Comgrove's ROBO Router/Engraver

[Bernd]

As promised, a description of the router/engraver.



The above picture was an advertisement for Comgrove ROBO Router/Engraver. They are no longer made. If you do a search on "tabletop router/engraver", you'll see several types and sizes of machines.

Now on with ROBO (have no idea why they called it that). I ordered it off of Amazon.



It basically came as a kit. All the parts laid out. The screw gun shows relative size of router/engraver.



The machine completely assembled.



The back of the machine showing the offline controller's mounting spot.



The off line controller showing the control buttons.



The SDHC slot.





First test cut. Several circles surrounded by square.



This basically describes the machine I bought. When this one electrically dies, I plan on getting another router/engraver. I'm looking at getting a Genmitsu 4040-PRO. It has a larger work envelop than the ROBO at 15'7" X 15.7" X 3.1". Here's a link to Amazon on what it looks like and price.
  https://tinyurl.com/rjczpenn

I have actually two tabletop CNC machines, the ROBO and a Sherline CNC. Both are very useful tools since you can work almost any kind of material used in model railroading or structure builds. I find 3D printers limited in what they can do because you can only add stock, not remove stock as you can with a CNC or any machine tool. I believe 3D printers are great if you want to make a master for casting something in resin or even plaster. Even though I have a 3D printer I found learning 360 Fusion or any other 3D CAD program as being very time consuming. And if you don't use the program enough you forget how to use it. Also having grown up in the machine tool industry where I learned how to operate the larger machines in making parts, learning to use the tabletop machines was easy for me.

Next post I'll go into what it took to make those windows.

To be continued.

Bernd

[Bernd]

Continuing on with using the ROBO CNC to do the windows.

My first attempt at making the window framing wasn't very successful. I'd seen many videos on using ACC to glue the stock down and then cut. It stuck to the wood alright, but the cutter was another problem. There was some awful vibration in cutting the brass.

First though I needed to program the machine to do its job. There three steps needed before you can cut the first part. The first step is to use a CAD program to draw up the part. I use DraftSight 2025 x64, it's a 2D drafting program and I do pay a yearly licensing fee. It's easy to use and is close to the old AutoCAD10 I had used almost 20 years ago.

This first picture shows a screen shot of the CAD program in use.



Once the part is drawn up and to your satisfaction the drawing gets exported as a DFX file. The second program then takes the DXF file and converts it to G-Code that the machine understands. I use CAMBAM, it's a CAM (Computer Aided Manufacturing) program.



In the CAM program is where you enter all the parameters for the machine to cut the part, the feeds and speeds for axis motion, depth of cut and how many times around the part before reaching final depth. Since the material was only .010" (.251mm) thick, one cut did it. It takes all that information to produce a G Code. The green and blue lines outside the white lines show the path of the cutter. The small green rectangles denote tabs that keep the part attached to the main material, so it doesn't get tangled in the cutter when cut loose from the main material.



When all that info is input you then tell the software to produce the G code.



This code then gets loaded into the machine software to cut your part out. But before cutting the first part a "dry run" is done. That means you don't cut any material, you just want to prove your programing is correct or as correct as possible.

This is a screen shot of the machine software showing the cutter in yellow orange at the zero (home position) with the red arrow as X axis and the green arrow as Y axis.



Starting out with a nice clean piece of .010" (.251mm) thick brass so the glue will hold.



And of course, some disasters before getting a good part. Five cutters gave up their life for this operation before I got it tuned in.  Since it's been three years since I did this project, I don't remember what caused all of these misfortunes. I do remember part of it was the excess vibration.



I did finally get good ones once I fixed a couple of problems. Here you can clearly see the tabs that hold the window frame onto the main material. Why that one didn't finish the cut was and still is a mystery to me.



In the end I did get good ones of the run once I fixed two problems which I'll go into next.



Continued in the next post.

Bernd

[Mr. Critter]

This is going through an awful lot of expense and trouble to detail an old Suydam kit from the age before seatbelt mandates.  By which I mean, I understand completely. 

Chapeau.

[Bernd]

Continuing on.

Now that you've seen the disaster of the first window almost having been cut out and the end mills broken I'll show you what I found wrong and corrected.

The first attempt was with just gluing the part to a wooden base on the machine. If you look closer you can see I broke the cutter. Also missing are the holding tabs. Program Engineers fault.







If I remember correctly the part also had moved on me. Had an idea of using some line up guides to keep the part from moving. Here I'm setting the cutter height to the top of the wooden base. I'm going to cut what amounts to square line up tool.









Glued to pieces of 1/4" square wood in the slots.











And that didn't do it either. To much vibration in the cutter. Time for some investigation.

More to come.

Bernd

[Bernd]

This is going through an awful lot of expense and trouble to detail an old Suydam kit from the age before seatbelt mandates.  By which I mean, I understand completely. 

Chapeau.

Perhaps, but did I mention my second hobby is home shop machining. It's a learning curve of getting to know the machine and what it is capable of. It's not a get it out of the box, set it up and magically cut a good part. This was only the beginning of using the machine. I understand that it seems like a lot of trouble for somebody that's probably never use a tool such as this. Also remember these are China made machines and are not held to the tight and ridged tolerances industrial machines are held to. That's probably why you don't see many model railroaders using this type of equipment to build models with. The big brothers of the tabletop machines are the ones that make the RTR product so many modelers have on their layout or the one-man operation providing a niche market product for you to glue onto your model. I'm just trying to show what is capable in modeling if you have these types of machines for your use.

Bernd

[Bernd]

Continuing on.

I determined the vibration was coming from the motor. I'll spare you all the detail of how I went about it and give the Readers Digest version.

I traced it down to the collet on the spindle. A closer look at the collet showed it was a defective collet. The collets used on this machine are ER11.



Here is the culprit collet. Note the differences of where the arrow points. This caused the cutter to not run true on center causing vibration during cutting. The cutter actually scribed a circle as it rotated.





A new collet was obtained, and a new holding fixture was made. An aluminum base plate was attached to the router table and a holding fixture was added with a dowel locating pin.





It was properly squared up to the base.



Clamps were made to hold the part down and fixture to the base. Here I'm using a drawing of the window frame to properly align the frame and cut a trough in the fixture with a larger diameter cutter for the cutter that is going to be used on cutting out the frames to run in. This eliminates the need for the part cutter to also cut the aluminum underneath.



Cutting out the trough into the fixture.



Next a piece of brass was clamped into the fixture and cut.





Once the parts were cut the tabs needed to be cut to release the part.





12 window precisely cut frames.





With these done it was time to install them on the engine house.

Bernd