I have completed a few projects using my Maslow CNC “hanging router”. Although I’m not yet an expert on its use, I feel like I have enough experience for a general review. The bottom line is that it provides excellent value for the cost for a hobbyist, but will not replace a professional gantry style CNC router for professional use.

 

The source of the Maslow’s sub $500 cost is its unique motion system, which relies on gravity working against two variable length chains to position the router sled, which must slide on a flat work piece. Because you provide your own router, build the frame yourself, and cut out the final round sled using a temporary sled that you cut by hand, the electro-mechanical parts of the Maslow can ship in a large USPS priority mail box.

My Maslow is the 2nd generation that includes a ring for two chain carriages to roll along. The rolling chain carriages allow the two support chains to virtually “end” at the center of the sled where the router bit is positioned. This mostly eliminates negative effects of sled rotation and simplifies the kinematics of the machine. Earlier versions tried to model and account for the sled rotation with chains anchored off-center, or used a mechanical linkage system to achieve a similar effect. In my opinion, the ring and carriages is the best solution.

I also bought the optional 3rd motor to control the Z (up and down) axis of my router automatically, which I greatly recommend, as otherwise you will have to adjust the Z height manually every time the machine starts a new pass or you want to add a tab to hold your finished piece.

Because the Maslow’s sled rides on top of your work piece, you are limited to cutting flat sheets, and it is optimal for cutting flat pieces out of these sheets.This is not to say that you can’t cut pockets, or even 3D contours, but your working area has to be small enough that the sled can ride around fully supported on surrounding uncut support material.

In the same way, if you get the sled near the edge of the work piece, it may “fall off the edge” and tilt the router bit unless you are holding one side down manually. So although you can put a 4×8 sheet on the frame, unless you build a skirt of the same thickness around the work piece, you can’t cut all the way to the edge.

I have certainly “overhung” the edge of a sheet, or screwed a scrap piece to one side to act as a skirt so that I could cut right up to the edge of a piece, but if you don’t want to worry about the sled tilting, I’d recommend keeping your design 6 inches away from the edge, which gives an actual work area of 3 feet by 7 feet for a 4×8 sheet, and makes it harder to make use of small scrap pieces.

And even with a skirt, the Maslow suffers from loss of control near the far bottom left and right edges of it’s workspace, as the acute angles on the chains don’t provide enough force to hold the bit stable as the chain angle gets closer to vertical, which can lead to some “wavy” lines in these areas.

The Maslow is not intended to be a performance machine. At a maximum design speed of 48 inches per minute it moves slowly enough that you may need to turn down the RPM’s of your router or choose a bit with fewer flutes to perfectly match feed & speed guidelines. That being said, it is an open source machine, so you can hack the firmware and overdrive the motors if you want, just keep in mind that it does not currently have any acceleration control built in.

To give you an idea of how long it takes to cut out a part, this piece which is about 26 inches long takes about seven minutes to cut out of 11/32 plywood (with two passes). However, to drill the seven holes in the part takes another 13 minutes due to conservative plunge rate defaults in makercam. So, each of these parts takes a total of 20 minutes, plus the manual time needed to cut the tabs holding it to the base sheet when you are finished. (The advantage of having Maslow drill the holes can also be seen in the above photo, as all of the holes are positioned quite nicely!)

I was making 32 of these pieces, so I decided to use the Maslow to cut them out, but to drill the holes manually using a jig I also created using the Maslow, which was just a pocket the same size as the part with the holes pre-drilled in it.

 

The Maslow can return to the same position very accurately, so I have no complaints about it’s repeatability. However, due to the non-Cartesian movement space, it is quite susceptible to calibration errors, and unless you get it calibrated just perfectly, it has slightly different errors at different locations in the workspace. I calibrated it once and I think I did a relatively good job, but I can measure slight inaccuracies in different parts of the work area. For example, I measured the distance between these sets of holes made in the top and bottom of a sheet, and they were generally within 1-3 millimeters, which is quite good on a percentage basis, but isn’t in the same league as a gantry style machine.

I cut all of these parts facing the same direction, and you can see that they align nicely when stacked up.

When I modeled the hole drilling jig, I did not make it any larger than the part. (I probably should have enlarged it by a mm, but I figured that since I’d be sanding the parts before putting them into the jig it should work.) Of note is that I cut the jig out vertically, while the parts were cut out horizontally. This difference in orientation may have caused some of the issues I had.

Most of the parts didn’t quite fit in the jig even after sanding, both because the parts were about 1-2 mm too long, and because the curve didn’t quite line up. It was close, and I was able to use each end of the jig individually (with the other end of the part hanging out a bit) to drill the holes I needed, but in the future I’ll try enlarging the outline of any jigs like this before cutting them out, and cutting the jig in the same orientation as the part.

As another example, I cut out these pieces which bolt together into a ring that was designed at a 24″ inside diameter, and the circle was within a 16th of an inch in both dimensions. Because these parts only had two holes, I decided to use the Maslow to drill those holes, so I didn’t try the Jig approach on these parts.

   

For the price, it’s hard to beat, and for cutting “large scale” pieces I’ve found the accuracy to be good enough for everything I’m doing at this scale.

A few final notes on safety. You MUST attend the machine while it is working. As with any CNC machine, when you have a high speed bit cutting flammable sawdust out of flammable wood, if something goes wrong and the bit stops moving, the friction of the bit can easily start a fire. This has happened to other CNC machines, and has already happened to at least one person’s Maslow (not mine!).

You should also invest in a pair of ear protectors, as being in the same room as a router running for hours and a vacuum or other dust collection system can do some damage to your hearing otherwise.