Aluminum Cast Damages – Initial Analysis
Written by admin, 24 March 2021
The aluminum cast damages as well as its steel support’s damages form the foundation for aluminum cast repair and fabrication of new steel support. First, we must analyze damages in both, aluminum cast and in its steel support structure. Second, we must find correlations and interactions between these damages to develop a constructive solution plan.
Gathering evidence is not as simple as it looks. Many damages hide from the naked eye and only very careful observations and then proper measurements confirm these damages. During the gathering process, I like to work alone without any disturbances, although presence of assistant / helper is necessary. These type of investigations simply excite me.
Aluminum Cast Damages – gathering evidence
Pictures tell the story
I always say that in welding business pictures tell the story. In gathering evidence for aluminum cast damages, pictures are paramount. Let me share my slightly different technique when taking pictures for aluminum cast damages and for structural damages of aluminum cast’s support. I tend to take pictures of multiple angles from the same point. This technique follows my initial visual inspection when looking on elements. During a visual inspection, I tend to change slightly my visual angle on the element to notice certain details better.
I realize that this method is time consuming, but it simply allows me to see more. More importantly, I very rarely miss details.
Videos describe the details
I like taking videos of process how aluminum cast works in the production process. In case of this aluminum mold, I have taken multiple videos of crew activities during the production process and I have taken them also from different point of views. In this way, I have
- developed a sequence of tasks how the canoe forms are produced,
- recognized the list of hand tools used during the process,
- recognized challenges in the production process.
These videos should show how the things work and engage. They are very important if you plan to improve the production process through making things more ergonomically friendly.
Interviews of technicians working with aluminum cast
In my opinion, developing a good working relationship with technicians directly operating the equipment is extremely important for the project’s success. These technicians know their equipment and they notice its malfunction details. I always tend to ask very specific questions to these technicians to reveal the details.
Top management role in gathering information
Top management involvement and support is extremely necessary for gathering information. Workers have to understand that during the information gathering process, I interrupt their tasks and ask questions. Therefore, the top management must clearly communicate to them that during my information gathering process their production targets are secondary to my information gathering. Such position is in best interest of top managers from the long-term business perspective.
Aluminum cast damages and their evaluation
After very careful analysis and multiple inspection of this more than 16 foot aluminum cast mold supported by approximately 19 feet still support , I have noticed following damages or strange malfunctions.
Damages of aluminum cast lid
The damages of aluminum cast lid consisted of:
- damages of lid’s step – ups
- bowing of flats
- damages of lid’s top surface at the bows
- locating pin missing
- severe deflection of lid’s bows that is causing lack of sealing
- damages of lid’s flats from inside in area of lid’s bows
After careful prioritization, the two most important damages, damages of lid’s step -ups and severe deflection of lid’s bows that is causing lack of sealing have concerned me the most.
Damages of lid’s step – ups
These lid’s step -ups have contained the threaded bores with ½” threaded steel rods. The mold’s lid supporting steel structure supposed to hold the lid by the ½” steel threaded rods. Unfortunately, the ½ inch steel treaded rods were not hold by tread to the mold’s lid but by the pin that was inserted into the holes made in damaged aluminum step – up and the treaded rod. These holes for the pins were severely elongated and pins were bent. I knew that the lid is going to break free from its steel support rather very soon.
These damages were so severe that the aluminum mold lid was at risk of disengagement from its steel support. Please keep in mind, the form maker lifts the whole almost 19 feet structure using a crane and a lifting jig attached to the lifting points of the lid’s steel structure. Therefore, the situation has become rather hazardous since disengagement of threaded rods from the lid would cause the fall of the whole structure. The 3561-aluminum alloy used for this aluminum mold is a rather soft alloy and the hazard was clear.
