Thanks

it is much appreciated. I keep thinking about getting one but don't have a clue as to using it! Any info is valuable.

My start with 3D printing

I have been following developments in 3D printing ever since the first printers came out, but did not want to put in the time investment in learning how to effectively use a new tool.  I did however, eventually want to take on the task of learning 3D printing, and more importantly, re-learning how to do 3D CAD design after a 39 year hiatus (did some design with Computervision CADDS 3 my first year out of university). 

Since I anticipate retiring in the next year, I felt now was as good of a time as any to get started on the journey.  For my first printer, I selected a Prusa Mini.

https://www.prusa3d.com/original-prusa-mini/

Here are the reasons that I chose the Prusa Mini.  The reasons were valid for ME, your mileage may vary.

• I wanted a lower cost entry into 3D printing, but I did not want to receive a "box of parts" that required detailed assembly.  The Prusa mini was up and running within 2 hours of my breaking the seal of the printer, and was ready for it's first test print.
• The Prusa Mini has a 180mm cube print area.  Plenty of size for what I am looking to accomplish with my first printer. 
• I do not want to make a hobby out of assembling a printer, and searching for fixes on the web for poor designs.  Not all kits seem to suffer from this, but enough of them do that I didn't want that level of "education".  That ruled out a lot of the Prusa knock-off printers that sell for far less money. 
• For me, a FFF (Fused filament fabrication) printer made sense as a first printer, as I did NOT want to deal with the mess, or the odor of a SLA or DLP printer.  I was willing to sacrifice resolution for ease of operation, and cleanliness.  I want to push the limits of the FFF technology before going on to next steps.  The FFF also provides me a way to validate CAD designs that I may elect to have printed by Shapeways.  The best affordable SLA or DLP printers still do not match the resolution of a Shapeways print.
• Prusa printers have an excellent bed plate design that for PLA filament does not require any sort of preparation other than cleaning with 91% isopropyl alcohol and a micro cloth, which they supply one of in the kit. 

After assembly and test, it was time for my first prints.  Prusa sends along some files to print, so my first print was a nut.  Just sitting there watching the printer go through its paces was enjoyment.  Print was successful.  I followed that up with a "Benchy", which is a small boat with complex shapes.  After that I printed a bolt  All of this was done with Prusament PLA filament, with the print resolution at 0.15 mm.  I followed that up with a bolt, and two "Baby Yodas":   The Baby Yoda was my first downloaded print file, and the first time I used the "slicer" solfware to create the g-code file. I used the Prusa Slicer.  I colorized one of them for "Twin A" using the ink markers I use for "painting" some of the laser kits I've built.  The green was out of my wife's "Stampin Up" marker assortment.   

These test prints also allowed me to become accustomed with setting up the printers "Z" axis height to get good bed adhesion.  That took a few tries to get what the documentation identified as the correct height.  Getting this first layer height is critical to getting a good print. 

Here are some of the test prints.  Printing "Baby Yoda" also gave me my first encounter with "stringing".  Went to learn about that, and it turns out that a good way to get rid of them is use a heat gun (very carefully).  I tried the wife's hair dryer, that didn't get it done, it simply does not get hot enough.  All it did was make the plastic soft.  Need to add a heat gun to my tool collection.  

So at this point, I was ready to start using this printer for what I bought it for, which is model railroading.  Before I move on to that though, I ran into my first printer issue.   More on that in my next post.

Regards,

Jerry

I think you will find that

I think you will find that you can do some fantastic things with the printer. I have been using mine for about 2 years now and make both mechanical parts for the layout  and actual models. I have mostly built buildings and detail parts for the layout. You are only limited by your imagination.

Don't be afraid of trying things that don't turn out the first time, I throw our a lot of parts that just don't work the first time around. A case in point is the roof for the structure I am working on. It is the roof and eaves all in one. When I printed in in one direction it didn't turn out well, but rotated and printed again it was fine.

I think you will enjoy modeling with the printer, I use mine almost daily. You can check out what I have done on my blog here.

Greg

Thanks for commenting..............................

Rick:

Follow everything you write, and I'm very grateful for what you have shared here on your backdrops, printed buildings, and modeling in general.  I know that if you did dive into 3D printing that you would soon surpass me in creativity and knowledge.

