Retrofitting a 1986 Maho MH400E

I also have some experience working with resins, mainly silicone and polyurethane. I used an AC vacuum pump connected to a paint/pressure pot via a custom acrylic lid with sealant, a gauge and an inlet. Worked really well, but in the end pressure casting always produced the best results. After pouring the resin into the mold, you need to put the mold in the pressure pot, close the lid and turn on the air compressor. I have no idea how any of this corresponds with metal casting, whether the metal remains liquid long enough to pull any of the degassing/pressure casting tricks off. It was tricky with PU resins already, and mostly impossible to degass first and pressure cast later, so I'd end up choosing one or the other.

Since I posted pictures of the face plate casting to a few forums, I got a few questions in addition to Bobs recurrent "where are the sand muller photos" question. Thought it would be easiest to make a video showing the garden shed foundry.



Pulling a vacuum on a molten metal is way beyond my pay grade. That is the sort of technology used to produce turbine and compressor disc billets of titanium or super alloys. You basically need an induction furnace for that to be an option. Precision Cast Parts Inc is privately owned, but doesn't even fit into Warren Buffets garden shed. In a fuel fired furnace like mine, that is not an option. To degas an aluminium melt, you bubble argon up through it, or use degassing tablets. I dont think copper alloys or cast iron as as susceptible to gas porosity as Al.

The comment I made on degassing was related to removing the air mixed into the ceramic investment (similar to plastic of paris) which formed the mould around Paul. This is very similar to degassing epoxy, and any similar equipment could be used. Not sure if I will do enough investment casting to invest in a vacuum pump though. (bad pun intended.)

It would be nice if I could find a supplier for small quantities of ferrosilicon. The most abundant source of cast iron I have available is brake discs from my mechanic friend. I understand from Luckygen1001 that these are not an ideal source, as the iron tends to chill to white iron.

I read that sea shells are added as a flux to make the slag more fluid. I have a bag of shells from the last beach holiday, but forgot to throw any in this melt.
Mark

OT - SWMBO and I did the public tour of the Voest-Alpine steel mill in Linz yesterday. Very impressive to see a blast furnace being tapped, even if behind glass in a viewing cabin. The wind belt must be at least a story high. Shame photography was not permitted.

If you get a chance to visit a steel mill, don't miss it.
Mark

Mark
Really enjoyed the "Tour of my foundry" . Your sand muller is not lacking any thing from what I saw. Hope you wear it out from use.
The Luckygen1001 web site to me is interesting ,in that he seems to pour mostly gray iron.. Did note his ramming of the sand molds didn't use excessive force , thus a lack of vents an risers needed. Also noted his pouring a test coupon for macro analysis of the melt.
Years ago real time analysis of the molten gray iron was mostly a guess for many commercial foundries . Think that now the analysis time needed would only be a few minutes . Am wondering how much has filtered down to the backyard foundry availably? Moisture level indicators for house plants or wood workers use can be used for moulding sand ,but what is cheaply available for the molten iron?
When you were watching a furnace being tapped did you notice people tossing stuff into the pouring ladle before it was filled?

Small quantities of ferrosilicon and sources for all of the other metallurgical grade of herbs an spices. I can sadly say that if you get into a group buy make sure it is a defined grade, money up front, no refunds period and a stated place an amount of time for dispersing the goods into their containers with absolutely no exceptions.
No offence to any wood workers ,but CAD systems an 3-D printers have really removed a huge problem of coming up with a quick pattern for casting. Even multi part patterns or incorporation of curves or art-nouveau/deco styling should be easy compared to making them from expensive wood.
Having a Linux CNC mill removes most of the - how can this be machined - problem.
Did notice the back yard fence is a MAHO green. Someone has a great sense of style.
Bob

Mark,

Thanks for posting the videos of your foundry. Very nice setup. It's early in the morning here so I watched the videos without sound in order to keep the wife and kid from waking up. Did you mention how your furnace holds up to the temps needed for getting a good grey iron melt? I've melted a few crucibles of grey iron and ended up glazing the inside of the furnace...looked like gum on the bottom of a shoe when I opened it up. What did you use for the refractory?


