HydroP - Similar Mat Drop Table for Polystyrene Machining

[Florian_G]

Hello the community,

First, thanks to all the work and beautiful knowledge shared here.

I’m computer scientist, and shaper of surf - board - foil as hobbyist.

Most of the time, I’m learning the hard way, making lots of mistakes along the way, but I’m ok with that. I like also to try things a bit differently, even if it’s a failure at the end, my goal is to learn and have fun.

My MPCNC project will be called the HydroP.

HydroP will be very similar to the Drop in MPCNC of Mat.

What I am trying to achieve : Designing a board or a piece of polystyrene or 90kg/m3 PVC on Blender, then using a slicer to generate GCode (Ultimaker) (maybe do some translation on this GCode?), GRBL and UGS machining the piece.

I am sourcing for now regular block of polystyrene (EPS or XPS), that are 1200x600x100mm maximum. I am planning to glue the multiple machined block together / make a stringer in the X axis for bigger piece / board.
In order to have HydroP dropped in the polystyrene block, I am aiming at a 1100x500x100mm machining area, and make a table (again similar to the Mat one).

Because I am machining very light material, I hope the working area will be ok with a good wood custom table.

For the spindle, I ordered a 400W from Vevor ER11 52mm, and some 100m and 150mm meshes for milling of Dia 4 and 6mm.

For the electronic, simple Arduino Uno with CNC shield, motor driver for NEMA17, and GRBL.

Next steps :

• printing time of the MPCNC with black and red PLA, like the original one on my Ender 3S+
• Read over and over the assembly instructions
• Assemble following instructions
• Make the table (squared, similar to Mat)
• Mount the Spindle
• Make some test on first polystyrene block
• Make a first small board

If you have any advice or if you think I’m making some error, please don’t hesitate to tell me, it will be highly appreciated.

And of course thanks Mat for your sharing of your CNC and work.

[Florian_G]

Let’s go for the 3d printing time of all the parts on my Ender 3 S1 Plus, with a glass bed.

My Ultimaker Cura slicer settings :

• Print Speed : 50mm/s
• Infill 75% for the core, otherwise 55%
• Infill Algorithm Cubic
• Nozzle 0.4
• Layer Height 0.25mm
• Build Plate Temperature 65
• Printing Temperature 210

See you in couple of days.

[Florian_G]

I’m not happy with the result of the first 4 bottom corners.

I changed the nozzle for a brand new one (same 0.4mm), I’m doing again the level of my bed very precisely, and I’m trying to have good stick of the part to the bed (leveling + alcohol cleaner + 65 degrees should be good for that). Changing a bit the settings too :

• Print Speed : 50mm/s
• Infill 55% pour les 45%+
• Infill 75% pour les 45%+
• Cubic Infill Algorithm
• Ultimaker Cura version 5.4.0
• Nozzle 0.4
• Layer Height 0.25mm
• Build Plate Temperature 65
• Printing Temperature 200

I’m also adding a skirt in order to check the leveling for all the parts.

Printing now the 4 corners top, should be good.

[Florian_G]

Finally 4 parts that should be good enough.

Settings are ok now, the only problem is the bed leveling on the glass bed that is very sensitive.

I will not print more than 12 hours in a row to not waste any PLA in case of problem.

[robertbu (Robert Bunney)]

Designing a board or a piece of polystyrene or 90kg/m3 PVC on Blender, then using a slicer to generate GCode (Ultimaker) (maybe do some translation on this GCode?), GRBL and UGS machining the piece.

For generating the g-code, you want to use some sort of CAM software that can import a mesh (usually a STL). The most popular on this forum is EstlCAM. The second most popular is Fusion 360. Fusion has a free (personal) edition that has some restrictions. Fusion 360 provides an integrated CAD and CAM solution, though the learning curve is significantly steeper than EstlCAM. I don’t know enough about the curves associated with surf boards, but it is likely you can use Fusion 360’s CAD for the design.

