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.

Fasteners: Part One

Well, I changed course here a bit.  Bear with me, folks, as I did it with good reason.

After much research and shopping around for a supplier of metric fasteners at inexpensive prices, I found Marshall's Industrial Hardware out of San Diego, California.

Their website layout is kind of first-generation, but their prices are hard to beat anywhere.  I won't bore you with the numbers yet (saving that for Part Two), but they were at worst half as expensive as their nearest competitor.  Needless to say, I made the order.  Tony went in with me on this one also, so we got the quantity discounts that really made it a sweet deal price-wise.

The only thing that has me a little irked so far is that they charged me almost $19 for UPS Ground shipping and then sent the order in two packages by USPS Priority Mail.  I'm still awaiting delivery of the second package, and a response to my inquiry about why they switched the shipping on me without telling me or remitting the difference.

After all the kvetching I did earlier about how fastener prices could be a force multiplier, when I saw how low prices were at Marshall's, I was emboldened to splurge a little and buy a few extras of certain low quantity items.  I figure most of these are small, easily damaged or lost, and the extra expense of having spares might pay for itself in time saved during the build phases.

I also looked at the frame assembly and realized that it would be more pleasing to the eye if built with button-head screws instead of socket heads.  We have plenty of both styles on hand, so we can "plan B" and go back to socket heads if it adversely affects the frame.

That first box got here today, and I've kept it sealed until such time as I can meet up with Tony (seems like a good tradition).  We'll divvy up the goodies over dinner at Bear's Bar and Grill or maybe Hooter's.

So... one more box, one more post, and then we start putting frames together.  It's going to be tough waiting - I wanna get buildin'!

Update:  The second box arrived the next day while I was sleeping (I work nights).  Bigger box, and now the difference in shipping cost is only about $4 and change.  Oh, well.  I guess them's the breaks - I haven't heard back from their customer service yet.  I guess it's like Steve Martin once said, "I've got four dollars - I guess I'll throw it in the street..."  Still, this switcheroo kinda bugs me just a little.

Next:  Fasteners - Part Two:  Let's Do Lunch!

Unboxing Day

Remember in my last post when I so hopefully said it would be "later today" when we met up, opened the box from Misumi, and divvied up the goodies?  Well, that was before my wacky work schedule and Tony's even wackier work schedule came into play.

So... on the afternoon of Saturday, 08 June 2013 the stars did finally align and I found myself at Tony's place to open the box.

Now, before we go much further here, I must apologize for my lack of skill with a camera.  Some of the photos to follow are a bit blurry.  Hopefully (there's that word again), as we go forward, my ability with the camera will improve.

This is a shot of Tony's Prusa Mendel printer, showing how he uses a plain bed covered with blue painter's tape as a substrate for his printed items.  The can of hairspray in the background is used as a sort of "tacking agent" to help the first layer stay flat on the bed.  The extra extruder gears are early rejects his daughter (she's two and cute as she can be) attached to various random points.  The little grey figure at left atop the left-hand Z Axis leadscrew dances around as the printer operates, much to her delight.

Next we see a shot of the box from Misumi just prior to opening.  I was surprised by how small the package was.

  

 

 That's a laptop in the background with about a 17" display, just for reference.

As can be seen here, Misumi sure packed the box with plenty of protection.  I was really impressed with the care and precision with which this shipment was put together.

With the big wad o' plastic removed, we can see the extrusion pieces neatly wrapped together with stretch wrap.  These folks weren't taking any chances.  Note also the bubble-wrap in the bottom.

  

There was this awful feeling I'd had for the two weeks since the box arrived that maybe I'd gotten the part number wrong and the extrusions would arrive without the center hole shown in the CAD drawing.  I'm glad to report those fears were totally unfounded.  The center hole goes the entire length of the extrusion, making tapping it for M5 a whole lot easier.

 

Finally, here's a shot of the Sanguinololu controller at the heart of Tony's Prusa.  We will likely be using this same setup on both our MendelMax builds, as it is very well integrated, inexpensive, and has proven to be quite reliable so far in service on the Prusa.

