A model that prints has to be a closed, manifold solid: every edge shared by exactly two faces, every face pointing outward, no faces crossing each other. Blender does not care about any of this. It will happily let you leave a hole in a mesh, or a flipped normal, or two overlapping shells, and the viewport will look fine.

The usual advice is to run the 3D-Print Toolbox add-on before exporting. Enable it under Edit, Preferences, Add-ons (in Blender 4.2 and later it is an extension you install from the Extensions tab), and a 3D Print tab appears in the sidebar. Check All reports non-manifold edges, bad contiguous edges, intersecting faces, zero-area faces and overhangs, and selects the offending geometry so you can go find it. There is also a Make Manifold button under Clean Up.

It works, but it makes you do the work. You select the problem, figure out what it is, fix it by hand, run the check again, and repeat until the report is clean. For a hobby part that is ten minutes of poking at vertices you will never see in the print.

The shortcut

Export the STL and drop it into PrusaSlicer. It checks the same things on import and repairs most of them automatically: flipped normals, holes, degenerate facets, edges that do not quite meet. You will see a warning triangle next to the object in the list on the right.

Select the object and look at the Info box below the object list. It tells you what it found and what it did about it.

This test cube had its top face deleted and one bottom triangle flipped. PrusaSlicer flipped the triangle back on its own. The four open edges around the missing top are still reported, but the slicer closes open loops when it slices, so the cube prints as a solid cube. Hover over the triangle in the object list and the tooltip breaks the errors down the same way.

To fix it, left-click the triangle in the object list, or right-click the object and pick Fix by Microsoft algorithm. On Windows this hands the mesh to the built-in 3D model repair service and gives back a closed solid. The warning goes away and you can slice with no doubts about what the printer will do.

The repaired mesh does not have to stay in the slicer. Right-click the object, export it as an STL, and import that file back into Blender. Now the clean, closed version is the one you keep working on, and the hole is gone from the source model too.

When to go back to Blender

Automatic repair guesses. It fills a hole with the flattest patch it can and joins overlapping shells however they happen to intersect. For a missing face on a box that guess is right. For a hole in a curved surface, or two parts that were meant to be a single body, the guess can be wrong in ways that are hard to see in the slicer preview. Check the sliced layers at the spot where the repair happened. If they look wrong, that is the time to open the 3D-Print Toolbox and fix the mesh properly.

For everything else, let the slicer do it. It is the last program to touch the model before it prints, it already checks every file you give it, and it has been repairing meshes for longer than most of us have been exporting them.

The fix is to make Blender's native unit the millimeter. Do this once, in the Scene tab of the Properties panel, under Units:

• Unit System: Metric
• Length: Millimeters
• Unit Scale: 0.001

Now one Blender unit is one millimeter. Type 40 and you get 40 mm. Export the STL with Scale at 1.000 and leave Scene Unit unchecked. The slicer reads it at the right size with no scaling on either end.

Import works the same way. An STL made for printing comes in at Scale 1.000 and is the right size immediately.

Save this as your startup file (File, Defaults, Save Startup File) so every new project starts in millimeters.

Two things change when you do this. The default cube is now 2 mm across, so scale it up or delete it. And the viewport clip end is 1000 mm, so raise it under the View tab of the sidebar if a large part disappears when you zoom out.

Don't bother rotating the part in Blender. Every slicer has a "place on face" tool that drops a flat surface onto the bed in one click.

If you would rather leave Blender in meters, the old workaround still works: export at Scale 1000 and import at 0.001. But every export and import is a chance to forget, and setting the unit scale once removes the step entirely.

Every plant pot seems to come with a saucer that’s almost the right size — too small, too big, wrong color, or just plain ugly. I got tired of that, so I built one I can resize on demand.

It’s a parametric planter saucer, designed in Blender with Geometry Nodes. Eleven inputs control the shape: side length, height, corner roundness (crank it up and the square becomes a circle), wall taper, material thickness, and the little ribs underneath that lift it off the surface so water can drain out of the pot. Same base file, infinite variations.

This is especially handy if you’re starting seedlings and trying to make the most of a windowsill, grow shelf, or heat mat. Off-the-shelf round saucers waste a ton of space between pots. With this one you can dial in a square footprint sized to your specific seedling pots, pack them edge-to-edge, and fit noticeably more plants in the same area. Set the fillet radius low for sharp corners that tile tightly, or round them off for individual pots — your call.