Greg:

Your efforts in 3D printing, particularly your elevator, were one of the main reasons that I chose to jump into 3D printing.   I can't thank you enough either for the time you have taken to share your efforts and knowledge.

The amount of valuable information that a modeler can pick up from this forum is nothing short of amazing.

Regards,

Jerry

You’ve chosen well

The Prusa Mini is a great entry point machine. I started with a Monoprice Select Mini and spent a lot of time “tweaking” it. I’ve since added a Prusa Mk3s to the mix. I have a .25mm nozzle on order and will try and remember to update you on its performance. Some of the smaller pieces I think will benefit from this nozzle. Filament can make a difference, too. I typically use HatchBox, 3D Solutech, and Prusa filament. These photos are all of pieces printed on the Monoprice. The gas can and firewood finished up nicely. Keep posting your results.

An early printer issue..........................................

I had used the red Prusament PLA that was shipped with the printer.  This was not a complete spool, but just a smaller sealed packet of material.  I still have a package of the black material. 

When I ordered the printer, I also ordered a spool of Prusament Galaxy Silver PLA.  Since I needed to how to change spools, no time better than the present.  So change I did.  
 

Once the silver material was loaded, it started to "click".  Wasn't quite sure what was causing it, but let the bolt finish printing.  The bolt printed quite fine.   When I went to start the next print (Baby Yoda), the printer would not print at all.  At this point, I was not sure exactly what the problem was, so I started reading the troubleshooting information in the manual, and searching for information on the web. 

The good news - There is an enormous amount of troubleshooting information out there.  In my particular case, the problem resided mostly in one area, a clogged extruder gear.  When I first opened the extruder cover, it looked like the extruder was stripped.  It wasn't, it was just clogged with material.  Cleaned that per the information on-line and in the manual.  Still would not print.  Tried unloading the filament, which took place. 

However, the printer would still not print, so I had to research things further.  Suffice it to say that I became quite familiar with the hot end and extruder design on this machine.  Had to take off the fittings for the filament on the hot end and the extruder (the "bowden tube"), where I discovered the filament broke at the extruder gear.  After getting that taken care of I reloaded the printer.  Printed the Baby Yodas, had stringing on both of them, so I was going to check the length of the PATG tubing that goes down to the extruder nozzle. There was obviously some sort of friction causing the filament to have resistance in the tubing. 

I cleaned the extruder again also.  Put everything back together, and tried a print.  Everything worked just fine, no clicking. 

The bad news - Even if you purchase a fairly completely assembled printer, you will probably at some point in your printing experience going to have to get "intimate" with the printer. 

The really good news - The Prusa support information at their site quickly led me to the problem, and there is a large enough community that pretty much any problem I am likely to encounter has been documented, and a fix either developed, or a troubleshooting procedure to rectify the problem.  This reaffirmed in my mind that the Prusa printer was a good choice. 

Suffice it to say that having this minor problem helped me get over the hurdle of thinking I would damage this printer if I have to work on it.  Now that I've had this experience with the Mini, I would not have any fears about tackling a kit built printer.  If you go into a 3D printer, don't expect your journey to be without a few bumps in the road. It is part of the learning experience.  These devices are not really "mature" like a kitchen appliance, they will probably present you with problems to sort out.  

My next installment will discuss what I found on Thingverse that I downloaded for free, and will get extensive use on the Spokane Southern railroad.

Regards,

Jerry

and surprises

Jerry - the Bowden tube setup was an issue on my first printer, but it’s not insurmountable. Take a look at Capricorn tubing. The tighter tolerance seems to have helped my Mini. Without a direct drive model, then it is what it is. Insuring that everything is assembled as tightly as possible will help as well. 

Read up on retraction. The settings for that (speed/distance) can help minimize stringing. I fiddled around a lot to reduce/eliminate it on my Mini. And some filaments are just more prone to stringing as well.

Consider the “maintenance” that you had to do as part of that learning experience. I wouldn’t be as comfortable with my new printer without all of the tweaking I had to do on the Monoprice Mini. The Prusa support info is great. I’ve used it on my new printer with success, too. Besides Thingiverse take a look at Prusa.org, and SketchUp/3DWarehouse. Keep posting...

Thanks Trailguy!

Ordered tubing and a tubing cutter (I know darn well I won't cut it square enough, even with a v-block and a razor blade).  Thanks for the tip.