For the electronic, simple Arduino Uno with CNC shield, motor driver for NEMA17, and GRBL.

I’ve seen a couple of people on this forum using this control board, but you might also consider a MKS GEN L V1.0, or a RAMPS 1.4 board. V1 has drop-in Marlin firmware for these boards. Given that you are working in foam, your cutting speed can be high, so you may benefit from running at 24V instead of 12V. Not all RAMPS 1.4 boards can run at 24 volts.

I am sourcing for now regular block of polystyrene (EPS or XPS), that are 1200x600x100mm maximum. I am planning to glue the multiple machined block together / make a stringer in the X axis for bigger piece / board.

Given your ER11 collet, it is going to be difficult, if not impossible, to find router bits for contour cutting 100mm foam. Maybe, if the depth of the rest of this milling is not too high, you can do the contour cutting by hand. You could do double-sided milling, and stick to the few router bits you find that are at least 50mm. You might also consider milling 50mm foam and gluing the top and bottom together, or you might pick a spindle that has an ER16 collet. Note that if you go with 50mm foam, you avoid the work of doing double-sided milling (assuming you want to mill both the top and the bottom).

Because I am machining very light material, I hope the working area will be ok with a good wood custom table.

Your 1200 x 600 x 100 is a large for a Primo. For wood, it would be too large, but it should be okay with foam. You may benefit from mid-span supports for the longer rails, and corner braces.

Drop in MPCNC of Mat.

I don’t know if it is any better, but you could build a traditional machine and just slide the stock through. There are solutions to keep the cable chain out of the way so that stock can be slid through.

[Florian_G]

Hello Robert,

For generating the g-code, you want to use some sort of CAM software that can import a mesh (usually a STL). The most popular on this forum is EstlCAM. The second most popular is Fusion 360. Fusion has a free (personal) edition that has some restrictions. Fusion 360 provides an integrated CAD and CAM solution, though the learning curve is significantly steeper than EstlCAM. I don’t know enough about the curves associated with surf boards, but it is likely you can use Fusion 360’s CAD for the design.

I’m an extensive open-source user. I spent quite some time on Blender to model my boards / box etc. Blender is an open-source 3d graphics computer software with a wide variety of plugins. One of the available plugin is BlenderCAM. It can generate g-code for GRBL. As you can see on the following screenshot, the Orange curve is the resulting gcode spindle path calculated from BlenderCAM.

I’ve seen a couple of people on this forum using this control board, but you might also consider a MKS GEN L V1.0, or a RAMPS 1.4 board. V1 has drop-in Marlin firmware for these boards. Given that you are working in foam, your cutting speed can be high, so you may benefit from running at 24V instead of 12V. Not all RAMPS 1.4 boards can run at 24 volts.

Good to know, thank you very much.
I have no prior knowledge in electronic - CNC nor automatic milling (except my 3d printer…). I’m trying to stay low cost, and have sufficient results. I can also iterate afterward on the HydroP MPCNC in order to improve it to 24 Volts.

Given your ER11 collet, it is going to be difficult, if not impossible, to find router bits for contour cutting 100mm foam. Maybe, if the depth of the rest of this milling is not too high, you can do the contour cutting by hand. You could do double-sided milling, and stick to the few router bits you find that are at least 50mm. You might also consider milling 50mm foam and gluing the top and bottom together, or you might pick a spindle that has an ER16 collet. Note that if you go with 50mm foam, you avoid the work of doing double-sided milling (assuming you want to mill both the top and the bottom).

You are totally right.
After double thoughts and some time of processing, I will probably do multiple layers of milling depending of my router bit with a “V” shape angle “box” radius around the model to not mill at 90deg. And thus leaving some “space” for the router bit and spindle to plunge.
The maximum Z milling will be 100mm and should be enough for all my projects, because for the bigger boards I plan to CNC will be composed of maximum ~6 blocks glued together (left - center - right * bottom + top).