It's going to take me a while to finish up on the Master BOM, and it's beginning to look as though McMaster-Carr will get the order for fasteners when I'm done.

I'll also be ordering the spiral point M5 tap and tap handle from them, so once the order is received the real fun of the build will commence.  Now, where'd I put my try square and level? 

Next time, we will be covering the assembly of the lower frame elements.        

Organizing a Bill of Materials

Tony and I should meet up and open the box from Misumi later today.  Hopefully, I'll have more to post on that later on.

Meanwhile, I've been going through the MTW Build Guide with a fine tooth comb, trying to sort through the Parts Overview and create a rational Bill of Materials for our builds.  I'm finding the organization of the existing parts lists/BOM to be somewhat, um, disorderly.  There is little consideration given to the sequence in which these parts need to be ordered, which I believe is because the Build Guide is geared to the MTW MendelMax kits.  There are also very few actual supplier part numbers given, nor, for that matter, is a list of suppliers evident in any detail.

Since it is my aim to source as many parts as I can myself and only buy kit parts for what I can't find or make myself, my BOM (in its final form) will be organized a bit differently to permit taking advantage of economies of scale and quantity purchasing to contain build cost.

Just as an example of how a well-organized BOM can make a difference, take the case of M5 X 10 mm SHCS (Socket Head Cap Screws).  These are used in many different areas of the build, and knowing how many are needed for all phases of the build, one may buy them in bulk from a low-cost supplier to get a better deal.  

 Pricing from several sources, I have so far found a better price for these in quantities per 100 than I have in smaller quantities.  This quantity jibes well with the number needed for the build, too.  I have been as yet unable to find a local supplier who keeps these on the shelf in large quantities, and so will have to order and have them shipped, adding to the cost of purchase.

There are significant variations in price for M5 x 10 mm SHCS at different suppliers.  The highest price I found per 100 is about $30, while the lowest is nearer $9, and I'm not done looking, because every penny off the unit price of a fastener at this quantity saves a dollar on the total cost.   Prices of fasteners, in particular, can have a real force-multiplying effect on the cost of a build if not researched carefully prior to purchase.

As assembly phases are completed, I will be posting the relevant as-built BOMs.  Then, after the printer is fully assembled and in debug phase, an as-built Master BOM will be published.  Why am I waiting until I have an as-built?  This is to prevent my mistakes from becoming yours.  I'll talk about mistakes made and pitfalls encountered along the way plenty in this blog, but not in the BOM.  That document is intended to become an accurate reference for this build, and to be useful to anyone who might be following along.

It is my intent to use a numbering system for items which organizes parts in order of build phases, and further by function.  It goes something like XXX-XXX where the first group is an assembly group, and the last is the item number in that group.  A partial list of assembly group numbers might run like this:

000 - Common Parts/Fasteners - used in nearly all phases.
          010 - Fasteners
          020 - Printed Plastic Parts
          090 - Calibration & Debug Common Parts
100 - Frame Components - used in constructing the Frame
          110 - Specialty Fasteners for Frame Assembly
          120 - Frame Assembly Printed Parts
          180 - Aluminum Extrusion Frame Members
          190 - Frame Debug & Calibration 
200 - Y-Axis
          210 - Y-Axis Specialty Hardware
          220 - Y-Axis Printed Parts
          230 - Y-Axis Drive Components.
          290 - Y-Axis Debug and Calibration

Note the skip between 120 and 180, 230 and 290.  There's room in there for other functional groups as needed.  A lot of this will be echoed in further Assembly Groups, e.g., something ending in "20" will always be a Printed Part.  

Yeah... I'm somewhat of a detail freak for stuff like this.

Boring stuff until you need to know what's used when and where.  I'll develop this more as we go along, integrating it into the as-built BOMs.  Meanwhile, I hope to have some photos of the Misumi unboxing in the next entry.  

Ciao for Now!

Getting Started: Ordering Materials for The Frame

So, last time I gave my reasons for selecting the MendelMax design.  This time I'll cover how I acquired framing components.

Shortly after settling on the basic design, I wanted to get this build started so I began the search for a supplier of frame components.  I started with McMaster-Carr (I've bought from them before for work-related stuff), and I even made a spreadsheet to optimize my ordering of their pre-cut extrusions.