Been on the Prusa.org site quite a bit, especially when researching the clicking issue.  Downloaded the "Bady Yoda" file from Prusa's model site.  I may have stumbled into the 3DWarehouse site once, but will give that a better look. 

On retraction, I can find the setting within Prusa slicer to enable that feature, will give that a try with the current print I am attempting (9 of the same part printing at once, with a lot of stringing).  I'll try doing a batch with that setting enabled.  If that doesn't minimize / eliminate the problem, then I think I need to go back and take your advice, and make sure the assembly / materials within the Bowden extruder and hot end. 

Regards,

Jerry

Freeware that I wanted to try for my railroad...................

Once I had tried a few of the files sent on the thumb drive with the printer, I wanted to see if what the print quality would be for items that I actually want to have on my railroad.  I also wanted to do a LOT of printing to ensure that there weren't any other gremlins lurking in the printer that I needed to sort out.  I was not sure what to expect, and I've been pleasantly surprised with the quality of what has come out.  I also started learning a few more things about the Prusa Slicer software, print setup, Z axis resolution, printing speed, and retraction. 

Some background is in order.  I model 1952, in the area south and east of Spokane WA.  I have a fairly large railroad, and my new (been building it for 10 years now) extension has three town areas that are going to need a bunch of houses.  

When I was researching 3D printing over the last few years, I had found files on Thingiverse for Sears mail order  homes.  The 1:1  homes were offered in the Sears catalog, and you can learn more about them at these sites:

https://www.modulartoday.com/searshomes.html

https://en.wikipedia.org/wiki/Sears_Modern_Homes

http://www.searsarchives.com/homes/index.htm

They were not the only manufacturer of mail order homes (or kit built if you prefer).  Montgomery Ward was also a large supplier, as were others.  What is important from my perspective it is has the potential to save me a huge sum of money purchasing Walthers / Woodland Scenics / other kits to get what I want for my railroad. 

I'd like to offer a huge shout out to Kabrumble, and his files offered up on Thingiverse. Here is a link to his work:

https://www.thingiverse.com/search?q=kabrumble&type=things&sort=relevant

I started by printing out the "Ionia" house.  Interesting bit on this house, it looked like a Sears home, but the wikipedia site and searsarchives.com had no mention of it.  I was able to fine an Ionia brochure on Pintrest, and I've downloaded that for my records. 

Here is what I wanted to initially accomplish with this exercise:

• Make sure I understood what was required to download files from Thingiverse, or for that matter, other repositories of 3D printable files.  There is a LOT of great content out there for free.
• Learn the process of taking that file, and generate the "g code" to drive my printer.  This means that I started to learn about Prusa Silcer, and what it could do to help me out. 
• See what the final product looked like, and whether or not what I can get out of this printer is good enough to display on my railroad. 

Here is a photo of the first first three parts of the Ionia house that I printed.  I did the foundation at 0.15mm Z-axis resolution, and then switched over to 0.1mm Z axis resolution for the wall section and the roof:

The siding on the walls had some defects which look to be extruder issues.  The walls were the last thing I printed when I was getting clicking from the extruder.  But, at the end of the day, the print exceeded my expectations.  The ONLY negative on the prints so far, which is actually the design, not the print, is I do not like the windows that he designed for this building.  Now that I am getting my conversant with a CAD software, I will redesign, and reprint those.  No biggie, especially considering the price (FREE),

I also printed out the  "Hamilton" house, which is a bigger bungalow. The print quality on the walls was MUCH better.

So, what did I learn about this exercise:

• Walthers and Woodland Scenics have sold me their last house kit.  If I can't find one that is already designed, I'll do my own.  This printer does a great job and meets my expectations.
• Printing out somebody else's files does not guarantee 1st time quality of the print.  There were small columns used to support the roof on both of these houses.  Both failed miserably when I printed them the first time.  I had to put a "brim" on them to provide better adhesion to the table (configurable in Prusa Slicer, and in Cura.  I also slowed down the printing speed to 30%, and did them at 0.1mm resolution.  They came out perfectly. 
• On the Hamilton, the chimney was a complete fail when I sliced it in Prusa Slicer.  The angle between the wider and narrow portion did not properly slice in Prusa Slicer (there were errors in the file, and I could see that it was not going to print correctly, which I confirmed by actually printing).  Not having any knowledge at this point about MeshMixer files (that is the format the files for these building download it), I took a chance, and sliced it in CURA.  Worked just fine.  CURA also auto generated a brim for good bed adhesion by putting on a substantial brim (I had to do that manually in Prusa Slicer). 
• I learned about how feedrates can help me in printing smaller detailed parts. 
• I'm still not completely convinced that my extruder and hot end are working perfectly, and will sort that out over the coming week. 

