MTW and The Trouble Ticket and A Design Change

I really should have addressed this much sooner.  The trouble ticket I opened with MTW has been closed by me.  In the interval between receiving the report of the bent rod and opening the ticket, Tony managed to straighten the bent rod.  I really shouldn't underestimate his resourcefulness like that.

MTW had offered us the option of photographing the bent rod to show need and then shipping us a replacement free of charge.  They really owned the problem.  Tony was just there way ahead of us in true maker fashion.

I can't really say enough good things about how MTW reacted and owned the situation - their service department takes service seriously.  I just wanted everyone who might be reading to know that.

The design change I mentioned in the title is to the Y-Axis, and is a temporary one.  This all started when I finally decided to order the slide I wanted from Trinity Labs.  Unfortunately, Trinity Labs has been going through something of a rough patch - one of their principals (who was doing a lot of heavy lifting for them) took ill and had to put aside business in favor of recovering from his condition.

By the time I was ready to place an order, Trinity Labs was no longer operating their store on the web.  This being the case, I've begun casting about again for a Y-Axis slide solution, and hoping Trinity Labs gets their situation sorted out.  I also hope their employee recovers full health and well-being.

So... to get things going in the meanwhile, I have implemented an old-style rod-mounted Y-axis ala' the original MendelMax design.  Eventually, when Trinity returns to business or, failing that, when I find a viable and affordable alternative,  maybe a Y-axis slide is in the future of this build.  For now, this slide configuration seems to be going together nicely enough, and looks as if it will support a level of accuracy that is at least acceptable.

Tony was able to put three LM8UU linear ball bearings and a pair of 5/16" rods in my hands for free (generous guy, Tony is) that he had laying around from his old Prusa build. 

I haven't had time to take any photos yet, but when I do, I will update this entry with them and some more details about how the axis is configured.

Meanwhile, the next step will be getting some stepper motors and a controller together.

Stay tuned, folks!  Maybe by another couple of entries we'll actually have a printer bed moving and doing alignment and testing.

Upper Frame Assembly

Well, the box from MTW arrived a few weeks ago, and last weekend we had the time to sit down and check the components.  One of the two sets of 8mm rods appears to have just enough of a bow in them to be unusable.  This morning I've filed a ticket with MTW to see what can be done about this, but, meanwhile, I have put the Misumi extrusion corners to work.

It struck me as odd how, in the Build Guides, a complicated blind-drilling and special Torx fasteners are used to fasten to cross-members to the upper frames.  This, and the use of printed braces across the corners seemed to me, at least, to be a strange approach to which an inexpensive solution is already available - extrusion corners.

The order of assembly I followed is definitely not standard, as the constraint problems to be solved are different for this assembly technique.  The steps below achieved the best results without too much fiddling.

Start with four extrusion corners.  Check they are square, and smooth off any molding flash with a good file so they are clean and completely square.

Next, take the cross-members.  Install an extrusion corner onto each end of the cross-members loosely enough to slide into position using 5mm X 10mm SHCS with a flat washer.  

Since I installed my corners on the inside of the frame,  my next step was to measure from the end near where the corner was attached a distance of 80mm.  Tighten the corner gently (not fully, just enough to hold them still) such that its vertex is at this distance from the end.  Repeat with the other end of this cross-member and another corner.  (If using corners on the outside, measure 60mm.)

Build the other cross-member exactly as this one.  Once this is completed, check your corners are on squarely, and all are at the same distance from each end of each member.  Adjust as necessary.

Now it's time to assemble the uprights.  Attach one upright to each end of a cross-member with 5mm X 10 SHCS with a flat washer on each.  Tighten these screws gently.

Once both uprights are in place, use your square and check they are square by placing it in the vertex opposite the extrusion corners.  If adjustments are needed, be sure to check both squareness and distance.  Once adjustments are complete, tighten and recheck.

If the corners are placed correctly, the outer edges of the uprights will be at 60mm distance from the outer ends of the cross-member, and the inner edges of the two uprights will be 260mm distance from each other.

Repeat these steps for the other cross-member and uprights, then, when all is checked and squared, place the two assemblies side by side resting on the top surfaces of the cross-members, with the uprights sticking up. Compare these assemblies to each other - they should be identical in all respects.  If not, check, tighten, recheck, and adjust as needed.  The 260mm dimension is the crucial one as this is the width of the frame to which the uprights must attach.

Once both upper frame assemblies are built, check the printed parts for the lower vertices.  The inner and mating bottom surfaces should be true, straight, and free of any plastic flash which might interfere.  Trim as needed, then proceed.