Here is where I made my first mistake:  I bought a chop saw from Harbor Freight for cutting extrusions to length, thinking I would be buying from McMaster-Carr and cutting my own.  The day after doing this, I discovered Misumi's website, and read a lot of recommendations on MendelMax.com stating their prices were unbeatable (they are) and they cut stock to ordered lengths.  Yup, I'd just bought a tool I wouldn't be using on this build.

This wasn't the end of the world, and I'm sure I'll be using the saw for future builds, so all is not lost, but that money would have bought a whole lot of fasteners, washers, and other fiddly bits.  The point here is that I rushed in when I should have done just a bit more reading.

As I got closer to go-time, Tony told me, "Hey, when you get ready to order, let me know.  I want to tag along.  This is going to be awesome."

"What?  Are you gonna transplant your Prusa into a Max frame?"  I asked.

"No, man, I just got that working well, and we'll need it to print parts.  I'm gonna build a Max along with ya." he replied, smiling.

I took him at his word, and, after consulting the Trinity Labs and  MTW Build Guides have ordered:

• 8 ea.   20 mm X 300 mm long square t-slot extrusions, black anodized finish.
• 8 ea.   20 mm X 340 mm long square t-slot extrusions, black anodized finish.
• 14 ea. 20 mm X 420 mm long square t-slot extrusions, black anodized finish.
• 200 ea. T-slot nuts, 5mm.

I live just down the road from a Fastenal store, so I figure I'll check locally for cap screws, washers, etc. to complete the frame build.

Tony's printing test parts on the Prusa, so we'll soon have the printed parts for the frames ready.

Yesterday the package from Misumi arrived.  It's still sealed until I get with Tony and we divvy up the goodies.  The entire order shipped for a touch less than $136 and was delivered in five days.

Yeah... this is gonna be awesome.

Beginnings

This whole thing got started when I met a friend at work who already had a 3D printer.  Tony's printer is a Prusa Mendel and he has used it to do some really cool stuff.  Anyhow, talking to him I became intrigued with this technology.

I'd heard of 3D printing, but always thought it to be out of reach economically speaking.  Most of the units I'd seen were selling in the thousands of dollars, and, being an electronics technician by training, I'd often wished I could find a kit and build one.  I didn't give it much more thought until I met Tony.

He steered me toward reprap.org and told me to ask him about anything I saw there.  I warned him I was going to be asking a lot of questions, as I was really fascinated with the idea of an affordable 3D printer.  

As I learned about the open source, maker-driven culture of 3D printing that was growing up around me, I felt that old familiar itch coming back from my days in the DIY electronics hobby long ago.  I knew right then I would be starting this project.

We began an active chatter in email, with me peppering Tony with all sorts of questions about why he chose the Prusa design, what sort of capabilities his printer had, what would he do differently, on and on.  Tony answered my questions candidly, patiently, and in such a way that I began to believe I could do this.

The more we talked and emailed, the more I became convinced I wanted to build a MendelMax design.  What motivated me to choose this design?  There were several features I found compelling:

• The frame of the MendelMax is built from off-the-shelf aluminum extrusions. I already had experience with using extrusions to build things at work.  I liked how it went together quickly, was easy to get squared up, and was light, rigid, and had a nice appearance.  I felt this would make the printer more steady, repeatable, and accurate.
• The design for the MendelMax is robust, and was already mature enough that several iterations of it were in existence. A wealth of data about the design and its various modifications was easily accessible.  (I did not want to be designing my first build from scratch - we'll save that for next time!)
• Parts for the MendelMax are readily available. I didn't feel like having to spend a lot of money for exotic hardware.
• I believed the MendelMax to be the best bang for the buck.  It struck the right balance of price and performance.
• The design is modular.  This meant I could spread out the expenses over the entire build.  It also means that the MendelMax will provide a good testbed for new ideas going forward.

Now you know why I chose this design.  Incidentally, I'll be building some variant of the MendelMax 1.5+, which has a rail-guided Y-axis. 

Next entry we'll look at where and how I acquired the frame components.