Monday, January 30, 2012

Endstop Issues and CNC Router Progress

I finally received my new stepper controllers from Pololu.  I put one together and slapped it in the extruder slot on the Sanguinololu and it promptly burned out.  That makes 4 controllers that have burned out, all when installed as the extruder controller.  Since I had it working once with the original controllers I moved one of them to the extruder and replaced it with the remaining new one.  Success!  I finally have all 3 axis as well as the extruder working properly.  I don't have any more spare Stepsticks so I am going to order a couple more since I still don't know why they have been burning out.

I still have a couple of small issues to deal with.  One of my endstops has burned out during all the messing around with the boards.  I have spares but I also have to make up some new cables since the new board sits in a different spot on the machine and the old ones aren't long enough to reach it.  I have also sprayed lithium grease into another of the endstops by accident so it registers as closed all the time.  I think a Q-tip and some rubbing alchohol should sort it out.

I also have a more serious and confusing issue to resolve.  I tried to load an STL file into Pronterface but I got an error.  It apparently couldn't find one of the Skeinforge modules.  I know that a new version of pronterface has come out since I loaded mine so I will try updating the whole thing and see if that makes any difference.   My installation of pronterface has been working fine for controlling the Mendel so I don't know exactly why there is an issue with the STL files but I am much more comfortable with software than hardware so I am sure that I can resolve it.

I have also been collecting all the bits and bobs needed to complete my DIYLILCNC router.  I had the laser cut pieces made up in September and bought the electronics at the same time.  Over the last couple of weeks I have purchased the bearings, belts, gears, motor shaft couplers, Acme rod, nuts and flanges and all the nuts/bolts/washers for assembly.  I still have to pick up the steel rod, square aluminum tubing and threaded rod but I can source them locally.  I also need to buy the correct Dremel tool to fit the carriage design.  Basically, I am ready to begin assembly.  The first step will be to prime and paint all of the MDF laser cut parts

One final bit of news.  I finally bit the bullet and bought a power supply on Ebay.  It is 30V, 5A so it should be good for anything that I am likely to want to do with it in the near future.  It should be here next week

USA Brand Precision Lab GQ-A305D Variable 30V 5A DC Power Supply s/CV & CC mode

Monday, January 23, 2012

I am still waiting on new Stepsticks (the first ones that I ordered couldn't handle 1/16th stepping) so I thought that I would do a short report on one of the nicest machines that I have seen for a while.  There have been a number of new printers that have appeared over the last few months but this one uses a unique open-source linear bearing system and is a truly elegant design.

It is called the Quantum ORD Bot and was created by Barton Dring who also created and sells the Makerslide linear bearings.  First, here's some info the bearing system:

Makerslide Rail
The system is basically a 20mm x 40mm aluminum extrusion along with a set of  parts designed to work with it.  Any parts that fit standard 20mm extrusions can be used and, in addition, Dring sells V-notched wheels that run along a pair of V rails integrated into the extrusion.  The wheels are designed to accept standard 5mmx16mmx5mm bearings as hubs which are simply press fit to install, and various spacers are available to mount them to flat stock. 

Makerslide standard carriage with wheels mounted

V-wheels with standard 16mm skate bearings
The Makerslide store sells a set of standardized parts like the carriage that can be integrated into your designs or you can buy the wheels and mount them to your own carriage.  The parts can be ordered at the Makerslide Store and he will even cut it to your order prior to shipping.

The whole purpose behind this is........ well, I'll let Barton explain it himself:

"The biggest design, cost and fabrication hurdles in a new CNC design are the linear bearings. There are a lot of commercial and DIY solutions out there, but none support an easy, low cost and rapid fabrication philosophy. I want to create a solution to this. The idea is to use a method that seamlessly integrates into standard aluminum extrusion systems. 

The basic bearing concept is not new. I have used it for years in my own designs and many high end commercial systems use it. It is the V wheel running on V rail. The problem with the commercial systems is that they are expensive, require a lot of accurate fabrication to integrate and don't seamlessly integrate into standard extrusion systems. 

MakerSlide is a V rail integrated into a standard extrusion profile. Since it is based on a standard profile from several sources."

He financed the project through Kickstarter.  The parts are inexpensive and the cost of the rail is currently set at 1 cent/mm (or about $3.00/foot).  That is an incredible bargain in the world of precise linear control.   Makers with a supply of Makerslide rails and parts on hand could prototype their designs extremely quickly

Of course the next thing the world needed was a 3d printer designed around the Makerslide components and Mr. Dring took care of that as well.  Behold, the Quantum ORD Bot!

Quantum ORD Bot

It's a nice little 3d printer that uses the Makerslide as both structure and linear bearing system in all three dimensions.  The usual rat's nest of wires is run inside the extrusions so it has a very clean look to it.  Information on this machine can be found on Thingiverse or on his Buildlog blog posting.  The prototype has a small build area but it has already undergone a redesign to address that issue.

The best thing about this is that the parts can all be purchased for a very reasonable cost.  The worst thing about it is that there is increasing demand for the Makerslide extrusion as word spreads so it sells out very quickly every time a batch arrives at the store.  Still, this is a clean, elegant machine with a very stiff chassis.  It might be worthwhile taking a look at it if you haven't settled on a design yet for your next project.

Wednesday, January 4, 2012

Some Progress, Still Waiting

I am still waiting for my new pololu boards to arrive but I have managed to make some progress in the meantime. 

It was immediately apparent that my axis were not moving as they should.  The steps/mm were obviously incorrect but it took me a while to figure out what they should be.  I could see that the X and Y were moving in tiny increments and finally realized that I had to multiply by 16 to allow for the microstepping (Duh!).  That worked but then their movement seemed to swing too far in the other direction.  Luckily I found Josef Prusa's online RepRap Calculator (Calculator).  Once I had carefully entered the correct data (gear tooth counts, microstepping settings belt pitch angle, step angles and leadscrew pitch) it spit out settings that seem to be correct for my machine.

I think that the extruder setting is still off.   It seems to be pushing out more than 5mm of extrusion when I hit the jog button but I will wait until I have all three axis working to mess with it further.

I am working on the heated bed while I wait.  I got the PID out and wired it up yesterday.  since it runs on 120v AC I don't want to use it without an enclosure but I will give it a quick power up to confirm that it is working.  I have attached the heater pad to my build plate but I didn't get the thermistor wired up last night.  I should be able to finish it up tonight and give it a try.  Assuming that it works I will finish the enclosure and get everything tidied up.

I expect that the new stepper drivers should be here within the week.  I have ordered some ABS to complement the PLA that I already have on hand so I will be able to experiment with the different materials.