Here’s how the files are split up: the Blender source file is a free download on CGTrader — there’s a direct link in the Printables description. That’s where you grab it if you want to open it up and customize the saucer to your exact dimensions. The ready-to-print STL files live on Printables. If you’re just looking for a quick print, please grab the STLs from Printables — it genuinely helps me out over there.

You don’t need to know Geometry Nodes to use the Blender file. The Printables listing walks you through changing parameters, applying the modifier, and exporting at the right scale for your slicer.

One bonus for the AI-curious: I used Claude Code to build the Geometry Nodes setup, and there’s a readme inside the Blender file showing how you can do the same to modify it further. Just describe what you want changed.

→ STL files on Printables (the CGTrader link for the Blender file is in the description)

Total active effort: 7 minutes. The printer handled the rest (23 minutes of PETG stacking up while I went back to actual work).
Material cost: $0.17 in filament + a couple pennies of electricity. Rounded up: $0.20.

The Store Alternative

Nearest Home Depot: 5 miles away.
17 minutes each way + wandering + checkout time
= 40 minutes round-trip.
F-150 operating cost (IRS 2026 business rate):
$0.725/mile × 10 miles = $7.25.
Cheap plastic putty knife + tax: $1.05.
Subtotal before labor: $8.30.

The Expensive Part (Your Time)

Maybe you don’t cost your company $75 per hour. I’m sure you’re not free. There are laws against that (unless you’re an intern for a politician…and then you don’t need to worry about money or putty knives. You’ll need a much bigger tool to shovel manure).

Sorry about that side-track. Where were we?

Is a 3D Printed Putty Knife Any Good?

Yes — for a plastic putty knife. It’s stiff, flexes exactly where it should, and spreads compound or adhesive just fine. I’ve used it for two weeks with zero issues. (Printed in PETG for durability.)

Skip the Modeling — Download My Ready-to-Print File
Want to save even more time? I uploaded the exact putty knife model I designed to Printables.

→ https://www.printables.com/model/1438845-putty-knife

Just hit download, slice it, and you’re printing in under 5 minutes total. No Blender required.

(I modeled it myself because I enjoy the process, but 99% of people should just grab this file.)

A while back, I purchased a GAGE-IT from Home Depot. It’s a handy little tool made from a thin sheet of durable plastic, designed to quickly measure drill bits, bolts, and wire diameters.

The tool features a tapered slot with clearly marked imperial and metric measurements along the edge. To use it, you simply slide a round object into the slot until it fits snugly—where it stops corresponds to its diameter. It’s compact, inexpensive, and convenient for quick checks in the shop.

The tapered slot works great for measuring drill bits and wire. However, it doesn’t work well for screws. Because the plastic is so thin, it slips into the threads instead of measuring the screw’s outside (major) diameter. That makes it difficult to get an accurate reading.

I liked the simplicity of the tapered-slot concept, so I designed a new version that also works with screws. My version is 0.2″ thick—substantially thicker than the original—which prevents the gauge from slipping between the threads. This allows it to measure the true outside diameter of screws, bolts, drill bits, and other round stock more accurately.

I modeled the tool and printed it on a 3D printer, making it easy to reproduce or modify. The design is available on Printables here:

If you’ve ever been frustrated trying to quickly identify a screw size, this thicker tapered gauge might be a useful addition to your toolbox.

I started posting to Prusa’s Printables. You can trade in reward points for filament, Prusa merchandise or vouchers for a new 3D printer. If you are very popular, I suppose it is possible to accumulate enough points to earn a new 3D printer.

I currently have 12 models posted and have 130 reward points. A roll of filament is 350 points. A Prusa mini is 10,000 points and a Prusa MK4S is 25,000 points.

I am 0.5% of the way to a MK4S. Every journey starts with a first step.

I plan on using this site to post my models that are designed to be 3D printed. Models that are for rendering will still be posted to CGTrader.

During a Windows or Solidworks update, my system lost the ability to show me an icon preview of my Solidworks files. This makes it difficult to find parts and drawings, so I spent some time finding the solution.

Many responses to other Solidworks users experiencing the same problem steered people to folder options check boxes. This didn’t work for me. What I needed was to re-register certain DLL files with the Windows registry.