I appreciate any and all comments that you may have about what I am posting.  Not only is it helping me learn more, but I hope that by documenting what I'm going thru on starting up can make the learning curve a little easier for the next person to jump into the printing pool.

My next post will document my first foray into CAD design, and printing the file I generate, which is the ultimate reason I wanted to get into 3D printing.

Regards.

Jerry

Joeseph Prusa

Jerry could I also commend you on your choice of 1st printer.  3D  printing is a very big rabbit hole and your choice has made the entry a relatively simple one.

If you haven't already done so, could I suggest that you have a  look at the Joe Prusa story.  It is a fascinating glimpse into what makes a good businessman and the philosophy of "Open Source".   The expansion of Joe's production outfit in Prague has been extraordinary but he is also something of a philanthropist.  His  500 + machine Print farm was devoted to the production of 3D printed face masks and respirator components in the first few months of COVID 19 and these were all given to health care workers.  Part of his factory includes a maker space which allows public access to 3D printers, laser cutters, CNC mills and other maker tools.

Just Google and You Tube search "Joe Prusa" and you will discover an eco system of clever design and support for your purchase.  

By the way I don't own a Prusa printer but I certainly admire what he has done.

busy busy

Lots of progress. I haven't looked for it in PrusaSlicer yet, but CURA has a setting "Avoid printed parts when travelling". This is especially helpful if you're printing small easily upset pieces. Also, there are some free 3D repair apps that will look for/repair mesh issues like you described on the chimney. I like scratch building (frugal), but have done more with laser cutting at a local makerspace than 3D printing of structures. Your first prints look great. Thanks for the Thingiverse link. I missed that gentleman's work. And finding a mobile home/travel trailer just got solved. Thanks... keep posting.

Additional Resources

Good Evening All,

http://www.CULTS3D.COM contains free files which can be downloaded and printed for personal use.

Facebook has a "3D Printing for Model Railroads" group.

I've been printing for six months and it's been a learning experience.  I model in N scale, so I selected the Eligoo Mars resin based printer.  It has excellent resolution(0.01mm), but limited print size(2.5"x4"x6").  It's wonderful to be able to print small, hard to find items(battery boxes, electric meters, fire hydrants, etc.). 

My biggest cost saver has been printing vehicles from the 1930s-40s-50s.  The materials cost is $0.25 or less, compared to a commercial kit $10 or more. 

Bruce

Where did you find source files for the automobiles?  I’ve been looking for early 1970s autos for a while, and aside from the $20-$30 ones on Shapeways I haven’t had much luck.  Not much on Thingiverse, and I’m not aware of other sources.

Thanks!

Jeff

GrabCAD is another source, but it tends to be an actual car (working door panels, modeled engine, etc) that may be difficult or impossible to print.

Sketchup has a 3D Warehouse repository that you can download to Sketchup; thru Sketchup, you can clean the files and prep them for printing.

Thanks, Juxen

I didn’t know about the SketchUp repository.  Is it available to users of the free version?

Printer & file respository

Jerry thanks for documenting your foray into 3D printing, special thanks for the thingiverse link.

Another site that I have looked at for files is  https://www.myminifactory.com/

Although like with cults3d, not all the models posted are free.

Jeff to answer your question about 3d warehouse, it is available to everyone not just sketchup users:  https://3dwarehouse.sketchup.com/?hl=en

Finally there are a couple sites the search the 3d repositories:  https://www.stlfinder.com/, and  https://www.yeggi.com/, both of these return free and paid models although yeggi you can limit to free with advanced search options.

Automobile Files

Hi Jeff,

Cults3D has a "free" control you can check to only select free files.  Even so, I found searching by year gave more results than "Chevy", "Volvo", etc. Other sites I searched were:  CGTrader, TurboSquid, 3D Warehouse and Thingverse.  I know there are others...but that's as far as I got.  There is a 3D printing for Model Railroaders group on Facebook.