Your 1200 x 600 x 100 is a large for a Primo. For wood, it would be too large, but it should be okay with foam. You may benefit from mid-span supports for the longer rails, and corner braces.

Good to know thank you. I will do some mid-span supports and corner braces.

I don’t know if it is any better, but you could build a traditional machine and just slide the stock through. There are solutions to keep the cable chain out of the way so that stock can be slid through.

The way I’m thinking the “table” is 4 bracket of wood, joint by x4 25mm conduits that will support the MPCNC (that will replace the MPCNC feet). Something like that :

I will consolidate the brackets and conduits with probably epoxy resin if more solidity is needed.
The idea is that the weight of the machine will be enough to keep the block steady under the table.

[SupraGuy (Dan)]

@Florian_G

The idea is that the weight of the machine will be enough to keep the block steady

I would expect it to be very difficult to keep that square. The wood will want to move with humidity, and the joins are relatively small surface areas. An “X” brace would help quite a bit to keep things square.

It wouldn’t be too bad with a welded steel framework. That would remain solid.

[robertbu (Robert Bunney)]

@Florian_G

One of the available plugin is BlenderCAM.

Good to know. I’ve shied away from Blender being more comfortable with the design framework of a CAD solution. My comment about CAM was in reference to your original post where you wrote, “using a slicer to generate GCode.” Whatever you do, you want a CAM solution to generate the g-code. CAM will give you the various toolpaths, account for the bit widths, and more. These are not features you will get with a slicer.

I have no prior knowledge in electronic - CNC nor automatic milling (except my 3d printer…). I’m trying to stay low cost, and have sufficient results. I can also iterate afterward on the HydroP MPCNC in order to improve it to 24 Volts.

The problem with the CNC shield is that it only supports 4 stepper drivers. The Primo has five stepper motors. The typical 4-driver solution is to wire the stepper motors in series. This works well for wood milling speeds, but stepper motors wired in series will lose torque sooner due to fast movements. For your application, getting a five-driver control board will be beneficial for not losing torque at faster speeds and will simplify the wiring.

As for cost, the CNC Shield with drivers runs $27USD and the MKS Gen L V1.0 with drivers runs $38USD, so you are talking an $11 difference. This is US Amazon prices. The calculation would be different if purchasing from AliExpress or similar.

The MKS Gen L V1.0 is capable of 24V, so you can purchase a 24V power supply up front. No other changes needed to use 24V…and the cost is similar between the two voltages of power supplies.

Since your pipeline will be Blender and GRBL, there is a version of GRBL for Ramps boards.

I will probably do multiple layers of milling depending of my router bit with a “V” shape angle “box” radius around the model to not mill at 90deg. And thus leaving some “space” for the router bit and spindle to plunge.

I don’t know about BlenderCAM, but in Fusion 360, there is a setting you can use for contour cuts that will handle this issue. No need to do special modeling. And there are different approaches to a “contour” cut that also makes this unnecessary. Since machinists have had to deal with these kinds of issues, there is usually a CAM solution or approach to solve these kinds of problems.

The way I’m thinking the “table” is 4 bracket of wood

I agree with Dan. Your solution is not stiff enough to remain square, even with your lighter duty application. I don’t weld, so my first thought is to use 3D printed brackets for the corners and use conduit for the sides…perhaps two rows per side. If I instead made the edges in wood, I’d design boxes of some sort for each side. The boxes don’t have to be very big to be stiff and mitigate wood movement.

Edit: If you wanted your design, for the edges make a laminate out of 3 layers of 3/4" (18mm) plywood…maybe 3" wide.

[Florian_G]

Thank you very much again for your thorough explanation.

The problem with the CNC shield is that it only supports 4 stepper drivers. The Primo has five stepper motors. The typical 4-driver solution is to wire the stepper motors in series. This works well for wood milling speeds, but stepper motors wired in series will lose torque sooner due to fast movements. For your application, getting a five-driver control board will be beneficial for not losing torque at faster speeds and will simplify the wiring.