1. Load the command prompt window with Administrator rights
2. Type in these commands:
   
   regsvr32 “C:\Program Files\Common Files\SOLIDWORKS shared\swdocumentmgr.dll”
   
   regsvr32 “C:\Program Files\Common Files\SOLIDWORKS shared\sldwinshellextu.dll”
   
   regsvr32 “C:\Program Files\Common Files\SOLIDWORKS shared\sldthumbnailprovider.dll”

I found a near-solution at GoEngineer, but I had to tweak their instructions a bit because the sldthumbnailprovider.dll file was in a different folder.

(This was the fix for Solidworks 2024 on Windows 11)

It started with a handful of empty Altoid tins. I saved them because they fit the Arduino. They seemed like a good project box and who can’t use a little improvement on their breath?

The last few weeks, I have been utilizing my 3d printer to clean up the mess that I once called a work bench. I spent a couple of weeks designing and printing parts for the peg board. As most of the clutter was moved to the board, I was left with a bunch of hardware boxes from Home Depot and a half dozen of the Altoid tins I never used.

I sat down to Blender and modelled a little rack for the tins. It took about 1-1/2 hours to print and it worked great. The only problem was…I still had hardware from Home Depot. The containers they come in are great for hanging on their display cases, but they don’t work so well in my shop.

I can make racks…and I don’t need mints…so it’s time to print a container the same size as the Altoid tin. And then I came across a full package. Not even opened. Son of a gun! They almost fit.

So back to Blender. I redesigned the rack to hold three slightly taller containers. The length and width were unchanged, but the height was increased. It worked, but I couldn’t leave it there. I had to go taller. So I made a rack that was the same size and held two containers with the same length and width of the Altoid tin…but even taller.

If you read this post to the end…you must want one. The model is free to download at Thingiverse: https://www.thingiverse.com/thing:6534033

Then I rendered it in Blender. If you want the Blender file, use the contact form and just ask. I will send it to you.

Today I released the 2nd video in a series of four comparing two different tilt pad bearings. Like the previous video, the animations were done in Blender. The sound editing was done in Adobe Audition.

The first video covered why 5 pads are used instead of 4 or 6.

Today I released the 1st video in a series of four comparing two different tilt pad bearings. I created animations and 3D renders for the video in Blender. I also used the Blender Video Sequence editor to put it together.

The audio was mixed in Adobe Audition. It’s my first time using that program. It’s a huge step up from Audacity which I used in my past mixes…because it’s free. Audition has a function for remixing the background music to a length that matches the dialogue. It works great. I also discovered that it has a feature called “ducking” that increases the background music between pauses.

I used elevenlabs.io to clone my voice and then transcribe the text into audio. Elevenlabs is an AI tool. I splurged and signed up for the $1 per month upgrade fee. This tool was a lot faster than recording it with a microphone, and much faster when making tweaks to the script after the original recording. I think it sounds pretty good, but not great. There are definitely portions of the recording that sound off.

I tried to use AI to create an image or video of a Highland games competitor lifting a heavy rock. I’m new to these tools, so I’m not saying it can’t be done, but the results I got were ridiculous. Here’s one that made me laugh out loud. I asked it to make a guy in front of a barrel lifting a large rock.

I did a lot of experimenting with animated white lines over a blueprint background. These were easy to make and fast to render. One of the new techniques that I used was to add a grease pencil to a scene and then use the line art modifier to trace a 3d model. The 3d model is a simple white diffuse material and the line art is a brighter white. It’s rendered over a transparent background. It’s then brought into the video sequence editor over a blueprint background. The compositing blend is set to “add”. To make the overlay more or less bright, you can multiply the color.

For those who are not familiar with tilt pad bearings, they are a type of hydrodynamic bearing commonly used in high-performance machinery, such as turbines and compressors. They consist of a series of pads that are tilted to create a film of lubricant between the rotor and the stator, reducing friction and wear.

When following a Blender tutorial, it can be frustrating when the results don’t match what the instructor is showing, despite typing in the exact values. The key to resolving this issue may be checking your units. Most tutorials are created using meters as the unit of measure, but your Blender custom startup may be set to inches or another unit. This discrepancy has tripped me up when working with procedural shaders and geometry nodes.

So the next time you are watching a tutorial, pay attention to the units. This simple step will save you time and frustration, helping you to replicate the tutorial accurately and continue learning effectively.