I was looking for pre-1955 cars, so there may have been more available due to copyright expiration.  The most common type of model I found were hollow shells for R/C racing cars.  I wanted to print N scale automobiles for my model railroad...so needed solid bodies.

Since I wanted to print 1:160 scale models, I had to make a few adjustments.  Mirrors, door handles, headlights and bumpers tended to be too delicate to survive the manufacturing process.  I could print them...but they rarely survived the cleaning and painting...sometimes they didn't even make it off the printer platen.  The other issue I ran into was hollow bodies.  The design looked good, but the panels were paper thin and distorted during printing.  I had to be content with making some of the details oversized, or omitting them entirely.

Eventually I got in the routine of printing a single copy of the file, then making adjustments and printing a second copy to get the bugs out of the design.  I've been printing using clear resin...I've got a thing for translucent windows in vehicles...a slight flaw in my character.

Thanks Bruce!

I’ll check those out.  I’m looking for 1975 vehicles to build loads for auto racks, Chrysler and Ford specifically, and aside from the ridiculously-priced ones on Shapeways haven’t had much luck.  I have a resin printer, so I’m optimistic about getting pretty good detail — if I can find a source file.

Also, thanks for the heads-up on windows!  I, too, want clear windows so I may be investing in some clear rein soon. 

Next steps in the learning process.

Up to this point everything I had printed was downloadable content.  It allowed me to understand how to take a file, and get it printed with acceptable results from a FFF printer.  But I didn't purchase this printer just for that function, I purchased it so that I could design and print my own parts. 

The journey so far had been very pleasurable.  But I wanted to start moving on to the next step. 

While researching printers, I also started to examine what 3D design software was out there.

A little background on me.  My degree is in Manufacturing Engineering.  I spent 8 years in the field with two different employers primarily in metal removal (machining).  I used to program machining and turning centers manually, meaning I did NOT utilize a post processor program to generate my tool paths.  When I look at a 3D printer startup and end block in the slicer software, it is quite familiar to me. 

When I was starting my career, I had the opportunity to play with Computervision CADDS3, which allowed me to draw my own 3D files in CAD, and then generate my own tool paths.  But I never got to actually cut metal with them as the company did not trust the output files that Computervision was generating for the machine tools we were using (for those who may have worked in the field, Kearney and Trecker MM series machining centers, and Monarch turning centers). 

In 1989, I got tired of seeing vast swaths of my employer's factory getting outsourced, I transferred into Field Service (my employer is an MP&E supplier to the railroad industry).  So for the last 31 years, I have only kept up with developments in manufacturing from the periphery.  For all intents and purposes, I am jumping back into CAD (Computer Aided Design) software with very weak base knowledge. 

Before purchasing a printer, I read all I could about various software platforms that were available, including Sketchup, TinkerCad, Blender, and others.  I started doing sketches in TinkerCad, and was not really happy with the object oriented design.  My personal impression was that I would quickly run into the limitations of the TinkerCad program, and have to change platforms anyway.  What do I want to design with my printer?  Here is the list in order of complexity:

• Open load blocking patterns.  First up is what I need to make several open top loads with IH Farmall tractors on it, since I am modeling an IH fictitious factory on my railroad.
• Buildings.  Need to create an aluminum reduction facility (the Kaiser Mead works has been my rough pattern), a secondary aluminum processing facility (like Reynolds Aluminum in McCook IL, or Kaiser Trenton near Spokane WA), and a silicon production facility (the Rock Island plant near Wenatchee WA is serving as the pattern). 
• Freight Cars.  There are a whole host of late steam era freight cars that I want to take a whack at printing, possibly with less detail (think molded on grab irons) than a resin kit.  I have a pile of those to build in retirement too. 

Both TinkerCad and Fusion 360 are AutoDesk programs.  When I read on the MRH forum that I could acquire a Fusion 360 license for hobby use, I immediately signed up.  I didn't do a darn thing with it for about 3 months. 

But now, I have a printer, and software, so time to get to work.  What project would be a good starting point?

Well, I found one on a friends layout.  Based on my limited use of TinkerCad, I started looking at the project in terms of simple shapes that would go together.  It looked like a good place to start.  Here it is.

The IC / ICG, now CN has a bridge over the Kankakee River.  My friend wants to replicate a scaled down version of that bridge on his layout.  He even did line drawings of what he needed, and as a fill in, had it taped up to the sub-roadbed where the bridge will go.  I offered to take a crack at 3D printing this bridge, since I figured the project was within what I was capable of doing.  So off I merrily went with the drawings. 