Indeed, I was thinking of wiring them in series. I bought A4988 stepper motor driver.

As for cost, the CNC Shield with drivers runs $27USD and the MKS Gen L V1.0 with drivers runs $38USD, so you are talking an $11 difference. This is US Amazon prices. The calculation would be different if purchasing from AliExpress or similar.
The MKS Gen L V1.0 is capable of 24V, so you can purchase a 24V power supply up front. No other changes needed to use 24V…and the cost is similar between the two voltages of power supplies.
Since your pipeline will be Blender and GRBL, there is a version of GRBL for Ramps boards.

Ok, let’s switch to MKS Gen L V1.0 Ramp board with 24V power supply.

Given that you are working in foam, your cutting speed can be high, so you may benefit from running at 24V instead of 12V. Not all RAMPS 1.4 boards can run at 24 volts.

I’m a bit confused for the stepper motor driver and the voltage. The NEMA 17 are 12V, the board 24V if I understand well.

• So the stepper motor driver are running at 24V too from the board ?
• Should I change the stepper motor driver to be compatible with this board ? Any advice on which stepper motor driver to get ?
• What will run faster exactly with the MKS Gen L V1.0 board - setup ?

As you can see I’m quite new to the CNC world. I will search in parallel the answers.

[Michael_Melancon (Mike M)]

@robertbu

Good to know. I’ve shied away from Blender being more comfortable with the design framework of a CAD solution.

Well, if you are feeling particularly adventurous…let me introduce you also to…Blender CAD!!! https://www.cadsketcher.com/

[robertbu (Robert Bunney)]

@Florian_G

I’m a bit confused for the stepper motor driver and the voltage.

Stepper motors run fine at 24V, and, if your control board supports the voltage, no changes other than the power supply are required.

Should I change the stepper motor driver to be compatible with this board ?

No need to change the stepper drivers. The A4988 stepper driver’s voltage rating is 35V, so they will handle 24V. If you are purchasing your drivers separately, I have a preference for DRV8825 drivers, but I don’t have much of a logical reason for this preference. The DRV8825 drivers are slightly more expensive.

Stepper drivers modulate current to the stepper motors. Voltage (within reason) doesn’t seem to matter to stepper motors, and only matters to the stepper drivers with respect to their maximum voltage rating. I know of one person on this forum that runs standard NEMA 17 motors at 42V.

• What will run faster exactly with the MKS Gen L V1.0 board - setup ?

Stepper motors lose torque the faster you turn them. At some point, there is not enough torque to reliably move the router bit through the material. Do an image search for “stepper motor torque curve speed” to get an idea of this curve. When there is not enough torque to do the job, you lose steps, and usually the project is ruined.

At the speeds used for CNC routing of wood, the steppers never run fast enough for torque falloff to be an issue…except perhaps in rapids (non-cutting moves). But, since foam has so little resistance, you can mill it substantially faster, so that the torque falloff may become an issue. It has been a while, but when I was milling large cosplay props, I was able cut at high speeds. Given how big the pieces you want to mill, faster is better.

The higher the voltage you run the steppers, the slower the drop-off of torque which means the faster you can push the router around without losing steps. If you want to explore this fact, search the forum for “back EMF,” and people more educated on the issue than I am explain the reasons. Wiring the steppers in series results in the torque curve falling off faster meaning you will reach the point where you lose steps at a slower router movement speed (federate).

A side note for the future. The DRV8825 and A4988 drivers set their max current manually by rotating a potentiometer on the board. Here is one reference on how to set the current on these drivers. Builders using these drivers, not setting the current is a somewhat common problem that comes across the forum.

Another note. The MKS Gen L V1.0 board is a drop-in replacement for the Ramps 1.4 boards, but it is more reliable. The clone Arduino Mega boards shipped with Ramps 1.4 kits historically had issues with burned out pins and burned out regulators.

[Bigchepin (Gato)]

@Michael_Melancon

Blender CAD!!!

