[jpvonoy]

Hello CNC Zone!

I've been soaking up the vast resources on this site for a while and am now finally putting it all to use. I want to document my build here to hopefully return something to this forum in exchange for all I've learned.

I was not happy with the performance of any of the plans I've seen, nor with the prices of kits and commercial machines. So, like many of you, I decided to come up with my own design. Not to mention, it is more fun to design and build your own, right?

I laid out a set of performance and cost goals and then designed a machine to meet those goals. However, this thread is not about that machine. This is a build log for a proof-of-concept machine that is lower cost and easy to build (therefore the wood frame). This will allow me to learn and flush out any issues. I did attempt to design the wood frame so that it will hopefully have enough performance to make parts for the originally designed machine.

My rough goals for this wood framed version of the machine:

1. Working envelope of slightly greater than 24" x 36" x 6" (approx. 915 mm x 610 mm x 150 mm).
2. Accuracy and precision in the ballpark of 0.001" over 12".
3. Performance - will leave this for later discussion.
4. Learn and test the concepts needed to build my originally designed machine.
5. Have a machine to start making parts for the next machine.
6. Have fun!

I will give some design details in my next post.

Jeremy

[jpvonoy]

Unfortunately I did not start a design thread, so I will just summarize the design here before getting into the build details. Since I'm already building there is probably not a lot of room for changes, but I am always happy to receive constructive criticism that I can apply to the next version of the machine.

Here are the major components, with the wood frame design as seen in the attached images of my model. I am using Fusion 360 for the modeling and design simulations. I'm very impressed with the capabilities of Fusion 360, being that it is free for hobby use. I do run into quite a few bugs, but I can't complain for the price I'm paying! Also, they are continuously improving, rolling out updates all the time and they personally respond in a timely manner to inquiries on their support forums.

• HIWIN HGR15 linear profile rails (X=1200mm, Y=800mm, Z=350mm)
• HIWIN HGH15CAZAH bearing blocks on Y axis
• HIWIN HGW15CCZAH bearing blocks on X and Z axis
• Ballscrews: 1204 on Z Axis, 1610 on X and Y axis
• BK/BF10/12 supports for all screws
• NEMA23 381 oz-in stepper motors (4 total, 2 on X-axis)
• Gecko G540 stepper drivers
• 48 vdc power supply
• Mounts for DeWalt DWP611 (shown) and DW618 routers
• Linux CNC

All of the frame components and the base use a torsion box design and will be made with birch plywood with MDF webs.
Attachment 344456
Attachment 344460
Attachment 344458
Attachment 344462

[jpvonoy]

I started with the Z axis since the parts are small and if I make any mistakes, it will be easier to redo with less wasted material. Working with the dimensions and images from my solid model, I started by cutting all the plywood pieces to make up the Z axis carriage, laid them out for a test fit, then glued and clamped them together.

This is the Z Axis design:
Attachment 344486
Top View (Looking Down):
Attachment 344488
Lower Quarter View:
Attachment 344490

Gluing up the first pieces:
Attachment 344492
Looks just like the model It is fun to see something come to life that you have been working on designing for months (maybe closer to a year now)!
Attachment 344494
Lots of clamps:
Attachment 344496

My table saw left burn marks on the wood. That will get sanded down a bit later to make it look nicer. I spent some time tuning up the table saw to align everything properly. Maybe I need a new blade as well.

[jpvonoy]

Here is the Z axis carriage after unclamping from the glue-up and giving it a light sanding to remove the burn marks left by the table saw. I am using aluminum bar stock to mount the profile rails. I chose this method in case I wanted to mill a perfectly flat surface on these or to mill shoulders (the preferred mounting method for HIWIN rails). At this point the bar stock is just positioned for a test fit. They will be epoxied in place after drilling and tapping the rail mounting holes.
Attachment 344640

After making this first piece for the Z axis, I noticed it had a very slight warp to it. I don't think it will be a problem, since I can lay the bar stock on a flat surface, coat the carriage with a thick epoxy, and lay it on top of the bar stock, so that the rail mounts will remain perfectly flat and in the same plane. The epoxy should take up any space due to the slight twist.

I now realize that I will need a perfectly flat work surface to make the other parts on. I also will need a perfectly flat base for the machine, so I decided to go ahead and build up the torsion box base at this point. The machine base will serve as my assembly table for the rest of the build.