Here is the Google Earth snapshot of the bridge in real life:

The model version of the bridge only has four courses of the bridge instead of the five shown, plus the course over the road.  He also shortend up on the center to center distances a bit (selective compression) to meet the space available. 

Here is a shot of the line art showing how it will sit in the space, and the line drawing I'm working with for the four main courses:

I'm doing this project in AutoDesk Fusion 360.  I chose Fusion 360 due to the advanced features of the program, which should meet my needs going forward for every project I do.  There is also a wealth of videos on YouTube, and on the AutoDesk web site to help get the new user familiar with the latest version of Fusion 360. 

The bridge as drawn is 10" between centers, which is too big for my Prusa Mini.  No problem, cut it in half.  I designed the inner spine first, and I purposely did NOT put arches on this part as there is actually straight walls behind the appx. 1 real foot facade. Here is the Fusion 360 view:

I printed two halves of this file.  One of the BIG nice features of Fusion 360 is it allows me to take the Fusion 360 file directly into Prusa Slicer.  Once I had that in the slicer, I specified 15% infill.  What does that mean?  It means that the center is hollow, with a structual pattern that only fills 15% of the space.  It is quite amazing how strong and light this print actually is.

Here is a photo showing both sides glued together. 

So far, this project is a success.

• Dimensionally, this thing is spot on.  Before I 3D printed this part, I created a drawing from Fusion 360 to a PDF, printed it out actual size, and laid it over the drawing from my friend.  It was spot on within the limits of his drawing skills. 
• The Prusa Mini has fulfilled all of my expectations of it at this point
• It took me about 4 to 6 hours of learning Fusion 360 to get to this point.
• Shop vernacular got a mild workout to get to this point. 
• I glued these two assemblies together with Oatey PVC cement.  I couldn't get enough Plastruct cement to the party to get a good joint.  I've stress tested the joint with about 5 plus pounds of weight directly over the joint.  VERY strong!
• I had to do some light filing on the ends of the part to make them flat.  About on par with the level of filing I have to do on a plastic kit to flatten snipped off sprues. 

After this step, I was encouraged, and ready to move on to the next phase, which is drawing the facade that goes on the front.  More on that in the next blog entry.

Regards,

Jerry

Fascinating Blog

What a fascinating and inspiring blog!

What keeps me from going and buying the printer right away and following your footsteps is my full time job, unfortunately.  I always had the impression that if printing at home, I would be quite limited in terms of resolution and detail, but from what you are indicating, in many cases that is not a limitation.

I sure will continue to follow.

Windows

While I have not tried this product I do use one like it with excellent results, just can't find it listed right now. Also there may be better prices but this listing shows the directions.

https://www.ebay.com/itm/Testors-ModelMaster-Clear-Parts-Cement-and-Window-Maker-0-5-fl-oz-8876C/303550538618?epid=691331345&hash=item46ad05a37a:g:vOUAAOSwel9epIUg

Michael H

orientation

When you printed the two bridge halves, what orientation did you print them in? Which side was down in other words?

@jerry Great work on the bridge.

Your first project? What a great result! 
Just a thought, you might consider putting a peg (or two) on one half of the bridge and corresponding hole(s) on the other, to help with aligning the two halves, although you’ve done a great job without them. If you do this, remember to allow some clearance so the two parts fit together. how much clearance will depend on your printer, but I think 0.1-0.2mm should work. There’s stuff called (I think) MagiGoo, which is specifically intended for gluing PLA parts together. 
I’ll be watching your posts with great interest, it’s going to be fun.

Hi EW:Below is a snapshot of

Hi EW:

Below is a snapshot of how the part was laid on the printer bed.  I had to flip the import from Fusion 360 90 degrees to get it into the orientation I wanted.  Keep in mind this part is common for both sides. 

One note here on the printing of this part.  After I printed the first part, I noticed some slight distortion of the plate bed surface in the corners of the part.  It can't be more than 0,001", but it seems that heat concentrated in the bed at these points.  Was not expecting that, but these beds don't last forever (otherwise, they wouldn't sell replacements). It did not affect the quality of the second part. 

I checked my g-code file again, and since this was a non-visible part, I used 0.2mm resolution for the Z-axls.

Regards,

Jerry