A “Build” modifier can be used when animating text in the Blender 3D viewport, but it has the drawback of “building” the text from right to left. I prefer the text to be revealed from left to right.

One way to accomplish this is with a material node tree.

If you read the node tree from right to left, you see that a mix shader shows either an emission or is completely transparent. The emission/transparent factor is controlled by the coordinate nodes on the left. Use the “Generated” texture coordinate node. This is preferable to the “Object” texture coordinates because the scale of the object does not affect the value in the “Less Than” math node.

Set two key frames for the “Less Than” threshold. At the start of the reveal, the threshold is 0.000. At the end of the reveal, the threshold is 1.000.

If the text you are revealing is not on the XY plane, you may need to add a Mapping node to rotate the coordinate system.

NOTE: If you are using the EEVEE render engine, go to the material tab and change the Blend Mode from Opaque (the default) to Alpha Blend in the Settings group.

I purchased a set of diamond wheels from Harbor Freight. Spent less than $10. In order to protect my investment, I 3D printed a box to hold the arbor and wheels.

The first iteration held the arbor but I didn’t make a slot at the end of the arbor. This oversight means I would have had to disassemble the wheel from the arbor to put it away. I know me, and I know that means eventually this would keep me from putting the pieces back in the box. I reprinted the box for the final design and released it to Thingiverse this morning.

Link to Thingiverse: https://www.thingiverse.com/thing:6476550

The design was created in Blender and processed for printing with PrusaSlicer.

Here is a Blender quick tip for changing the display object transparency:

Select the object

Go to the material panel. If it doesn’t already have a material definition, create a new material.

Expand the Viewport Display panel

Click on the color box

Change the Alpha value. 1 is the default (no transparency) and 0 is fully transparent.

As an engineer that works with rotating turbomachinery, nearly all my drawings require centerlines. To add a centerline to a CAD drawing is a piece of cake. For some reason, Photoshop doesn’t make it so easy.

Here is a quick and easy way to draw centerlines in Photoshop.

Select the Pen Tool from the tool palette

Change the fill to “none”, change the stroke color and define the width of the centerline

Next to the stroke width box is the line type drop down selection. Click on the arrow to show the pre-defined lines. There is a solid line, a dashed line and a dotted line. Click on the dashed line and then click “more options”.

Define the centerline which is a short dash – long dash repeating pattern. If you selected the dashed line before hitting “more options”, you should already have a 4 in the first “Dash” box and a 2 in the first “Gap” box. Add a 12 to the second “Dash” box and a “2” to the 2nd “Gap Box” and then click “Save” so you can speed up the process in the future. Then click OK.

Now with the pen tool still selected, Left click (do not drag) for the start of the centerline. Then move the mouse to the end of the centerline and left click again. Hit “Enter” to finish the line.

If you want to edit the line at a later time, use the “Direct Selection Tool”, then click on the line. You can change the color, width or line style. You can also click on an end point and move the end point.

My photogrammetry skills are getting better thanks to some new equipment and a podcast that inspired me to invest in some new equipment. My first model armed with new knowledge and prototype equipment is a partially burned log from my fire pit.

For the last month, I have been working on a design for an automated photogrammetry turn table. The table is made from 3D printed components and uses an Arduino to rotate the table in small increments and then fire my Canon DSLR. The turn table is functional at this point, but I’m adding some additional features like a knob to control amount of rotation and a pause button.

In the middle of my build, I listened to Andrew Price discuss photogrammetry with Mason Menzies on the Andrew Price Podcast. The discussion is on YouTube and other podcast platforms. They discussed equipment, how to take good photogrammetry pictures and how to process the photos and models. To sum up the photography issues, you want your photos to have no shadow and no glare. You can achieve no shadows with a ring light and you can achieve no glare with cross-polarization.

Polarization limits light waves to a single plane. If you have a polarizer on your lens and another on your light, and the two polarizers are at 90 degrees from each other, then the glare is dramatically reduced.

After the discussion, I purchased a polarizing filter for my camera and a ring light. Mason actually suggests buying a 400w ring flash, but that sucker costs over $500, so I delayed this purchase. I wanted to make sure that cross-polarization made a significant difference.

