Gas station without pumps

2018 June 27

Three boxes this morning!

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I got three boxes this morning: two via FedEx and one via an unmarked van.

One of the FedEd boxes was from Digilent—I ordered the new Impedance Analyzer attachment for the Analog Discovery 2.  I plan to check it out later this week with some precision resistors.  The design looks a little strange to me (using latching relays with 100mΩ contact resistance rather than lower impedance FETs), and there is no mention of using precision resistors for the reference impedances, so I suspect that it is not quite as good as it should be.  I also ordered the Breadboard Breakout for the Analog Discovery 2, as the female headers on the flywires that it comes with are getting a little loose.  I’ll probably test that out in the next week or two also.

Another FedEx box was from eBay for a new toaster oven (the Breville BOV845SS).  Our old one still works, but the buttons on it are getting a bit unreliable, and I was unable to take the box apart to clean the contacts (one of the screws I needed to remove had its head stripped without my being able to get it out).  The new one does a better job of producing uniform toast, so I like it better already. (I had toast for lunch today, so that I could test the toaster oven.)

The third box was the most fun: a Monoprice Delta Mini 3D printer. I spent a chunk of the day trying to get it to work. The gcode file included on the micro SD card printed ok for about 20 minutes, then retracted the filament a long way and continued “printing” without laying down any more plastic. I tried it twice and it failed at about the same point each time, so I suspect a corrupted gcode file, but I don’t currently have any way to read the micro SD card to see. (I have an SD reader, but it is old enough that it doesn’t include a micro SD slot.)

I then downloaded Cura and Printrun-Mac-18Nov2017 to try driving the printer directly from my Macintosh. I downloaded the Make Magazine test files from Thingiverse and Cura profiles from https://www.mpminidelta.com/slicers/cura.  The profile files on that wiki only work with Cura 3.2 and 3.2.1, so I had to download version 3.2.1 of Cura also.

I had no problem getting Cura to load and slice the stl files, but I could not get my Mac to talk to the printer (it saw the USB device  as

Malyan 3D Printer:

Product ID: 0x0300
Vendor ID: 0x2e26
Version: 2.00
Speed: Up to 12 Mb/sec
Manufacturer: Malyan System

but did not create a serial port for it).

Several online sources also concluded that Mac OS X cannot talk to the printer via USB. This is generally believed to be a firmware bug in the printer.  The printer is running version 44.160.3 of the firmware, which seems to be a very recent version, so Malyan System has not fixed the USB bug yet.

I have one very low-speed HP laptop that runs Windows (which we refer to as the “Barbie” laptop, because of its bright color and toy-like capabilities), which was originally purchased (used @ $75) for testing PteroDAQ on Windows.

The Barbie laptop had no trouble talking with the printer using Printrun, and I tried printing the Make magazine 4_DimmensionalAccuracy.stl file (note: the double “m” in “dimension” is Make’s spelling error, not mine).  Cura estimated a 45-minute print time, but Printrun estimated 67 minutes, which was fairly accurate—there must be some speed setting in Cura that is wrong about what full speed is for the printer.

Make’s preview of 4_DimmensionalAccuracy (from their Thingiverse folder).

The MDM_4_DimmensionalAccuracy.gcode file printed ok, but I had trouble getting it off the build plate. A wrench to twist it off worked best (after putting a small gouge in the plate trying a technique with a screwdriver and mallet). The nominal 20mm dimension of the object turned out to be 19.35mm, which is rather smaller than desirable. The layers were 24.35 by 24.30mm, 19.35×19.35mm, 14.50×14.55mm, 9.70×9.75mm, which is fairly consistently 3% smaller than they are supposed to be.

Make’s 2_XY-test preview file, from their Thingiverse folder.

My second test was with Make’s 2_XY-test.stl file, which I sliced with 0.2mm layers, 10% infill, and a Cura-generated raft (“build plate adhesion” checkbox). The raft did seem to make popping the print off the build plate easy (though not having much area in contact with the plate probably helped also).  Removing the raft did delaminate a little of the bottom layer in one place.  The texture of the vertical walls changes rather abruptly each time there is a hole in one wall, probably due to a change in the way the head moves when a continuous circuit is possible and when it has to either reverse or skip the hole. (Sorry, no photos—it is now too dark out for natural-light photos, and I’ve never had much luck with flash on macrophotography.)

I’m now convinced that I can get the printer to work, so I need to pick a tool for building models in STL format and pick some project(s) to work on.  My son thinks that I should use OpenSCAD, which is a “programmer’s CAD tool”, providing easy ways to create shapes using programming language and view the results, but not edit them interactively.  Given how very frustrating I found the SolidWorks GUI last fall, I think he may be right—I’ll look into OpenSCAD.

One of the first things I’ll print, though, is a design by someone else—extension legs to raise the printer and improve the air flow underneath.  Lengthening the legs by just 1cm will greatly reduce the noise the printer makes.

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