Now trap a T-slot nut in the forward facing and outboard sides of each upright and attach the lower vertices onto the ends of each upright, trapping the T-slot nuts, using 5mm X 10mm SHCS.  (On the parts I had, a flat washer would not fit in the recess, so I tightened snugly, but not overly tight.  This should not be a big deal.) 

When installing the vertices, it is important they face the same direction on both uprights.  (Yeah, I started one backward... caught it before I was done threading up, though.)  I used 5mm X 10mm BHCS (button heads) with flat washers to fasten the  sides of the vertices to the sides of the extrusion using the already trapped T-slot nuts.

The resulting assemblies may now be mated to the lower frame using the T-slot nuts already trapped there for the purpose during assembly of the lower frame.  I used 5mm X 10mm BHCS with flat washers here, and found them to be of positive benefit - my 3mm hex key had a lower profile and better clearance on the inner side of the vertices than did the 4mm used for SHCS. This allowed for faster assembly with less re-positioning between wrench turns.  At this point, tighten the screws gently.

Once both upper frames are in place, check for square with respect to the lower frame and with each other.  If it is not possible to square them in both respects, something is wrong - check your upper frame assemblies and the lower frame, and adjust as needed to bring both into true squareness before proceeding.

Finally, integrate the two upper frames by installing the end supports to couple the cross-members.  Remember to trap the T-slot nuts needed before installing the end pieces.  After both ends are in place and loosely fastened, check again for squareness and that the cross-members are running parallel to each other.  

Tighten and re-check. Adjust as needed.

Once everything is assembled, it should look something like this:

Here's a side view:

 As can be seen, the Y-Axis slide is not yet mounted on the support rail.  This is because we do not yet have the parts in hand.  Once these parts are ordered and arrive, the real fun will begin - installation of the motion components!

At least now it's starting to look like a MendelMax!  Resolution of our trouble ticket and getting the Y-axis gear in hand will get us to the point we can start installing the rest of the mechanicals.

From there, it looks like motors, leadscrew development work on the Z-axis, (yeah, we're experimenting here as I may have already mentioned), and then electrical and electronic controls will complete the assembly.

Tony has diverged, and is working his hybrid Max/Max 2.0 design, so I will be following his work as he progresses.  I am intrigued by what he has put together so far - it has the potential to be a very solid design, and one that existing MendelMax users could easily convert to if desired with just a few printed parts, some  extrusion corners and a bit of re-assembly.

That's it for now.  Next time, look for info on the installation and setup of motion components.

Upper Frame Mounts Ready and Emergency Stop Feature

First things first:  many thanks to my build buddy, Tony, for providing me with parts printed on his Prusa at no cost (he wouldn't even let me pay for filament).  Without his kind assistance, I'd be buying printed parts, and that would drive up the cost of my build tremendously.  I suppose this means that the next round of printed parts will be on me after I get the Max up and running.  Believe me, I'll be more than happy to print for Tony or for the next friend of ours who wants to join us in the adventure that 3D printing has become.

The latest addition to my inventory are the four vertices for the upper frame members to attach to the lower frame.  With these in hand, at least the frame can take shape, and my experiment on the upper cross members can commence.

That will come later (probably this weekend).  I just wanted to take the opportunity to say, "Thank you, Tony" for all the parts!

While I'm here, we had the chance to chat briefly at work about the Emergency Stop feature I want to implement on our printers.  Tony tells me the Sanguinololu controller can issue the appropriate commands to control an ATX style power supply unit.  This means we could also implement a system stop feature in software, too.  As of now, our plans still include a hard-wired "hot loop" to stop the motors and extruder when the E-stop is depressed.

I'm thrilled to be moving forward on the build again.  It looks like our next move will be the acquisition of the Y-axis slides, then the rest of the motion components (GT2 belts and pulleys, stepper motors, etc.)

Gotta run for now, or I'll be late for work (there's that four-letter word again!)

 

Y-Axis Bed Support & Other Stories

It all started after the package from MTW arrived...  

(See last post)

This was a relatively small box, but it contained, in addition to most of our X and Z motion components, the Misumi extrusion corners I've been so interested in trying out.

I brought the box to work with me, and Tony and I wasted no time in divvying up the stuff - rods, linear bushings, etc.  When Tony first saw the Misumi corners, it was apparent he'd figured out why I ordered four extras.  It started him on a path of experimentation which I might pursue a bit later on, myself, after this project is up and running.