Here is an update on my MAHO project.

First machine being rebuilt is one of the 600E machines. I stripped it down a couple weeks ago after a failed startup. I hooked up the main transformer and found it to be "leaking" voltage through the frame, gave me a nice little zap. Not wanting to chase wires, I removed the controller, box, and transformers. Much smaller machine with all that stuff pulled off.

I machined the servo caps and drilled/tapped the rear of the servo rotor (glad it wasn't hardened) to add encoders. I know this is a Linux CNC forum so forgive me for saying that I tested the setup using Mach3. I wired the x axis to a gecko driver and was able to get the axis traveling accurately.

Christmas left me with an Amazon gift card so I put in an order for a Centroid Acorn. I have one on my lathe and have been very happy with it, really like the ability to rigid tap and the the options built into the board.

Here is my full breakdown if anybody is interested:

Power supply $85-
I'll be using drives that aren't rated for the 170 volts the machine originally used. To power the servos I'll be using a 30amp VARIAC transformer I got off ebay. I have power running through the rectifiers and capacitor the were on the machine.

AMT 102 Encoders $24 each-
These are and easy install and easy to upgrade. I've used them in the past with good results.

Servo Drives-
I'll be using leftover drives from other machine builds. If the DG4S work well, I'll probably buy one more and turn up the voltage of the VARIAC
(1) Gecko 320X $100
(2) DG4S-016035 $160 per drive

Spindle Motor- $100
Bought a used 220v 5hp 3phase motor off ebay.

10HP VFD- $170
Ebay

Controller- $299
Centroid Acorn purchased off Amazon

PC-$180
Refurbished laptop off ebay.

Software- $180

All in will be around $1,600. Get rid of the Centroid needs and you could do it for under $1,000. Affordable by CNC standards. I figure I can make some of my money back by selling off some of the old parts.

Will post some pictures when it's wrapped up.

eflor8234
Interesting to hear about your foundry furnace. You mentioned the furnace interior becoming gummy. Wonder if you were using fire brick for the lining? Mark talks about the lining he is using and his referral to " Luckygen1001" You-Tube site is very useful. Also Keith Rucker - Vintage Machinery has a 8 part You-Tube series on making a oil fired furnace . Think part 7 is about casting the lining.
What size crucibles are you using and where are you getting ferrosilicon and all of the other metallurgical grade of herbs an spices needed ? Maybe we could gather up a care package for Mark's foundry.
Your Maho conversion---
Wonder what is your source for 3 phase 380 volt shop power ? Sounds as if your conversion is geared toward also converting to single phase voltage input. Am wondering what your thoughts are about the hydraulic pump ( 3 phase - 380 volt ) motor needed for tool holder clamping-unclamping in both vertical an horizontal spindles ? The lubrication pump is single phase 220/110 volt. Will the Centroid Acorn be able to incorporate the Maho transmission gear shifting ?
Think Spring an stay warm
Bob

Can the centroid or MACH 3 close the position loop with the Heidenhain scales, or are you just closing the loop between the motors and the gecko's, and leaving the controller to drive open loop?

As a comparison my retrofit cost about:
$100 - Old PC
$400 - MESA 5i25/7i77 plug and go kit plus 7i84
$20 -a couple of patch cables.
$140 - 2x 602 EXE's to fix existing failed components.
$100 - misc wire, ferrules, buttons, etc

So for under $800, I have the gearbox control, the µm accuracy Heindenhain scales in the loop, the hydraulic pump, and coolant pump under machine control. If you hadn't ripped everything out, you'd have $800 to pay for a repair or replacement of the transformer.

I have paid more than that because I made the custom control module, but that is optional.