In order to build a perfectly flat torsion box, you need to start with a flat surface. Following an idea on another website, I made two small torsion box beams. This allowed me to practice the techniques for making a torsion box, and then I could use these to create a flat work surface for building the torsion box machine base. You'll see later what I mean. Here's a picture of the two torsion box beams being constructed. The bottom one isn't glued yet, just assembled to have a flat place to glue up the top one.
Attachment 344644

[jpvonoy]

With the torsion beams completed, I laid them out across two sawhorses and used shims under the legs to get the torsion beams level in both directions. I placed a sheet of MDF on top of these beams and proceeded to build up the base for the machine.
Attachment 344722
As you see, the pattern of webs is not uniform. I was originally planning to have it filled with the square pattern you see at the ends. However, I changed my mind and decided to go with a sparser pattern. It should provide plenty of rigidity for this prototype.
Attachment 344724
The glue-up was done in two stages, first to attach the sides and all the webs to the base, then to attach the top. Many clamps and weights were used to hold everything together while the glue dried. With the top in place and everything glued up, the assembly is very stiff and doesn’t flex at all when I lift a corner.
Attachment 344726

[fretman_2]

Looking great!

[jpvonoy]

Thanks fretman_2! Having a nice flat surface to work on, I decided to start building up the gantry. I printed out some screenshots from my solid model and wrote in the dimensions by hand, not wanting to take the time to create all the drawings in the CAD software. Then I got busy cutting out all the pieces of plywood on the table saw. I used a dado set for cutting the slots in the top and bottom pieces.
Attachment 344810

I took this image to show how the pieces will fit together. The top is slid back slightly for better visibility:
Attachment 344812

Next I cut out all of the web pieces from 1/2" MDF. Here are all the gantry pieces laid in place for a test fit:
Attachment 344814

Once again, I glued the pieces together in stages to make sure I could keep everything aligned properly. The number of clamps I own also limits how much I can do at once.

[Buoyen]

Very interesting build and looks good so far! I'll watch this!

[jpvonoy]

While the glue-ups were drying on the gantry, I went back and did some more work on the Z-axis. I finished the router mount for my smaller DeWalt DWP611 router. I glued in a few pieces of wood with threaded T-nuts driven into the wood. The two mount pieces get bolted into those T-nuts so that I can install other mounts for my larger DW618 router or anything else I may want to mount in the future.
Attachment 345042

Next I started drilling and tapping the aluminum bar stock to accept the Z rail mounting screws. I decided to initially install the rails without any machining and see how it works out for this proof-of-concept machine. If necessary, I can always go back and have these machined flat, or have shoulders machined to mount the rails against. The bar stock is still not attached to the carriage in this picture. It is just a test fit prior to epoxying the bars in place.
Attachment 345044

[jpvonoy]

My first major problem with this build. After all the glue was dry on the gantry, I rotated it 90 degrees on my work surface (the machine base) to see what it would look like in its final orientation on the machine. One corner of the gantry sat above the surface by about 3/32”. I first thought it had warped somehow after the glueup, but back in the position where I constructed it the gantry laid perfectly flat against the base. After doing a lot of checks with a straight edge and feeler gauges I found that my base was not perfectly flat as I initially thought. It was flat along the edges in both length and width, but there was some variation throughout the center. So, between the 40 or 50 thousandths of twist introduced where I constructed the gantry, and another 30 to 40 thousandths in the final orientation, I ended up with the gantry having this 3/32” warp or twist in relation to the base.

The way I decided to fix this was to create a large planing jig for my router. Following some videos online, I mounted two long pieces of plywood (with the factory cut sides up) along the sides of my machine base and used a level and two wires running from corner to opposite corner to get the rails level and without any twist. Then I built a sled for the router that would slide along these two rails, allowing me to run the router over the whole surface with a 1 ¾” surfacing bit. I waxed the router sled and the rails, and used some clamps for stops. My wife helped out by holding the shop vac to collect the dust while I routed the entire surface of the machine base. I clamped one end of the base to my leveled workbench so that the corner with the twist would be up the air and would get milled down. If you want to see more details, this is one of the videos that provided inspiration: youtube.com/watch?v=qtkBZHLJyD0

Attachment 345116

Attachment 345118

After routing the top, I flipped the base over and repeated the operation on the other side. In theory, these two sides should now be parallel and without much twist. This will hopefully get me back to square one for having a flat work surface to build the machine on.

Rather than re-constructing the whole gantry on this newly flattened surface, I decided to use the same planing jig to get the top and bottom of the gantry to be flat and parallel. This seemed to work well and now the gantry sits perfectly flat against the base.

[jpvonoy]

After planing the gantry, I realized that the front face, where I intended to mount the Y axis rails, is no longer perpendicular to the base. Since I was planning on using epoxy for the rail mounts anyway, I figured I could just use epoxy for leveling the front side of the gantry.