The way he tells it, he got to comparing dimensions on the upright frame members between MendelMax 1.5 and 2.0, and, finding them to be similar, decided to experiement with some printed parts from the MendelMax 2.0 to create something of a hybrid.  It might be better, though, if I just show you, though, since Tony was good enough to take a couple of pictures:

Here's the side view:

and a view from the front:

An observant reader will note the use of Misumi corners at the rear of the frame.  Tony was impressed with how much more rigidity the frame displayed just from using the corners to join the pieces together.

As I said, this line of experimentation has promise, but I will be pursuing a path to a more conventional MendelMax 1.5 with only a couple of minor tweaks.  As this experiment continues, though, we will cover it here.  Who knows?  A resounding success might convince me to change my mind, but it's too early for that yet.

So... I mentioned the Y-Axis Bed Support?  I dug out my lower frame assembly (which I had left sitting on a flat surface under some boxes during the long wait) and put it on the glass top of the kitchen table, fully expecting it to still have that slight twist I mentioned.  Nope... all nicely flattened out.  This being the case, I went ahead with installing the bed support extrusion.

It's been a while since I worked with extrusion corners, and the ones we got from MTW were cast.  They're accurate enough (they checked square), but had some sprues left from casting that I took a file to and smoothed down, just for appearance's sake.  (My prior experience with extrusion was with Bosch stuff - very high quality/very pricey.)

After knocking off the rough spots, I mounted the corners onto the inside of the frame, using the already trapped T-slot nuts staged for this purpose during the Lower Frame assembly, and 5 mm X 10 mm socket head cap screws.  

With the corners loosely in place on the frame, I first lined up one set of corners  loosely to the left side of the bed support extrusion.  (It's worth noting that having the extrusion pre-cut to length accurately by Misumi was a real time saver, as it avoided any misalignment.)  After this was done, I started the other set of corners on the right side, running them up loosely, also.

Now began the process of measuring and aligning the support extrusion to be square and centered in the frame.  I started at the back of the frame, measuring 150mm from the centerline of the extrusion to the outer edges of the frame on each side using a good steel rule.  

When I got this end in position, I began running up the screws, gently at first, and re-checking alignment as I got gradually tighter.  To assure repeatability of the measurements, I checked along the entire length with the rule now clamped in a combination square attachment.  

So far, so good, but as I got closer to the front end, I found I had to apply a bit of pressure to get the front end to line up with it.  (There was about 1 mm worth of deflection needed to square it up.)

Rinse; repeat.  Running the screws up at the front end gently, re-checking as I tightened a bit more.  Now the square and rule showed good parallel measurements on both sides for the entire length.

Finally, tighten all screws and re-check.  All is nice and square, true, and parallel.

Except... an almost imperceptible twist in the frame...  Oh, well, back under the boxes until the slide and my upper frame mounts are ready.

 

We're Cranking It Up Again... After A Long Wait

It has been a good long time since my last post, so I guess I'd better explain why:  it's down to plain and simple economics.  The past year has not been kind, and I've had far less disposable income than I might have wanted due to, well, "Manure Occurs".  Anyhow, with most of that behind me now, we are ready to surge forward again.

One of the more aggravating parts of the build so far is that I've had to scour far and wide in trying to find sufficient detail about certain parts.  You know, trivial stuff like dimensions and specifications that don't bother someone working from a kit, but are crucial for someone like me who is working from raw components for most of my build.  One resource I found very useful in this regard that I had to dig for was the MTW Hardware Kit Packing Slips for the MendelMax 1.5+.  Dimensions and actual part numbers for many items can be found here which will help others who are of the DIY persuasion.  These will eventually be added to the BOM we're putting together.

In the course of researching linear motion components, I came to a conclusion:  companies that sell these items generally do not prefer to sell to individuals - they sell to resellers who then sell to individuals.  That being the case, after consulting with my build buddy, Tony, the decision was taken to order linear motion components from two sources already well known to the 3D printing community:  MTW and Trinity Labs.  MTW has the X and Z axes parts at good prices, and, likewise, the Trinity Labs Y axis slide assembly is a very nice high-spec unit from PBC Linear for a nice price.

Totaling up the tickets for X, Z, and Y axis components brought us to the realization that we should probably split the order, if for no other reason than to keep peace with our respective families.

This first purchase was from MTW, which , if you've been paying attention is for the X and Z axes.  That might seem puzzling to some, since the Y-axis is the next one in order according to the Build Guide, so maybe I've got some more 'splainin' to do?