Ooo! @Michael_Melancon have you tried it out yet?

The meshing side of Blender has always been a challenge for me since my background is using traditional CAD applications. I use Blender to modify STL files so I think this plugin could be really helpful. Thanks for sharing.

[Michael_Melancon (Mike M)]

I tried it in it’s earlier days a bit, but I haven’t been back to it yet. Development seems to have slowed a bit on it by the looks of it.

[Florian_G]

3d printing still going on, I’m now happy with the result. This is the first Truck (55% infill) :

The MKS Gen L V1.0 has been ordered.

I don’t know how to weld. If I understand correctly your proposition, it would be to have conduit instead of wood for bracket ? I could probably 3d print 4 more corners.

[robertbu (Robert Bunney)]

For a pipe framework, you will need two pipes per side to mitigate twisting of the frame.

There are some interesting criteria for your build. You will be putting less stress on the router, the weight of the frame is somewhat important, and percision is somewhat less important. There are a lot of people on this forum that make things, so, with that criteria, you might get a lot of answers to how to make the frame. Here is what I suggest you try first. Note your use of metric units indicates you may not be in the US, so you may have to translate this idea to what is available locally.

Buy a sheet of plywood and cut 3" strips the long ways. In the US, the big box stores will cut the plywood for free, so I’d have them cut the strips. Plywood will be a lot more stable (in terms of wood movement) than solid wood.

Each side would be composed of two strips stacked and glued with 3" missing on each end to make a half-lap joint. Something like this (I’ve used different wood finishes to make the construction easier to see):

You would flip two sides, so the corners would come together to produce a flat top surface like this:

Then, once you were sure you had everything square, I’d add a plate to each corner, like this:

If the construction turned out to not be stiff enough, you just add one or two more layers, salvaging all the work done to date. For your size construction, I figure this frame will weigh about 20 lbs. If your lumber yard will cut the strips, the frame can be built using a hand saw and maybe a miter box. No power tools are required.

[Florian_G]

I’m at 2/3 time of the printing parts. Very happy with the results and consistency now.
I wasted a bit of plastic trying to prints the 4 corner parts in one, and resulting after ~8hours printing with one of the four parts moved from the bed plate… I’m staying with maximum 2 parts per print, and maximum ~12 hours print time.

I was thinking also for the filling 3d printing parts, is anyone already tried to fill the parts with epoxy ?

[Tokoloshe (Philipp)]

Filling them is not needed at all. But you are welcome to try.

[robertbu (Robert Bunney)]

Filling has the potential to be detrimental to the machine. In particular, any mass added to the moving parts must be accelerated and decelerated by the steppers. As long as you used the infill percentage recommended by Ryan, I suggest not filling any part that has to be accelerated by the steppers. For non-moving parts, I cannot see the harm, though I cannot see much benefit either.

[bitingmidge (Peter H)]

@Florian_G

is anyone already tried to fill the parts with epoxy ?

I agree with @robertbu completely, but I have played with filled parts on another project - be very careful if you are going to try that at some point - you have to limit the amount of fill to keep the temperature down.

I assume that working with Polystyrene you are used to using epoxy, so I also assume at some stage you’ve had a mix get away from you and go off in a ball of heat! It does the same to your prints as it does to your plastic cups!!

[Bigchepin (Gato)]

@Tokoloshe

Filling them is not needed at all.

…or any infill for that matter. But I don’t recommend it.

I actually made the first foot I printed for my Primo hollow thinking that I was going to test filling it for better heat stability in a hot Texas garage. It was one of the first parts that I printed for the build. By the time I finished printing all the rest of the parts I forgot that I printed one hollow and completed the assembly.

But I haven’t noticed any issues so I’m not planning on swapping it out any time soon. I also don’t know which one it is so I don’t want to completely dismantle my machine.

The heat this summer has been brutal in the garage so I haven’t used my Primo in a while. We’ll see if I notice any problems the next time I use it now that we have a cool front.

Good luck in your build!