With the gantry on its back, I made sure the gantry bottom was perpendicular to the machine base, since that is where the X Axis bearing guides will be mounted. To minimize the use of expensive epoxy, I made a dam out of 1/2" plywood covered with blue painters tape, which releases easily from epoxy, then sealed at the edges with clay. This dam allows the epoxy to flow only to the areas where the rail mounts and the ball screw bearing support mounts will sit for the Y-axis, with extra room allowed for the meniscus of the epoxy at all edges.
Attachment 345350

Once the epoxy was mixed with hardener, I poured a small amount into another contained and mixed in a little acetone to thin it out. I didn't want to thin the whole batch because acetone can change the strength properties of the cured epoxy. I poured the non-thinned epoxy throughout the area and let it settle for a few minutes, and then poured the thinned epoxy over the top to achieve a very flat surface.
Attachment 345352

Remember, all of this work is driven by the fact that I didn't start with a perfectly flat work surface. If the gantry had been properly square, I would have just attached my rail mounts and bearing supports directly to the wood face of the gantry. However, it is a good learning experience and I'm glad to have been able to test out the epoxy leveling method in case I want to use it for my next machine.

[jpvonoy]

With the epoxy leveling complete on the gantry face, it was time to prepare the Y Axis profile rails and their aluminum bar stock mounts.

With the Z Axis rails, I had clamped the rails against a straight edge and then used an automatic center punch to mark all the hole positions on the aluminum bar stock. Then I removed the rail and drilled all the holes on the drill press. That turned out to be less than ideal since the center punch was smaller in diameter than the rail mount holes and I wasn’t perfectly centered with each hole. Luckily there was enough play around the M4 screws to correct these minor errors. So, I tried a different method for the Y Axis.

Again, I clamped a straight edge against the registration surface on the side of the profile rail, then aligned that with the aluminum bar stock and clamped the bar stock together with the rail. Rather than using the small diameter spring-loaded center punch to mark each hole, I found a drill bit that exactly matched the diameter of the holes in the profile rail. I inserted this bit in each hole and gave it a good tap with a hammer, leaving a mark at the center of each hole. This allowed me to drill all the holes more accurately at the drill press. I still ended up with some slight errors from my less than perfect alignment of the drill bit with the marks on the bar stock. For the second rail I tried another method…

Third time’s a charm. Leaving the rail/bar assembly clamped together, I brought the whole assembly to the drill press. I aligned the first hole on one end with the drill bit and could easily see when it was centered. I drilled the first hole, then tapped it and put a screw in. Next I drilled and tapped the hole on the opposite end and put a screw in. Followed up with one in the center, gradually removing clamps as I went. Now I could drill all the holes without having to mark anything. This method was much faster and more accurate as well. With the holes drilled and the rail still attached, the rail acted as a guide for the tap to ensure it was vertical. The tapping operation went much faster this way as well.

I didn’t take a lot of pictures of this, but here are a few shots of the work and progress:
Attachment 345832

Rails laid in place on the gantry for fit check:
Attachment 345834

[jpvonoy]

Although I left enough space for the epoxy to form a meniscus at the edges, I decided I wanted to get the rails as far apart as possible, per the original design. So, I used a shoulder plane while the epoxy was only partially hardened and it planed down beautifully to remove the meniscus along the outer edges. After the base leveling epoxy was completely cured I bonded the aluminum rail mounts (with rails still installed) into place on the gantry, using an adhesive epoxy. I think I forgot to mention earlier during the Z Axis buildup, that all the aluminum bar stock was chemically etched prior to epoxying them to the plywood, in order to get the best bond. On one set of rails, I sanded the bonding surface with 120 grit prior to etching; another recommended method for better bonds. I’ll see how each method holds up and perhaps do some more formal testing of different bonding methods in the future.

To help align the rails, I placed identical length aluminum bar stock in between the rails at each end, where the ball screw supports will be mounted. Then I built part of the Y carriage and installed it on the rails, to hold them in alignment at the center.

Attachment 345984

Once the epoxy cured I put a dial indicator on one set of guide bearings and measured the error all along the length of the opposite rail. I loosened one to three rail mount screws at a time and made fine adjustments to the rail until I had no more than +/- 0.0005” error throughout the full length.
Attachment 345986

[Biggs427]

Looks nice!

Which epoxy have you used? What thickness?

I've subscribed to this thread as I am going to start my own build soon and there will be similarities with yours!

[jpvonoy]

Looks nice!

Which epoxy have you used? What thickness?

I've subscribed to this thread as I am going to start my own build soon and there will be similarities with yours!

I'm using two different epoxies, one for the leveling and a second for bonding the aluminum bar stock to the wood (or to the leveling epoxy for the case of the rails on the gantry).

