Conclusion

• This is a nicely thought out machine. Quality components. Steel and ally frame rock solid. Excellent heads. Happy with the print quality. One or two parts badly executed, such as the mains power connection, filament guides and supports but nothing beyond the average tinkerer with a 3D printer.
• Build platform needs improvement. Awkward to adjust bed level,  and the glass warps due to method of clamping and lack of support - the only part of the machine that is structurally weak.
  
• Assembly documentation only adequate at the moment, in some places poorly organised and others pretty poor. If you were building your first 3D printer, anticipate taking a much longer time to figure out how it fits together.
• Communication with MTW bordering on poor. Not happy with lack of communication during ordering and response to technical queries. Main support seems to be IRC which I thought died out around the time of the Spice Girls.

Quality of components

At the outset I would have been quite happy to have purchased a pre-built printer, for example a LulzBot or Ultimaker. But when reviewing the experiences of users of these machines it became obvious that each machine had its limitations, evident by the number of mods available to resolve fairly important issues, such as cooling, nozzle replacement, and dimensional accuracy.

The V-Rail system seemed like the way to go with a small 3D printer, and I started looking at making my own. Then I saw MTW's offering, which was more or less identical to the specs I was forming. The deciding factors in buying the MM3 was the use of laser cut metal to join extrusions, E3D hotends, and V-Rail for axes.

Based in Europe it would have been hard for me to have matched or bettered the price for parts, let alone factoring in the time spent researching suppliers, so the decision was made to buy from MTW.

Buying experience

The ordering process was straightforward through the MTW website. I ordered the dual extrusion version, electing not to include the deluxe kit; something I still wonder would not have been a good idea and worth the extra cash (See Self-Printed Parts below). I was excited about receiving the kit within a week so I sprang for priority shipping hoping to get it as soon as possible.

At the time shipping was anticipated by MTW at 3-4 days. I heard nothing for a full week and called them. There was an excuse provided about staffing levels, and the same day the order was despatched.

This experience dented my confidence in MTW, but I had to be generous and assume that their explanation was genuine. It did take the buzz out of buying the thing.

Shipping

If you're based in Europe as I am, importing this could be a drama depending on how well prepared you are. Heard of and EORI number? HS Code? Well, if you haven't, start googling about VAT and duties payable in your country and what you'll need to do to get your package delivered.

Fedex are probably not alone in requiring prepayment of tax and duty, so don't expect to receive it until you have paid them. They also require an EORI number from you, which means making an application for one, online with HMRC if you are in the UK. This can be time consuming, depending on whether you are VAT registered or not.
The final bill calculated by the shipping agent is a total of duty, VAT and a handling fee, and you'll need to check that they got that figure right or at least in your favour. There is no duty payable on 3D printers, and the HS classification is 8443321090. VAT is calculated on the total invoice value including shipping. The handling fee from Fedex was about 11 GBP.

My consignment was shipped via Fedex. The delivery was placed on hold when it arrived but there was no indication of that in their tracking system. Getting the parcel released took two days, involved 20 phone calls totalling 2 hours, in addition to the EORI number application. Fedex were useless, and most of the delay was spent in getting some wonk's calculator to work properly and let me pay to have my goods released.

The whole purchasing experience up to this point was exasperating, partly due to the earlier delay with MTW. I have vowed never to buy from the US again.

Assembly

To preface, at the start of the build process I had no hands on experience with 3D printers. I've seen them and researched some of the components so I had a good idea of how they went together. I spent time reviewing the installation guide before deciding to buy and again before the printer arrived.

The build process from box opening to printing something took two long days, about 24 hours. I'd watched a review video* from a guy who said it took him 11 hours, so this was my expectation at the outset. So, why so much time?

The early part of the build was very straightforward. The fit of metal plates to extrusions are in close tolerance and I found that I'd completed the whole structure correctly without having to go back and redo anything.

What slowed me down was the time spent following the assembly guide. All the information required was there, just not very clear. The photos were important to understand the text but there were too few of them, and of poor quality - generally under exposed shots of black plate and extrusion.

As the assembly moved on to wiring, the guide became fuzzy. For example, there is no information about the printed cable chain or its wiring length, something that cost me a number of hours later on (see next section). I was assembling a dual extruder and found myself going back and forth between sections relating to fans and connections trying to figure out what to do. I missed one instruction altogether, about X-motor wiring running through the extrusion, because that information was found after assembly in a completely unrelated section.

I did spend additional time on properly routing cable after watching that guy's* assembly video. It looked a mess and a recipe for problems later on. All of the motor wires were unsheathed, shortened or lengthened and routed to the RAMBO board around the edge of the base frame, as were other components.

Self-Printed Parts

At this point I was in a position to print the cable chain and had a bunch of cables loosely strapped to the end of the X carriage. Time to print the remaining parts required to complete assembly.

One of the additional parts is absolutely necessary - the cooling fan bracket(s). These should have been provided with the kit so that the printer was fully assembled before printing anything. I felt it was an unnecessary shortcut by MTW to have omitted this part from the kit.

The cable chain is the finishing touch to the MM3 - not necessary but it transforms the printer from something looking very home made into a polished product. All of their sales literature includes photos of the model including it for good reason - without it, the cables are an ugly dangling mess.

Printing the chain parts took two days and was my learning curve for bed levelling, adhesion and software control. It took more than 11 hours of print time, plus finishing, before I was ready to assemble the parts on the printer.

There is no mention in the documentation of how much wire length is required to fit along the cable chain so I'd made a generous estimate and already lengthened several sets of wires running from the head to anticipate this part of the build.

It turned out that I'd under-estimated the requirement quite a bit and had to lengthen all of the cables running from the head. Even if you weren't being as anally retentive about cable neatness as I was, you will have to lengthen the longest cable (left extruder heating element) by 7" or 18cm, and the shortest cable (right filament motor) by 13" or 33cm.

The lack of information about the cable chain at an earlier stage of the build and inadequate information about wiring and cable routing meant that this was the only aspect of the build I had to repeat to end up with a working machine.

In hindsight I would be very tempted to have included the deluxe kit that MTW offer as an upgrade, just for the time spent reworking the wiring. It includes the cable chain and other optional parts.

Dual Extruder

I bought the dual extruder kit and, despite the caveats in documentation to setting up a second extruder at the same time and the generally woolly instructions in this regard, had no problems at all. This is largely due to the well made E3D mounting block which makes nozzle adjustment pretty easy.

It makes sense to assemble the right extruder (mount, tensioner, motor, head, wiring) along with the left one, otherwise there's extra work in routing cables. I left the wiring unattached and did not modify the firmware at this point.

When I set up the left nozzle, I made sure that it was not seated at its highest point in the block before tightening fully. I set it a millimetre down from that height. With the right extruder, I seated it fully up and lightly tightened. This way I was able to work with the left nozzle for calibration and initial printed parts without the right nozzle interfering mechanically.

When the time came to commission the right extruder, I'd got the bed level already, and adjustment of the right nozzle to the same height was a simple process of dropping the right head height in the mounting block to match the height of the left, using the same technique with a bit of paper under each nozzle after homing the Z axis. Works perfectly.

Improvements

Since completing the assembly I spent some time working my way around the parts of the printer that had not been well thought out by Makers Tool Works. Areas requiring immediate attention included the power cables to the heated bed which were loose underneath the bed and snagged the chassis, and the filament holders and feed tubes whose supplied and self-printed parts are rudimentary.

Read my other articles in this section relating to each of these parts, and download files that you can print for yourself.

* Tom Sanladerer- see this video for details