While trying to find linear guide rods, I submitted a trouble ticket to MTW because they did not have the correct length 10 mm rods for the Z axis (405 mm) listed in their store.  Since they were good enough to give me a link to be able to purchase these rods, and, indeed, put these items back up on their site for sale, we thought it might be a good idea to buy these pieces first.  Here's what we grabbed from MTW:

Cart Items

SKU

Qty

Item Price

Item Total

10 mm Bushings, Set of 4

LB-10

2

$8.95 USD

$17.90 USD

8 mm Bushings, Set of 4

LB-8

4

$8.95 USD

$35.80 USD

90 Degree Extrusion Bracket

90-D-BRACKET

16

$1.50 USD

$24.00 USD

Precision Linear Shafting, 10 mm x 405 mm, Set of 2

SHAFTING-10-LONG

2

$19.95 USD

$39.90 USD

Precision Linear Shafting, 8 mm x 445 mm, Set of 2

SHAFTING-8-445

2

$19.95 USD

$39.90 USD

Subtotal:

$157.50 USD

Shipping:

$16.30 USD

Grand Total:

$173.80 USD

Now this order encompasses enough parts for both of us, so divide the extended costs by two to find what each of us paid.

The Misumi corners are something else I should explain, since it would appear I ordered double what is called for by the MTW Build Guide.  Four of these corners will be used to mount the bed rail for the Y-axis to the upper level of the lower frame assembly.  What I intend to use the others for is to square up and connect the upper frame members at the top, instead of using the holes drilled through at 70 mm on the upper cross-members.  This should, in theory, make for very rigid and accurately squared joints without all that messy drilling.  At $1.50 each, I'll probably buy several more of these before it's over.  (More on that as the build progresses...)

The Trinity/PBC slides for the Y axes will be our next investment if all goes according to plan.

I'll be tinkering as I have time this weekend doing some testing, and will be updating our BOM as I catalog these newest parts in.

To say I'm excited to finally be moving forward again is a mild understatement.  Look for more info here as things unfold.

Lower Frame Assembly

Well, it's about time I posted again.  I'm on vacation this week, so it ain't like I don't have the time...

Last Friday, I got my lower frame assembly done.  I gotta say, it went together much like the MTW Build Guide said it would, but it used a total of 40 T-Nuts instead of 36 per the guide's lower frame materials needed section.  Any difficulties I encountered were due to some failure to read carefully on my part, but the pictures in the build guide kept me straight (for the most part).

One aspect of the build is still bugging me, though.  I have a slight twist in the assembly which I have managed to minimize but not quite eliminate.  I'm letting it sit for a few days and will tackle it again when I feel like it, maybe carving a bit on the plastic parts to see if I can bring this frame into a true and square relationship with itself.

I'm building on the kitchen table, the top of which is 3/8" glass plate and reasonably flat.  This gets covered with an old white bed sheet to enable me to see well enough when I drop small parts, etc., and to serve as a good lay-down area for parts in progress.

All I can figure is I've either got something in a slight bind, or have a defect somewhere I haven't yet seen, hence the time away.  When I come at it again, my eyes will be "fresh", and I might spot what was right in front of me the whole time.

I am getting ahead of myself, though, as I should probably mention that I used a straight fluted high-speed steel tap for all the 5mm x 0.8mm threads tapped into the extrusions.  I didn't bother with a tapping guide of any sort, just picked up a set of tapping wrenches at Harbor Freight, some WD-40, and an old shodo brush I trimmed down to use for cleaning the flutes between tappings, and went for it.

Now, the usual procedure for tapping in aluminum calls for a much more expensive cutting fluid like Tap Magic for Aluminum, but I found by working slowly and patiently, I was able to get straight starts, and achieve very clean looking cuts with the straight tap and WD-40 with minimal effort.  As I may have mentioned before, the center section of Misumi square extrusions has a pre-extruded hole that is perfect for 5mm X 0.8 threads.

NOTE:  ALWAYS wear eye protection when working with taps!  There is the potential for eye injury during tapping operations.

The biggie is to get the tap started squarely.  Once the first three or four threads are cut, check for squareness, and correct as needed.  A tap that is not square will cause binding and inaccuracies in your build.  Correct as needed NOW if the tap is not running straight.

Oh, and always use a tapping wrench, not a Crescent wrench, pliers or other jack-leg tool - the tap won't run straight, and bad things will happen.  The set I linked above is under $8 at Harbor Freight, and it's money well-spent!

Generally, run the tap in a half-turn or a bit more, then back out about a quarter-turn.  Go more once a few threads have been cut, but don't force it.  Better to go slower than faster.