For leveling, there are specific leveling epoxies I've seen recommended in other threads, but I just used a standard layup epoxy since I had some on hand (bought from US Composites for other projects; I could get you exact product number if you are interested). Since this is just a proof-of-concept machine I'm going for low cost here. If I make another machine I will probably use a specific epoxy designed for leveling. To compensate for not having a thinner epoxy, I poured most of the thickness with the standard epoxy and then covered the whole surface of that with a thinned down epoxy (same epoxy but thinned with acetone). This way I got the strength and adhesive properties of the standard layup epoxy and then the perfectly flat surface of a watery epoxy. I went with a thickness of about 1/8". I calculated the volume required based on the dimensions of the area I had to fill and mixed just enough epoxy so that I could pour it all in and end up with exactly 1/8" thickness. Since it was thick, I did my best to pour it evenly throughout the fill area. It then settled out fine and had even coverage.

For bonding the aluminum to wood, I've read that it's very hard to get a good bond to smooth aluminum. A few adhesive type epoxies were recommended, West Gflex seemed best, but once again for cost I went with an epoxy that is used by aircraft builders to bond aluminum to wood. It's called System Three T-88 Structural Adhesive. I also read that it's important to first degrease the aluminum, then either sand the aluminum to rough it up, chemically etch it, or at a minimum just wipe it down with acetone. I tried a few methods as a learning experience to see how they hold up over time.

[ger21]

There are a couple of ways to get the epoxy to act like it's thinner.
1) If possible, warm up the surface before pouring the epoxy. Heat thins the epoxy.
2) Warm up the resin and hardener separately before mixing. You may need to work much quicker if you do this, to prevent exotherm (runaway overheating while curing rapidly)
3) After pouring, use a hair dryer or heat gun on low heat to warm up the epoxy.

As for bonding to aluminum, West Systems recommends sanding epoxy into the aluminum. This prevents it from oxidizing while sanding, and is supposed to be comparable in bonding strength to chemical etching.

[jpvonoy]

Thanks Gerry. I think I will try those methods in the future. I have seen plans for simple wooden boxes with an incandescent light bulb inside to act as a heating element. The bottles of epoxy can then be placed inside to warm them up prior to use. I would like to build one of those. I will also experiment with using a heat gun to preheat the surface and then to post-treat the epoxy to remove bubbles and give it nice flat surface.

The next bit of progress on the machine was back to work on completing the Z and Y axis components. I spent some time in Fusion 360 learning to create drawings from the components in my model. This allowed me to print out a scale drawing to use as a template for quickly and accurately placing all of the holes in the following part. An 8.5" x 11" sheet of paper just fit all the holes for this piece.
Attachment 346562
Attachment 346564
Attachment 346566

In order to get the ball nut coupler to be flush with the Y carriage, I had to use a router table and a hand chisel to lower the plywood carriage slightly:
Attachment 346568
Attachment 346570

The final task on this part was to make the Z stepper mount out of plywood. I glued it together and clamped it to dry overnight.
Attachment 346572

[1Jumper10]

Nice craftsmanship!

[jpvonoy]

With the Z and Y Axis components almost complete, I couldn't wait to get the Z frame components built up. I cut all the plywood pieces on the tablesaw, then figured out what angle to cut out the MDF webs. Once I made one that fit well, I used the waste piece with a stop on my cross cut sled to quickly cut out the rest of the webs:
Attachment 346700

I assembled these in place on the machine base and once again glued everything up and used a lot of clamps. The waste pieces from the MDF webs came in handy again to make a squared up clamping surface.
Attachment 346706

Attachment 346710

[jpvonoy]

I do not see how to edit my previous post. I was able to edit one the other day…? Anyhow, I meant to say “X-axis frame components built up”, rather than “Z”.

So, after building the first side, I just repeated the operations for the second side. I had cut all the plywood at once in the beginning to make sure the dimensions were identical, using the same saw setup. Next step was to drill and tap all the holes in the aluminum bar stock for the long X rail mounts. I followed the same process as detailed earlier to make sure the rails were straight and aligned properly.

I made plywood stepper motor mounts and bearing support mounts, all from the same birch plywood stock that I’ve been using for everything on the machine. Here you can see the left and right sides of the frame, along with the rails placed on top. The ball screw assemblies are in the center, but they will be mounted to the outer portion of the frame sides.
Attachment 347316

Here is a picture of the completely assembled Z axis attached to the Y axis. The only parts missing are the linear bearings that will be mounted to the bottom of the gantry.
Attachment 347318

It's looking like a CNC machine!