I can definitely see the advantage to a 400w flash over a video lamp. First of all, the polarizing filter cuts down on a lot of light entering your camera. Plus, you need to overpower the room lights to remove the shadows and you can’t be too close to the subject. If you’re close to your subject, the front is much lighter than the back and this isn’t good for photogrammetry. The farther you move from your subject, the more consistent the light gets, but the less bright it is.

As a test of cross-polarization, I set up my camera with my new polarizing filter and a sheet spread across a flashlight. It works and I’m ready for the bigger investment.

Since I don’t have the flash yet, I was not able to reduce the glare I would like. To mitigate the glare problem, I purchased a can of vanishing scanning spray recommended by Mason. It’s made by AESUB and I purchased it on eBay. A single can cost me $50. Since this was a piece of junk wood and I didn’t need the spray to disappear, I probably should have just used Dr. Scholl’s foot spray.

I took 60 photos with the tripod set at one height. I then lowered the tripod and took another 60 photos. Then I lowered the tripod and took another 60 photos for a total of 180 photos.

The raw images were loaded into Adobe Lightroom, and as Mason suggests, I cut down on the contrast by lowering the highlights and lifting the shadows.

The modified photos were loaded in Zephyr Lite for the photogrammetry calculation and then exported as an OBJ file. These files are being prepared to post on CGTrader.

In the Shader Editor of Blender, holding down the Shift key while right-clicking and dragging on a link between nodes combines all of the links that cross the selection area into a single, curved link.

This can help to reduce clutter in your shader network and make it easier to see the relationships between nodes. By combining links in this way, you can simplify your shader network and make it easier to understand.

To use this feature, simply hold down the Shift key while right-clicking and dragging over the links you want to combine. The links will become curved and grouped together, reducing clutter in your shader network.

So give this quick tip a try the next time you’re working in the Shader Editor of Blender and see how it can help to simplify and improve your shader networks!

By default, links in the Blender shader editor are straight lines, but did you know that you can change them to be curved like a noodle? This can help you create a more visually appealing and organized shader network, making it easier to see the relationships between nodes.

Here’s a quick tip on how to change the shader links in Blender to be either straight or curved:

Step 1: Go to the User Preferences

In the top bar, go to the Edit menu and select User Preferences. This will open the User Preferences panel.

Step 2: Open the Themes tab

In the User Preferences panel, go to the Themes tab. This tab allows you to change various appearance settings for Blender, including the appearance of links in the shader editor.

Step 3: Change the Link Style

In the Themes tab, look for the Node Editor section. Scroll to the bottom of this section and find the “Noodle Curving” value. Set the value to zero for straight lines. For curved noodles, increase the value from 1 to 10 where 10 is the “curviest”.

Step 4: Save your Changes

Once you’ve made your changes, make sure to save them by clicking on the “Save User Settings” button.

And that’s it! Your shader links should now be either straight or curved, depending on the setting you chose in the User Preferences.

By changing the appearance of the links in the shader editor, you can create a more visually appealing and organized shader network, making it easier to see the relationships between nodes and to troubleshoot any issues that may arise. So try out this quick tip and see how it can improve your workflow in Blender!

Note: This tip was written for Blender version 3.4.

Bonus tip:

If you have Node Wrangler installed, press Control, the right mouse button and drag across the noodle to remove it.

I just spent the last hour in Blender trying to bake a diffuse texture from a model created with photogrammetry to a lo-poly model created in Blender. I checked and double checked every setting. I went back to tutorials that I watched years ago. I looked for new issues that might be caused by the latest version. I finally found the problem.
The software I use for photogrammetry is Zephyr. It outputs the textured models in several formats. The two formats that can be imported into Blender are OBJ and FBX. I chose FBX. I chose poorly.
No matter what I did, I could not bake the texture from the FBX model to a low poly model.
When I went back to Zephyr and exported as OBJ, all my problems went away.

A classic song lyric goes,

And I went down to the demonstration
To get my fair share of abuse
We’re gonna vent our frustration
If we don’t, we’re gonna blow a 50-amp fuse

You Can’t Always Get What You Want by the Rolling Stones

I wasn’t frustrated, but I beat them by 10 amps. This week I blew a couple of 60 amp fuses. As a reminder that I need to order more spares, I have two blown fuses on my desk. I decided that they could be used to test what kind of results I can get modeling with photogrammetry. I get questionable results when I have labels that are on cylindrical surfaces. Since your eye knows what to look for when looking at text, texture errors in the labels really stand out.