 

If the tap starts to drag a little, more oil down the bore will help, but it doesn't take much, so don't waste it.  It may also help to back-turn and then go forward by a lesser amount than before a couple of times, then resume.  Patience is a real virtue here.

[NOTE:  NEVER FORCE A BOUND (STUCK) TAP, as taps are made of very hard, brittle metal and are subject to break off in the bore, leaving you an ugly mess to get out of.  The best way here is to go slowly and carefully and avoid getting a tap stuck in the first place.  There are special tools available to extract broken taps, but it can get really dicey getting one out.]

Once the tap is ran in a sufficient distance to support the fastener to be used, back it out, and clean the tap and the extrusion over the trash bin (canned air helps here) to get ready for the next tapping operation.

Now would be a good time to check-fit the tapped end with the correct fastener by running it in until it bottoms out.  If it does not run up all the way to the top of its threads, prep the tap and cut a few more threads until it does.

I did all my tapping and parts prep in about an hour and a half, with frequent short breaks in between to clean as I went so I didn't make a big nasty mess in the kitchen.

It took me another two hours or so to assemble the frame.  It's worth noting here that I used button head cap screws instead of plain old socket heads for a more finished look, and that I used an Allen bit set and screwdriver type handle that made assembly go very easily and kept me from over-tightening anything.

That brings me to my "oopsie-for-the-day".  It's embarassing, really.  After all my careful planning, I neglected to order any 5mm flat washers!  A quick trip around the corner to a nearby Fastenal store corrected that problem.  Under five bucks later, two bags of 100 each (one bag for me and one for Tony) were in my hot little hands, and I was on my way.  The guy (J.C.) at Fastenal was really quick finding what I needed, and got me processed in short order.  It's good to know they're now carrying metric stuff, and they're right around the corner (literally) from where I live, so I can hit them up if I forget to buy other stuff like this.

I'm not sure which direction I'll be going next time, whether I will get to hang out with Tony some more and give him a hand with his lower frame, or if we'll be talking about linear motion components next.  Only time will tell.

I've also got some ideas about small modifications to the design to make it easier to square up... but more research is really needed before I'm there just yet.

The only way to find out will be to stay tuned, folks...

 

 

Fasteners: Part Two

The putative subtitle here was to be "Let's Do Lunch"...  Well, the best-laid plans all go south when wives are involved.  Short version?  My wife and daughter were present at the unboxing, and talking Tony's ear off while I counted fasteners.  It wasn't an unpleasant meeting, but it definitely wasn't our usual printer talk that went on.

I had called Tony a couple of times yesterday to see if we were still on for lunch, and got no answer.  (I think I mentioned we both work some crazy schedules, right?)  Finally, my family and I went to lunch (we're down to one vehicle, and everyone wanted to go out...).

I grabbed all the hardware, just in case, and we headed out.  Sure enough, I got a call from Tony while lunch was just landing on our table.  I told him, "Yeah, come on, we're at McAllister's.  You want anything?"

"No, I've already had lunch with my Dad." came the reply.

So, just as we had finished lunch and were nibbling nachos and cheese to fill in the corners, Tony arrived and we got down to the unboxing.  I didn't bring the camera as it would have slowed down everything anyway.  Tony listened to my wife and daughter talk about Japanese cinema and Anime' (common interests for us all, to my pleasant surprise...) while I counted and divided the various sizes of fasteners at the table.

Tony presented me with another pleasant surprise:  the printed parts for the lower frame are ready, along with other parts I'll need down the road.  With these and the fasteners, this thing can finally start to take shape.

I have to say, the stuff from Marshall's was of exceptional quality.  The coatings on all the black fasteners were hard, glossy, and complete, and the zinc plating on the washers was bright, clean, and covered well, not the cheap "wash" type of zinc plating I've seen on more expensive stuff.

The packing of certain items was disconcerting, as various sizes of fasteners ordered in small quantities were mixed together in two bags which required some sorting, but most other items were ziplocked or boxed, and all boxes had their fasteners in an inner plastic bag and were coated with light machine oil to prevent rust.

So, all in all, it went well.  When I got home, I counted out my stuff again to make sure I'd gotten it right and discovered four extra 5 mm nuts in my kit.  I'll get those to Tony today at work if I can remember where I put them...  I'm also bringing some movies for him to watch.

So...   A pleasant outing, overall.  Now to get building.  Oh, and total cost for this purchase?  $87.04 for both of us, including shipping.  Not too shabby, seeing as it could easily have been twice this much.

Next:  Extrusion Prep and Lower Frame Construction.