I had no choice but to replace the step – ups of the lid with aluminum cuboids that would be welded to the lid. The design involved machining of much taller 3561 aluminum cuboids with the tapped thread. These planned cuboid were 1 inch taller that original step-ups. I intended to install non-removable ½” threaded rod into the aluminum cuboid and then weld the cuboid to the mold’s lid. As simple as it sounds, obviously the plan contained two rather risky tasks:
- Machining of 3561 aluminum cuboids
- Welding of cuboids to the aluminum mold’s lid
You can find the description of welding cuboids in “Aluminum Welding of 3561 Casting Alloy” and machining of cuboids in “Custom Metal Fabrication” article.
Extensive damages of threaded bores in the step – ups.
The leading causes of extensive damages of threaded bores in the aluminum cast step ups included too shallow bores and significant horizontal forces caused by angular positions of clamps.
Shallow bores in the step -ups.
From the first look I have noticed that these step – ups are not high enough to provide positive support for ½ inch steel threaded rods. These step – ups were about 1 – ¼” high and considering bore shape and an additional protection of the flat they were engaging actively with a threaded rod for maximum of 5/8”. These bores were simply too shallow. Even for threaded bores in mild steel I would recommend at least ¾ inch deep engagement. That is why I have planed as mentioned above to increase the height of new step – ups by 1 inch.
Additional horizontal damages to the bores
These bores were much bigger than 9/16”. Clearly, they were damaged by large size helicoil and forces acting in many directions on the steel rod. Definitely, these damages have not indicated a strong vertical and linear pull. In fact, these damages have indicated rather significant angular pull enforced by clamps.
As you can clearly see on the picture the position of clamp forms an angle between steel support of the lid and the steel support of the bottom mold. The length of threaded rod on the lid has contributed significantly to increased leveraged force acting on the soft aluminum alloy.
Bowing of flats
The mold flats were bowing down. Although, I have expected bowing of flats at the middle of this canoe’s mold, but I did not expect bowing of flats at each canoe’s bow. These old clamps had caused the bow but there was also another factor that have contributed to the damaging aside of clamps’ force. I will mention this factor later on. The structural integrity of flats is very important for sealing effect of the whole mold structure. Additionally, a severe bowing of flats could have put the use of high-power clamps into a doubt.
Clearly the angular position old clamps were causing the bowing of both flats that is the flat of the lid and the flat of the bottom mold. Therefore, when technicians increase the tension of these clamps than the clamps have caused more bowing of the flats. This was a vicious circle. The clamps position has amplified the problem additionally due to the leverage of the element B.
The solution to the issue was relatively simple. I had to position the clamps parallel to the structure into the linear position to eliminate the angular force acting on the steel structure. Also, I wanted to eliminate the element C completely.
Damages on top surface of the mold’s lid
These damages were located where are the canoe’s bows, but they were on the top surface of mold’s lid. They were very concerning since the mold’s thickness in these places has been reduced from ¾” to ¼” over the distance of 5 inches. Both canoe’s bows had the same severe damages. I have marked these areas on the picture below.
I have found that steel blocks used by the canoe’s form maker to provide the support for C clamps were damaging the aluminum cast. The form maker has been using C- clamps to close the lid on top of the bottom mold for years.
Locating pin missing
The locating pin for lid’s alignment to mold’s bottom was missing and the hole was severely damaged. Not only the hole was elongated but also full of product. The product presence in this place indicates usually lack of proper seal.
The mold had to sustain the incline of 25° in the oven and the form maker have suspected that the bottom mold slides down a little during the incline.
Severe deflection of lids bows that causing lack of sealing
The operator has clearly indicated to me that the lid and the bottom mold does not seal properly at approximately 4.5 feet from the canoe’s each bow (as marked on the picture above). After the initial inspection, I could not believe my findings. The gap between the lid and bottom was about 1 inch at the canoe’s bow without clamps’ engagement. This gap continued through 4.5 feet on the left and right side of the mold and at the distance of about 3 feet was still about ¼ inch. In conclusion, this mold without use of clamps was sealing only through about 7 feet.