The hot face is one of the Comprit products by RHI. This is an industrial refractory product rated for 1650°C (3000°F) processes. Apart from a couple of cracks and slag spatters, the heat does nothing except ensure a high Mullite content, and therefore great strength at temperature. My first furnace had a mullite hot face made to a recipe on Alloy avenue. But I cut corners on the lid and used hardware store chimney grout. It turned to lava and dripped during the first firing. Myfordboy has an excellent how to video series on making a furnace with a cast refractory hotface and Kaowool insullation. I'd recommend copying that design. Mine is similar, but takes advantage of scrap Calcium silicate insulation I already had.
Mark

Mark,

I'm not too concerned about the linear encoders or the gearbox. On a machine this old and having no way to properly test anything, I'd rather just stick with what I know...at least on the first machine. My experience with older CNC machines is that it's only a matter of time before something gives up, and that part is usually expensive. I'll be using this machine for my business and it won't be making parts that need really tight tolerances. Speed control will be a breeze using the VFD. If I really need a low gear or high gear, I can change the gears manually. I don't see that being needed very often.

It seems the hydraulic unit is tagged as 380v but works fine with the 220v 3 phase, no issue releasing tools. Controlling the solenoids with a relay block is straight forward. I know there are benefits to the linear scales and the gearbox, but they aren't important for my application. It's more important for me to be able to have a capable machine that is cheap to repair and easy to troubleshoot. If I have an issue with any of these parts I'll be able to diagnose in a couple minutes and have a new part within a couple days.

Not knocking your route, I may try it on the next machine.



Bob,

I don't stock any of the foundry herbs. It is more of a hobby project than anything else. It's a diesel fired furnace and yes, I was using fire brick. Sounds like I need to upgrade. Most pouring I've done has been Si bronze and aluminum.

I'll be running the machine off of three phase 220v. Speed will be controlled by a 0-10v signal sent from the controller to the VFD. I'll find a happy medium gear and use that as the baseline.

Also....it's getting cold.

eflor8234
Happy -almost New Year --
Can get by using fire brick for most of the non ferrous metals an pottery but at temperatures needed for iron the result can be a crucible glued to the furnace bottom . Noodle about the Keith Rucker videos as I remember he said the name of refractory he is using.
Kaowool is available this side of the Atlantic as are the cast able refectories. What size crucibles are you using?

Interesting the hydraulic pump running on 220 volt , could be interesting to know what the motor current draw is per phase.
Guess my question about your 3 phase power should have been - do you have 3 phase power or are you using a phase converter to derive it? Ohio doesn't trust home owners to have 3 phase power.
What are you going to do with the transformer you removed ,as I might be interested in it?
Could you get a photo of the Exe Board (converts the heidenhain scale 11micro amp signal to 5? volt level) . Am interested in the components side of that board.

Bob

Bob,

Happy New Year.

You're right about the fire brick. I used it without issue melting aluminum and bronze. Higher temps quickly glazed it. My daughter enjoyed collecting the "blue jewels" when I chipped away some of the melted brick. At some point I'd like to rebuild the furnace and will look into some of the higher temp options you guys have mentioned. I'm not sure which size crucible I have. A friend of mine has a small production foundry near me. He gave it to me the last time I visited his place. I'm not at my shop but I'd guess it's about 14" tall and 8" wide at the top. It's heavy when full of bronze.

I had to build a rotary phase converter for my shop. Local power company wanted $12k to run a three phase line under the road to my shop. I'll know I've made it big when I can pay them to bring it over.

All the transformers from this machine have gone the way of the scrap yard but I have another 600E that hasn't been touched. It has the large transformer that is separate from the machine and then the other three or four that are in the box. I can load a pallet if you're interested. Are you near a Fastenal location?

Here are some pictures of the EXE board and the machine as it currently sits.

Question about the scales and EXE board. Can these be run to a DRO like you'd find on a typical manual machine? I have a couple manual machines that would benefit from a set of scales.

Erik