if you start down this road later on.

The Process

I started by looking at pre-built systems like those offered by Torchmate and Gotorch. I decided I had more time than money, and based on what I’ve read I’m hoping to be able to build my table for about half of what I would have to spend for a turnkey system.  Reading other build logs on forums such as CNCzone helped me wrap my mind around the process. I’m also looking forward to actually building the table and learning all the requisite skills. In time, we’ll test the soundness of this logic.

Once I chose building over buying, I looked around at different kits and plans. I’m planning a future post that will give an exhaustive comparison of the different offerings. For now I’ll just say I decided on a gantry kit from Shopdroids. I’m planning on using a comprehensive electronics kit from CandCNC. Shopdroids has plans and parts lists available for download after you purchase one of their gantry kits. The plans are fairly generic and it is expected that the builder will customize them for his/her needs.  I used Blender 3d modelling software as a free CAD substitute for designing my table. I had quite a bit of experience with this software from previous projects. I’ll go into detail on the workarounds required for this in a future post.

One of the obstacles I’ve had to overcome is the fact that I live in an apartment. I love almost everything about my seaside apartment. One thing it lacks, however, is a garage/workshop space. I’m insanely fortunate, however, to have been granted access to one of my coworkers’ hangars during the build process.

Once I had a workshop lined up and I’d finished my design I started gathering tools and equipment as well as getting quotes for materials. Another post to look forward to is a description of the tools and equipment I’ve acquired and how I decided what to get. Going forward you can also expect to read about how these items worked out for me.  I’m currently awaiting delivery of this tool before I can begin construction.

That’s all for now…

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-Adam