I knew that the bottom mold was not deflecting therefore it was clear that the lid was bent up and was causing this gap. The main question is why? I had some suspicious regarding this very important damage.
Damages of lid’s flats from inside in area of canoe’s bows
These damages of the lid were minor and not as severe, but I have noticed change of vertical deflection of lid’s shape at each end of the mold. As I said, both ends of the mold where canoe’s bows are, were bent up more radically than the previously described damage.
The form maker has explained that the lid for a long time has attacked the bottom mold first with the bows and they had to change the tensioning of the threaded rods. But since the gap was about 1 inch between the flats, I have concluded that the lid must be on severe stress.
Damages of aluminum cast bottom mold
I expected some problems with the damages of the mold’s bottom, but I could not confirm any damages. Simply put, the steel structure supporting of the bottom mold was too fragile to turn the bottom upside down. Any attempt to lift the canoe’s bottom mold by its supporting structure was very risky. Consequences of such lift were difficult to predict and therefore, I have decided not to lift the bottom mold by its structural support at all. Nether less, I have proceeded to bottom mold’s investigation as much as I could.
Damages of thread in aluminum bores of the mold’s bottom
These damages were much smaller in comparison to damages in upper lid. The bottom mold have not experienced any separate lifting by itself since it has always joined with the lid during the lifting task. However, the bottom mold has experienced significant dragging and disengagement effect in the oven and in the cooler that is why some of many of these threaded rods were moving perpendicularly to the cast. The distance between the step-ups and the first rigid point was very significant providing excessive leverage for the perpendicular movement. Overall, the bottom support steel structure was a complete designing failure.
If the perpendicular movement has already damaged the thread in the step-ups, I was planning to repair it with helicoil or replace the step-ups.
Damages of steel support for aluminum cast
The objective of steel support for aluminum cast is to provide solid support and maintain the shape of the aluminum cast during the manufacturing process. If the steel structure does not support the aluminum cast than the manufacturing process damages the aluminum cast. The metal structure does not properly support the aluminum cast or sometimes even damages it due to following reasons:
- The structural support has a completely faulty design for the whole aluminum cast, and it does not counteract forces acting on the cast,
- The steel support has a partially wrong design and only counteracts forces acting on the cast in some places but in other places it does not provide any support,
- Damages to steel support interfere with steel structure properly supporting of the aluminum cast,
- Unproper repairs to steel support interfere with the steel structure support of aluminum cast,
- The steel support has a damaging effect on aluminum cast since it causes bent and/or stress in the cast.
The structural damages of steel support for the aluminum cast mold were rather severe and all 5 factors mentioned above have contributed to the aluminum cast damages.
Causes of concerns for the steel support of the aluminum cast lid
Although the steel support of the aluminum cast lid looked much better than the steel support for aluminum bottom mold, following aspects has caught my attention:
- Lack of long structural elements supporting the whole length of the structure
- Main joints were poorly designed and poorly welded
- Unfortunate position of mounting plates
- Long connecting elements were causing damages in most sensitive points – supporting structure positioned to far from lids center weight
- Wrong position of clamps
- Missing clamps at canoe’s bows
- Existing clamps are in very poor shape
- Product accumulates close to the hopper
Definitely some of my concerns were more important than others. The most important concerns included lack of long structural elements, unfortunate position of mounting plates and wrong position of clamps. As far as hopper goes, I knew that this will have to be resolved later on.
Lack of long structural elements supporting the whole length of the structure
The top lead support structure had not contained long and uncut elements supporting the whole structure throughout its own length. The welds showed cracks in multiple places and the structural elements showed bowing in unexpected places.
Main joints were poorly designed and poorly welded
Elements holding structure mounts were joined to the main structure in extremely poor fashion. These joins were done in low angle with missing bottom welds and missing structural support for the top weld.
