Making a Fireplace Pilaster, or, Putting the 'forge to work

Backstory: We needed a new mould at work for one of our fireplace elements. Unfortunately our existing mould was out of square and our original master model lost to the mists of time.

We could get it CNC’d , but those guys are always busy and the quote was something like $800 so I thought, hey, why not see if the 'forge can earn its keep for a change.

The piece we needed was 4’ long, 8" wide and 6" tall, and looks like this:

Here Goes.
First I thought, ok, I’ll just cut out (48" x .25" strips = ) 192 pieces of the profile, glue them all to a piece of MDF, and sand it smooth. How hard could that be?


I traced it out on a piece of paper, took some measurements, fired up inkscape, and popped out this baby:


Looking good! However, I had a few concerns…

It was going to take an entire 4x8 sheet of 1/4" MDF, and take over 8 hours of continuous cutting, even with some creative packing.snip1

So, I redesigned it. I thought, I’ll make the back side a flat piece of MDF, then it’s a smaller profile to cut.


I made a 2" section (8 pieces), got it all glued up and lightly sanded as a test. At this point, I was pretty confident it was going to work, my material usage was a lot more efficient, but the cut was still over 6 hours.


I realised now that the top section was going to be a nightmare to sand, and the front section, being flat, might as well also be a flat piece of MDF. So I built a pretty simple frame, with all the flat sections of the profile as finished face MDF to minimise sanding, and aligment notches for the laser cut pieces. Oh, yeah and this is when it went from 4" to 6" deep. Because why not.


With this design, I was able to really maximise my machine output! (the little square was just so I was left with a tidy scrap). I had 34 pieces per operation, which meant I only needed to run the machine 6 times, at about 50 minutes apiece. 5 hours, over a weekend, that’s not so bad.


Taking Shape:



While I was gluing the pieces into the frame, I realised that my top section varied by 1mm from one end to the other. Dammit. Oh well, too late now, we’ll fix it in finishing.

As you can see, and can probably imagine, there are many ridges. 192 ridges. These are due to the angle of the laser cut in the 1/4" material. I wasn’t too concerned about this, I figured it would sand out.


Took it to the shop, buzzed it with the orbital.


A coat of filler-primer to see what we’re missing. This was my first time using this filler primer. Usually we just use regular old spray primer. I wasn’t super impressed really. Maybe I’m missing something.


Bondo’d a few spots and sanded some more.


A few coats of epoxy paint and it’s off to the fiberglass man! I was going to cap off the ends but he said not to bother.


I was very happy with how this turned out! For about $20 of materials, plus finishing stuff which is pretty constant regardless of how it’s made.

I had it from concept to completion in under a week, and now I know it can be done in a weekend if we really need it fast. It’s nice to not have to rely on other trades to get your stuff done!

The Bad News

As it turns out, cutting 1/4" home -depot-MDF for 6 solid hours really makes a mess of your machine. Near the end of it, the exhaust fan stopped working and the room filled up with smoke. Luckily the only connection between that room and the rest of the house is a cat flap and a sealed door.

Here’s what my fan looked like (started cleaning one blade)

This thing is a bitch to get at. Glowforge 2.0 hardware revision idea: access door for removal and cleaning of exhaust fan. No, I wasn’t cleaning it with a drill bit, it’s just to stop it spinning.


Little bit concerned about the air-assist fan too.

If anyone has any cleaning tips, let’s hear them.

Anyway, hope this helps guide and inspire! You guys are all amazing.


Wow, what an amazing way to solve a problem and save a bunch of money in the process! The way you handled it was genius, especially the way you kept improving the design for the best result. Shame about your fan giving out, at least you were able to finish :+1:t3:

I completely agree that a revision needs to be made in order to give the user an easier way to clean our machines. Regardless of the average user, every machine will need to be cleaned eventually, and unless the glowforge team intends to have a professional cleaning service, this will definitely be the cause of failures for people in the future.

There are a couple of detailed guides here on the forum for cleaning tips, but I’m surprised that the team hasn’t put together a more detailed way to do it, and what materials are recommended as well as being safe to use. Guess maybe in another few years we might get that :stuck_out_tongue_winking_eye:


Great job. Quick question if you don’t mind. I recently got some HD MDF in 1/4” and I can’t seem to figure out good settings for cutting. Do you mind sharing what settings you used? :smiley:


Great write up. I admire the work you did on this. I agree with you cleaning the interior parts were not the main concern of the design team.


I found early on that I could clean the gunk off my work with alcohol hand cleaner, but it took quite a while to realize I could use it to clean the Glowforge as well.


Outstanding work.

Given the machine gunk issue, I wonder if acrylic might have been a better option?

Heck given how you post processed the piece, a rigid foam would maybe work too(though foams are a bit flammable).

I’m with you on fan issues. One of the biggest design oversights on the machine.


Given how it was processed just two or three pieces with a sheet of fiberglass cloth stretched tight would work as well. I have many times seen small boats made that way with ribs every foot or two and the shape obviously changing at each rib. if all the same it would be easier.


MDF seems to vary a lot by manufacturer. The stuff I’m using cuts at [removed non proofgrade settings] on my basic, but I’ve had other stuff that won’t go through at the same speed. Start with the settings for thick draftboard and adjust up or down from there.


Link to @Jules’ fan cleaning tutorial:

Caution: Dirty Pictures....or...How I Cleaned the Exhaust Fan 🤔


If I recall, GF was mulling a tube replacement service – presumably the fans would be cleaned as well during that?

I have been hoping for a redesign that would allow easy access like a removable plate. I would even go for a fan entirely outside that could be removed and cleaned. the removal is possible I guess for basic users but the pro blocks that access. With even just the screen removable and replaceable it would be a big step in the right direction, it could screw in or have a bayonet fit and have whatever rules they wanted about operating without the screen, but yes it is the most glaring design failure.


Per forum rules we’re not supposed to discuss non-PG settings except in the “Beyond the Manual” section (to keep the FNLs from deciding we can’t discuss them anywhere at all!). Easy option is to move the whole thread there, but if you don’t want that for whatever reason, you can create or add to a “MDF settings” post over there and just link to it from here.

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Amazing work!

I’ve also been smoked out due to sticky exhaust. The problem is usually chunks, though. Some people have used pipe cleaners, I used long cocktail toothpicks to get inside and scrape. Then shop vac to suck it out the best I can. It’s not as clean as I’d like, but it solved the problem and is much better.