RepRap Ormerod Commissioning and First Print

Commissioning, adjustments, axis compensation and a first print.

Upon completing the construction of the Ormerod I started to go through the process of commissioning the printer. However, I ran into a couple of issues and then ran out of time due to other projects.

Having recently picked up where I left off, it quickly became apparent that there have been numerous updates to firmware and documentation — which made everything go a lot smoother this time round.

Replacement Duet board

The Duet controller board that shipped with some of the earliest kits had an assembly error that meant that they needed to be plugged in to both the power supply and USB, and as such could not operate without a PC connected and with simply a network connection. Thankfully, RepRapPro offer a board swap service for those early kits and I decided to take advantage of this.

Firmware update

With the new board fitted I downloaded an up-to-date copy of the RepRap firmware and followed the instructions for loading it on to the Duet's microcontroller and Micro SD card, remembering to edit the sys/config.g file to configure the printer IP address and default gateway.

Proximity sensor reflector

Since constructing my machine it has been recommended to add a small piece of self-adhesive foil at the X axis home position, so as to make it easier for the infra-red sensor to locate this.

Commissioning

Next I Followed the commissioning instructions and tested the heaters, and axis movement and homing, and I'm pleased to say that everything worked exactly as it ought to — heaters got up to temperature, each axis could be moved without problems and homing worked perfectly.

Setting the Z probe

The first step in axis compensation is to set the Z probe so that it is able to correctly position the extruder when homing the Z axis. This involves raising and lowering the Z axis and taking probe readings, so that you can then set the appropriate values in the config.g file on the SD card.

At this point I ran into difficulty as I didn't get consistent results if I repeated the process. So I went round checking all the fasteners to ensure that there wasn't any play in the frame etc. However, the problem was finally solved by rotating the glass print bed, and my suspicion is that it may have been caused by a slight wrinkle in the foil at one of the corners giving less predictable reflection.

The configuration value I ended up with was a probe reading of 639 for a Z height of 0.7mm.

Fine tuning extrusion

Setting the extruder was straightforward enough and involved marking the filament, extruding 100mm and then marking it again. By then reversing the filament and measuring the distance between the two marks it was possible to ascertain how far out of calibration the machine was.

With my printer I found that with the default setting I was getting 102mm of PLA being extruded, and from this could calculate the correct calibration value to enter into config.g.

Bed plane compensation

The Ormerod printer supports bed plane compensation, which removes the need for manually levelling the print bed. I first attempted to use fully automatic bed plane compensation — which is noted as being an experimental feature! — but this didn't quite work out.

Manual bed plane compensation involves picking four points on the bed (ideally as near to corners as practical), and with the first as Z0 ascertaining how far the other 3 corners deviate from this. In my case I found that the second position was at Z0.6, the third at Z0.3 and the fourth at Z0.4.

Four commands are run which set these four points and the corresponding Z values before calculating compensation. Rather than adding these to config.g it is recommended to put them in a new file called setbed.g, which is to be run prior to printing.

Bed clips

I found that the bulldog clips used to clamp the glass plate to the bed sat too high and would get caught by the extruder fan duct. Some forum users suggested using alternate clips, else removing the chrome plated grips and grinding down the clip on one side. I decided do the latter and the result can be seen above.

First print

I skipped the orthogonal axis compensation step as I was eager to attempt to print something and confident that the machine had been assembled fairly square.

Above can be seen a short video of the very first print — a snowman — and the result below.

The large jump between layers was caused by momentarily leaving the printer unattended and the filament getting caught and jarring the machine. However, aside from this, the print is still a little rough and the reason is that there is some play as a result of the Z runner not holding secure against the X axis.

Z Runner mount

The Z runner mount that shipped with early kits did not allow for adjustment and fixes for this include applying layers of tape to the Z axis extrusion, so as to take up any slack. I didn't want to start sticking tape to the machine and instead I thought I'd see if I could print out an updated, adjustable mount.

I first cloned the GitHub repository for the Ormerod so that I had the most up-to-date STL files for all the parts. Next I loaded the Z runner mount STL file in the Slic3r software and exported a G-code file.

I could then load the G-code file in Pronterface and commence printing.

Next steps

The next step will be to fit the new adjustable Z runner mount in order to minimise the play between the Z and X axes.

Once this is fitted I'll probably print off the plastic parts used to calculate the values for orthogonal axis compensation, which should then complete the process of configuring axis compensation. 

Of course, should I wish, when I finally have the machine printing optimally I could decide to print a neater version of the adjustable Z runner mount, along with any other enhancements that the RepRap community have developed for the Ormerod at that point in time...

— Andrew Back