The mounting plates position was an engineering failure
Most disappointing, however was positioning of the very heavy mounting plates (D) attached to the lid’s structure. When we have rigged at points ( F ) and then lifted the lid, these mounting plates contributed significantly to deflection at both ends. The deflection on both ends was 2 inches and 3.5 inches at the rigging points. The significant deflection caused bending of threaded still rod going parallel to the centerline of the mold (G) .
At that time, I had not realized how bad this situation really was. Later on, I’ve found out that instead the steel supporting the aluminum cast, actually the aluminum cast was supporting the steel. The lid was under severe bending force caused by weights on both ends. That is why the lead was touching the bottom mold at closing since it was coming at wrong angle causing damages where the canoe’s bows are.
Long connecting elements were causing damaging forces in most sensitive points
The elements (B) going from the top structure and containing the ½” rods were not touching the aluminum step-ups of the lid. Only the threaded nut with large washer was designed to provide the positive tensioning into the step up. Consequently, the step – up was under tension in both positions, during the lift and in the oven or cooler. (B)
This design has also contributed to the 1 inch gap making sealing extremely difficult. The rods in the middle of the lid structure were too long and the rods closer to each end of the lid were slightly too short. This was a typical failure on behalf of the fabricator. As a consequence, the steel support has deflected up the lid while in standing position on the floor.
Clamps’ wrong position caused twisting of flats and damages to aluminum bores
These ( B) elements had clamps’ latches positioned very high ( C ) and combined with clamps angular position they were causing damages to the aluminum bores. Under the force of clamps, the high leverage force of these elements has caused twist of flats and damages of aluminum bores caused by steel rods. The bending of the steel rod was acting perpendicular to the centerline of the lid.( E)
Missing clamps at each canoe’s bow
The steel support structure was missing 2-3 clamps on left and right side of the mold at each end. I mean, these clamps were either missing, malfunctioned, or broken. Clamps’ latches were bent and did not allow for proper engagement. As I have already mentioned, the form maker was using C- clamps to close the gap.
All remaining clamps were in poor shape
In fact, all remaining clamps were in poor shape. They were uncomfortable to close and their rod’s adjustment was not functioning. All the clamps were wired to prohibit opening during mold’s operation in oven and in cooler.
Product accumulates close to exit of the hoppers
Since beginning of my inspection, I have noticed product accumulation near the hoppers. At the initial analysis I just made a note of this issue but in order to develop some inside I had to remove the hoppers. Therefore, I placed this issue to ”surprise me” category
A disastrous supporting structure for a bottom aluminum cast mold.
I had difficulties to comprehend what kind of objectives were set for the steel support of the bottom aluminum cast except keeping the whole structure in vertical position. The bottom aluminum cast structure flaws were as follows:
- Light and thin-walled elements
- Extremely poor welding technique
- Lack of long and strong elements providing support along the whole bottom support structure,
- No support for the bottom mold in the middle
- Lack of support for the mold near the canoe’s bows
- Unbalanced fabrication therefore clients’ technicians had to weld additional weights.
Disengagement and dragging – the assembled unit operation
The joint structure of lid and mold’s bottom have experienced effect of disengagement when the assembled mold was put to cooler and was rotating. Same was happening in the oven. In the mounting position, the bottom mold’s steel support structure was sagging from the lid’s steel structure showing significant gap.
When the old unit was put to cooler the bottom mold’s support structure was disengaging from the top structure with the gap showing at about 1- ¾ inch. Additionally, during rotation at about 10 rpm the bottom mold’s steel support was dragging at the 90° position at about 1”. I had to use the estimate here since the whole unit was rotating pretty fast and I was not able to measure the drag more precisely.
Due to dragging and disengaging effect we have not measured the deflection of the whole assembled unit. I mean the unit formed by aluminum cast lid and its steel support together with bottom aluminum mold with its steel support. Measuring the deflection of the whole assembled unit was pointless since the whole unit has lost its rigidity and integrity long time ago.