The following story is about how I converted the photogrammetry model into a good mesh with good topology. If you’re interested in how I messed up and blew a couple 60 amp fuses, then jump to the end.

To start with, I put the fuse standing up on one end on a desk in my office. There is a big window on one side. On the other side, I set up an LED light strip. This gave good lighting from two sides.

I took 84 photos with my iPhone all around the fuse. The photos were imported into Zephyr, and I created a sparse point cloud with the default settings.

Before moving ahead with the dense point cloud, the sparse point cloud was rotated to be more in line with the XYZ coordinate system, and then I used the bounding box to limit the amount of points it would use for the dense point cloud and mesh.

After creating the dense point cloud with the default settings, I manually removed some of the points. With the dense point cloud more focused on the fuse, I used the densification function to increase the density of the existing point cloud.

Then I created a mesh. Again, I used the default settings.

While all this was happening in Zephyr (photogrammetry takes a lot of computing time), I was modeling the basic shape of the fuse in Blender. I used dial calipers to measure the fuse. It’s a pretty simple geometry, so it didn’t take long.

With the Blender model created and the Zephyr mesh ready, I exported the Zephyr mesh as an STL file. I imported the STL file in Blender. It is important to import the model with the proper import settings in this step. In the “Transform” properties, the Forward direction is Y+ and the Up direction is Z+.

Now Blender has two fuse models. The untextured model has clean geometry. The imported Zephyr model has the textures, but the geometry and topology are a mess. It also has weird bumps and dimples. It is important not to move the textured model in Blender. You can lock the transform location in the Object Properties panel to make sure of it.

I moved the clean geometry to the textured model, scaling and rotating it until it lined up closely. I then modified the clean geometry so the details lined up with the textured geometry.

Now export the clean geometry as an STL file, again making sure that the forward direction is Y+ and the Up direction is Z+. Now back in Zephyr, import the clean geometry created in Blender. It should line up with the mesh created earlier only it won’t have any colors.

Run the “Make Structured” function on the imported mesh. This will apply the photos onto the mesh. Then run the “Create Texture Mesh” for the final photogrammetry mesh. Export this mesh as an OBJ file.

Import the OBJ file into Blender. It should be located in the same place as the simplified untextured mesh created earlier. Parent the two models together with the simplified untextured mesh as the parent and the Textured mesh from Zephyr as the child. Select the parent and reset the position, rotation and scale using Alt-G, Alt-R and Alt-S. Make the textured mesh active and unparent it from the simplified mesh, making sure to apply the transforms.

Add some seams and unwrap a UV map to the untextured mesh. Create a material for the mesh and then bake the textured mesh created in Zephyr onto the simplified mesh.

Add some lights and a back drop and I have a new model for CG Trader:

https://www.cgtrader.com/3d-models/industrial/other/60-amp-fuse

So how did I blow a 60 amp fuse?

Our shop has a wash tank. The tank holds water with a cleaning agent in it. It gets heated to 160 deg. F. The temperature controller on it failed.

We have 4 other pieces of equipment that use temperature controllers: 2 ovens and 2 centrifugal Babbitt casting machines. They all use Auber temperature controllers. The wash tank used another controller that is no longer being manufactured. You can buy one on eBay, but I decided the better option was to change the wash tank to use an Auber controller. This would allow me to keep only one spare controller in stock.

The controller has one big difference. The one in the wash tank controlled a contactor and the Auber controller controls a solid state relay. For the upgrade, we removed the contactor and installed the 3 phase solid state relay on a heat sink. The contactor was rated for 40 amps, so I purchased a 3 phase solid state relay and heat sink rated for 40 amps.

We turned the dip tank on and after a short time, the solid state relay basically exploded. It overheated. Obviously, we need to update the fuses to the dip tank. The fuses should be rated lower than the solid state relay (but that wouldn’t have helped in this case).

The reason it overheated was because I purchased a heat sink for 40 amps…SINGLE PHASE. The dip tank uses 3 phases so the heat sink needs to dissipate 3 times the heat.

I bought a new solid state relay and a new heat sink. The new heat sink has a fan. We cut a hole in the side of the control box. The heat sink and fan are outside the box and the solid state relay is inside the box.

We ran the dip tank all day and there were no explosions.